6. localisation of function Flashcards
what is the theory of localisation of function?
different areas of the brain responsible for specific behaviors, processes or activities.
what are the functions of the hemispheres
activity on the left side of the body is controlled by the right hemisphere and vice versa.
outer layer of both hemispheres is called the cerebral cortex.
some functions are dominated by one hemisphere = lateralisation.
what are the functions of the visual cortex
what is seen in the left visual field is processed in the occipital lobe in the right hemisphere and vice vera.
the left visual field is the left of what both eyes see. therefore damage in the occipital lobe in the left hemisphere would cause blindness in the right visual fields of each eye.
what are the functions of the auditory cortex
temporal lobes process auditory information - allows us to perceive sounds in the environment.
signals are sent from the auditory cortex to other parts of the brain to process high level information. for example wernicke area to understand language comprehension.
what are the functions of the motor cortex
sits at the back of the frontal lobe in both hemispheres.
controls involuntary behavior.
motor cortex in the left hemisphere processes movement in the right side of the body and vice versa. therefore damage to this area of the brain would result in a loss of control of fine movements.
what are the functions of the somatosensory cortex
processes sensory information from the body - heat, pressure and touch.
the area is present in both hemispheres and is separated from the motor cortex by the brain central sulcus.
each part of the somatosensory cortex is allocated to a part of the body - some of the body takes up more than others.
where is language processed
left hemisphere
what are the functions of broca area
broca found an area in the brain that was responsible for speech production = broca area.
damage to this area causes aphasia - slow and laborious speech that lacked fluency.
case study - tan could understand spoken language but was unable to produce any coherent words - could only say tan. broca conducted a post mortem examination on the brain and discovered that he had damage to his left frontal lobe = responsible for speech production.
what are the functions of wernicke area
wernicke researched patients who could speak fine but lacked the ability to understand and comprehend speech. the language they produced was fluent but meaningless.
wernicke coined an area in the temporal lobe = wernicke area which was in charge of language comprehension.
strength - brain scan evidence
researchers used brain scan evidence to demonstrate how wernicke area was active during a listening task and broca area was active during a reading task = brain has different functions. case study to support this - tan.
= different areas were active at different times while doing different tasks so brain does not work alone as one. the activity of the brain while completing various tasks shows not all areas are active at the same time.
strength - tulving and HM
suggests that semantic and episodic memories reside in different parts of the prefrontal cortex. there now exists a number of highly sophisticated and objective methods for measuring activity in the brain which provide scientific evidence of localisation of brain function.
case study - HM lost the ability to form new memories. he was able to recall childhood events but lost the ability to recall experiences a few years before his surgery.
strength - neurological evidence
psychologists researched 44 people with OCD who had undergone a cingulotomy. post surgical follow up at 32 weeks - third had met criteria for successful response to surgery and 14% for partial response.
= success of procedures like this strongly suggest that symptoms and behaviors associated with serious mental disorders are localised.
however, study used a small sample of people with OCD so lacks population validlity.
support - phineas gage case study
iron pole went through his left cheek passing behind his left eye taking out most of the frontal lobe of the brain.
damage to his personality as he turned from someone who was calm and reserved to someone who was quick tempered and rude.
= supports theory as it was believed that the area damaged was responsible for personality.
weakness - lashley research
removed areas of the cortex in rats that were learning a maze- no area was proven to be more important than any other area in terms of the rats ability to learn the maze.
the process of learning appeared to require every part of the cortex rather than being confined to a particular area.
furthermore this study cannot be generalised to humans (brains work differently) as our brains are more complex.
= learning is too complex to be localised and requires the involvement of the whole of the brain - perhaps cognitive functions are distributed in a more holistic way.
weakness - plasticity
when the brain has become damaged (illness or accident) and a particular function has been compromised or lost, the rest of the brain appears able to reorganise itself in an attempt to recover the lost function.
described this as the law of equipotentiality whereby surviving brain circuits ‘chip in’ so the same neurological action can he achieved.
= brain works together as one to repair damage - functions are not localised to one region as other regions can take over specific functions following brain surgery.
