Biopsychology (not mine)

fMRIs

• Method used to measure brain activity whilst a person is performing a task

• Works by detecting the changes in both blood oxygenation and flow that occur as a result of neural activity in different parts of the brain

• When a brain area is more active, it consumes more oxygen and blood flow is directed to the area

• Produces 3D images

Evaluation of fMRIs

• temporal resolution- shows brain activity 1-5 seconds after it occurs which is slow in comparison to ERPs

• Expensive - £500 per scan so small sample size

• Spatial resolution- accurate within 1-2 mm which is the most accurate of all 4 scanning techniques

• Non invasive

• Uncomfortable- need to stay still for 2 hours

EEGs

• Measure’s electrical activity within the brain via electrodes that are fixed to an individuals head using a skull cap

• Sensors record the brainwave patterns that are generated from the action of thousands of neurons providing an overall account of brain activity

EEGs evaluation

• temporal resolution- shows brain activity every millisecond in real time which allows for easier prediction

• Non invasive

• Uncomfortable

• Cheaper- £160 per scan so used more

• Spatial resolution- less accurate as it only detects activity in general areas of the brain

• Can’t record deep brain activity

ERPs

• Measures brain activity in response to a sensory cognitive motor event or stimulus

• Stimulus is presented hundreds of times to create an average result

ERPs evaluation

• same as EEGs

• Background noise and extraneous material should be completely eliminated to get pure data relating to the task they have been given

Post mortems

• analysis of a persons brain after death

• Exploring the physical brain of a person who displayed a certain behaviour when they were alive

Post mortems evaluation

• more detailed examination of anatomical and neurochenical aspects that we can’t do with scans eg; research into schizophrenia

• Investigating humans is better than generalising to animals- validity and ethics

• Invasive however the person is dead

• Small sample sizes reduces validity

• Drug treatment and age can impact brain

Localisation of brain

The theory that different areas of the brain are responsible for specific behaviours, processes or activities

Hemispheres of the brain

• Left and right hemisphere

• Some of our physical and psychological functions are controlled or dominated by a specific hemisphere- lateralisation

• Left side is controlled by right hemisphere and right side is controlled by left hemisphere

Cerebral cortex

Covers the brain and appears grey due to the location of cell bodies

What are the 4 lobes the cortex is subdivided into

• frontal lobe

• Parietal lobe

• Occipital lobe

• Temporal lobe

  
  

Motor centre

• located at the back of the frontal lobes

• Controls voluntary movement in the opposite side of the body

• Damage to this area may result in loss of control over fine movements

Somatosensory centre

• at the back of both parietal lobes

• Where sensory information from the skin eg: related to touch is represented

• Receptors for face and hands occupy over half of the somatosensory centre

Visual centre

• in the occipital lobes in the back of the brain

• Each eye sends information from the right visual field to the left visual cortex and from the left visual field to the right visual cortex

• This means damage to the left hemisphere can produce blindness in the right visual field of both eyes

Auditory centre

• located in the temporal lobes

• Analyses speech based information

• Damage can produce partial hearing loss

• Damage to a specific area of the temporal lobes in the left hemisphere (wernickes area) may affect the ability to comprehend language

Brocas area

• small area in the left frontal lobe responsible for speech production

• Damage to the Broca’s area can cause Brocas Aphasia which is associated with slow laborious speech that lacks fluency

• Patient Tan - could only say Tan

Wernickes area

• found in left temporal lobe

• Responsible for language comprehension

Damage results in Wernickes aphasia- can produce language but have problems understanding it so they produce nonsense words

Evaluation of localisation of function

• evidence from neurosurgery- damage to the areas of the brain has been linked to metal health conditions

• Holistic theory

• Phineas Gage- was oreoearing to blast a section of rock with explosives to create a new railway line. He dropped a tamping iron onto the rock causing the explosive to ignite. The explosion hurled the metre length pole into his left cheek passing behind his left eye and exiting through his skull taking a portion of his brain with it - most of his left front lobe

• He survived but the damage to his brain left a mark on his personality he turned into someone who was quick tempered and rude- suggests frontal lobe is responsible for regulating mood

• Lacks temporal validity

• Difficult to make meaningful generalisation as it is a case study

Hemispheric lateralisation

Idea that the 2 halves of the brain are functionally different and that certain mental processes and behaviours and mainly controlled by one hemisphere rather than the other as in the example of language

Where are the main language centres

• in the left hemisphere

• Broca’s area is in the left frontal lobe

• Wernickes area is in the left temporal lobe

• Language is lateralised - performed by one hemisphere rather than the other

Which functions are not lateralised

• vision

• Motor

• Somatosensory centres

The motor centre of the brain

• motor centre in the brain is cross wired

• Right hemisphere controls movement on the left side of the body

• Left hemisphere controls movement on the right side of the body

Vision explained

• both opposite and same sided

• Each eye receives light from the left visual field and the right visual field

• The left visual field of both eyes is connected to the right hemisphere and the right visual field of both eyes is connected to the left hemisphere

• This enables the visual centres to compare the slightly different perspective from each eye and aids depth perception

Split brain research

• split brain operation involves severing the corpus callosum that connects the right hemisphere and the left hemisphere

• Used to treat epilepsy- stops electrical storms across hemispheres

• Split brain research studies how the hemispheres function when they can’t communicate with each other

• Sperrys research (1968) - devised a system to study how 2 separated hemispheres deal with for example speech and vision

• Procedure- 11 people who had a split brain operation were studied using a special set up in which an image could be projected to a participants right visual field and the same or different image could be projected into the left visual field. in the neurotypical brain the corpus callosum would share information between both hemispheres. However, presenting the image to a person who has a split brain meant that information cannot be conveyed from one hemisphere to another

• Findings- when an image was shown to a participant in the right visual field (linked to the left hemisphere) the participant could describe what was seen- but they could not do this if the image was shown in the left visual field- they said there was nothing there. This is because in the connected brain messages from the right hemisphere are replayed to the language centres in the left hemisphere but this isnt possible in the split brain

• Although participants couldn’t give verbal labels to images projected to the left visual field that could select a matching object out of sight using their left hand

Kim peek- a natural split brain

• was born with an absence of a corpus callosum

• Peeks powers if memory were remarkable- he had a word for word recall of over 12000 books

• He could read 2 pages of a book in around 10 seconds employing his split brain to simultaneously read 1 page with his left visual field and 1 page with his right visual field

Evaluation of hemispheric lateralisation

• lateralisation in the connected Braun

• Age and lateralisation- lateralisation may decline as we get older - Szaflarski used fMRIs to assess brain activity during a verb generation task in 170 healthy right handed participants aged 5-67 years- findings revealed that left hemisphere dominance for language increases from age 5 to 20, stabilies between 20 - 25 and gradually decreases from 25 and onwards

Evaluation of split brain research

• Kim peek

• Generalisation issues- none of the participants in the control group had epilepsy which is a big extraneous variable- any differences that were observed could have been due to epilepsy

• Standardised and controlled procedure (blindfold used every 1/10)

• Turk et al (2002) studied JW who had damage to his left hemisphere but developed his language through the right hemisphere leading him to be able to talk about information presented to both visual fields

Plasticity definition

• describes the brains tendency to change and adapt as a result of experience and new learning- involves the growth of new connections

Functional recovery definition

• the brains ability to redistribute or transfer functions usually performed by damaged areas of the brain to undamaged areas of the brain- form of plasticity

Synaptic pruning

• as we age rarely used connections are deleted and frequently used connections are strengthened

Research into plasticity

• Maguire et al (2000)- studied the brains of London taxi drivers and found significantly more volume of grey matter than a control group

• As part of their training London cab drivers must take a complex test which assesses their recall of city streets and possible routes. The longer the taxi drivers had been in the job the more pronounced was the structural difference

functional recovery after brain trauma

• Functional recovery that occurs after trauma is an example of neural plasticity

• Occurs quickly after trauma then slows down after several months (may need rehabilitative therapy)

What happens in the brain during recovery

• axonal sprouting

• Denervation super sensitivity

• Recruitment of homologous areas

Axonal sorouting

• the growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways

Denervation super sensitivity

Occurs when axons that do a similar job become aroused to a higher level to compensate for the ones that are lost. However it can have the negative consequence of over sensitivity to messages such as pain

Recruitment of homologous areas

• recruitment of homologous areas on the opposite side of the brain meaning specific tasks can still be performed

Evaluation of plasticity

• plasticity may have negative behavioural consequences. Evidence shows that prolonged drug use cause the brain to adapt and leads to poor cognitive function and increased risk of dementia.

• Brain plasticity could be life long

• London black cap drivers

Evaluation of functional recovery

• real world application - neurohabilitation simply understanding axonal growth is possible encourages new therapies to be tried eg: constraint endured movement therapy is used with stroke patents where by they repeatedly practise using the affected part of their body

• Cognitive reserve- Eric Schneider et al (2014) revealed that the more time people with a brain injury had spent in education the higher their chance was at having a disability free recovery was.

Factors affecting functional recovery

• age- younger people’s capacity for neural reorganisation is greater than older

• Academic ability- people with a higher ability were more likely to functionally recover

Age

• Elbert et al concluded that the capacity for neural reorganisation is much greater in children than it is for adults meaning that neural regeneration is less effective in older brains

• Thus may explain why adults find change more demanding

Academic ability

• Eric Schneider et al (2014) revealed that the more time people with a brain injury had spent in education the higher their chance was at having a disability free recovery was

Case study of EB

• EB, a right-handed boy, had almost all of his left hemisphere removed at 2½ years old due to a tumour.

• His language abilities disappeared, but after intensive rehabilitation, they began improving from age 5.

• By age 8, his language had recovered well.

• At 17, tests showed his right hemisphere had compensated for the loss of the left hemisphere, although he had minor grammatical problems and slower object naming.

• Conclusion: The brain can reorganise and compensate for damage, particularly when injury occurs early in childhood, but recovery may not be complete