Biopsychology

The Brain
1. Localisation- the theory that specific areas of the brain are associated with particular physical and psychological functions.
  1. Peterson et al- used brain scans to show activity in Wernicke's area during a listening task and in Broca's area during a reading task, supporting that these different areas have different functions. Additionally, tulving found that semantic and episodic memories are located in different parts of the frontal cortex. These support localisation.
    1. Unique cases of neurological damage support localisation theory, such as Phineas Gage. Gage survived, but suffered severe damage to his brain after a metal rod shot through his cheek and frontal lobe during a work accident. His personality changed, going from someone who was calm and reserved, to someone who was quick-tempered and rude. Suggests frontal lobe is responsible for regulating mood.
      1. Lashley- suggests higher cognitive functions are not localised but distributed holistically. Lashley removed between 10% and 50% of the cortex in rats. No one area was more important than any other in terms of the rats' ability to learn a maze. As learning required every part of the cortex, this suggests it is too complex to be localised.
        Neural plasticity challenges localisation. When the brain has become damaged and a function has been lost, the rest of the brain is able to reorganise itself to recover the function. Although this does not happen every time, there are several case studies of stroke victims who have shown functional recovery.
2. Lateralisation- The dominance of one hemisphere of the brain for particular physical and psychological functions.
  1. Szaflarski et al found that language became more lateralised to the left hemisphere with increasing age in children and adolescents, but after 25, lateralisation decreased with each decade of life. This implies there are individual differences.
  2. Sperry sought to demonstrate that the two hemispheres were specialised for certain functions and perform tasks independently from one another. Normally the hemispheres are connected by the corpus callosum. An operation to cut this is sometimes performed to control epileptic seizures.
    1. Epileptics were studied who had had the operation. An image or word was projected to a patients RVF and another image to the LVF. In the normal brain, the corpus callosum 'shares' this information between hemispheres, but this cannot happen in a split brain. The object in the RVF was easily described by the patient. However they couldn't say what was in the LVF. This shows how the right hemisphere lacks language centres and was unable to pass the information onto the LH. Patients could select matching and associated objects/images with the object in the LVF using their left hand. Yet they still could not verbally identify what they were seeing.
    2. Sperry used a careful standardised procedure; presenting visual information to one hemispheric field at a time. An image was flashed up for 0.1 seconds, giving no time for them to move their eyes over the image and spread the information across both visual fields/sides of the brain. This gives the study high internal validity.
      1. Roland Pucetti suggested that the two hemispheres are so functionally different that they represent a form of duality in the brain (we are two minds) and this is only emphasised by a split brain patient). Others have argued the two hemispheres are highly integrated and work together in most tasks. This shows Sperry's work is prompting a complex debate
      2. The findings cannot be widely generalised, as split-brain patients are such an unusual sample of people. Only 11 patients took part in all variations of Sperry's research, and all had a history of seizures. This may have caused unique changes in the brain that influenced the findings. Cannot apply to normal brains
3. Motor Cortex
  1. Responsible for the generation of voluntary motor movements. Different parts of the motor cortex exert control over different parts of the body. These regions are arranged logically next to one another e.g. region responsible for hand is next to region for arm.
  2. Found in the rear of the frontal lobe (along the precentral gyrus). Both hemispheres have a motor cortex which controls the movement of the opposite side of the body.
4. Auditory store
  1. This area processes speech-based information. If damaged, it may produce partial hearing loss.
  2. It is located in the front of the temporal lobe and is found in both hemispheres.
5. Broca's area
  1. Named after Paul Broca, who looked at the case study of Tan. Tan could understand spoken language however could not communicate back- tan had a lesion in his left frontal hemisphere. Broca found that those with a lesion in their right hemisphere, did not have a speech difficulty. This led him to identify the existence of the language centre in the frontal lobe of the left hemisphere.
  2. A lesion here would mean patients can understand language but cant speak it.
6. Wernicke's area
  1. It is located in the left temporal lobe. A lesion here would mean patients can speak but are unable to understand language.
    1. Named after Carl Wernicke. He proposed that language involved separate motor and sensory regions located in different regions. The motor region, located in Broca's area, is close to an area that controls the mouth, tongue and vocal cords. The sensory region located in Wernicke's area, is close to the regions of the brain responsible for auditory and visual input. Input is thought to be transferred to the Wernicke area where it is recognised as language associated with meaning.
7. Somatosensory Cortex
  1. Detects sensory events arising from different regions of the body. Uses information from the skin to produce sensations of touch, pressure, pain and temperature.
  2. It is located in the parietal lobe, along region known as the postcentral gyrus. This area is dedicated to the processing of sensory information related to touch. It is found in both hemispheres.
8. Visual Cortex
  1. Visual processing begins in the retina , nerve impulses are then transmitted to the brain via the optic nerve. This information terminates in the visual cortex. The visual cortex contains several different areas, with each of these processing different types of visual information, such as colour, shape and movement.
  2. Found in the Occipital lobe of the brain, spans both hemispheres, with opposite sides processing opposite sides of the visual field.
9. Holistic distribution- The idea that all areas of the brain communicate and work together to produce a specific action/response.
  1. Plasticity- The brain's tendency to change and adapt (functionally and physically) as a result of experience and new learning.
    1. .Functional recovery- A form of plasticity. Following damage through trauma, the brains ability to redistribute or transfer functions usually performed by a damaged area to other, undamaged areas.
      1. The brain is able to rewire and reorganise itself by forming new synaptic connections close to the area of damage. Secondary neural pathways that would not typically be used to carry out certain functions are activated or 'unmasked' to enable functioning to continue.
        Axon sprouting- growth of new nerve endings which connect with other undamaged calls to form new neuronal pathways.
    2. During infancy, the brain experiences rapid growth in synaptic connections, peaking at about 15000 at 2-3. As we age, rarely used connections are deleted and frequently used ones are strengthened- cognitive pruning. It was thought that this does not happen in adulthood, but recent research has challenged this.
      1. Eleanor Maguire et al studied the brains of London taxi drivers using MRI and found significantly more grey matter in the posterior hippocampus than the matched control group. This part of the brain is linked with the development of spatial and navigational skills. The longer they had been in the job, the more pronounced the structural difference
        Understanding processes involved in plasticity has contributed to medical research. Movement therapy and electrical stimulation of the brain are used to counter the cognitive functioning damage in stroke victims. This suggests the brain may have the capacity to 'fix itself' to a point.
        The brain's ability to rewire itself can have maladaptive behavioural consequences, for example, prolonged drug use can result in poorer cognitive functioning and risk of dementia.
        Hubel and wiesel sewed one eye shut on a kitten and analysed the brain's cortical responses. The area of the visual cortex associated with the shut eye was not idle but continued to process information from the open eye. Demonstrates how loss of function leads to compensatory activity in the brain.
10. Hemispheres
  1. The corpus callosum is a bundle of nerve fibres located between the left and right hemispheres. It connects the two halves to allow for communication. If this were to be cut, there would be no communication between hemispheres.
  2. The nerve fibres that carry visual information from the eyes to the occipital cortex 'cross over' at a point called the OPTIC CHAISMA. Because they cross over, all information from the RVF is carried to the LEFT HEMISPHERE and all information from the LVF is carried to the RIGHT HEMISPHERE.
    1. This has implications for split brain patients- since without communication between the hemispheres, each will only 'see' images from one visual field.
Scientific methods
1. Post-mortem examinations
  1. Used to establish the underlying neurobiology of a particular behaviour. E.g. a person who displays an interesting behaviour while they're alive may suggest underlying brain damage. Researchers can examine their brains to look for abnormalities that may explain their behaviour.
    1. + provided the foundation for understanding the brain. Broca and Wernicke relied on post-mortem studies. They are able to be intrusive and split up the brain since the person is dead.
    2. - causation may be an issue. observed damage may not be linked to the deficits under review but to some other trauma or decay. They also raise ethical issues of consent from the patient before death.
2. Electroencephalogram (EEG)
  1. An EEg measures electircal activity in the brain. Electrodes are placed on the scalp to detect small electrical charges resulting from the activity of brain cells. These signals are graphed over a period of time.
    1. + invaluable in diagnosing conditions such as epilepsy, and understanding the stages of sleep. It also has extremely high temporal resolution, detecting brain activity in a single millisecond.
    2. - information is recieved from many thousands of neurons, producing a generalised signal. It is difficult to know the exact source of the neural activity.
  2. EEG data can be used to detect various types of brain disorder (such as epilepsy) or to diagnose other disorders that can influence brain activity. The four basic patterns are alpha, beta, theta, delta waves.
3. Functional magnetic resonance imaging (fMRI)
  1. Technique for measuring changes in brain activity while a person performs a task. It does this by measuring changes in blood flow in a particular area of the brain, which indicates neural activity. It measures blood flow using radio waves and a magnetic field.
  2. If an area of the brain becomes more active, there is an increased oxygen level in that area. The brain responds by increasing blood flow. As a result of this, researchers are able to produce maps showing which areas of the brain are involved in what activity.
  3. + Non-invasive. Does not rely on the use of radiation and is safe. It also produces images with high spatial resolution , showing detail to the millimetre.
    1. - fMRI is expensive and can only capture a clear image if the person is completely still. There is also poor temporal resolution because there is a 5-second lag between activity and image.
4. Event related potentials (ERP)
  1. Although EEG has many ciinical and scientific applications , in its raw form it is too crude and general. However, it contains all the neural responses associated with a specific sensory, cognitive and motor events that may be of interest to cognitive scientists. ERP is a way of teasing out and isolating these responses using a statistical averaging technique, all extraneous brain activity is filtered out leaving only responses that relate to a specific stimulus (types of brainwave that are triggered by particular events).
    1. + ERPs are more specific than raw EEG data, making it more easy to apply to research. Also, they have excellent temporal resolution.
    2. - lack of standardisation in methodology between studies, making it difficult to confirm findings in studies with erps. Also, background noise must be completely eliminated and this may not be achievable.
5. Techniques for studying the brain are often used for medical purposes in the diagnosis of illness. The purpose of scanning in psychological research is often to investigate localisation.
Biological rhythms
1. A biological rhythm is a pattern or cyclical variation over some period of time in physiological or psychological processes.
  1. Circadian rhythms- Repeats every 24hrs. I.e Sleep-waking cycle.
    1. The Sleep-wake cycle is an example of a circadian rhythm. It is governed by external and internal mechanisms. Exogenous zeitgebers- the fact we feel drowsy when its night and alert when its day shows the effect of daylight. Endogenous pacemakers- our biological clock 'left to its own devices' that makes us feel sleepy or alert.
      1. Siffre- Spent 6 months in a cave with no natural sounds or light. He has basic supplies and contact to the outside world by telephone. In these conditions, his physiology and behaviour remained cyclical, but his day was 25 rather than 24 hours long. This suggests the influence of some internal pacemaker, however exogenous zeitgebers play a role in synchronising this cycle to 24hrs.
        Aschoff and wever found a similar circadian rhythm- a group of participants spent four weeks in a WWII bunker, deprived of natural light. All but one (whose sleep/wake cycle extended to 29 hrs) displayed a rhythm of between 24 and 25 hrs.
        Practical application to shift work. Boivin found shift workers experience a lapse of concentration around 6am (circadian trough), where mistakes and accidents were more likely. Thus research into the sleep/wake cycle may have economic implications in terms of how best to manage worker productivity.
        Research shows there are times during the day or night when drugs are more effective. Guidelines have been developed for the timing of dosing for a range of drugs including treating cancer and epilepsy.
      2. Luce and Segal- individuals who live in arctic regions show normal sleep patterns despite the prolonged exposure to light.
      3. There is a basic rhythm governed by the SCN, which lies just above the optic chiasm and receives info about light directly from it.
  2. Infradian rhythms- Rhythms that are longer than every 24hrs. I.e the menstrual cycle.
    1. Pituitary gland releases FSH and LH. These stimulate the ripening of an ovary and the release of oestrogen. The ruptured follicle then starts to release progesterone. Progesterone causes the lining of the uterus to prepare for pregnancy. If the ovum is not fertilised the progesterone levels decrease and the lining of the uterus breaks down and the female menstruates.
      1. Mclintock and stern- Had a number of women wear a pad under their arm to absorb their sweat. These were then given to other women to sniff. They found that 68% of participants experienced changes in their cycles to bring them closer to their 'odour donor'. Those who inhaled the secretions from women who were about to ovulate, found their menstrual cycles shortened. Those who inhaled secretions from women who had just ovulated, their cycles became longer.
        research into SAD has practical applications. Phototherapy has been produced, a light box that stimulates strong light in the morning and evening. This relieves symptom in up to 60% of sufferers.
      2. Evolutionary benefits. Advantageous for our ancestors to menstruate together and become pregnant at the same time, so that offspring could be cared for collectively, increasing chances for survival.
        Criticised for methodological issues. there may be other factors that change a woman's menstrual cycle and act as a confounding variable (e.g stress, diet). Meaning mcclintock and stern's findings could be down to chance. Also, relies on them self-reporting onset of their own cycle (may be inaccurate).
    2. Pheromones- Biological chemicals that act as exogenous zeitgebers for the menstrual cycle.
    3. Seasonal affective disorder is a depressive disorder with a seasonal pattern. During the night, melatonin is secreted until dawn when there is an increase in light. During winter, the lack of light in the morning means secretion goes on for longer. This has a knock-on effect on the production of serotonin in the brain.
  3. Ultradian rhythms- Rhythms that are shorter than 24hrs. I.e sleep.
    1. Psychologists have identified 5 distinct stages of sleep. These are cyclical and span approx. 90 mins, 5 times every 8 hours of sleep.
      1. Stage 1: Heart beat slows down, reduced muscle tension, eyes roll a little. Brain activity becomes slower (alpha waves) .
        Stage 2: EEG pattern becomes synchronised with slower theta waves, interrupted by fast spiking activity called sleep spindles.
        Stage 3: Large amplitude, very slow delta waves present. Sleep spindles less common.
        Stage 4: Purely all delta waves, metabolic rate reaches it's lowest.
        Stage 5: REM sleep. high frequency, small amplitude waves, similar to an awake person (beta). Lose all muscle tone except for the eyes.
    2. Dement and Kleitman- 7 males and 2 females reported to a laboratory at bedtime where they were connected to an EEG. Participants were asked not to drink caffeinated drinks for the day. Everyone had periods of NREM and REM every night. High incidence of dream recall when awakened from REM. Very few reported dreaming in NREM. Eye movement varied according to the dream type.
  4. These are governed by internal body clocks (endogenous pacemakers) and external changes in the environment (exogenous zeitgebers)
    1. Endogenous pacemakers- Internal body clocks regulating biological rhythms.
      1. The Suprachiasmatic Nucleus (SCN) is a tiny bundle of nerve cells located in the hypothalamus. It is one of the primary endogenous pacemakers in mammals and in influential in maintaining circadian rhythms. The SCN lies just above the optic chiasm and receives information about light directly from here. It enables our biological clock to adjust to changing patterns of daylight.
        Ralph et al. took the SCN out of genetically abnormal hamsters with a 20 hr circadian rhythm and transplanted them into normal hamsters. Their cycle shortened to 20 hrs in the normal hamsters. This showed that the SCN and no other brain structure was producing the cycle.
        Stephan and Zucker investigated the effect of damage to the SCN on circadian rhythms in rats. Damaged SCN in rats and compared them to normal controls. They found damage eliminated normal circadian patterns of drinking and activity.
        Research into the SCN may obscure other body clocks. Body clocks are found in many organs and cells (lungs, liver, skin...). They are highly influenced by the SCN but can act independently. Damiola showed how changing feeding patterns in mice altered circadian rhythms of cells in the liver, but did not affect the SCN. This suggests there may be other influences on the sleep/wake cylce aside from the SCN
      2. The pineal gland and melatonin- The pineal gland receives info from the SCN and increases the production of melatonin at night (a chemical that induces sleep).
    2. Exogenous Zeitgebers- External cues that regulate biological rhythms.
      1. Light- Can reset the body's main pacemaker, the SCN, and thus plays a role in the maintenance of the sleep/wake cycle. It also has an indirect influence on key processes in the body such as hormone secretion and blood circulation.
        Campbell and Murphy- participants were woken at various times and had a light shone on the backs of their knees. This produced a deviation in the sleep/wake cycle of up to three hours. This shows that light is a powerful exogenous zeitgeber that can be detected by skin.
        Their study has yet to be replicated and has been criticised because there may have been some light exposure to participant's eyes- major confounding variable. Isolating one exogenous zeitgeber in this way does not give insight into the many other ones that influence the sleep/wake cycle.
      2. Social cues- In infants, the initial sleep/wake cycle is pretty random. By about 16 weeks, most babies are entrained. The schedules imposed by parents are likely to be the key influence, including determined mealtimes and bedtimes.
Connections and systems
1. The nervous system
  1. The nervous system is a specialised network of cells and our primary communication system. It has two main functions: to collect, process and respond to information, and to coordinate the working of different cells and organs in the body.
    1. CNS
      1. Brain is the centre of all conscious awareness. The outer layer, the cerebral cortex, is highly developed and is what distinguishes our higher mental functions from animals. The spinal cord is an extension of the brain and is responsible for reflect actions. It passes messages to and from the brain.
    2. PNS
      1. The PNS transmits messages, via millions of neurons, to and from the nervous system. The PNS is further sub-divided into the autonomic and somatic nervous systems. The ANS governs vital, involuntary functions in the body such as breathing, heart rate and digestion. The SNS governs voluntary functions such as muscle movement.
        The ANS is further sub-divided into the sympathetic and parasympatheic systems. The sympathetic deals with the fight or flight response (energy output) and the parasympathetic deals with the rest and digest response (energy conservation).
2. The endocrine system
  1. The endocrine system works alongside the nervous system to control vital functions in the body through the action of hormones. It works much more slowly than the NS but has widespread, powerful effects.
    1. Glands
      1. Glands are organs in the body that produce hormones. The major endocrine gland is the pituitary gland, located in the brain. It is called the master gland because it controls the release of hormones from the other glands in the body.
    2. Hormones
      1. Hormones are secreted in the blood stream and affect any cell in the body that has a receptor for that particular hormone.
    3. The endocrine and ANS often work together, such as during fight or flight.
      1. When a stressor is perceived, the hypothalamus triggers the sympathetic NS, changing the ANS from normal resting state, to aroused state.
        The stress hormone adrenaline is released from the adrenal gland.
        Adrenaline triggers physiological changes such as increased heart rate, pupil dilation etc. to prepare the body to take action.
        Once the threat has passed, the parasympatheic NS returns the body to its resting state. Adrenaline production is stopped.
3. Neurons and synapses
  1. By transmitting signals electrically and chemically, neurons provide the nervous system with its primary means of communication.
  2. Motor neurons connect the CNS to effectors such as muscles and glands. They have short dendrites and long axons.
  3. Relay neurons connect sensory and motor neurons to each other. They have short dendrites and axons.
  4. Sensory neurons carry messages from receptors in the PNS to the CNS. They have long dendrites and short axons.
  5. When a neuron is in RESTING state the inside of the cell is NEGATIVELY charged compared to the outside. When a neuron is ACTIVATED, the inside of the cell becomes POSITIVELY charged, causing action potential to occur. This creates an electrical impulse that travels in the neuron.
  6. Signals within neurons are transmitted electrically; however, signals between neurons are transmitted chemically across the synapse. When the impulse reaches the presynaptic terminal, it triggers the release of neurotransmitters from vesicle sacs. Once it reaches the post synaptic receptor site on the next neuron, the message is converted back into electrical impulses.
    1. Neurotransmitters generally have either an excitatory or inhibitory effect on the postsynaptic neuron.
      1. Adrenaline- excitatory, increasing the positive charge of the ps-neuron, making it more likely to fire.
        Serotonin- inhibitory, increasing the negative charge of the ps-neuron, making it less likely to fire.
        Dopamine- unusual neurotransmitter, both excitatory and inhibitory effects.

Next up

Biopsychology

Description

Resource summary

Media attachments

Similar

	Created by Laura Louise about 9 years ago