Biopsychology: The Brain (L6-10) Flashcards
What is localisation of function?
- refers to the principle that functions
- e.g. vision, hearing, memory, etc, have specific locations within the brain
What is contralateral organisation, LoF?
- hemispheres of the cerebrum mainly represent the opposite side of the
body - known as contralateral organisation
- e.g. the left hemisphere of the cerebrum controls movement, sensations and visual and auditory processing on the right side of the body and vice versa
What are the different areas of the brain, LoF?
- motor cortex
- somatosensory cortex
- visual cortex
- auditory cortex
- Broca’s area
- Wernicke’s Area
What does the motor cortex do?
- responsible for voluntary movements
- located in the frontal lobe of BOTH brain hemispheres
- different parts of the motor cortex control different parts of the body
- these areas are arranged logically next to one another
- damage to this area can cause a loss of
muscle function/paralysis in one or both sides of the body - depends on which hemisphere/hemispheres have been affected
What does the somatosensory cortex do?
- responsible for processing sensations such as pain and pressure
- is located in the parietal lobe of BOTH hemispheres
What does the visual cortex do?
- processes information such as colour and shape
- is in the occipital lobe of BOTH hemispheres of the brain
- visual processing starts in the retina where light enters and strikes the
photoreceptors - nerve impulses from the retina are transmitted to the brain via the optic nerve
- majority terminate in the thalamus, which acts as a relay station, passing the information onto the visual cortex
What does the auditory cortex do?
- processes information such as pitch
and volume - lies within the temporal lobe in BOTH hemispheres of the brain.
- auditory pathway begins in the cochlea in the inner ear
- where sound waves are converted to nerve impulses
- which travel via the auditory nerve to the auditory cortex
- basic decoding occurs in the brain stem
- the thalamus carries out further processing before impulses reach the auditory cortex
What does Broca’s Area do?
- area is named after Paul Broca who treated patients who had difficulty producing speech
- found that they had lesions to the LEFT
hemisphere of the frontal lobe - damage to the Broa’s Area causes Expressive Aphasia
- disorder affects language production but NOT understanding
- speech lacks fluency and patients have difficulty with certain words which help
sentences function like ‘it’ and ‘the’
What does Wernicke’s Area do?
- area is in the LEFT hemisphere of the temporal lobe
- Carl Wernicke found that patients with a lesion to this area could speak but
were unable to understand language - Wernicke concluded that this area is
responsible for the processing of spoken language - Wernicke Area is connected to the Broca’s Area by a neural loop
- damage to the Wernicke’s Area causes Receptive Aphasia
- disorder leads to an impaired ability to
understand language
Localisation of function, -ve evaluation:
no +ve
- some functions are more localised than others
- motor and somatosensory functions are highly localised to specific areas of the cortex
- higher functions, e.g. personality and consciousness, are much more widely distributed
- functions such as language are too complex to be assigned to just one area - instead involve networks of brain regions
- although some components of
language, such as speech production, may be localised, Broca’s Area
= equipoteniality theory (Lashley, 1930)
= holds that higher mental functions are
not localised
= theory also claims that intact areas of the cortex take over responsibility for a specific cognitive function following injury to the area normally responsible
- Dronkers et al. (2007) re-examined the preserved brains of two of Broca’s
patients
- MRI scans revealed that several areas of the brain had been damaged
- lesions to the Broca’s Area cause temporary speech disruption
- they do not usually result in severe disruption of language
- language is a more widely
distributed (and less localised) skill than originally thought
= may be that how brain areas communicate with each other is more
important than specific brain regions
= Dejerine (1892) reported a patient who
could not read because of damage between the visual cortex and Wernicke’s area
- Bavelier et al. (1997) found that there are individual differences in which
brain areas are responsible for certain functions
- found that different brain areas are activated when a person is engaged in silent reading
- observed activity in the right temporal lobe, left frontal lobe and occipital
lobe
- means that the function of silent reading does not have a specific
location within the brain
What is hemispheric lateralisation?
- refers to the notion that certain functions are principally governed by one side of the brain
What is the main function of the right hemisphere?
- dominant for visuo-spatial functions and facial recognition
What is the main function of the left hemisphere?
- demonstrated that in most people language centres are lateralised to the left hemisphere
- Broca’s Area was thought to be
responsible for the production of speech - however, this is now thought to
involve a wider network than just the Broca’s Area - damage to the Broca’s Area leads to expressive aphasia
- Wernicke’s Area is considered to play a
vital role in understanding language/interpreting speech - damage to the Wernicke’s Area leads to receptive aphasia
How are the 2 hemispheres connected?
- connected by a bundle of nerve fibres known as the corpus callosum
- enables information to be communicated between the two hemispheres
- many researchers suggest that the two hemispheres work together to form most tasks as part of a highly integrated system
Hemispheric lateralisation, +ve evaluation:
- makes sense from an evolutionary perspective
- increases neural processing capacity, which is adaptive
- using one hemisphere to engage in a particular task it leaves the other hemisphere free to engage in another function
- Rogers et al. (2004) found that hemispheric lateralisation in chickens is associated with an ability to perform two tasks simultaneously
- finding food and being vigilant for
predators
= patients who have extensive damage to their left hemisphere can experience
global aphasia (loss of speech production and speech comprehension)
= this suggests that language is lateralised to the left hemisphere
Hemispheric lateralisation, -ve evaluation:
- lateralisation patterns shift with age (Szaflarski et al 2006) with most tasks
generally becoming less lateralised in healthy adulthood
= JW (a split-brain patient) developed the capacity to speak using his right
hemisphere
= they could speak about information presented in either the left visual field or the right visual field, although he was more fluent if information was presented in the left
= would appear that language is not lateralised entirely to the left hemisphere - if one hemisphere is damaged, undamaged regions on the opposite hemisphere can compensate
- Danelli reported case of EB
- 17y/o Italian boy w entire left hemisphere removed at the age of
two and a half due to a huge benign tumour - EB’s language appeared almost
normal in everyday life in terms of vocabulary and grammar - but systematic testing revealed subtle grammatical problems as well as poorer than normal scores on picture naming
- and reading of loan words, words adopted from another language e.g. café
- language function can be largely preserved after removal of the left hemisphere in childhood
- but the right hemisphere cannot
provide, by itself, a perfect mastery of each component of language
What are split brain patients?
- in the past surgeons have cut the corpus callosum
- in order to prevent the violent electrical activity caused by epileptic seizures crossing from one hemisphere to the other
- patients who underwent this form of surgery are often referred to as split-brain patients
What is the issue with split brain patients?
- Sperry and Gazzaniga investigated SB patients, dot and dog tests
- information from the left visual field goes into the right hemisphere
- whereas information from the right visual field goes into the left hemisphere
- in split-brain patients the corpus callosum has been severed
- there is no way for the information presented to one hemisphere to travel to the other
How to investigate SB patients, dot?
- patients are asked to stare at a dot in the centre of a screen
- then information is presented in either the left or right visual field
- they are then asked to make responses with either their left hand (right hemisphere), right
hand (left hemisphere) - or verbally (left hemisphere)
- without being able to see
what their hands were doing
How to investigate SB patients, dog/cat?
- may be flashed an image of a dog in their right visual field and then asked what they have seen
- they will be able to answer ‘dog’ because the information will have gone into their left hemisphere where the language centres are
- if a picture of a cat is shown in their left visual field and they are asked what they have seen
- they will not be able to say because the information has gone into their right hemisphere, which has no language centres
- but they can draw a picture of a cat with their left hand because the right hemisphere controls
this hand
Split brain research, +ve evaluation:
- experiments on split-brain patients are highly controlled and scientific
Split brain research, -ve evaluation:
- disconnection between the hemispheres was greater in some patients than others
= some split-brain patients have experienced drug therapy for much longer than others - comparison groups were not considered to be valid as they were often people with no history of epileptic seizures
= many studies using split-brain patients have as few as three participant
= making it hard for results to be generalised to the target pop - data from this research is very artificial
- in real world a severed corpus callosum can be compensated for by the unrestricted use of both visual fields
- means the research lacks ecological validity
What is brain plasticity?
- ability of the brain to modify the structure and function
based on experience - allows the brain to cope better with the indirect effects of brain
damage - such as swelling or haemorrhage following a road accident
- or the damage resulting from inadequate blood supply following a stroke
Brain plasticity, +ve evaluation:
no -ve
- Kuhn et al. (2014) found a significant increase in grey matter in the hippocampus, visual cortex and cerebellum of the brain after participants
played video games for 30 minutes a day over a two-month period
= Davidson et al. (2004) 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 students who had no experience of meditation
- Maguire et al. (2000) found that the posterior hippocampal volume of London Taxi drivers’ brains was positively correlated with their time as a taxi driver
- there were significant differences between taxi drivers’ brains and those of a control group
what is functional recovery?
- where the brain recovers abilities previously lost due to
brain damage - is an example of plasticity
- research suggests that young
brains are more plastic - however, the brain is capable of plasticity and functional recovery at any age
- studies have suggested that women recover from a brain injury quicker than men do
What processes does functional recovery involve?
- neuronal unmasking
- neural reorganisation
- neural regeneration
What is neuronal unmasking, FR?
- dormant synapses are activated to compensate for damaged areas of the brain
- structural changes support neuronal unmasking
- such as axon sprouting, when undamaged axons grow new
nerve endings to reconnect the neurons whose links were severed by damage thus making new neural pathways - reformation of blood vessels, facilitates the growth of new neural pathways
- and recruitment of homologous areas, the intact hemisphere takes over the functions of the
damaged hemisphere
What is neural reorganisation, FR?
- transfer of functions from damaged areas of the brain to undamaged ones
- neural reorganisation is greater in children than in adults
What is neural regeneration, FR?
- growth of new neurons and/or connections, axons and dendrites
- to compensate for damaged areas
How does recovery work, FR?
- full recovery is not passive
- it depends on the extent of the damage and on various internal and external factors over time
- spontaneous recovery from a
brain injury tends to slow down after a number of weeks so treatment like physiotherapy - may be required to maintain improvements in functioning
Functional recovery, +ve evaluation:
- has practical applications to the field of neurorehabilitation
- understanding the processes of functional recovery has led to the development of techniques such as motor therapy
- and electrical stimulation of the brain to counter the negative effects and deficits in motor
and cognitive functions - following accidents, injuries and strokes
Functional recovery, -ve evaluation:
- variable factors affect recovery after trauma
- research found that those
with a university education recover better from a brain injury - going to university provides a cognitive reserve
- age is another important factor
- Elbert et al. (2014) concluded that the capacity for neural
reorganisation is much greater in children than in adults - gender also has an impact, women are more likely to recover from a brain injury than men
- physical exhaustion/stress/alcohol can all impair functional recovery
How can the brain be studied?
- post mortem examinations
- fMRI, functional magnetic resonance imaging
- EEG, electroencephalogram
- ERP, event related potentials
What are post mortem examinations?
- psychologist may study a person who displays an interesting behaviour while
they are alive - when the person dies, the psychologists look for abnormalities in the brain that might explain their behaviour
- post-mortem studies have found a link between brain abnormalities and psychiatric disorders
- e.g. there is evidence of reduced glial cells in the frontal lobe of patients with depression
What is fMRI?
- provides an INDIRECT
measure of neural activity - uses magnetic fields and radio waves to monitor blood flow in the brain
- measures the change in the energy released by haemoglobin, reflecting activity of the brain (oxygen consumption)
- gives a moving picture of the brain
- activity in regions of interest can be compared during a base line task and during a specific activity
Post mortem examinations evaluation:
1+ allow for more detailed examination of anatomical and
neurochemical aspects of the brain than would be possible with other methods of studying the brain
+ have enabled researchers to examine deeper regions, such as the hippocampus and hypothalamus
1- may lack validity as people die in a variety of ways and at varying stages of disease
- also length of time between death and the post-mortem, and drug treatments, can all affect the
brain
2- very small sample sizes, as special permission needs
to be granted
- means the sample cannot be said to be representative of
the target population
- so it is problematic to generalise the findings to the wider population
fMRI evaluation:
1+ captures dynamic brain activity as opposed to a post-mortem examination which purely show the physiology of the brain
2+ have good spatial resolution, refers to the smallest feature that a measurement can detect
1- interpretation is complex and is affected by poor temporal
resolution, biased interpretation, and by the base line task used
2- research is expensive leading to reduced sample sizes which negatively impact the validity of the research
What are EEGs?
- electroencephalogram DIRECTLY measures GENERAL neural activity in the brain
- usually linked to states such as sleep and arousal
- electrodes are placed on the scalp and detect neuronal activity directly below where they are placed
- differing numbers of electrodes can be used depending on focus of the research
- when electrical signals from the different electrodes are graphed
over a period of time, the resulting representation is called an EEG pattern - EEG patterns of patients with epilepsy show spikes of electrical activity
- EEG patterns of those with brain injury show a slowing of electrical activity
EEGs evaluation:
1+ EEG is useful in clinical diagnosis
+ it can record the neural
activity associated with epilepsy so that doctors can confirm the person is experiencing seizures
1- cheaper than an fMRI so can be used more widely in research
2- have poor spatial resolution
What are ERPs?
- electrodes are placed on the scalp and DIRECTLY measure neural activity, below where they are placed
- this is in response to a SPECIFIC stimulus introduced by the researcher
- event-related potentials are difficult to pick out from all the
other electrical activity being generated within the brain - establishing a specific response to a target stimulus requires many presentations of this
stimulus - responses are then averaged together
- any extraneous neural activity that is not related to the specific stimulus will not occur consistently, whereas activity linked to the stimulus will
ERPs evaluation:
1+ can measure the processing of a stimulus even in the absence of a behavioural response
+ it is possible to measure ‘covertly’ the processing of a stimulus
2+ cheaper than an fMRI so can be used more widely in research
3+ have good temporal resolution, unlike fMRI
1- poor spatial resolution, unlike EEG
2- only sufficiently strong voltage changes generated across the scalp are recordable
- important electrical activity occurring deeper in the brain is not recorded
- generation of ERPs tends to be restricted to the neocortex
