biopsychology 2

with evaluation

name the 4 types of examination

1. post-mortem examination

2. fMRIs

3. EEGs

4. ERPs

what is a post-mortem examination?

dead person who had unusual characteristics in life is physically examined through anatomical and neurochemical examinsations

allows us to see the amount of neurotransmitters present when they died

name 2 strengths of post-mortem examinations

1. can provide access to areas others can’t

   detailed anatomical structure and neurochemical aspects

   access to hypothalamus and hippocampus- allows deeper understanding

   found patients with schizophrenia had more dopamine in the limbic system which prompted research into treatments using this

2. research into broca’s area

   the only word this man could say was ‘tan’

   when he did a post-mortem showed a tumour in his broca’s area which damaged it

   led to learning that speech is produced in the broca’s area which allowed for more research

name 2 limitations of post mortem examinations

1. hard to establish causation

   confounding variables make it hard to establish causation.

   e.g. age, cause of death, medication taken, time. between death and examination

   lack of function may not be due to deficits in the brain. deficits or lack of function could be due to other illnesses or have occurred during death

2. ethical issues

   mostly done on patients with severe psychological deficits like HM. they might not be able to give fully informed consent- e.g. HM might not be able to consent due to amnesia but one was still done
   counterpoint: even though they’re invasive, they patient is dead so it doesn’t matter

explain fMRIs

measures blood flow in the brain during specific tasks

neurons use more oxygen when doing a task, so oxygen in that area is reduced.

this changes the magnetism of that part of the brain

this creates a 3D image of the brain

name 2 strengths of fMRIs

1. non-invasive

   doesn’t involve radiation or cutting into the brain so they are harmless- unlike PET scans.
   they are risk free so more patients are likely to do it, which means more data to help understand the brain

2. good spatial resolution

   can be very specific and pick up small areas in the brain
   allows psychologists to discriminate between regions with greater accuracy

   1-2mm resolution- significantly greater than EEGs and ERPs

name 2 limitations of fMRIs

1. poor temporal resolution

   can’t detect very quickly- delay of 1-4 seconds between when you do something and when the scan picks it uo

   EEG and ERP have 1-10 milliseconds

   makes it harder to predict accurately the onset of brain activity

2. correlation not causation

   only scans blood flow so it’s impossible to infer causation at a neural level

   blood flow may indicate activity within brain area but we are unable to conclude that that’s definitely associated with the particular function

   can only show localisation of function within the brain area- can’t show communication that takes place which might be necessary for neural functioning

what is an EEG?

measures electrical activity in the brain

electrodes are attached to the scalp with a skull cap

brain waves are shown and displayed on a graph

4 brain waves associated are: alpha, beta, theta and delta

what are the brain waves associated with EEGs?

alpha, beta, theta and delta

what are ERPs?

electrodes are attached to the scalp using a skull cap

stimulus is presented to ppt- e.g. asked to look at a picture

researcher looks for activity triggered by stimulus

has to be repeated to avoid anomalies

what is the difference between EEG and ERPs?

EEG- no stimulus

ERP- stimulus

what are the 2 strengths of ERPs and EEGs?

1. non-invasive

   it does not involve raditation or cutting into the brain

   they are harmless unlike PET scans and risk free so they are more likely to get people to do it = more data

   counterpoint: electrodes attached to the scalp is uncomfortable which means discomfort could affected the cognitive responses- FMRI doesn’t have this issue

2. good temporal resolution

   detects very quickly and there is no delay between when you do something and when the scan receives. scans every 1-10 milliseconds

name 2 limitations of ERPs and EEGs

1. poor spatial resolution

   can’t be very specific in where they pick up from and can’t access in depth areas to predict accurately where it’s coming from. can discriminate regions with greater accuracy. fMRIs don’t have this issue

2. correlational rather than causation

   only scans brain waves so it’s impossible to infer causation at a neural level

   waves may indicate activity within brain area but we are unable to conclude that that’s definitely associated with the particular function

   can only show localisation of function within the brain area- can’t show communication that takes place which might be necessary for neural functioning

label broca’s area and wernicke’s area

label the brain

what does localisation mean?

main functions are found in certain areas of the brain

shown by case study of phineas gage:

iron rod when through the brain and took some of the left frontal lobe

he experienced drastic personality change- e.g. impulsiveness, irritability and disrespectful

believed damaged area was responsible for emotion and personality

what is the motor cortex?

located in the frontal lobe

in charge of voluntary movements by sending signals in different parts of the body

discovered that different muscles are coordinated by different areas of the motor cortex by electrically stimulating motor area of dogs

this resulted in muscular contractions in different areas of the body depending on where the probe was inserted

regions of motor area are arranged logically- e.g. region that controls finger is beside the region that controls the hand and the arm and so on

what is the somatosensory cortex?

located in the parietal lobe

receives sensory information from skin to produce sensations related to things like temperature

different parts of the area receive messages from different body parts

this area was found to be highly adaptable- e.g. braille readers have larger areas for fingertips than non-braille readers (demonstrating plasticy of the brain)

what is the visual cortex?

located in the occipital lobe

receives and processes visual information

information from right visual field is processed in the left hemisphere’s visual area

information from the left visual field is processed in some of the right hemisphere’s visual area

visual area contains different parts which process different aspects of the information- e.g. shape, colour, size, movement

what is the auditory cortex?

located in the temporal lobe

analyses and processes acoustic information

information from left ear goes to right hemisphere

info from right ear goes to left hemisphere

processes sounds, volume, tempo and pitch

where are language areas?

only in the left hemisphere

name the 2 language areas and what they do

1. broca’s area- speech production

2. wernicke’s area- speech comprehension

explain broca’s area

speech production

discovered this area while studying patient known as tan

tan could understand language spoken to him perfectly but he couldn’t produce any coherent words and could only say ‘tan’

post mortem examination showed a tumour in his left frontal lobe

led to conclusion that broca’s area is responsible for speech production

people will damage to this area experience broca’s aphasia (slow and inarticulate speech)

what do people with damage to broca’s area experience?

broca’s aphasia

slow and inarticulate speech

explain wernicke’s area

speech comprehension

patients with damage to wernicke’s area were still able to speak perfectly well but can’t understand what they or anyone else said

this is known as wernicke’s aphasia

name 2 strengths of localisation of brain functions

supporting evidence

case studies on people with broca’s aphasia have damage to broca’s area and some with wernicke’s aphasia have this damage too

show the important role played by these brain regions for speech production and comprehension

phineas gage- showed important proof of localisation- most of frontal left lobe was removed by iron rod and he experienced drastic personality changes

counterpoint: evidence is based off case studies alone

case studies are done on small groups and therefore cannot be assumed just because their brain functions like that everyone else’s does

doesn’t allow for generalisations

phineas gage- may have had a personality change but that doesn’t mean everyone would + anger could be due to anger at the accident rather than damage to the brain

evidence from brain scans

showed area that was active during listening task was wernicke’s area and broca’s area was active during speaking and reading tasks

showed scientific proof that that brain function is localised in one place

tulving- brain scans showed episodic and semantic memories are stored in different parts of the pre-frontal cortex

scientific and objective support

name 2 limitations of localisation of brain functions

contradicting evidence

lashley- showed higher cognitive functions are not located in single parts of the brain.

removed 10-50% of cortex in rats that were learning to complete a maze

it did not make any difference to their learning which part of the brain was removed and their ability to learn wad damaged despite what part was taken

concluded its not any part of the brain responsible but the entire brain for higher functions + motor and sensory functions are localised but higher mental functions aren’t

dronkers- conducted MRI scans on Tan’s brain to confirm broca’s findings. Found damage in other area’s which may have contributed to the failure in speech production too. broca’s area may be involved in speech production but might not be the only region responsible

patients with broca’s aphasia may have damage to neighbouring areas of the brain

brain functioning is not fixed

lashley- brain has some degree of plasticity

undamaged parts of the cortex can take over specific cognitive functions after a brain injury/damage

suggests function isn’t localised if other uninvolved parts of the brain can take over and do those functions + suggests brain can recognise a lost function

there are limits to recovery but stroke patients have shown brain does have some plasticity

what is hemispheric lateralisation?

two halves of the brain are almost independent of each other- only joined by the small carpus callosum

they are functionally different

left= language

right = visual motor tasks, spatial awareness and facial recognition

what does the left side of the brain control?

language

what does the right side of the brain control?

visual motor tasks and spatial awareness and face recognition

what area allows the left and right side of the brain to communicate?

corpus callosum

what does contralateral control?

right hempishere controls left side of the body

left hemisphere controls right side of the body

what happens when the two hemisphere’s connection is cut during surgery? why would this happen?

two hemispheres can no longer communicate with each other

known as split-brain patients

used for very severe epilepsy

explain split-brain research

first to investigate hemispheric laterisation using split brain patients

wanted to examine the extent to which the hemisphere’s are specialised for the function

word/image was projected to the patient’s left visual field (processed in right hem) or their right visual field (processed in left hem)

when info is presented to one hem the information cannot be transferred to the other in split brain patients

used 11 split brain patients as ppts and had them do different tests

1. visual: picture was presented to ppts left or right visual field and they just had to describe what they saw

2. touch: object was placed in patient’s left or right hand (which was hidden from their view) and they had to describe what they felt or select a similar object

3. drawing: ppts were presented with a picture in either left or right field and they had to draw what they saw

results:

1. visual: ppt could say what the object was when it was in right visual field (bc lang is on the left) but not when it was in the left visual field

2. touch: object held in the right hand they could name but not in the left hand (lang is on left)

3. drawing: saw picture on the left visual field was drawn correctly- left hand could draw correctly (interpreted by right visual cortex) but the right hand couldn’t. if the right visual field had picture, the opposite was true

why does the brain change?

due to learning, experience, aging and injury

what is brain plasticity?

brain’s ability to change and adapt because of new experience, learning, injury, etc

brain continues to create new connections between different structures in the form of neural pathways

and alter existing pathways in response to changies

what happens to your brain from birth until 3

develops thousands of synaptic connections which connect with other neurons

continue to develop continues until 3

as we get older, the number of connections decreases as the ones we don’t use disappear and the ones we use a lot are strengthened

when can synaptic connections and neural pathways develop or decline?

at any point in life

what is functional recovery?

transfer of functions from a damaged area of the brain after a trauma to other undamaged areas

can do this through neural unmasking- where dormant synapses open connections to make up for nearby damaged areas

new connections recover any damage in specific regions

how does functional recovery occur?

brain seems to be able to rewire itself and reorganise itself following trauma by making new synaptic connections or by using connections that have been dormant for a while

connections that would not usually perform that function are activated and enable the function to continue

results in change of brain tissue structure

what brain structure tissue changes occur?

axonal sprouting- where damaged neurons make new axons to reconnect with undamaged neurons to rejoin/form pathways

recruitment of other brain areas- similar brain structures on the opposite side if the brain perform the function of the damaged area- e.g. if left motor cortex was damaged, the right motor cortex could take up the job of coordinating impaired movement