Consciousness (chapter 6) Flashcards
What is visual agnosia?
An inability to visually recognise objects
How is consciousness defined?
As our moment-to-moment awareness of ourselves and our environment
What are the characteristics of consciousness? [4]
- Subjective and private. Other people cannot directly know what is reality for you, nor can you enter directly into their experience
- Dynamic (ever-changing). We drift in and out of various states throughout each day. Moreover, though the stimuli of which we are aware constantly change, we typically experience consciousness as a continuously flowing stream of mental activity, rather than as a disjointed perceptions and thoughts
- Self-reflective and central to out sense of self. The mind is aware of its own consciousness. Thus, no matter what your awareness is focused on, you can reflect on the fact that you are the one who is conscious of it
- Intimately connected with the process of selective attention. Selective attention is the process that focuses awareness on some stimuli to the exclusion of others. If the mind is a theatre of mental activity, then consciousness reflects whatever is illuminated at the moment - the bright spot on the stage - and selective attention is the spotlight or mechanism behind it
What is selective attention?
The process that focuses awareness on some stimuli to the exclusion of others
What must scientists who study consciousness do?
Operationally define private inner states in terms of measurable responses.
What method is most often used to measure consciousness?
Self report measures ask people to describe their inner experiences. They offer the most direct insight into a person’s subjective experiences but are not always verifiable or possible to obtain. While asleep, most of us do not speak; not can we fill out self-report questionnaires
What do behavioural measures record (of consciousness)?
Performance on special tasks. Behavioural measures are objective, but they require us to infer the person’s state of mind
What do physiological measures establish (of consciousness)?
The correspondence between bodily processes and mental states. Through electrodes attached to the scalp, the electroencephalograph(EEG) measures brainwave patterns that reflect the ongoing electrical activity of large groups of neurons. Different patterns correspond to different states of consciousness, such as whether you are alert, relaxed or in light or deep sleep. Brain-imaging techniques allow scientists to more specifically examine brain regions and activity that underlie various mental states. Physiological measures cannot tell us what a person is experiencing subjectively, but they have been invaluable for probing the inner workings of the mind.
What is the problem with consciousness?
It cannot be seen, it is difficult to describe, and quite how one thought leads to another, and how an opinion, image or stimulus of some other kind can influence our behaviour is not easily described at all
What is the problem with brain scanning and consciousness?
If a researcher presents an image of a politician to a person in and MRI scanner, a brain scan will be produced. Interpreting what it is about the image that generated the activation seen in the scan is neither simple nor possible. Yes, portions of the brain that deal with visual images, perhaps familiar or famous faces, may have responded, but the person’s political opinion, memories of past experiences as a once politically active student, or the fat that the politician looks a little like the person’s great aunt who is expected for dinner at the weekend will not be coded into the scan. In short, the our consciousness cannot be ‘read’. Functional imagine techniques cannot presently accomplish feats such as these, although whether this may be possible in the future is open to debate
What is the Freudian viewpoint of the levels of consciousness?
Freud proposed that the human mind consists of three levels of awareness. The conscious mind contains thoughts and perceptions of which we are currently aware. Preconscious mental events are outside current awareness but can easily be recalled under certain conditions (E.g. you may not have thought about a friend for years, but when someone mentions their name, you become aware of pleasant memories). Unconscious events cannot be brought into conscious awareness under ordinary circumstances. Freud proposed that some unconscious content - such as unacceptable sexual aggressive urges, traumatic memories and threatening emotional conflicts - is repressed
What does repression refer to?
Certain unconscious content is kept out of conscious awareness because it would arouse anxiety, guilt or other negative emotions
Why has Freud’s ideas of consciousness been criticised?
Behaviourists sought to explain behaviour without invoking conscious mental processes, much less unconscious ones.
Cognitive psychologists and many contemporary psychodynamic psychologists take issue with specific aspects of this theory as it is outdated, have not taken further revisions and is non-scientific
Despite this, there is research that supports Freud’s general premise that unconscious processes can affect and modify behaviour
How do cognitive psychologists view consciousness?
They reject the notion of an unconscious mind driven by instinctive urges and repressed conflicts. rather, they view conscious and unconscious mental life as complementary forms of information processing that work in harmony.
To illustrate, consider how we perform everyday tasks. Many activities, such as studying, require controlled (conscious or explicit) processing, the conscious use of attention and effort. Other activities involve automatic (unconscious or implicit) processing and can be performed without conscious awareness or effort
When does automatic processing most often occur?
When we carry out routine actions or very well-learned tasks, particularly under familiar circumstances. learning to ride a bike and type both involve controlled processing; at first, a lot of conscious attention to what you are doing is needed as you learn. With practice, performance becomes more automatic and certain brain areas involved in conscious thought become less active. Through years of practice, athletes and musicians are able to execute highly complex skills with a minimum of conscious thought
What is a key disadvantage of automatic processing?
It can reduce our chances of finding new ways to approach problems.
What is controlled processing?
It is slower than automatic processing, but it is more flexible and open to change. Still, many well-learned behaviours seem to be performed faster and better when our mind is on autopilot, with controlled processing taking a backseat. tasks ranging from putting a golf ball to playing video games, in experiments suggest that too much self-focussed thinking an damage task performance and cause people to make a mistake under pressure
What is divided attention?
Automatic processing also facilitates divided attention - the capacity to attend to and perform more than one activity at the same time. We can talk while we walk, type as we read etc. Yet divided attention has limits and is more difficult when two tasks require similar mental resources. For example, we cannot fully attend to separate messages delivered simultaneously through two earphones.
What is visual agnosia?
E.g. a woman with visual agnosia, DF, could not consciously perceive the shape, size or orientation of objects, yet she had little difficulty performing a card-insertion task and avoiding obstacles when she walked across a room. In order to perform these tasks easily, her brain must have been processing accurate information about the shape, size and angles of objects. And is she professed no conscious awareness of these properties, then this information processing must have occurred at an unconscious level
There are many types of visual agnosia. E.g. people with prosopagnosia can visually recognise objects but not faces, some cannot even recognise their own faces. Despite the lack of conscious awareness, in laboratory tests the patients display different patterns of brain activity, autonomic arousal and eye movements he they look at familiar rather than unfamiliar faces. In other words, their brain is recognising and responding to the difference between familiar and unfamiliar stimuli, but this recognition does not reach the level of conscious awareness
What is blindsight?
Those are blind in part of their visual field yet in special tests respond to stimuli in that field despite reporting that they cannot see those stimuli
For example, owing to left-hemisphere damage from an accident or disease, a blindsight patient may be blind in the right half of the visual field. A stimulus (e.g. horizontal line) is flashed on a screen so that it appears in one of several locations within the patient’s blind visual field. On trial after trial, the patient reports seeing nothing, but when asked to point to where the stimulus was, she or he guesses at rates much higher than chance. On other tasks, different colours or photographs of facial expressions are projected to the blind visual field. Again, despite saying that they cannot see anything, patients guess the colour of facial expression at rates well above chance, On some tasks, guessing accuracy may reach 80-100%.
What is priming?
Exposure to a stimulus influences (i.e. primes) how you subsequently respond to that same or another stimulus
What can subliminal stimuli do?
They can prime more than our responses to word stems. E.g. when people are shown photographs of a person, the degree to which they evaluate that person positively or negatively is influenced by whether they have first been subliminally exposed to pleasant images (e.g. smiling babies) or unpleasant images (e.g. a face on fire). Likewise, being subliminally exposed to words with an aggressive theme causes people to judge another person’s ambiguous behaviour as being more aggressive.
What is the emotional unconscious??
Current psychodynamic psychologists tell us that emotional and motivational processes also operate unconsciously and influence behaviour. To illustrate this, consider why you may be in a good or bad mood . It could be because of immediate and very recent experiences of your environment of which you are not consciously aware. In one study, college students were subliminally presented with nouns that were either strongly positive (e.g. friends), mildly positive (e.g. parade, clown), mildly negative (e.g. Monday, worm) or strongly negative (e.g. cancer, cockroach). They then self-rated their moods on a range of psychological test. Even though they were not consciously aware of seeing the words as they were presented subliminally, students shown the strongest positive words rated their mood as most positive. Similarly, those who had been presented with the strongly negative words rated their moods as least happy (most negative)
Why do we have consciousness?
Koch (2004) noted that ‘evolution gave rise to organisms with subjective feelings. These convey significant survival advantages, because consciousness goes hand in hand with the ability to plan, to reflect upon many possible courses of action, and to choose one’. Koch suggests that consciousness serves a summarising function. At any instant, your brain is processing numerous external stimuli (e.g. sights, sounds) and internal stimuli (e.g. bodily sensations). Conscious awareness provides a summary - a single mental representation - of what is going on in your would at each moment, and it makes this summary available to brain regions involved in planning and decision-making. Other scientists agree that consciousness facilitates the distribution of information to many areas of the brain
What would a lack of self awareness do?
Would compromise your ability to override potentially dangerous behaviours governed by impulses or automatic processing. Without the capacity to reflect, you might lash out after every provocation. Without the safety net of consciousness, sleepwalkers may fall down the stairs or have cooked foods and then burned themselves severely while grabbing red-hot pans.
What is the neural basis of consciousness?
It simply describes a neurological state that correlates with a particular state of consciousness, or one that directly generates consciousness. This idea is also enriched and supported by a number of philosophers including Dennett. Neurons and synaptic connections form very quickly and increase in number after birth to a maximum number at about 6 months of age. From this point on, synaptic pruning takes place where unused connections are removed, leaving only those that are needed.
What is ‘Neural Darwinism’?
Came from Edelman (1987) and explains how the brain loses the weakest or least used connections, and retains the strongest and most useful. Hence the Darwinian ‘survival of the fittest’ analogy
What are the pathways for processing visual information?
One pathway, extending from the primary visual cortex to the parietal lobe, carries information to support the unconscious guidance of movements. A second pathway, extending from the primary visual cortex to the temporal lobe, carries information to support the conscious recognition of objects.
How have scientists studied the neural basis of consciousness?
Some have explored conscious perceptions that are created when specific brain areas are electrically stimulated, while others have tried to determine how consciousness is lost when patients are put under anaesthesia.
Still others have used a procedure called masking to control whether people perceive a stimulus consciously or unconsciously. In experiments, participants undergo brain imaging while exposed to masked and unmasked stimuli. This enables scientists to assess how brain activity differs depending on whether the same stimuli (e.g. photographs of angry faces) are consciously or unconsciously perceived
What have neuroscientists found about the processing of emotionally threatening stimuli?
They are processed consciously and unconsciously through different neural pathways. The pathway that produces conscious recognition involves the prefrontal cortex and several other brain regions that are bypassed in the pathway for unconscious processing
What have technological advances allowed to be done regarding consciousness?
Scanning, for instance, is allowing us to see things happening in the brain in a way not thought of previously.
However, it is extremely tempting to infer that people are thinking of an ‘experience’ when we can see that a stimulus generates a patch of activity in the brain, but conscious experience is more than a localised area of stimulation, so beware. Careful investigation can provide us with evidence that the person is experiencing a particular kind of experience. the scan allows us to infer things about general concepts, not the individual experiences themselves
What conclusion has been made about the neuroscience of consciousness?
There appears to be no single place in the brain that gives rise to consciousness. Instead, they view the mind as a collection of largely separate but interacting information-processing modules that perform tasks related to sensation, perception, memory, movement, planning, problem-solving, emotion and so on. The modules process information in parallel - that is, simultaneously and largely independently. However, there also is cross-talk between them, as when the output from one module is carried by neural circuits to provide input for another module. E.g. a formula recalled from memory can become input for problem-solving modules that allow you to compute answers during a mathematics examination
How is consciousness a global workspace?
It represents the unified activity of multiple modules in different areas of the brain. In essence, of the many brain modules and connecting circuits that are active at any instant a particular subset becomes joined in unified activity that is strong enough to become a conscious perception or thought. The specific modules and circuits that make up this dominant subset can vary as out brain responds to changing stimuli - sights, sounds, smells and so on - that compete for conscious attention
Subjectively we experience consciousness as unitary, rather than a collection of modules and circuits. Many factors influence these modules and, in so doing, alter our consciousness
What is ‘enactive’ consciousness?
The basic premise is that consciousness is not something that just happens to us, it is something that we do. Let us consider ‘perception’. The generally held view by science is that perception involves internal representations and that we interact with the world as guided by these. An ‘enactive’ explanation does not necessarily deny that there may be representations in the brain, but theorists such as Alva Noe say that our brains to not necessarily construct models based on what we perceive. Our perceptual world is an integration of the skills we have developed. Perception, then, is a skill, and ut depends on our actions and how we carry them out, how we enact them Consciousness in general can be considered in the same way. Whatever consciousness is, it is not something that happens to us, it is something that we ourselves do. In this way, the neural basis of consciousness can be questioned and given another dimension. It is not the brain that provides us with consciousness; it is our actions and our behaviour that generates our consciousness
What is attention?
The process of concentrating on some feature(s) of the environment to the possible exclusion of others
What is focussed attention?
The ability to respond to specific stimuli
What is the cocktail party phenomenon?
This phenomenon is manifest as the often dramatic result of focussing one’s attention as shown in a busy party situation. The tinkle of ice in glasses and the mingling of laughter and chatter all make for an engaging time for everyone. We all know that listening in on one particular conversation among the many going on around us can be done. It is often made possible because one of those engaged in one of the private conversations mentions your name, not loudly, but at a normal conversation level. Your attention is immediately drawn to their discussion, switching your attention quickly to this new source. The phenomenon describes the ability to attend to one conversation among many, but also the almost immediate attention switch facilitated by the mentioning of a salient word, such as your own name
What is dichotic listening?
Whereby participants are presented with two different sources of information simultaneously. One source is presented to each ear. The task is to attend to one of these ‘channels’ of information, perhaps by repeating the message as it is presented in a shadowing procedure. Following this part of the task participants reported as much of the unattended, or unshadowed, message as possible
What happens with dichotic listening when the left channel is shadowed and speech is presented to the right channel?
Participants are better able to report the unattended stream than if the situation is reversed. This is because we process speech in our left hemisphere, stimulated by material presented on the left. What was particularly interesting from the early dichotic listening work was the finding that certain aspects of the stimulus could be recalled. These include broad categorizations, such as whether the sound in the unattended stream was speech or non-speech and whether the speaker was male or female. These rather broad characteristics could be correctly recalled although the semantic detail and meaning of the unattended messages could not, This suggests that, in this case, some types of information were allowed through for processing, whereas others were possibly lost. This finding was the basis for the filter theories following.
What is the early filter model (Broadbent, 1958)?
What are its problems?
It attempts to explain why some words are attended to and do grab our attention, as in the cocktail party effect, and some are not. He said that we maintain our attention by engaging a filter of some kind. This filter is an early filter, meaning that a decision about what to allow through is made at a very early stage e.g. vocal characteristics.
There are some problems though. These early filter models are problematic as they do not explain how we switch our attention quickly when, for instance, we hear our name mentioned at the other side of the room. In order to do this we music have some kind of route into our attention that is not a conscious or deliberately placed filter as Broadbent describes
What is subliminal material?
Information can be presented at a very low level, or very quickly so that we are not consciously aware of it. Words, or stimuli, presented consciously, on a screen can be followed almost immediately with, and so linked to, mild shocks. Subsequent presentation of the word without the shock generates a mild stress response, such as sweating of the palms. This sweat raises the conductivity of the palm, and so can be measured electronically as a galvanic skin response (GSR). When the stimulus is presented subliminally, measurements of GSR show that the stimulus has been perceived, but not consciously. Early filter models would not predict this as the filter to allow material through would need to be deliberately placed very early in the process, consciously allowing material through or not, as described in the previous section. there must be some form of route that is not governed by a consciously placed filter, or else why would we let through the subliminally presented word?
What is the late selection model? (Deutsch and Deutsch, 1967)?
An alternative to early filter models is to hypothesize that the position of the filter is later in the attention process. They said that the filter, or the decision whether to ‘select’ the information for attention, is made not at the very start of the process, but just before the person responds. The problem with these models is that all material is processed until the very last point, where only a tiny fraction of it is used. This is a terrible wasteful view and can be criticised in terms of cognitive economy. Stretching limited resources like this only to waste a huge proportion of the material processed is wasteful and uneconomical.
What is the attenuation model (Treisman, 1964)?
To attenuate something is to reduce the effect or power of something.
This model describes attention similarly. All material is processed from the point that it is received right up until a response is made. Treisman suggests that rather than blocking unattended material entirely, with a filter or an attention age of some kind, it is attenuated. This model allows for all information to be processed, but only the unattenuated material makes it through to conscious attention. In a noisy environment of a club or cocktail party, the material we wish to ‘ignore’ is attenuated, leaving the material we wish to attend to standing out, allowing us to focus upon it. It goes on to say that each of the competing ‘streams’ of information being processed can be attenuated differently, allowing for different levels of attention as desired. This allows an explanation of how some stimuli can ‘grab’ our attention and how we can quickly switch attention in different circumstances, by swiftly altering the attenuation levels in each ‘stream’
What is the bottleneck analogy of attention?
Attention is finite.
Attention can be thought of in terms of a bottle. the material we may wish to allow out of the bottle (so that we can attend to it) is restricted by the narrowing of the bottleneck. this bottleneck provides a capacity control system. Treisman’s attenuation model says that the width of the neck is entirely flexible. When we want more information to come out of the bottle, we adjust the size of the neck accordingly.
What is selective attention?
Maintaining a focus of attention on a specific item even when faced with alternatives and distractions
How does visual search use attention?
Searching for a single in the crowd is facilitated by attending carefully to small parts of the crowd at a time, and ‘sweeping’ your attention across it, hopefully finding the face you are searching for. This is an example of an ‘exhaustive’ search where those faces, other than the one you are looking for, act as distractors.
Searches where the target shares many of the features of the distractors are hard, but where the features are different the target ‘pops out’ of the background. this ‘feature analysis’ may explain how our attention is quickly, as if automatically, focused when we hear our name in a cocktail party, or when we see the face of a loved one among many others on a busy shopping street
What is the feature integration theory?
A two stage process: first the whole scene is processed and the individual components of all items are dealt with. Those that clearly identify the item as not belonging to the target are rejected. Next, the remaining items are reassembled, or ‘glued’ together, and compared with material in memory that may help us identify the target successfully. Visual attention can now be thought of, in part, as allowing us to regenerate the information received to allow attention and processing of objects as internal representations.
What is attentional spotlight?
Posner develops the idea of visual attention in his attentional spotlight, which says that once glued together and reconstructed internally, our internally represented visual world has spatial characteristics just like the world around us. Visual attention then shines a ‘spotlight’ onto the parts of the scene we wish to attend to
What is the ‘zoom-lens’ idea?
The material lit by the attentional spotlight can be zoomed in on, as if with a camera lens. A narrow spotlight beam mans we focus on only a small part of the representation, a wider beam means we take in more
Objects or location?
The spotlight model and the zoom-lens modification suggest that attention focuses on locations rather than objects. However there is work to support and contradict this.
What is automaticity?
Practice makes perfect. It is reached when a task no longer requires conscious control e.g. riding a bike
How is an automatic process related to memory?
Our memory processes are capacity limited. It has been said that automatic tasks are capacity free. they are not limited by memory or attention limitations and as such, a number of them can go on in parallel, in the background if you like, while we carry out other tasks. Controlled processes on the other hand are capacity limited and take place in series. That is to say, one at a time. Controlled processing is carefully under our conscious control and as such is flexible, dynamic and changeable.
However, with very well-practiced and automatic task, changes are very hard to make. They become second nature. The most famous example is the Stroop test
What is divided attention?
The ability to respond, seemingly simultaneously, to multiple tasks or demands
What does how successful we are at completing tasks simultaneously depend on?
A number of things, including how practised we are at them, and the nature of the tasks themselves
How does rehearsal affect tasks/dual tasks?
The more we rehearse, the better we get. Repeating tasks over and over encourages a move from controlled to automatic processing. Developing skills through practice reduces the errors on that task.
How does difficulty affect performance on dual tasks?
The difficulty of the tasks (dual task performance)influences performance. Two easy tasks combined will result in fewer errors than two difficult tasks. Difficulty, of course, is entirely subjective.
Data-driven tasks are largely free of the demands of cognitive resources. Performance on them is limited by the amount of information we have to complete the task, not necessarily how skilled or clever we are. Where resources are limited we can improve performance by shifting them from one task to another. Removing the demands required to follow the narrative of a play by turning off the radio makes writing a tricky passage much easier.
How does similarity influence performance on dual tasks?
The idea of similarity is related to the idea of modality in perception and attention. Tasks requiring auditory attention arrive at the auditory modality and are dealt with accordingly. Those requiring visual attention are similarly dealt with within the visual modality. If one of the tasks is visual and another is auditory, then they do not compete for the modality-specific resources. Similarly, if both require memory resources then they will compete for them, and the result may be reduced performance. Finally, if tasks require the same mode of output, perhaps fine motor skills as in sewing and watchmaking, then performance is likely to suffer as a result
What is exogenous control?
Attention is drawn by an external stimulus, perhaps because it means we are required or needed to act in some way.
Salient warning words or noises are similarly compelling. These might include the word ‘FIRE’ or the sound of a gunshot.
In either case they elicit external or exogenous control over our attention.
What is endogenous control?
The internal equivalent to exogenous control. It may be that we expect something to happen in a particular position and so we are primed to move our attention in that direction.
E.g. the work or Posner (1980) where pps were cued to respond to the right or left of a fixation point with an arrow. The arrow provided a spatial cue within the environment, eliciting endogenous control of spatial attention to the left or right of the fixation point
How is attention influenced by cross-modal effects??
Information from one modality (e.g. the lips) adds to information from another (e.g. the ears). The result is improved performance. Sometimes, when endogenous or exogenous cues draw our visual attention to one position or another, attention from another modality (touch or hearing) may also be drawn to the same position. The results can be startling and are best described with reference to the ventriloquist effect.
What is the ventriloquist effect?
In ventriloquism the moving lips of the dummy act as an endogenous cue. Visual attention is drawn spatially to the position of the moving lips and the auditory information carrying localisation information about the origin of the voice are drawn to the same location. The effect is that we hear the voice of the ventriloquist as emanating from the moving lips of the dummy. In this case, auditory and visual attention is woven together in a truly multi-modal effect
What is inattention blindness?
A failure to notice an unexpected item in a visual scene.
What is change blindness?
A different, but closely related phenomenon to inattention bias where we fail to see if an item has changed in some way. Perhaps it is moved or an aspect of it is altered. Those that seek to trick us, usually in jest, use their not insignificant knowledge of attention direction and phenomena such as change blindness in their craft
What are event related potentials (used to measure attention)?
AN ERP is recorded as a series of waves, recorded from a net of recording points on a person’s skull. Research has looked at 2 peaks in the recordings, the first positive wave (P1) and the first negative wave (N1). They showed that when participants were actively attending to a display and the P1 and N1 waves arrived about 70ms after the stimulus and 130ms after the stimulus accordingly, and they were both larger than when the stimulus was not actively attended to. ERP’s are larger and stronger when we are not attending to them
What is the circadian rhythm?
A steady rhythmic state that lasts for 24 hours. During this 24 hours our body temperature, certain hormonal secretions and other bodily functions undergo a steady rhythmic change that affects out alertness and readies our passage back and forth between waking and consciousness and sleep.
These daily biological cycles are called circadian rhythms.
How are most circadian rhythms regulated?
By the brain’s suprachiasmatic nuclei (SCN), located in the hypothalamus. These SCN neurons have a genetically programmed cycle of activity and inactivity, functioning like a biological clock. They link the tiny pineal gland, which secretes melatonin, a hormone that has a relaxing effect on the body. The SCN neurons become active during the daytime and reduce the pineal gland’s secretion of melatonin, raising the body temperature and heightening alertness. At night SCN neurons are inactive, allowing melatonin levels to increase and promoting relaxation and sleepiness.
How do environmental cues keep SCN neurons on a 24-hour schedule?
Your eyes have neural connections to the SCN, and after a night’s sleep, the light of day increases SCN activity and helps reset your 24-hour biological clock. Without this, research shows, people drift into a natural sleep-wake cycle, called a free-running circadian rhythm, which is longer than 24 hours. Under more controlled conditions, the free-running rhythm averages around 24.2 hours. Yet even this small deviation from the 24 hour day is significant. If you were to follow your free-running rhythm, two months from now you would be going to bed at noon and waking at midnight
How do circadian rhythms influence early birds or night owls?
Compared to night people, morning people go to bed and rise earlier, and their body temperature, blood pressure and alertness peak earlier in the day.
How may cultures differ in their overall tendency towards ‘morningness’?
One study found that students from Columbia, Spain and India - regions with warmer annual climates - exhibited greater morningness than students from England, the USA and the Netherlands. In addition to this, a person may inherit the tendency and may be influenced by their physiology to be a morning or evening person. As with many things, both nature and nurture are likely to play a role in this aspect of a person’s behaviour.
How are circadian rhythms vulnerable to disruption by both sudden and gradual environmental changes?
Jet lag is a sudden circadian disruption caused by flying across several time zones in one day. Flying east, you lose hours from your day; flying west extends your day to more than 24 hours. Jet lag, which often causes insomnia and decreased alertness, is a significant concern for people who frequently travel. the body naturally adjusts about one hour or less per day to time zone changes. Typically, people adjust faster flying west, presumably because lengthening the travel day is more compatible with our natural free-running circadian cycle.
Night-shift work is the most problematic circadian disruption for society. Cause disruptions to normal cycles, then on days off or when reverting back to day shits is disrupts the then-alters circadian adjustments made and so your biological clock will have to be adjusted once again.
How can circadian disruptions cause negative effects?
Combined with fatigue from poor daytime sleep, circadian disruptions can be a recipe for disaster. Job performance errors, fatal traffic accidents, and engineering and industrial disasters peak between midnight and 6am. in some cases, night operators at nuclear power plants have been found asleep at the controls. On-the-job sleepiness is also a major concern among long-distance truck-drivers, airline crews, doctors and nurses
What is seasonal affective disorder (SAD)?
Is a cyclic tendency to become psychologically depressed during certain seasons of the year.
Some people become depressed in spring and summer, however, in the vast majority of cases, SAD begins in autumn or winter, when there is less daylight, and then lifts in spring
How may the circadian rhythms of SAD sufferers be influenced?
They may be particularly sensitive to light, so as sunrises occur later in winter, the daily onset of time of their circadian clocks may be delayed to an unusual degree, altering the beginning time of the person’s ‘biological’ morning. On late-autumn and winter mornings, when many people must rise for work and school darkness, SAD sufferers remain in sleepiness mode long after the morning alarm clock sounds
How might where you live influence SAD?
It has been suggested that the seasonal affective disorder increases in the USA, with latitude . The higher the latitude, thee fewer hours of daylight. This relationship was not seen in Europe, although there is some disagreement in the literature. It seems that climate, genetics and sociocultural context all influence SAD
How do circadian rhythms promote a readiness to sleep?
By decreasing alertness, but they do not directly regulate sleep. instead, roughly every 90 minutes while asleep, we cycle through different stages in which brain activity and other physiological responses change in a generally predictable way
How is sleep research often carried out?
In specially equipped laboratories where sleepers’ physiological responses are recorded. Electroencephalogram recordings of your brain’s electrical activity would show a pattern of beta waves when you are awake and alert.
Beta waves have a high frequency (of about 15 to 30 cycles per second, or cps) but a low amplitude, or height. As you close your eyes, feeling relaxed and drowsy, your brainwaves slow down and alpha waves occur at about 8 to 12 cps
What are beta waves?
When you are alert and awake
What are alpha waves?
Feeling relaxed and drowsy, your brainwaves slow down
How many stages of sleep are there?
4
Outline stage 1 of sleep —
As sleep beings, your brainwave pattern becomes more irregular, and slower theta waves (3.5 to 7.5 cps) increase. A form of light sleep from which you can easily be awakened. You will probably spend just a few minutes in stage 1, during which time some people experience dreams, vivid images and sudden body jerks
Outline stage 2 of sleep —
As sleep becomes deeper, sleep spindles - periodic 1 to 2 second bursts of rapid brainwave activity (12 to 15 cps) - begin to appear. Sleep spindles indicate that you are now in stage 2. Your muscles are more relaxed, breathing and heart rate are slower, dreams may occur, and you are harder to awaken
Outline stage 3 of sleep —
Sleep deepens as you move into stage 3, marked by the regular appearance of very slow (0.5 to 2 cps) and large delta waves. As time passes, they occur more often, and when delta waves dominate the EEG pattern, you have reached stage 4.
Outline stage 4 of sleep —
Stage 3 and 4 together are often referred to as slow-wave sleep. Your body is relaxed, activity in various parts of your brain has decreased, you are hard to awaken, and you may have dreams.
After 20 to 30 minutes of stage 4 sleep, your EEG pattern changes as you go back through stages 3 and 2, spending little time in each.
Overall, what cycle would you complete in a 60 to 90 minute sleep?
Cycle of stages: 1-2-3-4-3-2. At this point, a remarkably different sleep stage ensues. in the AASM classification stages 3 and 4 are described together as a single state (N3) with N3 starting when the brain is expressing 20% Delta waves.
What are delta waves?
Very slow (0.5 to 2 cps) and large
What is slow-wave sleep?
Stage 3 and 4 sleep together
What is REM sleep (or ‘R’)?
Rapid eye movements (REM), high arousal and frequent dreaming
Why is it called REM sleep?
Characterised by rapid eye movements (REM), high arousal and frequent dreaming. They found that every half minute or so during REM sleep, bursts of muscular activity caused sleepers’ eyeballs to vigorously move back and forth beneath their closed eyelids. Moreover, sleepers awakened from REM periods almost always reported a dream - including people who swore they ‘never had dreams’. At last, scientists could examine dreaming more closely by waiting for REM, awaken the sleeper and catch a dream
What happens both physically and in the brain during REM sleep?
During REM sleep,physiological arousal may increase to daytime levels. The heart rate quickens, breathing becomes more rapid and irregular, and brainwave activity resembles that of active wakefulness. Regardless of dream content (most dreams are not sexual); men have penile erections and women experience vaginal lubrication. The brain also send signals making is more difficult for voluntary muscles to contract. As as a result, muscles in the arms, legs and torso lose tone and become relaxed. These muscles may twitch, but in effect you are paralysed, unable to move. This state is called REM sleep paralysis, and because of it REM sleep is sometimes called paradoxical sleep: your body is highly aroused, yet it looks like you are asleep peacefully because there is so little movement.
How does the sleep cycle change as REM periods get longer?
Although each cycle through the sleep stages takes an average of 90 minutes, research shows that as the hours pass, stage 3 drops and REM periods become longer.
How does the brain steer our passage to sleep?
It does not have a single ‘sleep centre’. Various brain mechanisms control different aspects of sleep, such as falling asleep and REM sleep.
Moreover, falling asleep is not just a matter of turning off brain systems that keep us awake. There are separate systems that turn and actively promote sleep
What areas of the brain regulate our falling asleep?
Certain areas at the base of the fore-brain (called the basal fore-brain) and within the brain stem regulate our falling asleep.
What areas of the brain regulate our REM sleep?
Other brain stem areas - including where the reticular formation passes through the pons (called the pontine reticular formation) - play a key role in regulating REM sleep. This region contains neurons that periodically activate other brain systems, each of which controls a different aspect of REM sleep, such as eye movement and muscular paralysis
Brain images taken during REM sleep reveal intense activity in limbic system structures such as the amygdala that regulate emotions - a pattern that may reflect the emotional nature of many REM sleep dreams.
The primary motor cortex is active, but it signals for movement are blocked and do not reach our limbs.
Association areas near the primary visual cortex are active, which may reflect the processing o visual dream images.
In contrast, decreased activity occurs in regions of the prefrontal cortex involved in high-level mental functions, such as planning and logical analysis. This may indicate that our sleeping mind does not monitor and organise its mental activity as carefully as when awake, enabling dreams to be illogical and bizarre
How do environmental factors affect sleep?
In autumn and winter, most people sleep about 15 to 60 minutes longer per night. Shift work, stress at work and school, and night-time noise can decrease sleep quality. Routine can significantly influence our sleeping too - doing the same things at the same time has been shown to be beneficial
