localisation of function

• the motor cortex: is responsible for the generation of voluntary motor movements, it is located in the frontal lobe of the brain along a bumpy region know as the precentral gyrus
• the motor cortex: both hemispheres of the brain have a motor cortex w/ the motor cortex on one side of the brain controlling the muscles on the opposite side of the body
• the motor cortex: different parts of the motor cortex exert control over different parts of the body, these regions are arranged logically next to one another e.g. the region that controls the actions of the foot is next to the region that controls the leg and so on
• the somatosensory cortex: detects sensory events arising from different regions of the body, it is located in the parietal lobe of the brain along a region known as the postcentral gyrus
• the somatosensory cortex: the postcentral gyrus is the area of the cortex dedicated to the processing of sensory information related to touch
• the somatosensory cortex: using sensory information from the skin, the somatosensory cortex produces sensations of touch, pressure, pain and temperature which it then localises to specific body regions
• the somatosensory cortex: as w/ the motor cortex both hemispheres have a somatosensory cortex w/ the cortex on 1 side of the brain receiving sensory information from the opposite side of the body
• visual centres: the primary visual centre in the brain is located in the visual cortex, in the occiptal lobe of the brain however visual processing actually begins in the retina at the back of the eye where light enters and strikes the photoreceptors (rods and cones)
• visual centres: nerve impulses from the retina are then transmitted to the brain via the optic nerve, some nerve impulses from the retina travel to areas of the brain involved in the coordination of circadian rhythms but the majority terminate in an area of the brain called the thalamus which acts as a relay station passing this information on to the visual cortex
• visual centres: the visual cortex spans both hemispheres w/ the right hemisphere receiving its input from the left-hand side of the visual field while the visual cortex in the left hemisphere recieves its input from the right-hand side of the visual field
• visual centres: the visual cortex contains several different areas w/ each of these areas processing different types of visual information, such as colour, shape or movement
• auditory centres: the auditory centre in the brain is concerned w/ hearing, most of this area lies within the temporal lobes on both sides of the brain where we find the auditory cortex
• auditory centres: the auditory pathways begin in the cochlea in the inner ear where sound waves are converted to nerve impulses which travel via the auditory nerve to the auditory cortex in the brain
• auditory centres: on the journey from the cochlea to the brain the 1st stop is the brain stem, within the brain stem a basic decoding takes place e.g. the duration and intensity of a sound
• auditory centres: the next stop is in the thalamus which acts as a relay station and also carries out further processing of the auditory stimulus
• auditory centres: the last stop in this journey is the auditory cortex although the sound has already been largely decoded by this stage in the auditory cortex it is recognised and may result in an appropriate response
• Broca's area: this area is names after Paul Broca the French neurosurgeon who treated a patient who he referred to as 'Tan' because that was the only syllable this particular patient could express
• Broca's area: Tan had an unusual disorder, although he has been able to understand spoken language he was unable to speak nor express his thoughts in writing
• Broca's area: Broca studied 8 other patients all of whom had similar language deficits along w/ lesions in their left frontal hemisphere patients w/ damage to these areas in the right hemisphere fif not have the same language problems
• Broca's area: this led him to identify the existence of a 'language centre' in the posterior portion of the frontal lobe of the left hemisphere, this area is believed to be critical for speech production
• Broca's area: however neuroscientists have found evidence of activity in the Broca's area when people perform cognitive tasks that have nothing to do w/ language
• Broca's area: Fedorenko et al (2012) discovered 2 regions of Broca's area one selectively involved in language and the other involved in responding to many demanding cognitive tasks (such as performing maths problems)
• wernicke's area: shortly after Broca had discovered a 'speech production' area in the brain Carl Wernicke a German neurologist disocovered another area of the brain that was involved in the understanding language
• wernicke's area: this area names Wernicke's area was in the posterior portion of the left temporal lobe
• wernicke's area: whereas Broca's patients could understand language but not speak patients w/ a lesion in Wernicke's area could speak but were unable to understand language
• wernicke's area: Wernicke proposed that language involves separate motor and sensory regions located in different cortical regions, the motor region located in the Broca's area is close to the area that controls the mouth, tongue and vocal cords
• wernicke's area: the sensory region located in the Wernicke's area is close to the regions of the brain responsible for auditory and visual input, input from these regions is thought to be transferred to Wernicke's area where it is recognised as language and associated w/ meaning
• wernicke's area: there is a neural loop known as the arcuate fasciculus running between Broca's area and Wernicke's area at one end lies Broca's area responsible for the production of language and at the other lies Wernicke's area responsible for the processing of spoken language
• evaluation S: case studies on drain damage support the idea of some localisation of function e.g. cases of aphasia (loss of language) are associated w/ damage to Broca's area
• evaluation L: the equipotentiality theory (1st proposed by Lashley in 1929) suggests that apart from motor and sensory functions other cognitive functions are spread across brain regions rather than localised in 1 site
• evaluation L: Lashley experimented on rats during the 1930s and 1940s systematically removing different brain areas to locate the area responsible for memory, he found that it was the total amount of brain damage rather than the destruction of any 1 site that affected memory
• evaluation L: further challenges come from the fact that the brain can rewire itself after damage to relocate functions to an undamaged area