A Level || Psychology > Biopsychology - Year 13 > Flashcards
Biopsychology - Year 13 Flashcards
Localisation Of Function Definition?
Localisation of function is the idea that certain functions (e.g. language, memory, etc) have certain locations within the brain.
Hemispheric Lateralisation Definition?
Lateralisation is the fact that the two halves of the brain are functionally different and that each hemisphere has functional specialisations.
E.g.the left is dominant for language, and the right excels at visual motor tasks.
Motor Area Definition?
The motor area is responsible for voluntary movements.
It does this by sending signals to the muscles in the body.
Found in frontal lobe.
The motor area on one side of the brain controls the muscles on the opposite side.
Somatosensory Area Definition?
The somatosensory area receives incoming sensory information from the skin.
This information is used to produce sensations related to pressure, pain, temperature, etc.
Found in parietal lobe.
The somatosensory area on one side of the brain receives sensory information from the opposite side of the body.
Visual Area Definition?
The visual area receives and processes visual information.
The visual area contains different parts that processed different types of information including colour, shape or movement.
Found in the occipital lobe.
Information from the right-hand-side visual field is processed in the left hemisphere and so on….
Auditory Area Definition?
The auditory area is responsible for analysing and processing acoustic information.
Found in the temporal lobe.
Information from the left ear goes primarily to the right hemisphere and so on….
The auditory area contains different parts.
The primary auditory area is one of these parts and is involved in processing simple features of sound, including volume, tempo and pitch.
Broca’s Area Definition?
Broca’s area is found in the left frontal lobe.
It is thought to be involved in language production.
The Broca’s area only functions in the left hemisphere.
Wernicke’s Area Definition?
The Wernicke’s area is found in the left temporal lobe.
It is thought to be involved in language processing/comprehension.
The Wernicke’s area only functions in the left hemisphere.
Split-Brain Research Definition?
Split-brain patients are individuals who have undergone a surgical procedure where the corpus callosum is cut.
What Is A Corpus Callosum?
This connects the two hemispheres of the brain.
Plasticity Definition?
Brain plasticity refers to the brains ability to change and adapt because of experience.
Functional Recovery Definition?
Functional recovery is the transfer of functions from a damaged area of the brain (after trauma) to other undamaged areas.
The brain gives specialisation of damaged areas to undamaged areas so the brain can still function efficiently.
Localisation Of Brain Function A01?
Localisation of function is the idea that certain functions have certain locations or areas within the brain (definition again).
This idea has been supported by recent neuro imaging studies, but was also examined much earlier, typically using case studies.
We use the case study of Phineas Gage.
Phineas Gage Case Study?
This case study is to support the idea of localisation of function.
Phineas Gage (1848), while working on the rail line, experienced a drastic accident in which a piece of iron went through his skull.
Gage survive this but he experienced a change in personality, such as a loss of inhabitation and a new found anger.
This accident provided evidence to support the theory of localisation of brain function.
It was believed that the area the iron stake damaged was responsible for personality.
Motor Area A01?
Hozzig and Fritsch (1870) discovered that different muscles are coordinated by different areas of the motor cortex.
The discovered this by electrically stimulating the motor area of dogs.
This resulted in muscular contractions in different areas of the dogs body, depending on where the probe was inserted.
The regions of the motor area are arranged in a logical order, for example, the region that controls finger movement is located next to the region that controls the hand and arm.
Somatosensory Area A01?
Different parts of the somatosensory area receive messages from different locations of the body.
Robertson (1995) found that this area of the brain is highly adaptable.
He discovered this because by realising braille readers have larger areas in the somatosensory area for their fingertips compared to the normal sighted participants.
Visual Area AO1?
At the back of the brain, in the occipital lobe, is the visual area.
The visual area receives and processes visual information.
Information from the right-hand-side visual field is processed in the left hemisphere.
Information from the left-hand-side visual field is processed in the right hemisphere.
The visual area contains different parts that process different types of information including colour, shape or movement.
Broca’s Area AO1?
The Broca’s area is named after Paul Broca, who discovered this region while treating a patient named Leborgne.
Leborgne was more commonly referred to as ‘Tan’.
Tan could understand spoken language but was unable to produce any coherent words, and could only say ‘Tan’.
After Tan’s death, Broca conducted a post-mortem examination on Tan’s brain and discovered that he had a lesion in the left-frontal lobe.
This led Broca to conclude that this area was responsible for speech production.
People with damage to this area experience Broca’s Aphasia, which results in slow and inarticulate speech.
Broca’s Area AO3?
Due to the significance of Broca’s findings, Dronkers et al (2007) decided to conduct an MRI scan on Tan’s brain, to try and confirm Broca’s original work.
Although there was a lesion found in Broca’s area, they also found evidence to suggest that other areas may have also contributed to the failure in speech production.
Therefore, it is likely that the Broca’s area is not solely responsible for speech production, as other areas may also play a role.
Wenicke’s Area AO1?
At a similar time to Broca, Carl Wernicke discovered another area of the brain that was involved in understanding language.
Wernicke found that patients with lesions in Wernicke’s area was still able to speak, but were unable to comprehend language.
Wenick’s area is found in the left temporal lobe. People with damage to this area struggle to comprehend language, often producing sentences that are fluent, but meaningless (Wernicke’s aphasia).
Wernicke concluded that language involves a separate motor and sensory region.
The motor region is located in Broca’s area, and the sensory region is located in Wernicke’s area.
Wernicke’s Area AO3?
Research by Saygin et al (2003) found that some patients displayed symptoms of Wernicke’s aphasia without any damage to the Wernicke’s area.
This suggests that language comprehension is much more complex than originally thought.
Further evidence has also been found which suggests that some left-handed people process language in the right hemisphere.
Localisation Of Function AO3?
Criticism - Lashley proposed the equipotentiality theory, which suggests that the basic motor and sensory functions are localised, but the higher mental functions or not.
He claimed that intact areas of the cortex could take over responsibility for specific cognitive functions following brain injury. This, therefore, cast doubt on theories about the localisation of functions.
Criticism - Dronkers et al (2007) (on a previous flashcard) decided to conduct an MRI scan on Tan’s brain, to try and confirm Broca’s original work.
Although there was a lesion found in Broca’s area, they also found evidence to suggest that other areas may have also contributed to the failure in speech production.
Therefore, it is likely that the Broca’s area is not solely responsible for speech production, as other areas may also play a role.
Criticism - Psychologist suggests that it is more important to investigate how the brain areas communicate with each other, rather than focusing on specific brain regions. An example is a man who lost his ability to read, following damage to the connection between the visual cortex and the Wernicke’s area, which was reported by Dejerine.
This suggests that interactions between different areas produce complex behaviours such as language. Damage to the connection between any two points can result in impairments that are interpreted as damage to the localised brain region associated with that specific function. This reduces the credibility of the localisation theory.
Criticism - critics argue that the theories of localisation are Biologically Reductionist.
They try to reduce very complex human behaviours and cognitive processes to one specific brain region. Critics suggest that a more thorough understanding of the brain is required to fully understand complex cognitive processes like language.
Criticism - Psychologists argue that the idea of localisation fails to take into account individual differences. Herasty (1997) found that women have proportionately larger Broca’s and Wernicke’s areas than men, which can perhaps explain the greater ease of language use amongst women. THIS IS AN ISSUE AND DEBATE AND CAN BE USED TO DEBATE THE ABOVE POINT.
This, however, suggests a level of beta bias in the theory: the differences between men and women are ignored, and variations in size of areas observed during various language activities are not considered.
Hemispheric Lateralisation?
The two hemispheres are connected through nerve fibres called the corpus callosum, which facilitate interhemispheric communication: allowing the left and right hemispheres to communicate with one another.
Split-brain research allows us to investigate hemispheric lateralisation with the use of split-brain patients.
We use case study’s from Sperry and Gazzaniga to investigate hemispheric lateralisation.
Sperry And Gazzangia Case Study?
Case study to support hemispheric lateralisation with the use of split-brain patients.
Aim: The aim of the research was to examine the extent to which the two hemispheres are specialised for certain functions.
Method: An image/word is projected to the patients left visual field or right visual field. When information is presented to one hemisphere in a split brain patient, the information is not transferred to the other hemisphere as the corpus callosum is cut.
Sperry and Gazzaniga conducted many different experiments, including describe what you say tasks, tactile test, and drawing tasks.
Describe What You See: A picture was presented to either the left or right visual field and the participant had to simply describe what they saw.
Tactile Test: An object was placed in the patient’s left or right hand (they couldn’t see the object) and they had to either describe what they felt, or select a similar object from a series of alternate objects.
Drawing Task: Participants were presented with a picture in either the right or left visual field, and they had to simply draw but they saw.
Sperry And Gazzangia Case Study: Findings?
Describe What You See:
If the picture was presented in the right visual field (processed by the left hemisphere), the patient could describe what they saw. This demonstrated the superiority of the left hemisphere when it comes to language production.
If the picture was presented in the left visual field, the patient could not describe what was shown and often reported that there was nothing present.
Tactile Tests:
If the object was placed in the right hand (processed by the left hemisphere), the patient could describe verbally what they felt or they could select a similar appropriate object from the series of alternative objects.
If the object was placed in the left hand, the patient could not describe what they felt and could only make wild guesses. However, individuals could identify a test object presented in the left-hand by selecting a similar appropriate object from the series of alternative objects.
Drawing Tasks: When pictures were presented to the right visual field (processed by the left hemisphere) and the participants would draw the picture with their right hand, the picture was never as clear as the left hand. This shows the superiority of the right hemisphere for visual motor tasks.
When pictures were presented to the left visual field and the participants would draw the picture with their left hand, the pictures were consistently clearer and better than the right hand (even though all the participants were right-handed). This, again, demonstrates the superiority of the right hemisphere when it comes to visual motor tasks.
Sperry And Gazzangia Case Study: Conclusion?
The findings of the research highlights a number of key differences between the two hemispheres.
Firstly, the left hemisphere is dominant in terms of speech and language.
Secondly, the right hemisphere is dominant in terms of visual motor tasks.
Split-Brain Research (Hemispheric Lateralisation) AO3?
Strength - It is assumed that the main advantage of brain lateralisation is that it increases neural processing capacity.
Rogers at owl (2004) found that in a domestic chicken, brain lateralisation allows the Checking to find food and be vigilant for predators. Using only one hemisphere to engage in one of these tasks leaves the other hemisphere free to engage in other functions. This provides evidence for the advantages of brain lateralisation and demonstrates how it can enhance brain efficiency and cognitive tasks.
Criticism- ISSUE AND DEBATE. This research (above research) was carried out on animals. Therefore, it is impossible to completely conclude the same for humans. Much of the research into lateralisation is flawed because the split brain procedure is really carried out now, meaning patients are difficult to come by. Such studies often include very few participants, and often the research takes an eye geographic approach. Therefore, any conclusions drawn ore representative only of those individuals who had a cofounding physical disorder (split-brain). This is problematic as such results cannot be generalised to the wider population.
Criticism - Research suggests that lateralisation changes with age. Szaflarki et al (2006) Found that language became more lateralised to the left hemisphere with increasing age in children and adolescence.
However, after the age of 25, lateralisation decreased with each decade of life. This raises questions about lateralisation, such as whether everyone has one hemisphere that is dominant over the other and whether this dominance changes with age.
Criticism - It could be argued that language may not be restricted to the left hemisphere. Turk et al (2002) discovered a patient who suffered damage to the left hemisphere but developed the capacity to speak again in the right hemisphere. This suggests that perhaps lateralisation is not fixed and that the brain can adapt to following damage to sit in areas.
What Is Neural Processing Capacity?
‘Neural processing capacity’ is a posh term for the ability to perform multiple tasks simultaneously.
fMRI AO1?
Functional magnetic resonance imaging (fMRI) is a brain-scanning technique that measures blood flow in the brain when a person performs a task.
fMRI scans neurones in the brain that are the most active during a task.
Energy requires glucose and oxygen. Oxygen is carried by haemoglobin and is released for use by
active neurons, at which point the haemoglobin becomes deoxygenated.
Deoxygenated haemoglobin has a different magnetic quality from oxygenated haemoglobin.
An fMRI can detect these different magnetic qualities (more active places in the brain will have deoxygenated blood) and can be used to create a dynamic (moving) 3D map of the brain.
fMRI images show activity approximately 1-4 seconds after it occurs and are thought to be accurate within 1-2 mm.
An increase in blood flow is a response to the need for more oxygen in that area of the brain when it becomes active, suggesting an increase in neural activity.
fMRI Evaluation, AO3?
Strength: Non-invasive - fMRI does not use radiation or involve inserting instruments directly into the brain, and is therefore virtually risk-free. This should allow more patients/participants to undertake fMRI scans.
Strength: Good spatial resolution - greater spatial resolution allows psychologists to discriminate between different brain regions with greater accuracy. fMRI scans have a spatial resolution of approximately 1-2 mm. Consequently, psychologists can determine the activity of different brain regions with greater accuracy when using fMRI, in comparison to when using EEG and/or ERP.
Weakness: Poor temporal resolution - Temporal resolution refers to how quickly the scanner can detect changes in brain activity. fMRI scans have a temporal resolution of 1-4 seconds which is worse than other techniques (e.g. EEG/ERP which have a temporal resolution of 1-10 milliseconds). Consequently, psychologists are unable to predict with a high degree of accuracy the onset of brain activity.
Weakness: Indirect measure of neural activity - while any change in blood flow may indicate activity within a certain brain area, psychologists are unable to conclude whether this brain region is associated with a particular function.
(Further weakness that combines with ^)In addition, some psychologists argue that fMRI scans can only show localisation of function within a particular area of the brain, but are limited in showing the communication that takes place among the different areas of the brain, which might be critical to neural functioning.
EEG AO1?
An electroencephalogram (EEG) works on the area of the brain where information is processed as electrical activity in the form of action potentials or nerve impulses, transmitted along neurons.
EEG scanners measure this
electrical activity through
electrodes attached to the scalp.
Small electrical charges detected by
the electrodes are graphed over a
period of time, indicating the level of activity in the brain.
(This is not important in essay)EEG scanning was responsible for developing our understanding of REM (dream) sleep, which is associated with a fast, desynchronized activity, indicative of dreaming.
EEG can also be used to detect illnesses like epilepsy and sleep disorders, and to diagnose other disorders that affect brain activity, like Alzheimer’s disease.
Four Types Of EEG Patterns (EEG AO1)?
(This is part of EEG AO1).
There are four types of EEG patterns:
- alpha waves,
- beta waves,
- theta waves,
- and delta waves.
Each of these patterns has two basic properties that psychologists can examine:
- Amplitude: the intensity or size of the activity,
- Frequency: the speed or quantity of activity.
EEG patterns produce two distinctive states: synchronised and desynchronized patterns.
A synchronised pattern is where a recognised waveform (alpha, beta, delta and theta) can be detected, whereas a desynchronized is where no pattern can be detected.
Fast desynchronized patterns are usually found when awake and synchronised patterns are typically found during sleep.
Alpha waves are associated with light sleep, and theta/delta waves are associated with deep sleep.
ERP AO1?
Event-Related Potentials (ERP) use similar equipment to EEG, electrodes attached to the scalp.
The difference is that a stimulus is presented to a participant (for example a picture/sound) and the researcher looks for activity related to that stimulus.
ERPs are difficult to separate from all of the background EEG data, the stimulus is present many times (usually hundreds), and an average response is graphed.
This procedure, which is called ‘averaging’, reduces any extraneous neural activity which makes the specific response to the stimulus stand out.
The time or interval between the presentation of the stimulus and the response is referred to as latency.
ERPs have a very short latency and can be divided into two broad categories:
- Waves (responses) that occur within 100 milliseconds following the presentation of a stimulus are referred to as ‘sensory ERPs’, as they reflect a sensory response to the stimulus.
- ERPs that occur after 100 milliseconds are referred to as ‘cognitive ERPs’, as they demonstrate some information processing.
EEG And ERP Evaluation, AO3?
Strength: both techniques are non-invasive. EEG and ERP do not use radiation or involve inserting instruments directly into the brain and are therefore virtually risk-free.
Strength: EEG and ERP are much cheaper techniques in comparison with fMRI scanning and are therefore more readily available. This should allow more patients/participants to undertake EEG/ERPs, which could help psychologists to gather further data on the functioning human brain and therefore develop our understanding of different psychological phenomena, such as sleeping, and different disorders like Alzheimer’s.
Weakness: EEG/ERP have poor spatial resolution. EEGs/ERPs only detect the activity in superficial regions of the brain. Consequently, EEGs and ERPs are unable to provide information on what is happening in the deeper regions of the brain (such as the hypothalamus), making this technique limited in comparison to the fMRI, which has a spatial resolution of 1-2mm.
Strength: EEG/ERG have good temporal resolution. They can take readings every millisecond, meaning it can record the brain’s activity in real time as opposed to looking at a passive brain. This leads to an accurate measurement of electrical activity when undertaking a specific task.
Weakness (can be used as double paragraph with above): EEG/ERP is uncomfortable for the participant, as electrodes are attached to the scalp. This could result in unrepresentative readings as the patient’s discomfort may be affecting cognitive responses to situations. fMRI scans, on the other hand, are less invasive and would not cause the participants any discomfort, leading to potentially more accurate recordings.
EEG Weakness: Electrical activity is often detected in several regions of the brain simultaneously. Consequently, it can be difficult pinpoint the exact area/region of activity, making it difficult for researchers to draw accurate conclusions.
Strength ERP: ERPs enable the determination of how processing is affected by a specific experimental manipulation. This makes ERP use a more experimentally robust method as it can eliminate extraneous neutral activity, something that other scanning techniques (and EEG) may struggle to do.
Post-Mortem AO1?
In this study, researchers will study the physical brain of a person who displayed a particular behaviour while they were alive that suggested possible brain damage.
An example of this technique is the work of Broca, who examined the brain of a man who displayed speech problems when he was alive. It was subsequently discovered that he had a lesion in the area of the brain important for speech production. This later became known as Broca’s area.
Similarly, Wernicke discovered a region in the left temporal lobe, which is important for language comprehension and processing, which is now known as Wernicke’s area.
Iverson examined the brains of deceased schizophrenic patients and found that they all had a higher concentration of dopamine, especially in the limbic system, compared with brains of people without schizophrenia, highlighting the importance of such investigations.
Post-mortem studies allow for a more detailed examination of anatomical and neurochemical aspects of the brain than would be possible with other techniques.
They also enable researchers to examine deeper regions of the brain such as the hypothalamus and hippocampus, something that is not as easy with other methods of investigation.
Post-Mortem AO3?
Weakness: Difficult to detect causation through this study. The deficit a patient displays during their lifetime (e.g. an inability to speak) may not be linked to the deficits found in the brain (e.g. a damaged Broca’s area). The deficits reported could have been the result of another illness, and therefore psychologists are unable to conclude that the deficit is caused by the damage found in the brain.
Weakness: There are many extraneous factors that can affect the results/conclusions of post-mortem examinations. For example, people die at different stages of their life and for a variety of different reasons. Any medication a person may have been taking, their age, and the length of time between death and post-mortem examination, are all confounding factors that make the conclusions of such research questionable.
Strength: They provide a detailed examination of the anatomical structure and neurochemical aspects of
the brain that is not possible with other scanning techniques (e.g. EEG, ERP and fMRI). Post-mortem examinations can access areas like the hypothalamus and hippocampus, which other scanning techniques cannot, and therefore provide researchers with an insight into these deeper brain regions, which often provide a useful basis for further research. For example, Iverson found a higher concentration of dopamine in the limbic system of patients with schizophrenia which has prompted a whole area of research looking into the neural correlates of this disorder.
Strength/Weakness: While post-mortem examinations are ‘invasive’, this is not an issue because the patient is dead. However, there are ethical issues in relation to informed consent and whether or not a patient provides consent before his/her death. Furthermore, many post-mortem examinations are carried out on patients with severe psychological deficits (e.g. patient HM who suffered from severe amnesia) who would be unable to provide fully informed consent, and yet a post-mortem examination has been conducted on his brain. This raises severe ethical questions surrounding the nature of such investigations.
Why Do We Study The Brain?
Studying the brain allows psychologists to gain important insights into the underlying foundations of our behaviour and mental processes.
We use:
- EEG/ERP scans,
- fMRI scans,
- Post-mortem scans.
What Are Biological Rhythms?
Biological rhythms are cyclical patterns within biological systems that have evolved in response to environmental influences, e.g. day and night.
There are two key factors that govern biological rhythms:
- endogenous pacemakers (internal factors - the body’s clock),
- and exogenous zeitgebers (external factors 1 changes in the environment).
Circadian Rhythms AO1?
24-hour circadian rhythm (often known as the ‘body clock’), which is controlled by levels of light.
(Not too important for essay)The word circadian is from the Latin ‘circa’ which means ‘about’, and ‘dian’, which means ‘day’.
The sleep-wake cycle is an example of a circadian rhythm, which dictates when humans and animals should be asleep and awake.
Sleep-Wake Cycle Steps:
1. Light provides the primary input to this system, acting as the external cue for sleeping or waking.
Light is first detected by the eye, which then sends messages concerning the level of brightness to the suprachiasmatic nuclei (SCN).
- The SCN then uses this information to coordinate the activity of the entire circadian system.
- Sleeping and wakefulness are not determined by the circadian rhythm alone, but also by homoeostasis. When an individual has been awake for a long time, homeostasis tells the body that there is a need for sleep because of energy consumption.
- This homeostatic drive for sleep will increase throughout the day, reaching its maximum in the late evening, when most people fall asleep.
Body temperature is another circadian rhythm. Human body temperature is at its lowest in the early hours of the morning (36oC at 4:30 am) and at its highest in the early evening (38oC at 6 pm).
Sleep typically occurs when the core temperature starts to drop, and the body temperature starts to rise towards the end of a sleep cycle promoting feelings of alertness first thing in the morning.
Circadian Rhythms AO3?
Strength: Research has been conducted to investigate circadian rhythms and the effect of external cues like light on this system. Siffre (1975) found that the absence of external cues significantly altered his circadian rhythm. When he returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was. This suggests that his 24-hour sleep-wake cycle was increased by the lack of external cues, making him believe one day was longer than it was, and leading to his thinking that fewer days had passed.
Weakness: Siffre’s case study has been the subject of criticism. As the researcher and sole participant in his case study, there are severe issues with generalisability. However, further research by Aschoff & Weber (1962) provides additional support for Siffre’s findings. Aschoff & Weber studied participants living in a bunker. The bunker had no windows and only artificial light, which the participants were free to turn on and off as they pleased. Aschoff and Weber found that the participants settled into a longer sleep/wake cycle of between 25-27 hours. These results, along with Siffre’s findings, suggest that humans use natural light (exogenous zeitgebers) to regulate a 24-hour circadian sleep-wake cycle, demonstrating the importance of light for this circadian rhythm.
Weakness: It is important to note the differences between individuals when it comes to circadian cycles. Duffy et al. (2001) found that ‘morning people’ prefer to rise and go to bed early (about 6 am and 10 pm) whereas ‘evening people’ prefer to wake and go to bed later (about 10 am and 1 am). This demonstrates that there may be innate individual differences in circadian rhythms, which suggests that researchers should focus on these differences during investigations.
Weakness (Combine in double paragraph with ^): It has been suggested that temperature may be more important than light in determining circadian rhythms. Buhr et al. (2010) found that fluctuations in temperature set the timing of cells in the body and caused tissues and organs to become active or inactive. Buhr claimed that information about light levels is transformed into neural messages that set the body’s temperature. Body temperature fluctuates on a 24-hour circadian rhythm and even small changes in it can send a powerful signal to our body clocks. This shows that circadian rhythms are controlled and affected by several different factors, and suggests that a more holistic approach to research might be preferable.
What Are Endogenous Pacemakers & Exogenous Zeitgebers?
Biological rhythms are regulated by endogenous pacemakers, which are the body’s internal biological clocks,
and exogenous zeitgebers, which are external cues, including light, that help to regulate the internal biological clocks.
Endogenous pacemakers and exogenous zeitgebers interact with one another to control and fine-tune biological rhythms and therefore it is necessary to consider these concepts together.
Endogenous Pacemakers AO1?
Endogenous pacemakers are internal mechanisms that govern biological rhythms, in particular, the circadian sleep-wake cycle.
Although endogenous pacemakers are internal biological clocks, they can be altered and affected by the environment.
For example, although the circadian sleep-wave cycle will continue to function without natural cues from light.
Research suggests that light is required to reset the cycle every 24 hours. (See Siffre and Aschoff & Weber)
The most important endogenous pacemaker is the suprachiasmatic nucleus, which is closely linked to the pineal gland, both of which are influential in maintaining the circadian sleep/wake cycle.
The suprachiasmatic nucleus (SCN), which lies in the hypothalamus, is the main endogenous pacemaker (or master clock). It controls other biological rhythms, as it links to other areas of the brain responsible for sleep and arousal.
The SCN also receives information about light levels (an exogenous zeitgeber) from the optic nerve, which sets the circadian rhythm so that it is in synchronisation with the outside world, e.g. day and night.
The SNC sends signals to the pineal gland, which leads to an increase in the production of melatonin at night, helping to induce sleep.
The SCN and pineal glands work together as endogenous pacemakers; however, their activity is responsive to the external cue of light.
Put simply:
Low levels of light from retina —> Melanopsin carries signals from retina to SCN —> Axon pathway to pineal gland —> Melatonin is released —> Sleep.
Exogenous Zeitgebers AO1?
Exogenous zeitgebers influence biological rhythms: these can be described as environmental events that are responsible for resetting the biological clock of an organism.
They can include social cues such as meal times and social activities, but the most important zeitgeber is light, which is responsible for resetting the body clock each day, keeping it on a 24-hour cycle.
The SNC contains receptors that are sensitive to light and this external cue is used to synchronise the body’s internal organs and glands.
Melanopsin, which is a protein in the eye, is sensitive to light and carries the signals to the SCN to set the 24-hour daily body cycle.
In addition, social cues, such as mealtimes, can also act as zeitgebers and humans can compensate for the lack of natural light, by using social cues instead.
Endogenous Pacemakers And Exogenous Zeitgebers AO3?
Strength: Morgan (1955) bred hamsters so that they had circadian rhythms of 20 hours rather than 24. SCN neurons from these abnormal hamsters were transplanted into the brains of normal hamsters, which subsequently displayed the same abnormal circadian rhythm of 20 hours, showing that the transplanted SCN had imposed its pattern onto the hamsters. This research demonstrates the significance of the SCN and how endogenous pacemakers are important for biological circadian rhythms.
Weakness (use in double paragraph with ^): This research is flawed because of its use of hamsters. Humans would respond very differently to manipulations of their biological rhythms, not only because we are different biologically, but also because of the vast differences between environmental contexts. This makes research carried out on other animals unable to explain the role of endogenous pacemakers in the biological processes of humans.
Strength: There is research support for the role of melanopsin. Skene and Arendt (2007) claimed that the majority of blind people who still have some light perception have normal circadian rhythms whereas those without any light perception show abnormal circadian rhythms. This demonstrates the importance of exogenous zeitgebers as a biological mechanism and their impact on biological circadian rhythms.
Strength: There is further research support for the role of exogenous zeitgebers. When Siffre (see above) returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was. This suggests that his 24-hour sleep- wake cycle was increased by the lack of external cues, making him believe one day was longer than it was. This highlights the impact of external factors on bodily rhythms.
Weakness: Despite all the research support for the role of endogenous pacemakers and exogenous zeitgebers, the argument could still be considered biologically reductionist. For example, the behaviourist approach would suggest that bodily rhythms are influenced by other people and social norms, i.e. sleep occurs when it is dark because that is the social norm and it wouldn’t be socially acceptable for a person to conduct their daily routines during the night. The research discussed here could be criticised for being reductionist as it only considers a singular biological mechanism and fails to consider the other widely divergent viewpoints.
Infradian Rhythms AO1?
Another important biological rhythm is the infradian rhythm.
Infradian rhythms last longer than 24 hours and can be weekly, monthly or annually.
A monthly infradian rhythm is the female menstrual cycle, which is regulated by hormones that either promote ovulation or stimulate the uterus for fertilisation.
Ovulation occurs roughly halfway through the cycle when oestrogen levels are at their highest, and usually lasts for 16-32 hours.
After the ovulatory phase, progesterone levels increase in preparation for the possible implantation of an embryo in the uterus.
It is also important to note that although the usual menstrual cycle is around 28 days, there is considerable variation, with some women experiencing a short cycle of 23 days and others experiencing longer cycles of up to 36 days.
Extension (Not too important for essay): A second example of an infradian rhythm is related to the seasons.
Research has found seasonal variation in mood, where some people become depressed in the winter, which is known as seasonal affective disorder (SAD).
SAD is an infradian rhythm that is governed by a yearly cycle. Psychologists claim that melatonin, which is secreted by the pineal gland during the night, is partly responsible.
The lack of light during the winter months results in a longer period of melatonin secretion, which has been linked to the depressive symptoms.
Exam Hint: While it is logical to assume that infradian rhythms, in particular the menstrual cycle, are governed by internal factors (endogenous pacemakers) such as hormonal changes, research suggests that these infradian rhythms are heavily influenced by exogenous zeitgebers.
Infradian Rhythms AO3?
Strength: Research suggests that the menstrual cycle is, to some extent, governed by exogenous zeitgebers (external factors). Reinberg (1967) examined a woman who spent three months in a cave with only a small lamp to provide light. Reinberg noted that her menstrual cycle shortened from the usual 28 days to 25.7 days. This result suggests that the lack of light (an exogenous zeitgeber) in the cave affected her menstrual cycle, and therefore this demonstrates the effect of external factors on infradian rhythms.
Strength: There is further evidence to suggest that exogenous zeitgebers can affect infradian rhythms. Russell et al. (1980) found that female menstrual cycles became synchronised with other females through odour exposure. In one study, sweat samples from one group of women were rubbed onto the upper lip of another group. Despite the fact that the two groups were separate, their menstrual cycles synchronised. This suggests that the synchronisation of menstrual cycles can be affected by pheromones, which have an effect on people nearby rather than on the person producing them. These findings indicate that external factors must be taken into consideration when investigating infradian rhythms and that perhaps a more holistic approach should be taken, as opposed to a reductionist approach that considers only endogenous influences.
Strength: (Support for above ^): Evolutionary psychologists claim that the synchronised menstrual cycle provides an evolutionary advantage for groups of women, as the synchronisation of pregnancies means that childcare can be shared among multiple mothers who have children at the same time.
Strength: There is research to suggest that infradian rhythms such as the menstrual cycle are also important regulators of behaviour. Penton-Volk et al. (1999) found that woman expressed a preference for feminised faces at the least fertile stage of their menstrual cycle, and for a more masculine face at their most fertile point. These findings indicate that women’s sexual behaviour is motivated by their infradian rhythms, highlighting the importance of studying infradian rhythms in relation to human behaviour.
Strength: Evidence supports the role of melatonin in SAD. Terman (1988) found that the rate of SAD is more common in Northern countries where the winter nights are longer. For example, Terman found that SAD affects roughly 10% of people living in New Hampshire (a northern part of the US) and only 2% of residents in southern Florida. These results suggest that SAD is in part affected by light (exogenous zeitgeber) that results in increased levels of melatonin.
Ultradian Rhythms AO1?
Ultradian rhythms last fewer than 24 hours and can be found in the pattern of human sleep.
This cycle alternates between REM (rapid eye movement) and NREM (non-rapid movement) sleep and consists of five stages.
The cycle starts at light sleep, progressing to deep sleep and then REM sleep, where brain waves speed up and dreaming occurs.
A complete sleep cycle goes through the four stages of NREM sleep before entering REM (Stage 5) and then repeating.
Research using EEG has highlighted distinct brain waves patterns during the different stages of sleep.
1. Stages 1 and 2 are ‘light sleep’ stages. During these stages brainwave patterns become slower and more rhythmic, starting with alpha waves progress to theta waves.
- Stages 3 and 4 are ‘deep sleep’ or slow wave sleep stages, where it is difficult to wake someone up. This stage is associated with slower delta waves.
- Finally, Stage 5 is REM (or dream) sleep. Here is the body is paralysed (to stop the person acting out their dream) and brain activity resembles that of an awake person.
On average, the entire cycle repeats every 90 minutes and a person can experience up to five full cycles in a night.
Exam Hint: When providing an example of an ultradian rhythm, answers should explicitly mention that the cycle occurs more than once every 24 hours. Furthermore, specific details in relation to the distinctive characteristics of the different stages are required to demonstrate understanding.
Extension: Another ultradian rhythm is appetite or meal patterns in humans. Most humans eat three meals a day and appetite rises and falls because of food consumption.
Ultradian Rhythms AO3?
Weakness: Individual Differences - The problem with studying sleep cycles is the differences observed in people, which make investigating patterns difficult. Tucker et al. (2007) found significant differences between participants in terms of the duration of each stage, particularly stages 3 and 4 (just before REM sleep). This demonstrates that there may be innate individual differences in ultradian rhythms, which means that it is worth focusing on these differences during investigations into sleep cycles.
Weakness (weakness of study above^): This study was carried out in a controlled lab setting, which meant that the differences in the sleep patterns could not be attributed to situational factors, but only to biological differences between participants. While this study provide convincing support for the role of innate biological factors and ultradian rhythms, psychologists should examine other situational factors that may also play a role.
Weakness: When investigating sleep patterns, participants must be subjected to a specific level of control and be attached to monitors that measure such rhythms. This may be invasive for the participant, leading them to sleep in a way that does not represent their ordinary sleep cycle. This makes investigating ultradian rhythms, such as the sleep cycle, extremely difficult as their lack of ecological validity could lead to false conclusions being drawn.
Strength/Weakness: Case study indicates the flexibility of ultradian rhythms. Randy Gardener remained awake for 264 hours. While he experienced numerous problems such as blurred vision and disorganised speech, he coped rather well with the massive sleep loss. After this experience, Randy slept for just 15 hours and over several nights he recovered only 25% of his lost sleep. Interestingly, he recovered 70% of Stage 4 sleep, 50% of his REM sleep, and very little of the other stages. These results highlight the large degree of flexibility in terms of the different stages within the sleep cycle and the variable nature of this ultradian rhythm.
Plasticity And Functional Recovery AO3?
Strength: Kuhn et al. found a significant increase in grey matter in various regions of the brain after participants played video games for 30 minutes a day over a two-month period. Similarly, Davidson et al. demonstrated the permanent change in the brain generated by prolonged meditation: Buddhist monks who meditated frequently had a much greater activation of gamma waves (which coordinate neural activity) than did students with no experience of meditation. These two studies highlight the idea of plasticity and the brain’s ability to adapt as a result of new experience, whether it’s video games or mediation.
Strength: Maguire et al. found that the posterior hippocampal volume of London taxi drivers’ brains was positively correlated with their time as a taxi driver and that there were significant differences between the taxi drivers’ brains and those of controls. This shows that the brain can permanently change in response to frequent exposure to a particular task.
Weakness (Can be used with ^): However, some psychologists suggest that research investigating the plasticity of the brain is limited. For example, Maguire’s research is biologically reductionist and only examines a single biological factor (the size of the hippocampus) in relation to spatial memory. This approach is limited and fails to take into account all of the different biological/cognitive processes involved in spatial navigation which may limit our understanding. Other psychologists suggest that a holistic approach to understanding complex human behaviour may be more appropriate.
Strength: There is research to support the claim for functional recovery. Taijiri et al. (2013) found that stem cells provided to rats after brain trauma showed a clear development of neuron-like cells in the area of injury. This demonstrates the ability of the brain to create new connections using neurons manufactured by stem cells.
While there is evidence for functional recovery, it is possible that this ability can deteriorate with age. Elbert et al. concluded that the capacity for neural
reorganisation is much greater in children than in adults, meaning that neural regeneration is less effective in older brains. This may explain why adults find change more demanding than do young people. Therefore, we must consider individual differences when assessing the likelihood of functional recovery in the brain after trauma.
A final strength of research examining plasticity and functional recovery is the application of the findings to the field of neurorehabilitation. Understanding the processes of plasticity and functional recovery led to the development of neurorehabilitation which uses motor therapy and electrical stimulation of the brain to counter the negative effects and deficits in motor and cognitive functions following accidents, injuries and/or strokes. This demonstrates the positive application of research in this area to help improve the cognitive functions of people suffering from injuries.
