localisation of function Flashcards
localisation of function
argument that the capacity to carry out different functions or abilities is located in particular areas in the cerebral cortex
cerebral cortex
outer layer of the brain
composed of highly folded grey matter
responsible for higher cognitive processes, such as vision, movement and consciousness
hemispheres
cerebral cortex is divided into 2 hemispheres (left and right)
connected by the corpus callosum, a dense pathway of around 300 million neural fibres
lobes
each hemisphere is sub-divided into 4 lobes
along the 2 main folds - central sulcus and lateral fissure which are used to identify the location of particular brain functions
motor area
responsible for planning and execution of voluntary motor movement, through the control of all skeletal muscles
motor area on one side of the brain controls the muscles on the opposite side of the body (contralateral representation)
motor area location
frontal lobe anterior to the central sulcus
cortical space
parts of the body requiring greater sensitivity (e.g. fingertips) have larger areas of the cortex dedicated to their control
parts of the body requiring less sensitivity (e.g. torso) have less cortical space
somatosensory area
responsible for skin sensation, including touch, pressure, temperature and aspects of pain
information from the bottom of the left side of the body is processed at the top of the right hemisphere - upside down, contralateral representation
Parietal lobe, posterior to the central sulcus
auditory area
responsible for auditory perception
receives input from the ear, via the auditory nerve, and a sub-cortical structure (thalamus)
Temporal lobe, posterior to the lateral fissure
visual cortex
responsible for visual perception
Occipital lobe, posterior of the cerebral cortex
broca’s area
responsible for the production of spoken language - contains the plans for the motor movement required to speak each word
when we wish to speak - instructions are passed from Broca’s area to the motor area which sends info to the muscles of the mouth and larynx to carry out the movements necessary for speech.
evidence for broca’s area
broca’s aphasia: paul broca identified a patient (Tan) who could comprehend language (e.g. could follow instructions by nodding or shaking his head) but had no fluent speech production at all
Only recognisable word he could say was ‘tan’
Autopsy revealed lesion to his left frontal love, in a region which became known as Broca’s area
Modern PET scans have confirmed Broca’s findings: lesions to Broca’s area cause Broca’s aphasia, where patients show intact language comprehension with significantly impaired language production
Wernicke’s area
Responsible for comprehension of spoken language
Contains a store of sounds of words required to understand speech
When we hear language, info is received by the auditory area (which recognises the sounds as language but does not understand the content) before it is passed to Wernicke’s area for comprehension
Evidence for Wernicke’s area
Wernicke’s aphasia: Karl Wernicke identified a patient who could not understand language but could produce relatively organised speech
Although he was able to say all word sounds, his spoken language made little sense because he lacked understanding (word salad)
A post-morgen revealed a lesion to his left temporal lobe, in a region which has become known as Wernicke’s area
Auditory area effects of stimulation
Stimulation produces simple auditory sensations (e.g. a buzzing noise)
