BIOPSYCHOLOGY

• Another limitation

  Case study evidence- challenges the role of exogenous zeitgebers. Miles (1997) recount the study of a young man blind from birth who had an abnormal circadian rhythm at 24.9 hours, Despite exposure to social cues , such as regular mealtimes, his sleep wake cycle could not be adjusted. This suggests that social cues alone are effective in resetting the biological rhythm.
• Evaluation of Exogenous Zeitgebers

  Environmental observations- They do not same effect in all environments. The experience of people who live in places where there is little darkness in summer and very little light in winter tell a different story from the usual narrative, e.g. the Inuit of the Article circle are said to have similar sleep patterns all year round, despite spending 6 months in almost total darkness. Suggests the sleep/wake cycle is primarily controlled by endogenous pacemakers that can override environmental changes in light
• Another limitation

  Interactionist system- endogenous pacemakers cannot be studied in isolation. Total isolation studies, such as Siffre's cave study, are extremely rare. He made use of his artificial light which could have reset his biological clock every time he turned on lamp. Everyday life pacemakers and zeitgebers interact and it may make little sense to separate the two for the purpose of research, suggests the more researchers attempt to isolate the influence of internal pacemakers, the lower the validity of research
• Evaluation on Endogenous pacemakers - Limitation

  Beyond the master clock- SCN research is that may obscure other body clocks. Research has revealed that there are numerous circadian rhythms in many organs and cells in the body. These peripheral oscillators are found in the organs including the lungs, pancreas and skin. They are influenced by the actions of the SCN but also act independently. Damiola (2000) demonstrated how changing the feeding patterns in mice could alter the circadian rhythms of cells in liver by up to 12 hours, whilst leaving the rhythm of the SCN unaffected, this suggests other complex influences on the sleep/wake cycle
• Exogeneous Zeitgebers


  They are external factors in the environment that reset our biological clocks through entrainment. This free-running cycle is then brought into line (entrained) by environmental cues, so there is an interaction of internal and external factors.

  Light- Scott Campbell demonstrated that light may be detected by skin receptor sites on the body even when the same info isn't received by the eyes. 15 ppts were woken at various times and a light pad was shone on the back of their knees.

  Researchers managed to produce a deviation in the ppts usual sleep/wake cycle of up to 3 hours in some cases, suggests that light is a powerful exogenous zeitgeber that not necessarily rely on eyes to exert its influence on the brain.

  Social cues- babies are seldom on the same week/cycle as the rest of family, in fact newborn babies' sleep cycle is random. about 6 weeks, the circadian rhythms begin and by 16 weeks babies' rhythms have been entrained by schedules imposed by parents, including adult- determined mealtimes and bedtimes.

  Research on jet lag, suggests that adapting to local times for eating and sleeping rather than their own feelings of hunger, fatigue, is effective way of entraining circadian rhythms and beating jet lag when travelling long distances.
• Animal studies and the SCN

  The influence of SCN has been demonstrated in animal studies, Patricia (2000) destroyed SCN connections in the brain of 30 chipmunks who were then returned to their natural habitats and observed for 80 days. The sleep wake cycle of the chipmunks disappeared and by the end of study a significant proportion of them had been killed by predators - presumably because they were awake active and vulnerable to attack when they should have been asleep. In another study, Martin Ralph bred mutant hamsters with 20 hour sleep/wake cycle, when SCN cells from foetal tissue of mutant hamsters were transplanted into the brains of normal hamsters, the cycles of the second group defaulted to 20 hours.
• Endogenous pacemakers

  Endogenous pacemakers- The Suprachiasmatic nucleus is one of the primary endogenous pacemakers in mammalian species and is influential in maintaining circadian rhythms such as the sleep/wake cycle. The SCN lies just above the optic chiasm- it receives info about light directly from this structure. This continues even when our eyes are closed, enabling the biological clock to adjust to changing patterns of daylight whilst we are sleep.
• Limitation

  Individual differences - significant variation between people. Tucker 2007, found large differences between ppts in terms of the duration of each sleep stage, particularly stage 3 and 4. Tucker suggest that these differences are likely to be biologically determined, this makes it difficult to describe normal sleep in any meaningful way.
• Strength

  improved understanding of age related changes in sleep. Sleep scientists have observed SWS reduces with age. Growth hormone is Mostly produced during SWS therefore this becomes deficient in older people. According to Eve van Cauter et al 2000, the resulting sleep deficit may explain various impairments in old age, such as reduced alertness. In order to increase SWS, relaxation and medication may be used, suggests that knowledge of ultradian rhythms has practical value
• Ultraradian rhythms


  Psychologists identified 5 stages of sleep that altogether span approximately 90 minutes. - A cycle that continues throughout the course of the night. Each stage is characterised by differ t brain activity using the EEG.

  Stage 1 and 2- light sleep where a person may easily be woken. 1- brain waves are high frequency and have short amplitude (alpha). Stage 2, alpha waves continue but there are occasional random changes in pattern called sleep spindles

  Stage 3 and 4- known as deep sleep SWS. The brain waves are delta waves with lower frequency and higher amplitude- difficult to wake this person up at this point.

  Stage 5 (REM) sleep- body is paralysed yet brain activity closely resembles that of the awake brain. During this time, brain produces theta waves and the eyes occasionally move around thus rapid eye movement, dreams are most often experienced during REM sleep, but may also occur in deep sleep.
• Limitation

  the methodological shortcomings- there are many factors that may effect change in a woman's menstrual cycle including changes in diet, exercise, these may act as cofounding variables which means that any supposed pattern of synchronisation is no more than would have been expected to occur by chance. This may explain why other studies eg Trevathan et al 1993 have failed to replicate the findings. This suggests that menstrual synchrony studies are flawed
• Evaluation on Infradian rhythms - strength

  Evolutionary basis- the menstrual synchrony research may be explained by natural selection. Synchronisation of female menstrual cycle, of the kind observed by Stern is thought by some to have evolutionary value. For our distant ancestors it may have been advantageous for females to menstruate together and become pregnant at the same time. In a social group, would allow babies who had lost their mothers during childbirth to have access to breast milk, thereby improving chances of survival- suggests that synchronisation is an adaptive strategy
• seasonal affective disorder


  depressive order which has seasonal pattern of onset, described and diagnosed as a mental disorder in DSM-5. SAD symptoms are triggered during the winter months when daylight hours become shorter. It's a particular type of infradian rhythm called circannual rhythm as it is a subject to a yearly cycle. It can be a circadian cycle as the disruption of the sleep/wake cycle, and this can be attributed to prolonged periods of daily darkness during winter. Hormone melatonin is implicated in the cause of SAD. During the night, the pineal gland secretes melatonin until dawn when there is an increase in light. During winter, the lack of light in the morning means this secreting process continues for longer. thought to have a knock-on effect on the production of serotonin in the brain
• Infradian rhythms

  synchronising menstrual cycle- although it is an endogenous system, evidence suggests that it may be influenced by exogeneous factors such as the cycles of other women. Stern and McClintock (1998) studied 29 women in history of irregular periods. Samples of pheromones were gathered together from nine of the women at different stages of their menstrual cycles via cotton pad and placed on armpits. The pads were worn for at least 8 hrs to ensure that pheromones were picked up. Pads were treated with alcohol and frozen, to be rubbed on upper lip of ppts. On day one, pads from the start of the menstrual were applied to all 20 women and day 2 so on. They had found that 68% of women experienced changes to their cycle which brought them closer to the cycle of their odour donor.
• Biological rhythms- Infradian and Ultraradian rhythms

  Infradian rhythm- type of biological rhythm with a frequency of less than one cycle in 24hrs such as menstruation and seasonal affective disorder.

  Ultraradian rhythm- type of biological rhythm with a frequency of more than one cycle in 24hrs, such as the stages of sleep.
• Another limitation


  generalisations are difficult to make. Aschoff, Sifre, Wever study are based on small samples of ppts. Seems that sleep/wake cycle may vary widely from person to person. research by Charles shows that some people have natural preference for going to bed early and rising early whereas other prefer the opposite. Even Sifre, in a later 1999 study, observed that his own sleep/wake cycle had slowed down since he was a young man. means that it's difficult to use research data to discuss anything more than averages, which may be meaningless
• One limitation

  studies investigated that the effects of shift work tend to use correlational methods. means it's difficult to establish whether desynchronisation of the sleep/wake Cyle is actually a cause of negative effects. there may be other factors. e.g. Solomon 1993- concluded that high divorce rates in shift workers might be due to the strain of deprived sleep and other influences such as missing out on important family events. suggesting that it may not be biological factors that create the adverse consequences associated with shift work,
• Another strength


  Medical treatment- circadian rhythms co-ordinate a number of the body's basic processes such as heart rate, digestion, hormone levels. These rise and fall during the course of a day which has led to the field of chronotherapeutic- how medical treatment can be administered in way that corresponds to a person's biological rhythms. For example aspirin is most effective for heart attacks when taken at night. Heart attacks more likely occur in the morning so the time taking matters and research has supported this. This shows that circadian rhythm research can help increase the effectiveness of drug treatments
• Strength of biological rhythms

  Shift work - provides an understanding of the adverse consequences that occur when they are disrupted- desynchronisation. e.g. night workers engaged in shift work experience a period of reduced concentration around 6 in morning (a circadian trough) meaning mistakes and accidents are more likely. Research also pointed to a relationship between shift work and poor health- shift workers are 3 times more likely to develop heart disease than people who work more typical work patterns. Shows the research into sleep/wake cycle have real-world economic implications in terms of how best to manage work productivity.
• Other research

  Aschoff and Wever 1976, got ppts to spend 4 weeks in WW2 bunker deprived of natural light. All but one of the who's extended to 29 hours) displayed a circadian rhythm between 24hrs and 25. Both Sifre and Bunker study suggest that the natural sleep/wake cycle may be longer than 24hrs but that is entrained by exogenous zeitgeber associated with our 24 hr day. (number of daylight hours, meal time and so on. Simon Folkard- studied a group of 12 people who agreed to live in the dark cave for 3 weeks, retiring to bed when the clock said 11;45 and awake at 7.45 am. Over the course of the study researchers speeded up the clock unaware to ppts. so apparent 24 hour day only lasted for 22 hrs. Revealed that one of the ppt was able to comfortably adjust to the new regime. This would suggest the existence of strong free running circadian rhythm that cannot easily be overridden by exogeneous zeitgebers.
• Siffr'es cave study


  is a self styled caveman who spent several periods underground to study the effects on his own biological rhythms. Deprived of exposure to nature light and sound, but access to adequate food and drink. He later performed a similar feat but in Texas in a cave for 6 months, and turns out, his free running biological rhythm settled down to one that was just beyond the usual 24 hours. (around 25 hrs) though he did continue to fall asleep and wake up on regular schedule.
• The sleep/wake cycle

  The fact we feel drowsy at night time and alert during the day demonstrates the effect of daylight0 an important exogeneous zeitgebers on our sleep/wake cycle. However, the sleep/wake cycle is also governed by an internal endogenous pacemaker - biological clock known as suprachiasmatic nucleus. SCN lies just above the optic chiasm which provides from the eye about light. Exogenous zeitgeber (light) can reset the SCN
• Biological circadian rhythms

  Biological rhythms- They are distinct patterns of changes in the body activity that conform to cyclical time periods. Biological rhythms are influenced by internal body clocks as well as external changes to the environment

  Circadian rhythms - Biological rhythms subject to a 24 hour cycle, which regulate a number of body processes such as the sleep/wake cycle ands changes in core body temp
• Post Mortem examinations

  Strength- Evidence was vital in providing the foundation of early understanding of key processes in the brain. Broca and Karl both relied on post Mortem in establishing links between behaviour, brain language decades before neuroimaging ever became a possibility.

  This technique was also used to study HM's brain to identify areas of damage which could then be associated with his memory deficits- means post Mortems continue to provide useful info.

  Limitation- Observed damage to the brain may not be linked to deficits under review but some other related trauma/decay. It raises ethical issues of consent from the individual before the death. Ppts may not be able to provide their informed consent, e.g. in the case of HM who lost his abilities to form memories was not able to provide such consent- nevertheless the post mortem had been conducted on his brain- this challenges its usefulness of post mortem studies in psychological research.
• Event- related potentials

  Strength- ERP's are derived from EEG measurements, they have excellent temporal resolution, especially when compared to neuroimaging techniques such as fMRI. This means that ERPs are frequently used to measure cognitive functions and deficits such as the allocation of attentional resources and the maintenance of the working memory.

  Limitation- There is lack of standardisation in ERP methodology between different research studies which makes it difficult to confirm findings. Another problem is that in order to establish pure data background noise and extraneous material must be completely eliminated. This is a problem as it may not be easy to achieve
• Electroencephalogram


  Strength of EEG has been useful in studying the stages of sleep and in diagnostic of conditions such as epilepsy. Unlike FMRI, EEG technology has extremely high temporal resolution. Today's EEG technology can accurately detect brain activity at a resolution of a single millisecond- this shows the real world usefulness of this technique

  Limitation- EEG lies on the generalised nature of the info received. The EEG signal is also not useful for pinpointing the exact source of neural activity. Therefore it doesn't allow researchers to distinguish between activities originating in different but adjacent locations
• FMRI Strength and weakness

  Strength- Unlike other scanning such as PET it does not rely on the use radiation. If administered correctly, it's virtually risk-free,non invasive and straightforward to use. It also produces images with high spatial resolution and providing a clear picture of how brain activity is localised.

  Weakness- FMRI is expensive compared to other neuroimaging technqiues and can only capture a clear image only if the person stays perfectly still. It has poor temporal resolution because there is around a 5 second time lag around the screen and the initial firing of neuronal activity. FMRI can onbly measure blood flow in the brain, it can not home in on activity of individual neourons and so it can be difficult to tell exactly what kind of brain activity is being represented on screen.
• Other ways of investigating brain

  Event-related potentials- using a statistical averaging technique, all extraneous brain activity from the original EEG recording is filtered out leaving those responses that relate to the performanceof specific task. Event- related potentials- types of brain wave triggered by particular events and linked to cognitive processes such as attention and perception

  Post- mortem examinations- technique involving an analysis of a person's brain following their death. Those whose brains are subject to a post mortem are likely to be those who have a rare disorder and have experienced unusual deficits in mental processes/behaviour during their lifetime. Areas within the brain damaged are examined after death as a means establishing the likely cause of the affliction the person suffered. This may also involve a comparison with a neurotypical brain in order to ascertain the extent of the difference.
• Ways of investiagting the brain


  FMRI - Works by detecting the changes in blood oxygenation and flow that occur as result of neural activity in specific parts of the brain. When a brain area is active it consumes more oxygen and to meet this increased demand, blood flow is activated to the active area. FMRI produces 3D images showing which parts of the brain are involved in particular mental processes and this has important implications for our understanding of localisation of function.

  EEG's- measure electrical activity within the brain via electrodes. The scan recording represents the brainwave that are generated from the action of millions of neurons. It's often used by clinicians as a diagnostic tool as an unusual arrythmic patterns of activity may detect neurological abnormalities
• Another limitation


  Lack of control with the sample selection- Epileptic patients have been taking anti- epilteptic medications for different periods of time which may have affected their ability to match words, recognise objects. Secondly even though all patients have gone through commissurotomy, there may have been differences in exact procedures eg differing extent of the lesioning of the corpus callosum. This would have affected the degree to which two hemispheres could relay info about themeselves. Therefore these two cofounding variables had not been controlled meaning that lateralised functions may be examples of unreliable causal conclusions
• Limitation


  Difference in function may not be so cleared cut -

  Given that the left hemisphere is the analyser, whilst the right is responsible for visual spatial tasks (Synthesiser), this has given a false impression that the two hemispheres are opposite in function and that they can receive such labels. But as suggested by Pucetti (1980), there have been cases of split brain patients who are left handed but produce and comprehend speech in the right hemisphere which oposses the predictions made by lateralisation theory and therefore each hemisphere is not restricted to specific functions.
• Another strength

  Strengths of methodology- experiments involving split brain patients made use of highly specialised and standardised procedures. Sperry's method of presenting visual info

  to one hemisphere field at the time was quite ingenious, Typically ppts would be asked to stare at the fixation point whilst one eye was blindfolded. the image projected would be flashed up fo 1/10th second meaning the split brain patient would not have time to move their eye across the image and so spread the info across both sides of the visual field.

  This allowed Sperry to vary aspects of basic procedure and ensured that only one hemisphere was receiving info at a time, thus he developed a very useful and well controlled procedure
• Strength

  Demonstrated lateralised brain functions - Sperry's work into the split brain phenomenon has produced an impressive body of research findings. Concluded that the left hemisphere is more geared towards analytic and verbal tasks whilst the right is more adept at performing spatial tasks and music. Research that the left hemisphere is the analyser whilst the right is the synthesiser - a key contribution to our understanding of brain processes.
• Key findings

  When picture of object was shown to a patient's right visual field, the patient could easily describe what was seen. But when the same object was shown to left visual field, could not describe what was seen and typically reported that there was nothing there. The patient's inability to describe objects in the left visual field was because of the lack of language centres in the right hemisphere, in normal brain messages from right hemisphere would be relayed to the language centres in the left hemisphere.

  Recognition of touch- although they could not attach verbal labels to objects projected in left visual field, they were able to select a matching object from a grab-bag of objects using left hand (Hemisphere). The left hand was also able to select an object that was closely associated with an object presented to left visual. eg able to pick an ashtray to the pic of a cigarette. they could not verbally identify what they had seen but could understand what the object was using the right hemisphere and selecting the corresponding object accordingly.
• Procedure

  Sperry devised a general procedure in which an image or word could be projected to a patient's right visual field( processed by left hemisphere and the same image, word could be projected in the left visual field processed by the right hemisphere. in the normal brain the corpus callosum would immediately share the information between both hemispheres and giving a complete picture of the visual word. However presenting the image to one hemisphere of a split brain patient meant that info couldn't to be conveyed from one hemisphere to the other.
• Split brain research

  Hemispheric lateralisation- For majority of us, language is subject to hemispheric lateralisation. Certain mental processes

  and behaviours are mainly controlled by one hemisphere rather than the other.

  Split brain studies- Sperry's (1968) involved a unqiue group of individuals who undergone same surgical procedure- operation called comissurotomy. Means that for these split brain patients, main communication line between the two hemispheres was removed. This allowed Sperry and his collegues to see the extent to which two hemispheres were specialised for certain functions and whether the hemispheres performed tasks independently of one another.
• Limitation


  Negative plasticity- Brain's abilit to rewire itself can sometimes have maladaptive behavioural consequences. Prolonged druge use has shown to result in poorercogntive functioning as well as increased risk of dementia in later life - Medina (2007), 60-80% of amputees have been known to develop phantom limb syndrome, the continued experience of sensations in the missing limb as if it were there., these sensations are usually unpleasant, painful and are thought to be due to cortical reorganisation in the somatosensory cortex that occurs as a result of limb loss (1998)
• Strength

  Functional plasticity tends to reduce with age. Brain has greater propensity for reorganisation in childhood as it is constantly adapting to new experiences and learning. Bezzola (2012) demonstrated how 40 hours of golf training produced chnages in neural representation of movement in ppts 40-60 years. Using FMRI, researchers observed reduced mortor cortex activity in novice golfers compared to the control group , suggestin more efficient neural representations after training, shows neural plasticity does continue throughout the lifespan
• Strength

  Practical application - Understanding the proccess involved in plasticity has contributed to the field of rehabilitation. After the damage to the brain, spontaneous recovery tendsto slow down after a number of weeks so forms of physical therapy may be required to maintain improvements in functioning. Techniques may include movement therapy and electrical stimulation of brain to counter the deficits in motor and cogntive functioning that maye experienced following a stroke for instance. This shows that although the brain may have the capacity to fix itself to a point, this process requires further intervention if it is to be completly successful.
• Research in functional recovery of the brain after trauma

  This is an example of neural plasticity. Healthy brain areas may take over functions of those damaged areas. Neuroscientists suggest that this proccess can occur quickly after trauma and then slow down after several weeks, at this point indiviudal may require rehabiliatative therapy to further their recovery.

  Brain during recovery - able to rewire and reorganise itself by forming new synaptic connections close to the area of damage. This includes structural changes such as reformation of blood vesseels, Axonal sprouting - the growth of new nerve endings which connect with orther undamaged nerve cells to form new neuronal pathways, recruitment of homologous areas on the opposite side of the brain to perform specific tasks.