investigating the brain and cycles

functional magnetic resonance imaging (fMRI)

fMRI works by detecting the changes in blood oxygenation and flow that occur as a result of neural activity in specific parts of the brain. oxygen is carried to the brain by haemoglobin in red blood cells. when a specific area of the brain becomes more active, it consumes more oxygen so more haemoglobin is present. to meet this increased demand, the blood flow to that particular area increases.

when a brain area is more active it consumes more oxygen and to meet this increased demand blood flow is directed to the active area (haemodynamic response)

fMRI produces 3-dimensional 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

strengths and weaknesses of fMRI’s

strengths:

• unlike other scanning techniques, fMRI does not rely on the use of radiation. if administered correctly, it is virtually risk-free, non-invasive and straightforward to use. therefore it can be used to measure brain activity without causing harm and has no risk of infection or complications

• it produces images that have very high spatial resolution, showing detail by the millimetre, and therefore providing a clear picture of how brain activity is localised. it can show exactly which specific are is active during a specific task

weaknesses:

• fMRI is expensive compared to other neuroimaging techniques and can only capture an image if the person stays perfectly still. because of the cost, many researchers can only use a small sample size, which impacts the validity and generalisability of the research

• it has poor temporal resolution - doesn’t show changes over time accurately. this means findings can be misinterpreted

• fMRI can only measure blood flow in the brain, it cannot tell us the exact activity of individual neurons and so it can be difficult to tell what kind of brain activity is being represented on the screen.

electroencephalogram (EEG)

EEG’s measure electrical activity within the brain via electrodes that are fixed to an individuals scalp using a skull cap

the scab recording represents the brainwave patterns that are generated from the action of millions of neurons, providing an overall account of brain activity

the 4 main types of EEG waves are alpha, beta, theta and delta

scientists can also measure brain activity through amplitude and frequency. amplitude is the intensity or size of activity, frequency is the speed or quantity of activity

EEG is often used by clinicians as a diagnostic tool as unusual arrhythmic patterns of activity may indicate neurological abnormalities such as epilepsy, tumours or disorders of sleep.

strengths and weaknesses of EEGs

strengths:

• EEG is valuable at helping diagnose conditions such as epilepsy and schizophrenia because the difference in brain activity can be detected on the screen. this is useful for clinical diagnosis

• it has contributed to our understanding of the sleep stages and sleep problems, strengthening the usefulness of EEG

• EEG’s are cheap to use, which means researchers can benefit from large sample sizes, increasing the validity, and generalisability of their studies

• it has extremely high temporal resolution, it records brain activity in real time. therefore, researchers can monitor response to tasks

weaknesses:

• EEG represents brainwave patterns and as such it cannot detect activity in deeper brain regions. therefore, if there were issues to a patients hippocampus, an EEG wouldn’t necessarily pick up this information

• EEG is not useful in pinpointing the exact source of neural activity and therefore it is hard to work out which area of the brain the waves originate form

event-related potentials (ERPs)

ERPs use similar equipment to EEG (electrodes attached to the scalp) however, a stimulus is presented to a participant i.e. picture or sound, and the researcher looks for activity related to the stimulus and investigate how an EEG wave pattern changes in response to the stimulus. this change is an ERP

the stimulus is presented hundreds of times and an average response is graphed. this is statistical averaging technique, and it reduces an extraneous brain activity which makes the specific response to the stimulus stand out

research has revealed many different forms of ERP and how, for example, they are linked to cognitive processes such as attention and perception. for example, the image shows the type of brain waves triggered by an auditory stimulus

strengths and weaknesses of ERPs

strengths:

• the limitation of EEGs being too general are partly addressed by ERPs - they are much more specific to the measurement of neural processes

• they provide a continuous measure of processing in response to a stimulus. therefore, this provides quantitative experimental data

• researchers have also been able to identify ERP’s of mental health issues like phobias. it has been found that people with phobias have ERP’s of a greater amplitude in response to images of the objects they feared compared to non-phobic individuals. this allows researchers more of an understanding of complex mental processes

weaknesses:

• there is a lack of standardisation in ERP methodology between different research studies, which makes it difficult to confirm findings

• it may not always be possible to completely eliminate background nose and extraneous material needed to establish pure data in ERP studies, therefore validity may be questionable

post-mortem examinations

this is a technique involving the analysis of a person brain, following their death.

in psychological research, individuals whose brains are subject to a post-mortem are likely to be those who have a rare disorder and have experiences unusual deficits in mental processes or behaviour during their lifetime.

areas of damage within the brain are examined after death as a means of establishing the likely cause of the affliction the person suffered. this may also involved comparison with a typical brain in order to determine the extent of the difference between them

strengths and weaknesses of post-mortem examination

strengths:

• post-mortem evidence was vital in providing a foundation for earlt understanding of key processes in the brain e.g. Broca’s and Wernickes area were identifies using post-mortem

• post-mortem studies improve medical knowledge and help generate hypotheses for further study e.g. Zhou analysed the brains of female-male transsexuals and found an area of the brain associated with gender to be larger in these individuals - more similar to that of a male - this demonstrates the beneficial nature of post-mortems in our understanding of gender development

weaknesses:

• causation is an issue within these investigations. observed damage in the brain may not be linked to the deficits under review but some other unrelated trauma or decay (e.g.g drugs or age) therefore, there are issues with cause and effect being established

• they raise ethical issues of consent from the patient before death. a patient may have significant brain abnormality when alive and are therefore too ill to give consent for their brains to be investigated upon their death. this poses an ethical concern as a post-mortem may still be carried out

biological rhythms

1. circadian rhythms - have cycles that generally occur once every 24 hours, such as the sleep-wake cycle or body temperature

2. infradian rhythms - have cycles that occur longer than 24 hours and can be weekly, monthly or annually

3. ultradian rhythms - last fewer than 24 hours and can be found in the pattern of human sleep

the timing of these rhythms are regulated by factors both inside and outside our bodies. factors inside our body are called endogenous pacemakers; those outside the body are exogenous zeitgebers

circadian rhythms

the most obvious circadian rhythm is the sleep-wake cycle. it is a 24 hour rhythmic cycle where there are differing levels of consciousness. people sleep for a certain time every 24 hours, and conduct other activities during wakefulness. the fact that we feel drowsy when its night time and alert during the day shows the effect of daylight (extraneous zeitgeber) in our sleep/wake cycle.

endogenous pacemakers and exogenous Zeitgebers on the sleep wake cycle

endogenous pacemakers refer to an internal body clock that sets many of our bodily rhythms, including sleep. the internal clock that has an effect on when we sleep and when we are awake is the suprachiasmatic nucleus (SCN). exogenous zeitgebers are external cues that have an influence on when we’re asleep or awake, such as light.

how do endogenous pacemakers and exogenous zeitgebers influence our circadian rhythm?

in the body:

• the main endogenous pacemaker is the suprachiasmatic nucleus (SCN) or biological clock. its a bundle of nerves located in the hypothalamus of the brain. the SCN is located above the optic area

• therefore, it can receive information about light directly, the SCN passes the information about day length/light to the pineal gland

• based on this information, the pineal gland will release melatonin (a chemical that makes us feel sleepy)

• during the night, the pineal gland increases melatonin production. with more daylight, less melatonin. the SCN is therefore to a degree related by light from our outside world

• however, in the absence of light, the SCN generates a rhythm related to its production of protein. when it reaches a certain level of protein it passes a message to the pineal gland and melatonin will still be released or inhibited

• so although daylight influences the SCN its not absolutely essential

external cues:

• the most influential exogenous zeitgeist is light and its an important factor in our environment that ‘resets’ our biological clocks, this is called entrainment. light enters the eye through the retina and this information is passed onto the SCN

• low levels of light into the retina goes → via the optic area to the SCN → SCN sends signals to pineal gland → pineal gland releases melatonin → induces sleep

• high levels of light into the retina goes → via the optic area to the SCN → SCN sends signals to pineal gland → pineal gland inhibits the release of melatonin → indices wakefulness

supporting research for the circadian rhythm

1. Siffre’s cave study:

in 1962 Siffre spend two months living in complete isolation in a cave to study the effects on his own circadian rhythm. he was deprived of natural light, a clock, a calendar and sound, but had access to adequate food and drink. he slept and ate only when his body ‘told him to’. therefore the only influence was his internal body clock. Siffre re-surfaced mid September, believing it to be mid august. he believed the dare to be a month earlier than it actually was. his lack of external cues made him feel a day was actually ‘longer’ than it was and fewer days had passed in total. a decade later he performed a similar feat for six months in a cave in texas

in each case, his ‘free running’ circadian rhythm settled to around 25 hours. just beyond the usual 24 hours. this shows the power of the suprachiasmatic nucleus because even without external cues he was able to maintain an almost accurate circadian rhythm. but because it was 25 hours it does show that our circadian rhythm adapts to light levels and exogenous zetigebers

2. Aschoff and Wever:

asked a group of participants to spend 4 weeks in a WW2 bunker where they were shielded from natural light, temperature changes or other environmental cues. they had access to artificial light which they could switch on or off. similarly to siffre, they displayed a circadian rhythm of 25 hours. these studies suggest the ‘natural’ sleep/wake cycle may be slightly longer than 24 hours but we use natural light to adjust out pacemakers

3. Simon Folkhard:

studied a group of 12 participants who agreed to live in a dark cave for 3 weeks, isolating them from natural light. the researchers manipulated the clock. participants would retire when the clock read 11:45pm and awoke when it read 7:45am. over the course of the study the researchers sped up the clock (unbeknownst to participants) so what they believed was a normal 24 hour day was in fact only lasting 22 hours. only one participant could comfortably adjust to the new regime. this suggests the existence of a strong free running circadian rhythm that cannot be easily overridden by changes in the external environment.

evaluations of research for the circadian rhythm

1. sample sizes and generalisation - the research often involves small groups of participants or only one individual. the people involved may not be representative. this therefore limits the degree to which meaningful generalisation can be made and applied to the wider population

2. confounding variables - although the participants in Aschoff and Wever’s study were deprived of natural light, they still has access to artificial light. siffre would turn on a lamp every time he woke up which remained on until he went to bed. it was assumed that artificial light would have no effect on his free running circadian rhythm. however, other research by Czeisler 1999, suggests the opposite, that artificial light can have an influence. this means that the use of artificial light could have been a confounding variable and affected the validity of the results

3. individual differences - linked with generalisation is that individual cycles can vary, some people have a natural preference for going to bed early and rising early whereas others prefer the opposite. there are also age differences in sleep/wake patterns. thus, individuals seem to have innate differences in their cycle length and onset and these individual differences can further complicate generalisation

4. practical applications to shift work - research has provided a better understanding of the consequences of disrupted circadian rhythms i.e. shift work. night workers can experience reduced concentration around 6am, making mistakes and accidents more likely. poor health has been linked to night shifts. this highlights economic implications and how changes in shift work patterns could help workers stay healthy and manage productivity

research supporting the SCN - Ralphs hamster study

Martin Ralph removed and transplanted the SCNs from hamsters and shows support to the importance of the SCN as an endogenous pacemaker.

mutant hamsters were bred so that they had a circadian rhythm of 20 hours rather than 24. the SCN cells from these abnormal hamsters were transplanted onto the trains of normal hamsters with a 24 hour circadian rhythm. these normal hamsters began to adopt the same abnormal circadian rhythm as their 20 hour donor.

furthermore, when hamsters with nocturnal patterns of activity had their SCNs replaced with SCNs from mutated hamsters which slept through the night and were active during the day (unusual), the hamsters followed the nee daytime activities of the donor’s patterns. further evidence from lesioning the SCN in rats showed a complete disruption to the animals sleep/wake cycle

this suggests the tranplanted SCN had imposed its pattern onto the hamsters and shows the significance of the SCN and how endogenous pacemakers are importance for biological rhythms

research supporting exogenous zeitgebers: Campbell and Murphy 1998

a study by Campbell and Murphy showed that light may be detected by skin receptor sites on the body, even when the same information is not received by the eyes. 15 participants were woken at various times and a light pad was shone on the back of their knees. the researchers found a change in their sleep/wake cycle of up to 3 hours in some cases

this suggests that light is a powerful exogenous zeitgeber that doesn’t need to rely on the eyes to exert influence on the brain

evaluations for SCN and exogenous zeitgebers

1. ethics in animals studies - generalising findings from animal studies to humans is questionable. the hamsters were harmed during the study

2. methodological issues in research - the findings from Campbell and Murphy’s study have yet to be replicated. critics have suggested that participants may have been exposed to a limited amount of light to their eyes which would be a major confounding variable and affect the validity of the results

infradian rhythms: the menstrual cycle

infradian rhythms have cycles longer than 24 hours. the best example is the female menstrual cycle because it occurs monthly. the cycle begins the first day of the persons period, when the womb lining sheds, to the day before their next period. the ‘average’ cycle takes about 28 days to complete however it varies with each person

being a biological rhythm the menstrual cycle is governed by changes in hormones. one of the most important hormones is oestrogen and this is at its highest around half way through the cycle during ovulation. at this point an egg is released from the ovary. after ovulation, another hormone called progesterone also increases in preparation for the possible development of an embryo and this ‘preparation’ is the womb lining starting to thicken with blood, getting the womb ready for pregnancy.

if pregnancy doesn’t occur the egg is absorbed back into the body, the lining of the womb sheds, and this is the menstrual flow.

the menstrual cycle is governed by internal factors (endogenous pacemakers) such as hormonal changes, research suggests that they can be heavily influenced by exogenous zeitgebers

research supporting the infradian rhythm

1. Reinberg (1967) conducted a study where one female participant spent three months in a cave with only light from a small lamp. reinberg noted that her menstrual cycle shortened from the usual 28 days to 25.7 days. this suggests that the lack of light (an exogenous zeitgeber) affected the woman’s menstrual cycle, and therefore demonstrates the effect of external factors on infradian rhythm

2. McClintock and Stern (1998):

• aim: to show that the menstrual cycle is influenced by pheromonal secretions from other women

• sample: 29 female university students, not taking birth control pills

• design: a longitudinal experiment with independent measures

• method: samples of pheromones were gathered from 9 of the women at different stages of their menstrual cycle, via a cotton pad placed under their armpit. the pads were worn for at least 8 hours to ensure pheromones were picked up. the pads were treated with alcohol and frozen (to eliminate bacteria). this was the control group.

  the odour from these pads were inhaled by the other 20 women (experimental group) by being rubbed on their upper lip. on day 1, pads from the start pf the cycle were applied to the 20 women, on day 2 they were given pads from the second day of the cycle, and so on.

• results: when the experimental group inhaled secretions from women who were about to ovulate, their menstrual cycles became shorter. when they inhaled secretions from women who had just ovulated, their cycles became longer. the experimental groups’ menstrual cycles were affected by the secretions form the control group. on 68% of occasions the recipients of the sweat donation had experienced changes to their cycle which brought them closer to their ‘odour donor’ (synchronised)

• conclusion: this possibly explains why when a group of women live in close proximity their menstrual cycles tend to synchronised and provides support for the role of exogenous zeitgebers (pheromones) in infradian rhythms

evaluation of the infradian rhythm

1. methodological limitations - McClintock’s research has criticisms that suggest there are numerous factors other than pheromones that could change a woman’s cycle, such as stress, diet, exercise etc. that may act as confounding variables. furthermore, research involves small samples of women and relies on women self-reporting the onset of their own cycle. therefore, these other factors both methodological and individual differences make the influence of pheromones on infradian rhythms questionable

2. replication - recent replication of research between woman’s cycles in close proximity has failed to find evidence of menstrual synchrony suggesting reduced reliability

3. evolutionary approach - evolutionary psychologists suggest a possible reason for women’s menstrual cycles synchronising is that it provides an evolutionary advantage for groups of women - in other words the synchronisation of pregnancies means that childcare can be shared among multiple mothers who have children at the same time due to a couple of reasons, firstly, women lactating at the same time and secondly, through the release of oxytocin - mothers are able to bond to babies. therefore, these factors mean that ultimately synchronisation of women’s menstrual cycles will enhance survival

4. application - some research has shown that differing levels o hormones during the menstrual cycle may lead to differences in performance in different exercises.
   typically, during the first half of the cycle, elevated oestrogen creates a good environment for high intensity training. recovery is quicker and motivation to train can become higher. research shows that when strength training is performed more frequently in the first half of the cycle and less in the second half, strength gains are between 14-40% greater than when strength training is distributed evenly across the cycle.
   during the second half of the cycle, the oestrogen and progesterone are elevated, an athletes core temperature will rise, meaning they can feel warmer during exercise. and as the athletes metabolism favours using fat as fuel, lower intensity aerobic training is most suitable. high progesterone levels can influence to neurocircuitry of the brain and sometimes affect coordination. but it can also relieve anxiety and promote good sleep, making it a good time to build in recovery from training. these hormone shifts explain why training schedules designed for men may not be suitable for female athletes. for female athletes, understanding their cycle and finding effective strategies to manage symptoms can reduce the number of days off or sessions when the quality of training is poor.

ultradian rhythms: the cycle of sleep

these occur less than 24 hours and a good example are the stages of sleep. a typical nights sleep takes you from stages 1 to 4 the back to 2 and finally to REM. one sleep cycle typically lasts about 90 minutes and during a typical night’s sleep we will repeat this cycle 4 or 5 times, although the cycles differ through the night.

sleep stages:

• stages 1 and 2 are ‘light sleep’ stages: brain patterns become slower, starting with alpha waves, progressing to theta waves

• stages 3 and 4 are ‘deep sleep’ associated mainly with delta waves

• stage 5 (REM sleep). the body is paralysed to prevent acting out our dreams. the eyes rapidly move from side to side (rapid eye movement - REM). the brain activity resembles a person who is awake

• stages 1-4 are NREM stages (non REM)

• stage 5 is REM stage

• on average the entire cycle repeats every 90 minutes and a person may have 4 or 5 full cycles per night

sleep cycle

looking at the table attached, on the y-axis we have the stages of sleep, on the x-axis are the hours of sleep

• as we fall asleep we enter stage 1 which is high frequency and low amplitude sleep

• as we progress through stages 1-4 sleep becomes deeper. stage 4 sleep is characterised by delta waves and is the deepest sleep stage, its difficult to wake up at this point. heart rate and blood pressure fall and muscles are very relaxed. we are in stage 4 for about 30 minutes

• we’ve been asleep for about an hour all together. then we start to ascend back through these stages in reverse order, after just over an hour, we enter REM sleep

• this completes one cycle

there are significant individual differences between people so each sleep cycle will differ. sleep cycles also differ with age

research evidence for the sleep stages and REM

1. dement and Kleitman

   • aim: the aim of this lab experiment was to investigate the relationship between eye movements and dreaming

   • method: the nine participants were seven adult males and two adult females. the participants were studied under controlled lab conditions.. participants had to report to the lab at bedtime where they were connected to an EEG. the EEG took measurements throughout their time asleep all night. P’s were asked not to drink caffeine

   • results: the results show that REM sleep is predominantly associated with dreaming and NREM sleep is associated with periods of non-dreaming. P’s were able to recall dreams when awakened during REM periods. if awakened in any other stages they were less likely to report dreaming

   • conclusions: from these findings (which are reliable) it can be said the stages of sleep follow a pattern throughout the night. dreams mostly occur during REM. participants did on average go into REM every 90 minutes but there were still individual differences

2. dement:

compared participants who had been deprived of REM sleep with a control group who had been deprived of the same amount of NREM sleep. he found that the REM deprived group were more irritable, more aggressive and unable to concentrate on various tasks. Borbely found that REM deprived individuals made 31 attempts to re-enter REM on the first night of deprivation, 51 attempts on the second night and over 60 attempts on the third night. dement and borbely’s research suggests that REM is a distinct and significant stage of the ultradian rhythm and is important for our psychological wellbeing

3. in 1964, randy Gardner remained awake for 262 hours. while he experienced numerous problems such as blurred vision and disorganised speech, he coped incredibly well despite his significant sleep deprivation. after his experience, he slept for just 15 hours and over several nights recovered only 25% of his lost sleep. he recovered about 70% of stage 4 sleep, 50% of his REM sleep and very little of the other stages. these results suggest the wide degree of flexibility in terms of the different stages within the sleep cycle and the variable nature of this ultradian rhythm

evaluation of the ultradian rhythm

1. individual differences - a significant problem when studying sleep cycles is the differences observed in people. this can be seen in dement and kleitmans research. Tucker et al also found differences in participants in terms of the duration of each stage, particularly stages 3 and 4 (NREM). these research suggest there may be innate individual differences in ultradian rhythms which means its worth focusing on these differences during investigations into sleep cycles

2. lack of ecological validity - sleep cycles are usually investigated with a higher degree of control in sleep labs. participants will wear caps with electrodes to monitor EEG patterns and asked to sleep and then be woken up at various points during their cycle. this is both invasive for the participant as well as being very artificial and may lead them to sleep in a way that doesn’t represent their ordinary sleep cycle. this lack of ecological validity could lead to false conclusions being applied to out understanding of sleep cycles

3. flexible - randy garners experience of remaining awake for 264 hours and subsequently recovering 70% of stage 4 and 50% of his REM sleep and little of other stages. this suggests the degree of flexibility interns of the different stages may not be as fixed as psychologists believed. however, we should consider that garners results could be unique to him, for example an older individual; may have very different results in the sleep they recovered. this means generalisation of such specific cases could be difficult to the wider population