4.2.2 LOCALISATION OF FUNCTION IN THE BRAIN AND HEMISPHERIC LATERALISATION (FUNCTIONAL RECOVERY) Flashcards
what is the cerebrum?
- largest part of the brain, divides into 4 lobes which all have a different function
- splits down the middle into 2 hemispheres
-> each has different specialisms (eg. left for language) - hemispheres communicate using the corpus callosum
what is the cerebellum?
- sits at the back of the cerebrum
- controls motor skills and balance and coordination
- coordinates muscles to allow for precise movement
what is the brain stem?
- regulates essential functions for life
- breathing, heartbeat, swallowing
- involves involuntary responses
what are two types of brain wrinkles?
1) gyrus
- the hills in the brain
2) sulcus
- the valleys in the brain (wrinkles)
what did scientists believe about science?
1) scientists believed the brain was holistic in its processing
- ie) all parts are involved in cognition
2) in 19th century, a new kind of thinking emerged
- what if different parts of the brain had performed different tasks / were associated to different places in the body
what is localisation?
the theory that specific areas of the brain are associated with particular physical and psychological functions
what happened to Phineas Gage?
- there was an explosion where the tamping iron went straight through his skull
- it was 3ft 8inches long / weighing 6kg
- he was walking, talking, sat upright
-> he threw up + this action caused some of his brain to fall out - the pre-frontal cortex is involved with personality and he damaged this
what happened during Phineas Gage’s recovery?
- his brain was left uncovered during treatment and got infected
-> he was then in an unconscious state until recovered - his employers couldn’t give him his job back as he was so different
-> ie) rude / swears / doesn’t care about offending others / he’ll ignore you if he doesn’t want to follow your order - his friends said he was ‘no longer Gage’
what does Phineas Gage’s case study support?
the idea of localisation, and the personality change can be explained by the damage to a specific area of the brain
both hemispheres have 4 brain lobes?
1) frontal lobe
2) temporal lobe
3) partial lobe
4) occipital lobe
what does the frontal lobe do?
responsible for emotion, decision making and organisation
- motor control (premotor cortex)
- problem solving (prefrontal cortex)
- speech production (Broca’s area)
what does the temporal lobe do?
responsible for:
- long term memory
- identifying and naming objects
- auditory processing
- language comprehension (Wernicke’s area)
what does the parietal lobe do?
responsible for processing sensory information and spatial awareness
- touch perception (somatosensory cortex)
- body orientation
- sensory input
what does the occipital lobe do?
responsible for processing visual information
- sight (visual cortex)
- visual reception and interpretation
where is the motor area
what does it do
what happens if damage is caused to it?
- at the back of the frontal lobe (both hemispheres)
- controls voluntary movement
- each hemisphere controls the opposite side of the body
- damage to this area could lead to loss of fine motor movements
where is the auditory area
what can damage to it cause?
- located in temporal lobes (nearest ears)
- damage can lead to hearing loss / difficulty understanding what you’re hearing
where is the somatosensory area
what does it do?
- at front of both parietal lobes
- sensory info from the skin is represented there
- amount of somatosensory area devoted to each body part devotes sensitivity
-> eg) our hands + feet take up over 1/2 of the area - is separated from the motor area by a ‘valley’ (deep wrinkle) called the central sulcus
what is lateralisation?
- cerebrum is divided into 2 hemispheres
-> left and right - each hemisphere is responsible for some specific functions
- = the dominance of one hemisphere of the brain for particular physical and psychological functions
where are the language centres of the brain?
- tends to be on the left side of the brain for most ppl
the brain is contralateral - what does this mean?
- the left side of the body is controlled by the right side of the brain and vice versa
- if someone has a stroke in the left side of their brain, it will be physically evident on the right side of the body
what is the right hemisphere responsible for?
- dominant in recognising emotions in others
- spatial information
- facial recognition
- drawing
- viewing objects in the left visual field
- controls left side of the body
-> known as minor hemisphere as it can’t process language
what is the optic chiam?
where the visual pathways cross over
what is the left half of the brain specialised for?
- controls right side of the body
- viewing objects in the right visual field
- known as the major hemisphere as it processes language
what is Broca’s area?
- Broca correctly identified the area of the brain responsible for speech
- they found not all words were equal in the Broca area and they were effected differently
- nouns + verbs seemed to be less effected but predisposition and conjunctions were no longer able to be used
who was Broca and how did he discover Broca’s area?
- was a neurologist
- one patient, Louis Lebornge (son of school teacher) suffered from epilepsy through childhood
- he was educated and a craftsman, but eventually lost the ability to speak
- Broca performed a post-morgen study on his brain
- found a lesion on the left temporal lobe
- Broca concluded this area was responsible for speech production as it was the only area of damage
what does Broca’s aphasia mean?
used today for patients who display problems producing speech
what is Wernickes Area?
- separate area of language processing which has a specific function
- Wernicke worked in a hospital in Germany
-> found patients who had damage near the auditory cortex had specific language impairments
-> inability to comprehend language and anomia - but found that the same ppl had fluent speech when they were able to access words quickly
- mans suggested this area was important for understanding language and accessing words
label this diagram of the brain
what did Roger Sperry do want to do?
investigate what would happen if our hemispheres weren’t connected
and whether they perform different functions
what was Sperry’s procedure?
- studied 11 patients who had a corpus callosotomy as treatment for their epileptic seizures
- the subjects gazes at a fixation point on an upright translucent screen where Sperry projected info into each visual field
- slides containing words / images are projected either side of the fixation point for 1/10th of a second
- in a series of test, ppts were asked to either say what they saw, draw it or pick it out from hidden objects
what did Sperry find?
- info presented to the left hemisphere could be spoken but not if it had been delivered to the right hemisphere
- info presented to the right hemisphere could be drawn or picked out from objects with left hand
the right hemisphere dominates when matching faces
how do we know this?
- because when faces are shown to LVF, it’s sent to the right hemisphere, the correct matching picture is selected
- when shown to the RVF, it’s sent to the left hemisphere and the matching. picture isn’t selected
what happens when using a composite picture (where each hemisphere sees half a face)?
- if RVF to left hemisphere, a verbal description can be given
- if LVF to right hemisphere, can select a matching picture
what is a commissurotomy?
the division of the two hemispheres by surgery
what can we conclude from Sperry’s study?
- when we separate the hemispheres we can clearly see that they act differently
- the right hemisphere can recall and identify stimuli but cannot verbalise this
- the left hemisphere is specialised for speech and writing
- right hemisphere is mute and can’t speak or write
-> can’t speak = aphasic
-> can’t write = agraphic
what are three negatives to Sperry’s study?
1) Sperry’s original ppts were epileptic
- can’t be said to represent normal brains
- their brains may somehow be different due to the epilepsy
- the control group (not spilt brain) weren’t epileptic
2) small sample size
- Sperry used 11 spilt brain ppts
- some ppl have more lateralised brains than others
- some ppl had more disconnection of the two hemispheres than others
-> this may mean that individual differences could influence results
3) sex differences
- although his work concluded that many functions are lateralised, subsequent work suggests that women have less lateralised brains
- this will influence the result of brain damage
- eg) Kimura reported more aphasia in men who had left hemisphere damage than women with it too
what’s a strength of Sperry’s study?
1) despite these criticisms
- Sperry created a well controlled and replicable standardised procedure
- (asking ppts to stare at a fixed central point and presenting stimuli only briefly ensured each hemisphere received info from only one visual field)
- has triggered a philosophical debate about the value of the mind
-> are our 2 hemispheres so functionally different that they can be considered as two minds?
what does plasticity mean?
the brains apparent ability to change and adapt both physically and functionally
what happens to the brain during recovery?
1) axonal sprouting
- the growth of new nerve ending which connect with other undamaged nerve cells to form new neural pathways
2) reformation of blood vessels
3) recruitment of homologous areas
- when a homologous (similar) area of the brain on the opposite side is used to perform a specific task
what did Maguire at al do and find?
- conducted structural MRI scans on 16 male London taxi drivers were compared with 16 male matched (same age, education etc) non-taxi drivers
- found posterior hippocampi in London cab drivers were significantly larger than the control group of non cab drivers
- found size of posterior hippocampi was reflective on how long they’d been a cab driver
- his research suggests the brain is plastic and able to configure itself to its environment and psychological demands
what did Danielli et al do and find?
- case study of EB who was 14yrs old
- at 2yrs old, EB had a hemispherectomy on left side of his brain to remove a tumour
- his language centres were removed, including Broca and Wernicke
- immediately after surgery, he’d lost all language function
-> but after 2yrs, he’s recovered his language ability without his left hemisphere - this supports brain plasticity, showing the brain can adapt and recover after trauma, especially early on in life
- researcgers completed fMRI scans and found the right hemisphere acted as it was the left, for language
what are two strengths of both Danielli and Maguire?
1) negative plasticity
- brains ability to rewire itself can sometimes have maladaptive behavioural consequences
- maladaptation itself isn’t a strength, but examples of it support the notion of the brain’s plasticity
- Medina et al found prolonged use of marijuana resulted in poorer cognitive functioning + increased risk to dementia
2) practical application
- used in real world + supports patients with changes / damage to brain
- contributed to the field of neurorehabilitation
- spontaneous recovery tends to slow down after a few weeks so physical therapy may be needed to maintain improvements in functioning
- eg) movement therapy, electrical stimulation to counter deficits in motor +/or cognitive functioning after stroke eg
what’s a negative of these studies into brain plasticity?
