PSYC1002 Flashcards
Abnormalities and perception
What is the incidence of a disorder?
number of new cases that occur during a given period
What is the prevalence of a disorder?
number of people who have a disorder during a specified period of time
What is abnormal psychology?
Scientific study (explanation) of ‘abnormal behaviour’
What is abnormal?
The 3D’s- neither on its own is necessary or sufficient
- Deviance
- Distress
- Dysfunctiona
What is deviance and what are the problems with it?
Unusual/unexpected/rare
Problems is that eccentricity or unusual lifestyles do not classify as mental disease
Classification this way can lead to an overly hostile/aggressive society towards people who are different then they
Attitude that anyone different from majority need treatment- starts social oppression
There are positively valued deviations
• Being extremely tall or being a fast runner
E.g. homosexuality- defined as a mental disorder until 1973 just because people showed a deviance from societal norms
People are seen as disturbed if they violate the unstated norms of society
• E.g. talking to yourself, intently staring at someone…
What is distress and what are the problems with it?
E.g. depression and anxiety are distressing and lead to affected to seek help
But bipolar disorder (manic phase) and narcissism, people don’t feel distress towards themselves when they have these- they feel happy and joyous
Psychopaths aren’t very distressed either
There is normal distress in everybody
• Mental disorder doesn’t mean you are distressed but being distressed doesn’t mean you have a mental disorder
Culture/society can cause natural distress towards oneself through judgement
• E.g homosexuality
What is dysfunctional and what are the problems with it?
Behaviour interferes with ability to carry out function in society
E.g. ADHD when people can’t concentrate on schoolwork interferes with school life
But pathological independent and psychopathy- they still work really well in society
Problem because it is defined by norms of surrounding society
• Function of people in society is determined by society itself and is influenced by the era
What are all the D’s affected by? In this case, are they effective means of classification
• All the d’s are affected by current social values and constructs
o Some people think behaviour is normal and some abnormal depending on their culture and context
• Henceforth, deviance, personal distress and maladaptive behaviour all determine whether behaviour is normal or abnormal
• We can attempt to define abnormal behaviour as behaviour that is personally distressing, personally dysfunctional and/or so culturally deviant that other people judge it to be inappropriate or maladaptive
Is psychological abnormality and normality on a continuum, or in well defined categories?
Continuum
What is the diagnostic and statistical manual of mental disorders?
Published by the American Psychiatric Association
Reflects biological/medical model of ‘mental illness’
Reflects the current state of knowledge about diagnostic categories and symptoms, rather than it being a reflection of reality
What are the different models of mental illness?
- Supernatural
- Biological
- Psychological
- Sociocultural
What is the supernatural model of mental illness?
o Mental disorders are caused by supernatural causes
o This is not empirically proven
o Cause: spirits, stars or moon, past lives
o Treatment- exorcism, prayer, etc.
What is the biological model of mental illness?
o Cause: internal physical problems (=biological dysfunction)
o Treatment: bleeding, diet, exercise, medication
Today, medication is commonly used
What is the psychological model of mental illness?
o Interpretations and values are such that it causes us suffering
o Eventually seek evidence to strengthen and confirm our beliefs
o Cause: beliefs, perceptions, values, motivation
o Treatment: psychotherapy
Breaks down false realities of the world
What is the sociocultural model of mental illness?
o Main causes of suffering is society’s expectations
o Causes: poverty, prejudice, cultural norms
There is the problem of culture-bound disorders, which occur only in certain locales
o Treatment: fix social ills
Are all models mutually exclusive?
No- all are as important as the others (except supernatural)
Describe a timeline of the biological/medical model
• Historically- mental illness= “madness”
o What we now classify as psychosis and dementia
o Gross distortions in perceptions of reality
o Bizarre disorganised thought, affect, behaviour
o Oldest model that is empirically verifiable
• Ancient Greece, Rome
o Hippocrates (460-377 BC), Galen (129-198)
Hippocrates suggested that mental illness was caused by physical disturbances in the body
• Middle Ages (6th-15th century)
o Europe: Catholic church took over authority
o Islamic civilisations upheld biological model
Ali al-Husayn ibn Sina (980-1037), Al-Razi (865-925)
• Europe 19th-10th century: some mental illnesses found to have physical causes (e.g. germs)
o Psychiatry became a legitimate field of medicine
o Starting point for many discoveries of bacteria and their effect on illnesses
o Biological emphasis was given impetus by the discovery that general paresis resulted from massive brain deterioration caused by syphilis
• Today: dominant model in psychiatry
o Assumes that psychological disorders can be
Diagnosed similarly to physical illness
Caused by biological disease processes
• Structural brain abnormalities (Shizophrenia)
• Neurochemical imbalance (depression)
Best treated with biological agents- medication, surgery, ECT…
What are limitations of the biological model?
o Need to avoid extreme reductionism
Certain complex psychological phenomena may be impossible to explain at the neural/molecular level
o Need to avoid over-extrapolation from animal research
Humans are more sophisticated/have more sophisticated motivations
o Need to avoid assuming causation from treatment
Avoid circular logic
o The medical model may not be applicable to conceptualising and diagnosing ‘mental illness’
Clear boundary between physical health and illness
• But continuity between mental health and disorder
What was the psychoanalytic model?
o Most dominant model of psychiatry during 1st half of the 20th century
o Don’t use classical psychoanalysis in psychology now
o Human personality is in constant conflict between three elements that develop in stages:
-Id
-Ego
-Superego
o Unresolved conflict between id, ego and superego can cause anxiety, distress, guilt and shame
o To avoid pain of unresolved conflict and to protect the consciousness, ego develops defence mechanisms
o Defence mechanisms can be more or less successful
o Defence mechanisms can create suffering and symptoms, especially when rigidly applied
Displacement depression
Projection paranoia
Reaction formation overprotection , dependence
Repression obsessiveness
o The same process explains both normal and abnormal behaviour, emotion and thought
o Revolutionised the concept of mental illness
o Popularised the concept of neurosis
o Made no clear dividing line between normal and abnormal conditions and processes
o Treatment
Insight
What is the id?
- Unconscious part of self
- Instinctual drive you are born with
- Motivation: libido-energy derived from id
- Instinct based on pleasure principle wants to feel good
- Unthinking and unreasonable motivation
What is the ego?
- Begins to develop at age 2
- Conscious self (thinking, problem solving, language)
- Second part of personality
- Reality principle
- Wants to mediate between Id and superego
What is the superego?
• Develops at about age 5-6
• Moral self, conscience
• Resolution of Oedipus conflict in male child
o Internalisation of values/expectations of society through identification with father
• In direct conflict with id
What are defence mechanisms of the ego?
Repress id impulses into unconscious
Distort id impulses into acceptable forms
• Displacement
o Displacing your hate from one thing to another
• Reaction formation
o Turning your hate into love
• Projection
o Projecting your hate on something that symbolises what you hate
• Sublimation
o Expressing the feelings in art
o According to the traditional model, only males can do this
A normal process, we all experience it
What are critiques of the psychoanalysis model?
- Limited empirical evidence
- Lack of falsifiability
What is the humanistic model?
o Psychological health:
Fully functioning, self-actualised persons
o Maladjustment results from:
Environment imposes conditions of worth
Own experience, emotions, needs are blocked
Self-actualisation thwarted
If grown in enriching environment, becomes:
• Self-actualised
• Independent, sensitive to the needs of others, loves life and loves life’s wonders
If grown in a society where there are expectations of worth
• Own emotions are blocked because trying to love life for someone else
• Unhappy
• Anxious
• Depressed
o Treatment: empathy, unconditional positive regard
o Critique: difficult to research
Not empirically verifiable
What is the behavioural model?
o Classical conditioning (Pavlov)
o Operant conditioning (Skinner)
o Maladjustment results from learning history
o Many treatment applications
Developing new learning experiences
o Critique:
Observational learning/modelling (Bandura 1974)
• Incorporated cognition to behaviourism
Ignored conditioning
Simple stimulus-reaction model
Talk about the cognitive model
o What we think influences what we feel and do
o Maladaptive behaviour results from
Latent core negative beliefs (Aaron, Beck)
• Interpretation of experiences: consistent with core negative beliefs
• Cognitive biases (overgeneralisation, selective attention, catastrophizing, personalising, magnification , mistaking feelings for facts)
• Negative automatic through
o Treatment-
Cognitive restructuring
• Cognitive-Behavioural model
o Dominant model in psychology
What is the vulnerability-stress model?
• Each of us have a degree of vulnerability (from high to low) for developing a psychological disorder, given sufficient stress
o Vulnerability can have a biological basis such as genotype or neurotransmitter issue
o Vulnerability can have a personality basis, such as low self-esteem
o Vulnerability can have an environmental basis, such as poverty or severe trauma
o Need stressor: some recent or current event that requires a person to cope
What is the International Stats Classification of Diseases and related health problems? (ICD)
o Published by World Health Organisation
o Mental disorders added for the first time in 1948
Initially collected data about physical disorders
o Currently in 10th edition ICD11 beta is just out
What were DSM-I and II
o Diagnosis strongly influenced by psychoanalytic theory
o DSM-I (1952) described depression as defence mechanism from anxiety to protect person from suffering loss that has ambivalent towards them
But what if person has not had loss or does not feel guilty? Is there depression or not
o Not very reliable way to diagnose
o Psychoanalysis has no empirical evidence
What are changes that occurred in the DSM?
• Changes in the DSM:
o Homosexuality removed from the DSM in 1973 (DSM-3)
Society’s ideas changed about homosexuality
o Generalised Anxiety Disorder (GAD) first introduced in DSM-III-R (1987)
o Binge Eating Disorder (BED) first included in DSM-5 (2013)
o Asperger’s Disorder deleted from DSM-5 (2013)
o No psychopathy in DSM anymore
Are ICD and DSM the same?
• ICD and DSM are not the same
o Problem as diagnosed differently according to where you live
English speaking countries- DSM
Europe- ICD
o Mixed Anxiety-Depression (ICD), Generalised Anxiety Disorder (DSM), Binge Eating Disorder (DSM)
How is anxiety activated?
Activated in response to perceived threat
• Realistic /objective threat to self
Physical vs social threat
• Social threat important as social rejection was dangerous in evolution
• Specific ‘prepared’ stimuli
Stimuli prepared by evolution
More likely to be uncomfortable or anxious in their presence
Insects, animals, heights, enclosed places, anger
• Novel stimuli
Something could go wrong
Elicits anxiety
o Threat appraisal
–> Expectancy of harm –> automatically elicits anxiety
What four components does anxiety have?
- A subjective-emotional component, including feelings of fear and apprehension
- A cognitive component, including worrisome thoughts and a sense of inability to cope
- Physiological responses, including increased heart rate and blood pressure, muscle tension, rapid breathing, nausea or dry mouth
- Behavioural responses- avoidance of certain situations and impaired performance on other tasks
What happens to the physical system during anxiety?
Sympathetic nervous system
Fight/flight response
Mobilises resources to deal with threat
• Wants to keep you safe
Symptoms: sweating, heart rate, trembling etc
Classic symptoms of autonomic arousal
What happens to the cognitive system during anxiety?
Perception of threat
Attentional shift to source of threat
Hypervigilance to the threat
• Difficulty concentrating on other tasks
What happens to the behavioural system during anxiety?
Escape/avoidance • Most common reaction to anxiety is avoidance • Safest is avoidance Freezing Aggression • Least safe results Do what is safest for survival
What is threat appraisal, and what is it influenced by?
-Generates expectancy of harm • Product of: Perceived probability • Overinflated probability vs probability consistent with reality • Judgement causes anxious harm if not consistent with reality Perceived cost • Often based on past Experience • Conditioning, reinforcement Observational learning Instruction
When is anxiety abnormal and what happens when it is? Why?
• Not qualitatively different from normal anxiety
Same physical, cognitive, behavioural aspects
Occurrence is excessive or inappropriate
• Anxiety occurs in absence of objective threat
• Anxiety is more intense than objective level of threat
Characterised by overestimation of threat
• Probability of negative outcome
• Cost of negative outcome
Can have genetic predisposition to anxiety, but there are a lot of psychological, environmental and social factors to it
• Heredity factors may cause over reactivity of neurotransmitter systems involved in emotional systems (such as low levels of GABA) and the over reactivity of the autonomic nervous system to perceived threats
What are the anxiety disorders in DSM-IV?
- Seperation anxiety disorder
- Specific phobias
- Social phobia
- Generalized anxiety disorder
- Obssessive compulsive disorder
- Post traumatic stress disorder
- Acute stress disorder
- Panic disorder
What is panic disorder in DSM-IV?
- With/without agoraphobia
- Unexpected/spontaneous panic attacks
- Anxiety about having another attack
- Avoidance behaviour becomes a lot more extreme and life becomes more restricted as afraid of having a panic attack and try to avoid places where they had one
- Agoraphobia- excessive fear of situations such as using public transport, being in a crowd, or being outside the home
What is acute stress disorder in DSM-IV?
Short term version of PTSD
What is posttraumatic stress disorder in DSM-IV?
- Thoughts/memories of traumatic experience
- Physical integrity has been threated (you or someone close)
- Avoid memories of traumatic event
What is OCD in DSM-IV?
• Obsessions- intrusive thoughts or impulses
o Fear of the thought
• Compulsions- Ritualised behaviours to relieve the anxiety caused by obsessions
What is generalized anxiety disorder in DSM-IV?
- Excessive and uncontrollable worry about a range of outcomes
- No focus on what the purpose feels
- Something to avoid in the future
What is social phobia in DSM-IV?
- Fear of negative social evaluation
- Don’t want to be embarrassed or criticized
- Avoid social situations
What is specific phobia in DSM-IV?
- Animal, natural environment, blood-injection-injury, situational, other
- Based on learning history
- Will avoid the specific stimulus
- Phobias- strong and irrational fears of certain objects or situations
What is seperation anxiety disorder in DSM-IV?
- Being away from primary caregiver
- Childhood anxiety disorder
- Avoidance behaviour: want to stay with primary caregiver all the time for fear that they will have an accident
What are the changes between DSM-IV and DSM-V?
From DSM-IV removed from DSM-V's anxiety category: -PTSD -Acute stress disorder -OCD Added to DSM V's anxiety category: -Selective mutism
PTSD and OCD have their own chapters in DSM-V
What is a panic attack in DSM-V?
o Abrupt and intense fear or anxiety
o Peaks within 10 minutes
o Classic symptoms of autonomic arousal
Heartbeat accelerates
Sweating
o Other associated physical symptoms
o Fear of dying, losing control, going mad
Mostly associated with unexpected panic
o Situationally bound panic
Occurs in presence or anticipation of feared stimulus
Can be associated with any anxiety or related disorder
Know when to expect it
o Unexpected panic
Associated with panic disorder
o Results of intense anxiety
What is a panic disorder in DSM-V?
o Unexpected/spontaneous panic attacks
o At least 2 panic attacks where the person cannot identify the trigger
o Anxiety/worry about having another attack
o Concerns about heart attack, going mad, epilepsy
o Significant behaviour change trying to avoid another attack
Avoid areas where they had a panic attack
• Can develop agoraphobia
o Symptoms must persist for one month or more
o Average duration is 10 years before receiving psychological treatment
Think they are physically ill instead of mentally so takes them time before they get psychological help
What is the cognitive theory of panic disorder?
Bodily sensations (shaking, breathing) misinterpretation of bodily sensations anxiety increased bodily sensations panic
• Worse in people who have body fear as they are extremely aware of body sensations
• Misinterpretation of normal bodily sensations is negative increased panic about them body sensations increase
• Interpretations are so quick most people don’t realise them
Panic attacks can be triggered by exaggerated misinterpretations of normal anxiety symptoms.
The person appraises these as signs that a heart attack is about to occur, and these catastrophic appraisals create even more anxiety until the process spirals out of control, producing a full-blown state of panic.
What is specific phobia and its causes in DSM-V?
o Extreme disabling fear or anxiety about specific targets
o Animal, natural environment, blood-injection-injury, situational, other
o Possible causes:
Classical conditioning (Bouton, Mineka and Barlow, 2001)
May not be a complete account (Menzies and Clarke, 1995)
• Conditioning event is not sufficient to cause phobia
• Conditioning event is not necessary to cause phobia
o Some people with phobias have had no encounter with their phobia
Some stimuli are more likely to become phobic than others
• Phobic fears: significant threat to survival during evolution
• Genetic preparedness (Seligman, 1971, Ohman 1975)
o Things that are man-made are less the subject of phobia
• Innate/unconditioned fears(Clarke and Jackson, 1983)
o Some people don’t unlearn the intense evolutionary fear
o May be due to overprotective environment
What is generalised anxiety disorder and its symptoms in DSM-V?
o Excessive and uncontrollable worry about a wide range of outcomes
o Physical symptoms are different from panic
Tension, irritability, restlessness, sleep problems
o Associated with
High trait anxiety
• High tendency to become anxious
• Most ambiguous information is interpreted as threatening
Reduced problem solving confidence/success
Intolerance of uncertainty
• Want to reduce uncertainty to 0
Reduced ability to tolerate distress
o Ongoing state of diffuse, or free-floating, anxiety and worry that is not attached to specific situations or objects
o Symptoms have to last for at least 6 months
What is OCD in DSM-V?
o Obsessions- Repeated, intrusive, irrational, thoughts or impulses. Causes severe anxiety
o Compulsions-Ritualised behaviours to relieve the anxiety caused by obsessions
o Can be either obessions or compulsions- doesn’t have to be both
o Associated with
Intolerance of uncertainty
• Not trusting self to have done something so need to check back
Inflated responsibility
• Think that if bad things happen it’s their fault
Thought-action fusion
• Specific to OCD thinking and actingis the same thing
Magical ideation
What is PTSD in DSM-V and the symptoms required to be diagnosed/ causes?
o Exposure to actual or threatened death, serious injury, or sexual violence in one (or more) of the following ways
Illness doesn’t count
Doesn’t count if you watch events on TV, has to happen in person
Directly experiencing the traumatic event
• Try to avoid but hard to avoid due to generalisation
Witnessing, in person, the event as it occurred to others
Learning that the traumatic event occurred to a close family member or friend
• In cases of actual or threatened death of a family member of friend, the event must have been violent or accidental
Experiencing repeated or extreme exposure to aversive details of the traumatic event (police officers repeatedly exposed to details of child abuse)
o Intrusion symptoms (1 or more needed)
Memories, dreams, flasbacks of the event
o Persistent avoidance of simuli (1 or more)
Memories or external reminders of the event
o Negative changes in cognition mood (2 or more)
Fear, negative beliefs about self, others, the world
o Changes in arousal, reactivity (2 or more)
Anger, recklessness, self-destructive acts, sleep disturbance
This is more prominent in DSM-V than DSM-IV
o Duration of symptoms is 1 month or more
o 50-60% of people experience traumatic event
o PTSD prevalence: 5-11%
Critical to identify people who need assistance to prevent post-trauma problems
o Risk factors:
Pre-trauma (coping style)
• If have avoidance coping style, more likely to develop a problem
Trauma (meaning)
• If look at the situation extremely negatively and not as a one-off incident, more likely to develop problem
Post-trauma (social support)
• If have no social support during questioning or legal processes, more likely to have problems
How are anxiety disorders treated?
Cognitive Behavioural Therapy
o Aim to reduce (biased) threat appraisal
How likely is it that the event will happen
How bad would it be if it did happen
Observe cost and probability of event
o Cognitive techniques
Given rundown of what anxiety is and how it works
Thought diaries to identify automatic thoughts
Thought challenging after thoughts are identified
• What’s the evidence against the thought/belief
• Pros and cons of having the thought/belief
Behavioural techniques
What are some behavioural techniques used to treat anxiety?
o Behavioural techniques-
Necessary to use exposure to treat anxiety as main behaviour of anxiety is avoidance
Exposure to feared stimuli
• Have to be sure they don’t have safety behaviours (such as lucky charms…) during this
• For panic disorders, expose to increased body sensations through exercise…
Exposure to feared outcomes
• In vivo vs imaginary exposure
o In vivo- in real life
• Flooding vs systematic desensitisation
o Systematic- step by step
o Flooding- worst experience in first session
Behavioural techniques also affect cognition
• Exposure to feared stimuli
o Reduces judgements of likelihood of harm
• Exposure to feared outcomes
o Reduces judgments of cost
o Exposure is essential in anxiety treatment
o Generalised Anxiety Disorder is hard to treat
Doesn’t have a clear fear focus as doesn’t have specific fear to tap into
What are DSM-IV depressive disorders?
• DSM-IV depressive disorders
o Unipolar- depressive mood/episodes only
Person only experiences one end of the mood spectrum
o Depressive episode: abnormally low mood
o Major Depressive Disorder, Dysthymic disorder
Major depressive disorder- episodic disorder and differs in how long and severe they are
How are DSM-IV bipolar disorders classified
o Manic episode: abnormally elevated mood Including 3 or more of: • inflated self-esteem, • grandiosity • decreased need for sleep • increased talkativeness • Distractibility • flight of ideas • increased goal-directedness • excessive pleasure seeking o Bipolar I Disorder, Bipolar II Disorder, Cyclothymic disorders Bipolar disorder/manic depression erratic changes in mood
Were bipolar and depressive disorders in the same chapter in DSM-V?
No
What is Bipolar I disorder in DSM-V?
At least one manic episode at least for 1 week
What is Bipolar II disorder in DSM-V?
One manic episode
4 days
Not quite as severe symptoms of full blown mania
Must have depressive episode
What is cyclothymic disorder in DSM-V?
Many light symptoms of both ends of the mood spectrum
Lasts for 3 years
Fluctuations in mood
What is major depressive disorder in DSM-V and what are the symptoms
o Intense state of sadness (dysphoria) and/or lack of ability to feel positive emotion (anhedonia) that leaves them unable to function effectively in their lives
o One or more major depressive episodes
o Single or recurrent depressive episode, not accounted for by other disorders
o Recurrent episodes are common
o Affective symptoms
Depressed mood most of the day, nearly every day
Markedly diminished pleasure/interest in activities
o Somatic symptoms
Significant weight loss or gain
Insomnia or hypersomnia nearly every day
Psychomotor agitation or retardation nearly every day
Fatigue/loss of energy nearly every day
o Cognitive/motivational symptoms:
Feelings of worthlessness, excessive guilt nearly every day
Diminished ability to concentrate nearly every day
Recurrent thoughts of death, suicide, suicide attempts
o 5 or more symptoms are needed, including 2 and 3 in a 2-week period
o Each episode increases likelihood of next depressive episode
What is DSM-V persistent depressive disorder and how is it classified?
o Less intense form of depression that has less dramatic effects on personal and occupational functioning, but continues for a significant amount of time largely unabated
o Depressed mood for most of the day, for more days than not, for at least 2 years
o Presence, while depressed, of two (or more) of:
Poor appetite or overeating
Insomnia or hypersomnia
Low energy or fatigue
Low self-esteem
Poor concentration or difficulty making decisions
Feelings of hopelessness
o No more than 2 months ‘normal’ mood in 2-years
o No major depressive episode during the first 2 years
o No manic features
Symptoms are milder but longer lasting than major depression
Symptoms can persist unchanged for long periods
May also develop major depression
What are recent depression trends?
- Depression is increasing and is diagnosed at an earlier age in next generation
- A lot more young women become depressed than men starting from late adolescence
_____ + ______ = depression
Cognitive vulnerability
Stress
What is the Schema theory (Beck) on depression?
o Pre-existing negative schemas
o Learned during childhood
o Activated by stress
o Result in information processing biases
Biased attention, memory, interpretations
o Negative thoughts become dominant in consciousness
Distorted view of self, world, future
o Attribute successes or other positive events to factors outside the self while attributing negative outcomes to personal factors
What is the learned helplessness theory on depression (Seligman)?
o Depression occurs when people expect bad events will occur and that there is nothing they can do to prevent them or cope with them
o Depression occurs as a result of negative attributions for failures that are personal or internal, stable, and global
What is the ruminative response style (Nolen-Hoeksema)?
o Talks about the way you think rather than content of thinking
o Ruminating on thoughts vs distracting self from thoughts
o Women more likely to have ruminating style than men
What are cognitive causes of depression?
- Cognitive vulnerability and stress
- Schema theory
- Learned helplessness theory
- Ruminative response styles
- Interpersonal factors
- Early traumatic losses or rehections create vulnerability for later depression by triggering a grieving and rage process that becomes part of the individual’s personality (Abraham, Freud
What is Lewinsohn’s behavioural perspective on depression?
o Depression is usually triggered by a loss, by some other punishing event or by a drastic decrease in the amount of positive reinforcement that the person receives from his or her environment
o As the depression begins to take hold, people stop performing behaviours that previously provided reinforcement
o Depressed people also tend to generate additional negative life events through pessimism, and make others feel depressed and anxious
o Eventually other, people begin to lose patience which drives them away and diminished social support
o This causes further depression
What are biological causes of depression?
- Both genetic and neurochemical factors have been linked to depression (twin studies).
- Behavioural inhibition system and the behavioural activation system are involved in the development of mood disorders
- Mania high BAS low BIS
- Depression High BIS low BAS
How are depressive disorders treated?
o Addresses cognitive errors in thinking
Aims to develop more realistic view of life (thought diaries and help person adjust thoughts in a way more consistent with reality), not positive thinking
o Includes behavioural components
Behavioural activation- increase reinforcing events
• Reintroduce things they enjoy
• If they hated it, look at cognitive aspect of why they enjoyed it before and now hate it
Behavioural experiments- test beliefs
• Empirically test beliefs
• Outcomes comparable to drug therapy
o Lower relapse rates than biological treatments
Meta-analysis: 29% vs 60%
o Following CBT treatment, has learned to see world in more realistic way
What eating disorders have been added to DSM-V that weren’t in DSM-IV?
- Pica
- Rumination disorder
- Avoidant/restrictive food intake disorder
- Binge-eating disorder
What eating disorders are in DSM-V?
o Pica
o Rumination Disorder
o Avoidant/restrictive food intake disorder
o Anorexia Nervosa
o Bulimia Nervosa
o Binge-eating disorder
Added officially as an eating disorder in DSM-V
Binge but don’t purge
o Other Specified feeding or eating disorder
o Unspecified feeding or eating disorder
What is anorexia nervosia?
• Restriction of energy intake, leading to a significantly low body weight for age, sex, developmental stage and physical health
o BMI <18.5
BMI- weight standardised against height
o Need to be severely underweight to be anorexic
• Intense fear of gaining weight or becoming fat even though underweight
• Body image disturbance
o Persistent lack of recognition of seriousness of low body weight
o Undue influence of body weight/shape of self-evaluation
What is restricting anorexia nervosia?
Restrict food intake or excessive exercise
What is binging/purging nervosia?
Overeating followed by purging
Overeating can be subjective or objective amounts of food
Purging normally achieved through self-vomiting or a lot of laxatives
What are psychological symptoms of anorexia nervosa?
o Psychological problems
Depressed mood, irritability, anger, social withdrawal, preoccupation with food, poor concentration
• Often associated with starvation syndrome
• Social withdrawal- can’t eat with everyone else due to different eating patterns and long list of forbidden foods
What are physical problems of anorexia nervosia?
Low body temperature, brittle hair/nails, increased body hair growth
Low aestrogen Osteoporosis (brittle bones)
• Stop having periods
Malnutrition, anaemia, immune system suppression
What are some comorbid disorders associated with anorexia?
• Depressive disorder
• Anxiety disorders (social phobia)
• Substance use disorders
• Personality disorders (Obsessive Compulsive Personality Disorder)
o Anorexics have rigid perfectionist behaviours and attitudes
What is the prevalence and course of anorexia?
o Affects 0.5-1% of females in western societies
o 90% of individuals with anorexia nervosa are female
-Mostly teens
• Course-
o Slow recovery (takes up to 10 years)
o 20% remain chronically ill
o About 50% develop bulimia
What is bulimia nervosa?
• Binge eating + compensatory behaviours
• Recurrent episodes of binge eating
o Eating in a discrete period of time an amount of food that is definitely larger than most people would eat during a similar period of time and under similar circumstances
o A sense of lack of control over eating during the episode
• Recurrent inappropriate compensatory behaviour in order to prevent weight gain
o Purging: self-induced vomiting, laxative abuse
o Non-purging: fasting, excessive exercise
• Body image disturbance
o Undue influence of body weight/shape on self-evaluation
• Can have normal or overweight body weight
o Unsuccessful anorexia
• Can be fast eaters that eat in secret spontaneously, or planned
• Feelings of shame and guilt after binge
What are psychological problems in people with bulimia?
o Comorbid mood disorders
o Anxiety disorders
o Substance abuse
o Personality disorders (Borderline personality disorder)
Emotional and impulsive- probably why can’t reach their goal of thinness
What are physical problems of bulimia?
o Associated with binges Stomach rupture o Associated with compensatory behaviours Scarring of oesophagus Electrolyte disturbances irregular heartbeat and heart failure Dehydration Salivary gland enlargement Loss of dental enamel
What is the prevalence, onset and course of bulimia?
• Prevalence-
o Affects 1-3% of females in western societies
o 90% of individuals with bulimia are female
• Age of onset-
o Late adolescence to early adulthood
• Course
o Long term outcome is better than for AN
10% still affected after 10 years
What is muscle dysmorphia?
• In men eating disorders are becoming recognised
o Muscle Dysmorphia
Keeps wanting to be more ripped
Change behaviour in way similar to eating disorders
Self-esteem strongly based on appearance
Less common than eating disorders in women
What are proposed biological causes of people with eating disorders?
• Genetic factors
o Genetic factors more general for neurotic disorders- not one specific gene for each disorder
o Family and twin studies suggest moderate heritability component for anorexia and bulimia
Also higher depression, personality disorders and substance use in families of people with eating disorders
o No adoption studies have been conducted
Hence, difficult to separate the effects of genetics and the effects of the environment
• Neurotransmitter disturbances
o Serotonin involved in appetite regulation
Mixed findings regarding direction of causation
What are proposed psychological causes of people with eating disorders?
• AN and BN have many features in common:
o Tendency to base self-worth on weight/shape
o Desire to attain unrealistic levels of thinness
o Intense fear of gaining weight
• High degree of overlap in proposed causes
o Cognitive behavioural theory- Transdiagnostic model (Fairburn)
Core low self esteem
Perfectionism
Distress intolerance
Interpersonal difficulties (fairburn)
What are psycho-social causes of eating disorders?
• Family factors
o Higher parental criticism, control and conflict
o Lower parental empathy and support
o Comments regarding child’s eating/body
o Parental modelling of eating/body concerns
• Peer factors
o Social approval
o Usually have some level of social anxiety
o Increase behaviour after positive feedback from peers
• Sociocultural values
o Emphasis on thinness as a key basis of attractiveness (especially for females)
o Values in society support eating disorders
What is the treatment for eating disorders?
- Hardest part is convincing the person that they need help
- Build their self-esteem on a wider range of factors than just weight
- More difficult to treat people with ED cause they don’t seek health or don’t recognise that there is a problem
What is sensation?
Refers to how your senses transform physical properties of the environment and body into electrical signals related to the brain
Based on the existence of different types of energy- see because energy interacts with objects in a specific way
Sensors take EM energy and transform it into electrical impulses in your brain that have a specific pattern
Senses defined based on kind of energy that makes them fire –> specific to stimulus
What is perception?
The process of actively organizing, selecting and interpreting these signals into meaningful representations of the world and interpolates what is missing when it perceives an object to be missing
Hemholtz- Unconscious inference
Need to interpret sensations for them to have meaning
Report things we need to know in an evolutionary point of view
We perceive what is important for our survival
Perception is the apprehension of the world by means of our senses – finds the relationships towards what we sense
Rely mainly on proximal stimuli to perceive the world
What are the six senses and what does each do?
• Vision- receptors in eyes respond to light
o Only 3 photoreceptors in eye
o Photoreceptors are at the back of the eye, behind a layer of blood vessels that cast shadows on the photoreceptors, which is ignored as not considered to be part of the world
o Brain can confuse eye movement with movement of the world
o Troxler fading-
Colors start to fade and appear to move- these movements are caused by micro-saccades
• Hearing- receptors in ears respond to sound vibrations
• Somatosensation- the awareness of the body
• Taste- receptors on tongue respond to chemicals
• Smell (olfaction)- receptors in the nose respond to chemicals
• Vestibular- inner ear senses gravity and movement
o Fluids at side of the head
What are issues with our knowledge of perception?
- The problem of qualia
- The fallibility of the senses
Describe the problem of qualia
o All of our different senses transform their physical input into electrical impulses in the brain
o Why do we experience on set of electrical impulses as sight, and others as sounds, flavors…
o How does the brain know what is causing the stimulation it receives?
o What can happen if it gets this wrong or mixed up?
Synesthesia
Describe the fallability of the senses (errors and illusions)
o Our knowledge of the world and ourselves is mediated by our senses. If our senses can make errors, then how do we know what’s real?
o The thatcher illusion
o Illusions indicate we don’t know exactly how things are structured in the world around us
o They provide insight into how perceptual systems break down
o Reveal the kinds of assumptions or general rules we are using to make inferences about the physical world
Describe the dimensionality issue
o Our knowledge of the world and ourselves is mediated by our senses. If our senses can make errors, then how do we know what’s real?
o The thatcher illusion
o Illusions indicate we don’t know exactly how things are structured in the world around us
o They provide insight into how perceptual systems break down
o Reveal the kinds of assumptions or general rules we are using to make inferences about the physical world
What do papillae do aesthetically and what are the 4 types of papillae?
Papillae gives the tongue its bumpy appearance The 4 types are- Filiform Fungiform-contains tastebuds Foliate-contains tastebuds Circumvallate-contains tastebuds
What do the filiform do?
No taste function, located at the anterior portion of the tongue
Different shapes in different species
Most numerous
Draws in food and acts as an abrasive for mastication
What does the fungiform do and where are they?
Resembles tiny mushrooms
Visible to eye on anterior portion of the tongue.
Huge variation between people cause different taste preferences
What does the foliate do and where are they?
Sides of the tongue- look like folds, taste buds buried in the folds
What does the circumvallate do and where are they?
Large visible structures like an inverted V on back of tongue
Is there variation in the number of papillae and taste buds in different people?
Yes
How do we taste?
- Chemical molecules make direct contact with chemoreceptors on our tongue. Huge dimensionality reduction into five categories of taste
- These categories aren’t intrinsic properties of the chemicals, it’s about their biological utility
- Taste discrimination does not change much with age but preferences do
- We’re not equally sensitive to different tastes
What is the biological utility of the sweet taste sensation?
Identify energy rich nutrients
-Innate preference for sweetness as need energy to grow a body
What is the detection threshold of the sweet taste sensation?
One part glucose in 200
-Least sensitive
What is the biological utility of the umami taste sensation?
Detection of amino acids
What is the biological utility of the salty taste sensation
Maintain electrolyte balance
What is the detection threshold of the salty taste sensation?
One part NaCl in 400
What is the biological utility of the sour taste sensation?
Acidity (dangerous at high levels)
-Critical for microbiome in gut (especially acetic acid)
What is the detection threshold of the sour taste sensation?
One part HCl in 130000
What is the biological utility of the bitter taste sensation
Potential poison
What is the detection threshold of the bitter taste sensation
One part Qunine in 2000000
-Most sensitive
What is the labelled line model of taste?
o Labelled – line model
In each tastebud, there is a specialised cell that detects the own flavour
• One type of cell signals one type of sensation
This particular cell fires an axon to the brain
The brain knows where the input is coming from
Each taste quality is specified by the activity of non-overlapping cells and fibres.
What is the cross fibre model of taste?
It’s WRONG
The across-fiber pattern-coding model proposes that individual taste cells respond to different taste qualities.
Thus, the code for a particular quality is determined by the pattern of activity across all of the afferent nerve fibers, rather than by activity in any single nerve fiber.
Compare the number of fungiform papillae on the tongue of nontasters vs supertasters
Nontasters have less on their tongue
What are supertasters and what foods/ groups of people are likely to belong in that category?
o Some humans are genetically prone to have more fungiform taste receptors around the tip and sides of their tongue
o More common among Asians and Africans
o More likely to occur in women
o Unlikely to enjoy eating Brussel sprouts and broccoli
o Unlikely to consume coffee and fatty foods
o Identified using 6-n-propylthiouracil (PROP)
Chemical that elicits bitterness
Supertasters will not tolerate it while non-tasters will practically not taste it
Is spiciness a taste?
No- it is pain and temperature from chemosensory irritation signalled by the trigeminal nerve
What does olfaction provide information about?
olfaction provides information about chemicals suspended in the air around us
How do we smell?
o Airborne molecules reaches receptors at top of nose
o Sniffing swirls air up to receptors, enhancing the aroma
o Millions of receptor cells at the top of each nasal cavity send messages through their axon fibres, forming the olfactory nerve, and route it to the olfactory bulb at the forward base of the brain
o From here, information is sent to the primary smell cortex located in the temporal lobe, as well as to various lower brain regions, especially aprts of the limbic system involved in memory and emotion
How many nerve cells do we have to detect odor and how many types of odors can we smell?
- Humans have about 5 million nerve cells to detect odor
* We can smell a trillion different types of odors
What is the shape pattern theory of olfaction?
o Wrong because receptors with different shapes can smell similar odorants and vice versa
o But theory suggest that odorant receptors can only smell odorants of a certain shape
What did Russel research?
o Russel (1976) had students wear undershirts for 24 hours without showering or using deodorants or perfume
o The undershirts were then sealed in a bag and given to the experimenter: who, in turn, presented each subject with three shirts to smell
The subject’s own shirt
A male’s
A female’s
o About 75% of the subjects succeeded in identifying their own undershirt based on its odour, and also correctly identified which of the other shirts had been worn by males and females
o The performance was not so good in smokers
Can our sense of smell adapt?
o We cannot escape the smell of ourselves, so we are always in some state of olfactory adaptation
o Smokers are usually unaware of the smell of smoke on themselves until they quit smoking
o This may make us more sensitive to smells that are not our own
What happens to our sense of smell as we grow up/ belong to a certain gender?
o Sense of smell increases in childhood and early adulthood, but decreases starting in middle age
o Women and young adults have the best sense of smell
o Need more concentrated odour to detect it, and once detected it will be judged as less intense
o The process of odour adaptation occurs sooner and lasts longer for older adults
What makes up flavour?
Taste, smell and temperature
What effect do pheromones have on us?
o Many mammals use a separate set of sensory receptor cells in their nose to receive social and sexual information from members of their own species
o Women alter their hormonal cycles when exposed to chemical signals from other women
o In recent year, scientists have become extremely interested in these signals as well as in the “accessory olfactory system”, or vomeronasal organ, that responds to pheromones.
o This signalling system is particularly important to animals that are inexperienced sexually
What are two major subsystems involved in touch?
• The somatosensory system- touch and proprioception
o Proprioception- awareness of body position
• Interoception- the sense of physiological condition of the body
Why is touch important?
• Premature babies gain weight faster and go home sooner if they are stimulated by hand massage
• Mothers are allowed to see, hear and smell- but not touch infant monkeys; their mothers become desperately unhappy
• The intimate relationship between touch and emotion
• Johansson 2005
o Women trying to light a match- much harder when nerve blocker is used and she can’t feel her fingertips
What are tactile afterimages?
o Opponent-like after-effects: texture contrast after-effects (after touching something rough, a medium rough surface feels smoother); can be observed for temperature as well
What are tactile adaptation?
o Importance of movement in perceiving spatial patterns in the skin; stabilized (that is, non-moving) objects on the skin are less salient than when the skin is first perturbed
We can adapt to permanent touches
Compare active and passive touch
o The tactile system has evolved to perceive best when it is exploring
o So active touch better for exploring than passive touch when you want more information on an object
What are the two types of sensors within the somatic sensory system?
o Detection of mechanical stimuli (light touch, vibration, pressure and cutaneous tension): identify shapes and texture of objects, to monitor the internal and external forces acting on the body at any moment
o Detection of pain and temperature: detect potentially harmful circumstances
How does mechanosensory processing work (receptors and process)?
- Detection of external stimuli: cutaneous and subcutaneous mechanoreceptors at the body surface
- Proprioceptors- receptors located in muscles, joints and other deep structures monitor mechanical forces generated by the musculoskeletal system
- Stimuli applied to the skin deform or otherwise change the nerve endings, which in turn affects the ionic permeability of the receptor cell membrane
- This induces a depolarizing current in the nerve ending, which triggers action potentials (sensory transduction)
What do proprioreceptors do?
awareness of limb and body positions, and what forces are being applied on them
What do muscle spindles provide info on?
muscle length
What do golgi tendon organs provide info on?
muscle tension
What do joint receptors provide info on?
positions and tensions on the joints
What are different types of mechanoreceptors?
Rapidly adapting: -Meissner corpuscles -Pacinian corpuscles Slowly adapting: -Merkel disks -Ruffini organ
What are the meissner corpuscles
Elongated receptors that generate rapid action potentials following touch
Where are the meissner corpuscles found?
Found beneath epidermis of hands and feet
Account for 40% innervation of the human hand
Common receptors of glabrous skin (hairless)
When do meissner corpuscles react the most?
low-frequency vibrations (30-50 Hz)
What are the pacinian corpuscles?
Onion-like capsule and fluid filled inner space
-Capsule acts like a filter
Where are the pacinian corpuscles found?
Found in subcutaneous tissue and gut
10-15% of cutaneous receptors in hand
Found in bills, wings and legs of some birds
What does stimulation of the pacinian corpuscle make you feel?
Simulation introduces a sense of vibration/tickle
In which frequency range does the pacinian corpuscle react?
230-350 Hz
Where are merkel disks located?
Located in the epidermis
Particularly dense in fingertips, lips and external genitalia
25% of the receptors in hand
What does stimulation of merkel disks make you feel?
Simulation introduces a sense of light pressure
What is the ruffini organ?
elongated, spindle shaped structures
Where is the ruffini organ found?
Located deep in skin, as well as in ligaments and tendons
Long axis usually aligned parallel to stretch lines in skin, and are responsive to stretching
They account for 20% of the receptors in the hand
What does the stimulation of the ruffini organ make you feel
Nothing
What does the nociceptor do?
- Report pain
- Terminate in unspecialised free endings, so categorized according to the properties of the axons associated with them
What are the Ao-myelinated axons?
• Aσ- myelinated axons, conduct at 20 m/s- first wave of pain (the initial pain)
o Mechanosensitive
o Mechanothermal
What are the C fibers?
• C fibers- unmyelinated axons, which conduct at 2 m/s (slower pain- the second wave of pain)
o Polymodal
Respond to a lot of things
Does the stimulation of Ao and C fibres occur simultaneously?
No-there is a gap between the two activations
Is there a high or low power of localisation for pain?
Low
What is hyperalgesia?
An increased sensitivity to pain
What is referred pain?
Pain that is felt somewhere else than its origin
How do thermoreceptors work?
The skin works to maintain a constant internal body temperature, sensation of warmth or cold are generally caused by departures from a reference skin temperature called physiological zero
What does the perceptual quality of a stimulu depends on?
• The perceptual quality of a stimulus (what and where it is) depends on the receptors that respond and where they project
o Nerve endings will determine to what and how they will respond
o Different position of body maps to different part of the brain
• The quantity or strength depends on the number of action potentials generated
What are two general types of touch fibers?
o Rapidly adapting (information about change or dynamical quality of stimuli)
Instantaneous
o Slowly adapting (information about shape, edges, rough texture, persisting features)
During the duration of the touch
How does the mechasensory pathway work?
- Mechasensory information about the body reaches the brain by way of a three-neuron relay
- First synapse is made by the terminals of the centrally projecting axons of dorsal root ganglion cells onto neurons in the brain stem nuclei
- The axons of these second-order neurons synapse on third-order neurons of the ventral posterior nuclear complex of the thalamus, which in turn send their axons to the primary somatic sensory cortex
What is the idea behind the two point threshold? How does it work?
• Not all parts of body represented with equal fidelity in the brain
• A measure of tactile acuity defined as the smallest separation at which two points applied simultaneously to the skin can be clearly distinguished from a single point.
• Large is insensitive, small is sensitive
• Provides information about size of receptive fields
• Certain body locations have a disproportionate amount of cortical area because of the increased sensitivity needed
• The maps are not fixed: cortical remapping
o Phantom limbs may appear on the face and stump
Look at diagram of the ear and try to label it
Look at notes
In summary, What is the :
- Pinna and eardrum for?
- Middle ear for?
- Inner ear for?
- Pinna and eardrum: directional microphone
- Middle ear: impedance matching and overload protection
- Inner ear: frequency analysis
What does the vestibular system do?
-Assists with control of gaze and posture
What does the inner ear contain?
• The inner ear contains sensory structures with receptor cells that detect gravitational forces, including angular and linear head accelerations in space
• The labyrinth of each ear houses five sensory organs, which provide input to the vestibular system
o Three semicircular canals or SCCs
Angular accelerometers
o Two otoliths
Linear accelerometers
How is acceleration signalled?
• Fluid in head flows opposite to the hair cells in the ears and bends the hair which signal acceleration
• Bending a vestibular hair-cell receptor in its preferred direction excites the neuron
• Being the same cell in the opposite direction inhibits the neuron
• When fluids flow in the semicircular canals, this bends the cupula and underlying hair cells, hence resulting in illusion of continued spinning after being still
o Adaptive signal
What is the vestibuloocular reflex?
o When moving ourselves, we generate large, rapid and complex head movements
o This has considerable consequences on the motion of objects in our visual field
o We need information about head movement to make precise and rapid compensatory eye movements to stabilise the images of objects on the retina
Compensatory movements in the opposite direction
Shortest neural arc
o Cannot make voluntary smooth eye movements
What is frequency measured in?
Hertz
1 Hz=
1 cycle per second
What do waves vary in?
- Amplitude: gives rise to perception of loudness
- Frequency: gives rise to perception of pitch
- Phase
- Period
What is the purity of a sound?
• Purity gives rise to the percept of timbre (or ‘colour’)
o Different frequencies that compose a particular sound
What Hz range can humans hear?
From 20 to 20000 Hz
What is 0 dB?
the minimum detectable sound level for humans
-measured on a log scale
When making music, what does the amplitude of the upper harmonics contribute to?
Timbre
How is the pitch and timber of an instrument conveyed
• The pitch of an instrument is mainly conveyed by the fundamental (or lowest) frequency, and timbre by the relative amplitudes of overtones
What can humans do to make them sound like they’re singing chords?
• Normal humans can generate one note of a given pitch when singing
o This note consists of a fundamental frequency, as well as range of underlying upper harmonics (overtones)
o Some people can shape their mouth cavity to increase the amplitude of one or more upper harmonics and reduce the amplitude of other intermediate frequencies
o This has the effect of making one or more harmonic frequencies “stand out” against the fundamental frequency to generate the percept of multiple notes
What does the middle ear do?
• The middle ear transmits the eardrum’s vibrations to the oval window, which transmits them through the fluid-filled cochlea – focuses the sound waves
What do the ossicles consist of and what is their purpose?
The purpose of the auditory ossicles (also called the ossicular chain) is to transmit sound via a chain reaction of vibrations that connects the eardrum to the inner ear and cochlea.
Made of:
Malleus
Incus
Stapes
What is perilymphatic fluid and why is it useful?
o Perilymphatic fluid (that is liquid) filling the cochlea is denser than air, so it offers more resistance
o Greater mechanical energy is required to transmit sound waves through the denser fluid filling the cochlea
What is the function of the middle ear and how does it do this?
Resistance matching
At the air-fluid boundary, most of the incoming sound is reflected rather than transmitted
o Oval window is 20 times smaller than the eardrum
Sound waves enter the ear canal and make the ear drum vibrate. This action moves the tiny chain of bones (ossicles – malleus, incus, stapes) in the middle ear. The last bone in this chain ‘knocks’ on the membrane window of the cochlea and makes the fluid in the cochlea move. The fluid movement then triggers a response in the hearing nerve.
How is impedance matched?
o For transduction to occur, the air pressure in the middle ear needs to be the same as the atmospheric pressure outside the eardrum
o The Eustachian tube equalizes the pressure every time you swallow or yawn
How does the basilar membrane work?
The motion of the stapes against the oval window sets up waves in the fluids of the cochlea, causing the basilar membrane (in the middle of the fluid) to vibrate.
Basilar membrane vibration-
First theory (Rutherford)- whole thing moves at once, like a diaphragm
• Problem- basilar membrane varies in thickness and stiffness
Basilar membrane- hard to study
Bekesy discovered how the basilar membrane works by constructing a crude model of the cochlea
• Put arm on rubber membrane, and brought a mallet to a tuning fork to see how it would vibrate
• Discovered that frequency sensitivity changes as you move along the basilar membrane due to its mechanical properties
Vibrations of the oval window induce pressure changes in the cochlear fluid that result set up a travelling wave on the basilar membrane
• The wave peaks in different places depend on frequency content
• High frequency travels furthest, low frequency the shortest
What does the wiggle do in the Organ of Corti?
o Wiggles cause voltage changes in hair cells in Organ of Corti
Movement of the basilar membrane causes the hair cells to move against the tectorial membrane, which causes the cilia to bend
When the cilia bend, the hair cells release neurotransmitter onto synapses with auditory nerve fibres that send signals to the brain
What happens after the organ of corti has been touched?
o The output of the cochlea is transmitted to the brain through the auditory nerve
For low frequencies, auditory nerve spikes are phase-locked to the stimulus
• Phase-locking declines with frequency- only up to 1000 Hz
What is phase locking?
Nerve fibers fire in bursts
– Firing bursts happen at or near the peak of the sine-wave stimulus
– Thus, they are “locked in phase” with the wave
– Groups of fibers fire with periods of silent intervals creating a
pattern of firing
What are the two cues to the frequencies in a sound?
o The place of excitation in the cochlea
o The frequency of firing
What is azimuth?
X axis
What is elevation?
Y axis
What are binaural sources of sound location?
To determine azimuth
- Interaural intensity differences
- Interaural time differences
What are monaural sources of sound location?
-Spectral information
Describe interaural intensity differences
• Created by sound shadow
o Sound attenuated for ear covered by shadow
o Makes intensity differences
o 90 degrees- biggest differences of intensity that reaches one ear over the over.
• Negligible for low frequencies- wavelengths are on the order of the width of the head
Describe interaural time differences
- Created difference in path length
* A sound wave coming from the side will hit the nearer ear, producing a time lag between the two ears
Describe spectral filtration- to determine elevation
To determine elevation we make use of the filtering properties of the pinna
Spectral information
• Plotting out different amounts of energies that make it into ears
Broadband sounds will be coloured differently depending on their elevation
Folds in ear are affecting what makes it into ear canal
Spectral filtration is different for everyone
• Amount by which different frequencies of transfer function are attenuated or amplified on their way to the eardrum
What is the cone of confusion?
- A region of ambiguity in the localisation of sounds
- IID and ITD is the same for sources at the two yellow dots, and they contain no information about the elevation of sounds
- Transfer functions will cause sounds to be coloured differently for the ambiguity in azimuth in the cone of confusion
How can a live concert be reproduced at home?
- A region of ambiguity in the localisation of sounds
- IID and ITD is the same for sources at the two yellow dots, and they contain no information about the elevation of sounds
- Transfer functions will cause sounds to be coloured differently for the ambiguity in azimuth in the cone of confusion
What are the three stages to vision?
- Form an image
- Transduce light energy into electrical impulses
- Transmit this information to the brain for interpretation
What are 4 different types of eyes?
- Compound
- Convex mirrors
- Pinhole
- Single chambered
How is an image made according to a pinhole eye, what happens when the hole gets bigger and why don’t we have pinhole eyes?
• One point of the world mapping onto one receptor – pinhole
• Reversed image
• Making the pinhole bigger makes things blurry
o Many different parts of the scene project to the same point and are summed
• We don’t have a pinhole because it would be too dark (pinhole too small to let light in)
How does the convex lens of our eye work and how does accomodation work?
• Convex lens of single chambered eye
o Diverging light reflected from all different directions of an object in the world have to converge onto a single point to form an image
o Single chambered eyes cannot focus on everything
Brain knows gradient of blur indicates where you’re fixating, and where stuff is
o Cornea performs most of the initial focusing of the incoming image
o Lens accommodation allows us to adjust our focus on objects at different distances
o Achieved by changing the shape of lens
o Focal plane varies as a function of lens curvature and object distance
Are our eyes adaptive?
Yes -lengthwise
How does far accomodation work?
o Lens becomes flatter to focus light from a distant object on the retina
o Near objects become focused behind the retina resulting in the blurring of the image
How does near accomodation work?
o Lens becomes rounder to focus light from a near object on the retina
o Light from far objects become focused in front of the retina (that is, blurred at the retina)
What is hyperopia?
Far sightedness
-Focal plane is behind the eye
What is myopia?
Close sightedness
-Focal plane is in front of the eye
What does mat surface do?
light hits and scatters
What does a reflective surface do?
Light hits and on ray of light bounces off
What is light made of?
Light made of photons that travel in a straight line
What nm range can we see?
400-700nm
How is the focal plane arranged in normal vision?
• Normal vision- light coming from the world converging exactly at receptor surface on the focal plane
What is scotopic vision?
Low light, rod dominated: more sensitive
What is photopic vision?
High light levels, cone dominated; less sensitive
How many photoreceptors do we have?
4-
1 rod
3 cones
Why do photoreceptors have different peak sensitivities at different wavelengths of light?
• Photoreceptors contain a different type of photopigment
o Each receptor contains a pigment- absorbs different wavelengths
• Different sensitivities of rods and cones depends on different photosensitives of photopigments
How is the blind spot produced?
- Blood vessels are in front and separated in depth from the photoreceptors –photoreceptors are all the way in the back
- Blind spot don’t have photoreceptors because ganglian cells need to go to brain (goes all in one spot)-spots in eyes where you’re completely insensitive to light: completely unaware of this
Do we see colours with rods? Why/why not?
No as you only have one type of rod
How many photon are needed for your rod to respond?
One
Why are rods useful?
Can see really faint light
What are two mechanisms of light adaptation?
• Pupil dilation/contraction
o Amount of light present changes pupil size
o When dilated- dark condition
o When contracted- light condition
o Change amount of light so we can adjust quickly to variations in light intensity
• Isomerization of the photopigments
How does isomerisation of photopigments work?
o Cones and rods filled with pigments
o When light strikes them, pigments change shape- isomerisation
o Induces current in photoreceptor
o When light bombards photoreceptors, not all pigments absorb photons at the same time-
o When in isomerised shape, photoreceptor cannot absorb additional photons and will not induce electric current
This process is something that takes time to overcome
Takes a while before it goes back to non-isomerised shape
During that process- insensitive to light
In high light levels, so many pigments in isomerised state that they will not be able to absorb photons for some period of time
This makes adaptation to the light level- as more photons become isomerised, become less sensitive to light levels as there are fewer photopigments available to absorb light
But in low light levels, loads are ready to absorb light
How many rods are there to cones?
• Rods: Cones(20:1)
120 million rods vs 6 million conesones
Where are rods and cones most densily located in the eye?
o High density of cones in the centre of the fovea
o No rods of centre of fovea, all in peripheral vision
What is the fovea?
• Fovea- highest spatial resolution part of eye
o When look at something, point fovea at that thing
o Do not have equal spatial resolution across the visual field
o Resolution falls linearly with distance from fovea(eccentricity)
Why do we see colour with cones?
- 3 different types of cones (different photopigments inside of them and so absorb energy at different levels) so can see colour
- Relative activation of the three cone types- all our experiences of colour
What is the trichromatic theory/fact?
- 1800’s: Young and Helmholtz
- Based on the observation that you could generate what seemed to be all of the colours we experience if you mix lights of just three different wavelengths in different proportions
o Our experiences of wavelengths are coloured
o There is short wavelength cone, medium and long
o Different cone types are stimulated at different degrees by different wavelength patterns- brain interprets wavelength
o Natural light- equal activation of all cones
o Collapse wavelength variability in 3 dimensions
o Colour is closely related to the proportions of responses of the 3 different types of cone receptors
o Millions of different perceived colours can be explained in terms of the responses of the three cone types
What is the opponent processes theory?
o Colour perception depends on six psychological primaries that are arranged in pairs (herin)
o Evidence
Do not perceive reddish greens or bluish yellow
Colour aftereffects
Where is trichromacy and opponency located?
• Trichromacy at photoreceptors
—Trichomacy at transduction stage
• Opponency at ganglian cells
—Difference in wavelengths generated at the short length of the spectrum and those in the medium/long wavelength (opponency between sums and differences of wavelengths through cone outpus)
What is the receptive field of a visual cell?
the retinal area that, when stimulated, can affect the firing of that cell
Why is there high definition at the fovea?
Because receptor fields are quite small -> perform sums and differences over very small areas (smallest receptor fields in fovea)
Why is spatial resolution small in the periphery?
Size of receptor fields increases as eccentricity from fovea increases
What happens between the centre and surroundings of the receptor fields?
centre is excited, surround is inhibited (receptor fields)
o Centre-surround opponency observed in ganglion cells
Ganglion cells are last layers of cells
What are 3 colour-vision deficiency types?
Red-green
Blue-yellow
Complete
How does red-green colour vision deficiency work?
L Cones and m cones overlap so much that they act as if they are the same cone class (only have 2 types of cones rather than 3 types of cones)
• Two types of overlaps
People who suffer red-green deficiency (anomalous trichromats) have trouble perceiving the number in these configurations. This type of deficiency is more prevalent in males because it is linked to a genetic deficiency carried on the X-chromosome
What is unilateral achromatopsia?
- Only experience colour on unaffected side and other side is achromatic
- Can be caused by brain injury
How is the visual field divided?
Visual fields are divided into left and right halves
• Left field go to right hemisphere
• Right field goes to left hemisphere
What is the concept of retinotopy?
o Adjacent points in the visual field project to adjacent locations in the visual cortex
What is cortical magnification?
More cortical tissue is allocated for processing the image in the fovea
• More cortical tissue for central than periphery
o Good because that’s where all the HD coming from- so need a lot to process that
What provides us information about depth?
- Oculomotor
- -Accommodation
- -Convergence
- Visual
- -Binocular
- -Monocular
- –Motion parallax
- –Static cues
- —Interposition
- —Size
- —Perspective
What is accomodation and how does it provide information about depth perception?
Capacity of lens to focus at different depths
• The only time you have both far and near things blurred is if you’re fixating on something that is relatively close
• How much muscle tension is required determines how curved your lens is
o If signal comes from brain on muscle tension can provide info on accommodation
• Also seen from blur gradient
How does size provide information about depth?
• Objects of a fixed physical size will project different sizes on your retina and objects of different sizes can project the same retinal size if they’re at different depths
• Don’t experience size change- experience change in viewing distance
Depth perception is linked to perceived size
How does convergence convey information about depth?
depth by sensing the angle of fixation
the movements of your two eyes in a synchronised way to look at things at different depths
Why are our eyes placed in front of our face rather than laterally?
• Animals with front eye placement are predators->advantage is much more precise information about depth, but you lose the capacity to keep track of stuff that may be after you
What are the different monocular cues? How strong are they?
Monocular cues- familiar size (weak one)
• Aerial perspective-low contrast things are further away than high contrasts
• Linear perspective- Lines parallel in space will converge to vanishing point in a picture plane
o Properties of set of parallel lines in the picture planes
• 1,2,3 point perspective
o Depends on number of vanishing points on the scene
• Perspective of objects according to context
o Ames room
Trapedoizal windows in room creates impression of a rectangular room, when it is in fact slanted
o Moon illusion
Appears to be extremely small in sky while horizon appears a lot larger because of lack of depth cues in the sky
What is binocular disparity?
• Caused by two different views by two different eyes
o Gap size reduced in one eye compared to the other eye when two objects at at different points
o Binocular disparity refers to the difference in image location of an object seen by the left and right eyes, resulting from the eyes’ horizontal separation (parallax)
Objects close to you will move at different speeds than the ones further away
