Biopsychology L9 - 13 Flashcards
Plasticity:
Ability of brain to change and adapt synapses, pathways and structures in light either various experiences or damage caused by trauma
Relative to an adult, how many neurons and synapses does a newborn baby have and why?
- More than an adult
- Needed as developing brain is exposed to vast range of experiences
Study showing plasticity in early infanthood:
Villablanca and Hovda (2000):
- If a baby is born w/ a severely damaged hemisphere and the whole thing is removed soon after birth, the adult will show few or no behavioural/cognitive impairments
What happens to cognitive functioning with age and what study was conducted investigating brain plasticity in the elderly?
- Naturally declines
- Boyke et al (2008) found evidence of brain plasticity in 60 year olds taught juggling as new skill. There was an increase in grey matter in visual cortex, which was reversed when practice stopped.
What research was conducted on meditation and what did they find?
- Davidson et al (2004) compared 8 practitioners of Tibetian meditation w/ 10 student volunteers
- Both grps fitted w/ electrical sensors and asked to meditate for short periods
- Much greater activation of gamma waves (which coordinates neuron activity) in monks
- Only slight increase in gamma wave activity when meditating
What conclusion did Davidson et al (2004) make?
Meditation changes workings of the brain in short-term and long-term
Strengths and weaknesses of plasticity (+2, -3):
+ Research support from both animal and human studies –> Kempermann et al (1998), Blakemore and Mitchell (1973), Maguire et al
+ No age limit to brain plasticity
- Negative behavioural consequences
- Generalisation issues in animals
- Ethical issues in animals eg Blakemore and Mitchell where rats were denied a normal environment
Kempermann et al (1998) study:
Compared to rats housed in ordinary cages, those in complex environments had an increased number of new neurons in hippocampus (part of brain associated w/ new memories)
Blakemore and Mitchell (1973) procedure + evaluation:
Kittens reared in an environment w/ black vertical stripes didn’t respond to black horizontal stripes
Evaluation:
- Study carried out on cats –> cannot generalise
Blakemore and Mitchell (1973) conclusion
Showed visual characteristics of visual neurons could permanently be changed by exposure to specific environments after birth
Maguire et al (2000) study:
- Studied London taxi drivers to discover whether changes in brain could be detected as a result of environment of spatial navigation
- Using MRI scanner, researchers calculated amount of grey matter in taxi driver brains and compared this to set of control pps
- Found front part of hippocampus was larger + positively correlated to how long they had spent driving taxis
Give one study showing plasticity can occur in old people:
- Bezzola et al (2012) showed how 40 hrs of golf training produced changes in neural representation of movement in pps aged 40 to 60
- Using fMRI scans, they found reduced motor activity beforehand which increased after training
What study showed plasticity may have negative behavioural consequences and how?
- Medina et al (2007)
- Brain’s adaptation to prolonged drug use leads to poorer cognitive functioning in later life
Functional recovery after trauma:
Transfer of functions from a damaged area of the brain after trauma to other undamagedareas
Common types of brain trauma:
1) Physical trauma
2) Cerebral hemorrhage –> blood vessel in brain bursts
3) Cerebral ischaemia –> when blood vessel is blocked by thrombosis (blood clot) or arteriosclerosis (thickening of blood vessel walls
4) Viral/Bacterial infections that destroy brain tissue
Why are behavioural effects of trauma likely to be one sided?
Blood supply to brain are often lateralised
What did researchers discover when studying stroke victims and when?
In 1960s, when brain cells are damaged during stroke, brain re-wires itself w/ other parts of brain taking over functions
What did Doidge (2007) find?
Secondary neural pathways that wouldn’t usually be used for some functions are activated
Different types of structural changes:
- Axonal sprouting = Growth of new nerve endings
- Denervation supersensitivity –> axons w/ similar functions are aroused to compensate for loss
- Recruitment of homologous areas on opposite side of brain
- Neuronal unmasking –> Wall (1977)
Disadvantage of denervation supersensitivity:
Oversensitivity to messages like pain
What did Wall (1977) discover about neuronal unmasking?
- Identified dormant synapses (synapses that exist but have blocked functions)
- If rate of input is increased, which usually happens after trauma, these synapses can be unmasked
Danelli et al (2013) case study:
- Italian boy EB who had large benign tumour removed from left hemisphere at 2.5 yrs
- Lost all linguistic abilities after operation
- This improved at age 5 after intensive rehab
- Continued until 8, where they were no longer language difficulties
- Tested at 17 to discover right hemisphere had compensated for LH
Strengths and weaknesses of functional recovery (+3, -1):
+ Practical application
+ No age limits
+ Link between educational attainment and functional recovery
- Gender differences
How does functional recovery have practical application?
- Contributed to neuro-rehabilitation field (doctors provide therapy and electrical stimulation to counter deficits as a result of trauma)
- Must be done because spontaneous recovery tends to slow down after few weeks
Give 2 researchers who studied age differences in functional recovery:
- Huttenlocher (2002)
- Elbert et al (2001)
What does Huttenlocher (2002) say about age differences?
- Functional recovery reduces w/ age
- Only option after trauma beyond childhood is developing compensatory behavioural strats
What did Elbert et al (2001) say about age differences?
Capacity for neural reorganisation is much greater in children than adults
One evaluation for stated age differences in functional recovery:
Studies have suggested even abilities thought to be fixed in childhood can be modified in adults through intense retraining
Which researcher discovered a link between educational attainment and functional recovery and what did he find?
- Schneider et al (2014)
- Patients w/ equivalent to college education are 7 times more likely to recover and be disability free a yr after moderate to severe trauma compared to those w/ just high skl education
- Cognitive reserve could be a factor in neural adaptation
Which researcher showed gender differences in functional recovery and what did he find (w/evaluation)?
- Ratcliffe et al (2007)
- Examined 325 patients for level of response for cognitive skills for rehab
- 16 to 45 yrs old at time of injury
- Received rehab then followed up a yr after
- Women performed slightly better than men on attention/ working memory tests
- Men performed better in visual analytical skills
Evaluation: - Results did not control for performance pre-injury
Different methods of studying brain (6):
- CT
- MRI
- PET
Spec: - fMRI –> uses for lie detection asw
- EEG –> detect brain disorders, identify state of brain
- ERP
- Autopsy
How do fMRIs work?
- Indirectly measures blood flow through oxygen concentration in blood stream
- Signal used is BOLD ( Blood Oxygen Level Dependent) contrast
How does measuring oxygen concentration tell us what the most active areas of brain are?
Most active areas will have neurons w/ most energy, which requires glucose and oxygen to be carried in bloodstream
Strengths and weaknesses of fMRI:
+ Risk free –> no radiation and non-invasive
+ Good spatial resolution of 1-2mm –> significantly higher than others
- Assumes causation
- Poor temporal resolution of 1-4 secs
- Cannot hone in on activity of individual neurones
Spatial recognition:
Smallest feature that a scanner can detect
What issues are there in assuming change in blood flow is because of neural activity?
- Psychologists unable to conclude 1 function is localised to a region of brain
- Some say it shows localisation of function but does not show communication between diff areas in brain
Temporal resolution:
Accuracy of scanner in relation to time
How do EEGs work, who developed this and when?
- 24 or 32 small recording electrodes distributed over skull
- Pick up electrical activity of millions of neurons
- Developed by Hans Berger in 1929
2 basic properties of EEGs:
1) Amplitude –> intensity of electrical activity
2) Frequency –> speed of electrical activity
2 distinctive states of EEG:
1) Synchronised pattern –> Recognisable waveform can be identified
2) Desynchronised pattern –> No recognisable waveform
Different waves in EEG:
1) Alpha
2) Beta
3) Delta
4) Theta
Strengths and weaknesses of EEG (+2, -2):
+ Good temporal resolution
+ Invaluable diagnosis of conditions like epilepsy and stages of sleep
- Cannot reveal what is happening in deeper regions, as it is just superficial
- Poor spatial recognition
How do ERPs work?
- Very small voltage changes triggered by specific events
- Similar procedure to EEGs
- Main difference is that stimulus is presented many times and psychologist looks for specific electrical response to this
- ERP summates brain reactions to each stimuli and calculates an avg
Strengths and weaknesses of ERPs:
+ Very short latency (ms) –> reflect very early stage of cognitive processing
+ Measures processing of stimuli even w/out behavioural response
- Poor spatial resolution
- Lack of standardisation in methodology
Give examples of 2 researchers who conducted autopsies and what they did:
- Broca –> man w/ speech issues when he was alive, found lesion in brain was responsible (Broca’s area)
- Iverson –> dead schizophrenics found to have higher concentration of dopamine especially in limbic system compared to normal person
Strengths and weaknesses of conducting autopsies:
+ Detailed examination of anatomical and neurochemical aspects
+ Harrison (2000) says it has been important for understand origins of mental illnesses eg schizophrenia
- Individual differences –> way ppl died, time between death and autopsy, drug use, age
- Ethical issues like informed consent
- Limited as it is retrospective –> follow-ups can’t be made
What 2 factors are biological rhythms controlled by?
1) Endogenous pacemakers (internal mechanisms)
2) Exogenous zeitgebers (external changes in environment)
What is one cycle on a graph?
Time between one peak and the next
3 biological rhythms and what each of them are:
1) Circadian –> happens once in 24 hrs
2) Infradian –> happens after 24 hrs
3) Ultradian –> happens more than once in 24 hrs
Biological rhythms:
Distinct patterns of change in body activity that follow cyclical time periods
Endogenous pacemakers:
Centres in brain that play main role in controlling biological rhythms
Exogenous zeitgeber:
Environmental factors that help synchronise biological rhythms w/ outside world
What resets circadian rhythms?
Levels of light
What are circadian rhythms driven by and what is the process of coordinating circadian rhythm?
- Suprachiasmatic nuclei (SCN), which is a pacemaker
- Natural light provide input, setting body clock to right time (photoentrainment)
- Message sent to SCN, which uses this info to coordinate
Examples of circadian rhythms:
1) Sleep-wake rhythm
2) Core body temperature
3) Hormone production
When are the strongest sleep drives?
- 2am to 4
- 1 to 3pm
What kind of control are we under in sleep-wake cycle and when does sleep drive increase?
- Homeostatic
- Increases if we have had insufficient sleep or are sleep-deprived
What key study supports sleep wake cycle?
Siffre (1975)
Siffre (1975) study:
- French cave explorer
First occasion: - Stayed 61 days underground (no exogenous zeitgebers like daylight) in Southern Alps in 1962
- Resurfaced on 17th Sep thinking it was 20th
Second occasion: - 6 months in a Texan cave
Both occasions: - Free running biological rhythm settled down to usual 24 hrs
What did Siffre (1975) conclude?
Sleep wake cycle is circadian (happens once every 24 hrs)
Weaknesses of Siffre (1975):
- Individual differences
- 1999 –> Siffre observed at 60, his internal clock ticked much slower than as a young man
When is core body temperature at its lowest and highest and when does sleep occur?
- Lowest: 4.30 am
- Highest: 6pm
- When temperature begins to drop and rise in last hrs of sleep
Which studies supported core body temperature?
- Folkard et al (1977)
- Gupta (1991)
Folkard et al (1977):
Children who had stories read to them at 3pm had much better recall and comprehension a week later compared to those who heard it at 9am
Gupta (1991):
Improved performance on IQ tests when assessed at 7pm compared to 2pm and 9pm
What hormone is released from pineal gland at what point in sleep wake cycle and what does it do?
- Melatonin
- Encourages sleep
Strengths and weaknesses of circadian rhythms (+1, -3):
+ Practical application in:
–> chronotherapeutics ( study of how timing affects drug treatments) –> to know when drugs should be given
–> understanding of consequences of disruption of circadian rhythms eg night shift workers
- Use of case study –> individual differences
- Small sample sizes –> pop validity?
- Exogenous zeitgeber of artificial light still present in most studies
What did Knutsson (2003) discover about night shift workers?
3 times more likely to develop heart disease
Which study shows presence of artificial light affects circadian rhythms and what did he do?
- Czeisler et al (1999)
- Altered circadian rhythms to 22-28 hrs by manipulating use of artificial light
Give one example of ultradian rhythm:
Stages of sleep
What 2 states does the sleep cycle alternate between?
- NREM –> non-rapid eye movement, includes light and deep sleep
- REM –> rapid eye movement
Sleep cycle:
- Stage 1 and 2: Light sleep –> brainwaves become slower and more rhythmic, starting w/ alpha and progressing to theta waves
- Stage 3 and 4: Deep sleep –> slower delta waves
- Stage 5: REM –> body is paralysed, theta waves
- Repeats every 90 mins
- Person can experience up to 5 cycles in 1 night
What does Kleitman (1969) state about 90 min cycle and what else supports this?
- Called it Basic Rest Activity Cycle (BRAC)
- Suggested it continues when awake but rather than sleep goes from state of alertness to state of physiological fatigue
- Other research shows human mind can only focus for about 90 mins
What study was conducted to support sleep stages?
Dement and Kleitman (1957)
Aim and procedure of Dement and Kleitman (1957):
- Aim: Investigate brain activity change throughout sleep
- 7 adult males + 2 females
- 61 night long study
- Reported to lab, where they were connected to EEG throughout night
- Asked not to drink caffeinated drinks day before
- Woken between 5 and 15 mins of REM, up to 6 times a night by bell
- Spoke into recording machine if they had been dreaming and details, if remembered
Findings of Dement and Kleitman (1957):
1) All pps had REM every night
2) High incidences of dream recall when woken up in REM, whereas fewer times in other stages
3) Brain activity very different in very vivid dreams compared to less clear ones
Conclusion of Dement and Kleitman:
- Stages of sleep follow typical pattern
- Dreams occur in REM
Strengths and weaknesses of ultradian rhythms:
+ Research support –> Dement and Kleitman (1957)
+ Support for BRAC –> Ericsson et al (2006)
- Individual differences –> Tucker et al (2007)
Ericsson et al (2006):
- Grp of elite violinists whose practice sessions were limited to 90 mins at a time
- Best violinists napped more
- Same pattern found among musicians, chess players, athletes, writers
- Supports fact that 90 mins is best + it is ultradian
Tucker et al (2007):
- Suggested sleep patterns are biologically determined
- Studied pps over 11 consecutive days and nights in lab
- Assessed sleep duration, time to fall asleep, amount of time in each sleep stage
- Differences in all characteristics
Give 2 examples of infradian rhythms:
- Menstrual cycle (monthly)
- Seasonal affective disorder (yearly)
Describe menstrual cycle:
- Ovulation occurs halfway thru cycle when oestrogen is at its highest, lasting 16 to 32 hrs
- Progesterone levels increase
- Cycle is around 28 days
- Endogenous system but suggested that iyt may be influenced by exogenous factors
Strengths and weaknesses of menstrual cycle:
+ Support to say it is governed by exogenous zeitgebers –> Reinberg (1967), Russell et al (1980), evolutionary psychologists
+ Important regulators of behaviour –> Penton Volk et al (1999)
- Methodological issues –> confounding variables eg stress, diet
- Environmental determinism –> focuses on exogenous zeitgebers whilst ignoring endogenous pacemakers
Reinberg (1967):
- Woman who spent 3 months in cave w/ only a small lamp
- Menstrual cycle shortened from 28 to 25.7 days
- Lack of light (external factor) affected cycle
Russell et al (1980):
- Sweat samples from 1 grp rubbed onto upper lip of other separate grp
- Cycles synchronised
- Pheromones (external factor) affects synchronisation
What do evolutionary psychologists say about synchronisation of cycles between women?
Evolutionary advantage, as synchronisation allows childcare to be shared across multiple mothers
Penton-Volk et al (1999):
- Women had preference for feminine faces at least fertile stage of cycle, whereas more masculine one at most fertile
- Sexual behaviour is motivated by infradian rhythm
What do some psychologists say is the cause of SAD?
- Lack of light during winter leads to secretion of melatonin constantly
- Linked to depressive symptoms
Strengths of infradian rhythms in terms of SAD:
+ Research support for role of melatonin –> Terman (1988)
+ Practical application for effective treatment –> Eastman et al (1998)
Terman (1988):
- Rate of SAD more common in Northern countries where winter nights are longer
- Affects roughly 10% of ppl in New Hampshire (north) and only 2% in southern Florida
- SAD is partly affected by light, leading to increased melatonin
Eastman et al (1988) and evaluation:
- Found phototherapy resets melatonin levels, which regulates serotonin levels, improving symptoms in up to 60% of sufferers
Evaluation: - 30% of pps also showed improvement when treated w/ placebo –> may not acc be effective
SCN features:
- Generates circadian rhythm
- Receives info about light levels from optic nerve
- Regulates secretion of melatonin
Strengths and weaknesses of endogenous pacemakers:
+ Research support –> Morgan (1995), DeCoursey et al, Folkard (1996)
- Lack ecological validity
- Unethical procedures –> DeCoursey et al (2000)
- Exogenous zeitgebers may have a more significant effect on sleep wake cycles than endogenous pacemakers –> Folkard (1996)
Morgan (1995):
- Bred a strain of hamster that had abnormal circadian rhythms of 20 hrs
- SCN neurons from these hamsters were transported to normal hamsters and vice versa
- Found both hamsters’ circadian rhythm changed from 20 to 24 hrs (vice versa)
- Shows importance of SCN to circadian rhythm
DeCoursey et al (2000):
- Destroyed SCN connections to brains of 30 chipmunks
- Returned them to natural habitat and observed them for 80 days
- Sleep/wake cycle disappeared and so significant proportion of them had been killed by predators by end
- Shows importance of SCN for sleep-wake cycle and survival
Folkard (1996):
- Studied uni student, Kate Aldcroft, who spent 25 days in lab
- No access to daylight or other exogenous zeitgebers that may have reset SCN
- Core temperature rhythm was still at 24 hrs by end showing the importance of endogenous pacemakers
How does Folkard (1996) suggest that exogenous zeitgebers are more important than endogenous pacemakers?
- Kate’s sleep wake cycle had extended to 30 hrs w/ periods of sleep as long as 16 hrs
- Shows exogenous zeitgebers may be more significant
Examples of exogenous zeitgebers:
- Light
- Social clues
What protein in the retina of the eye is critical in the role of light resetting the biological clock?
Melanopsin, which is sensitive to natural light
What happens if circadian rhythm is out of sync w/ light?
Disrupted sleep patterns, increased anxiety and decreased vigilance (jet lag)
What research was done on social cues and what did it show?
Aschoff et al (1971) showed individuals can compensate for absence of natural light by responding to social clues like mealtimes instead
How do infants have a sleep-wake cycle despite it usually being quite random at this age?
Parents impose mealtimes and bedtimes which affects the cycle
Strengths and weaknesses of exogenous zeitgebers:
Research support:
+ Role of melanopsin in setting circadian rhythms –> Skene and Arendt (2007)
+ Use of light exposure to avoid jet lag –> Burgess et al (2003)
- Conflicting research evidence –> Vetter et al (2011)
Skene and Arendt (2007) in role of melanopsin:
- Vast majority of blind subjects who still have some light perception have normal circadian rhythms
- Pathway from retinal cells containing melanopsin to SCN is still intact
Burgess et al (2003):
Found exposure to bright light prior to east-west flight decreased time needed to readjust to local time on arrival
Vetter et al (2011):
- Compared sleep-wake and activity-rest patterns over 5 weeks
- 2 grps: one in warm artificial light, the other in artificial blue light
- Everyone kept daily sleep log and wore devices measuring their movement
- Pps in warm light: synchronised circadian rhythms w/ natural light of dawn
- Pps in blue light: synchronised patterns to office hrs
- Natural light is important in influencing sleep-wake cycle
