Localisation of Function Flashcards
What does localisation of function refer to
The principle that specific functions, for example language, memory or hearing have specific locations in the brain
When was there a growth in interest in localisation of brain function
In the early 19th century, undoubtedly influenced by phrenology
What area of the brain is responsible for the generation of voluntary motor movements
The motor cortex
Where is the motor cortex
In the frontal lobe of the brain, along the precentral gyrus
How does the motor cortex work
Both hemispheres have one, they are lateralised. Different parts of the motor cortex exert control over different parts of the body, with regions arranged logically next to each other, for example the region that controls the foot is next to the region controlling the leg
What area of the brain detects sensory events
The somatosensory cortex
Where is the somatosensory cortex
It is in the parietal lobe of the brain, in the postcentral gyrus. Both hemispheres have one, and they are lateralised
What does the somatosensory cortex do
It processes information related to touch. Using sensory information from the skin it produces sensations of touch, pressure, pain and temperature which it localizes to specific body regions.
What is the visual centre of the brain
The visual cortex
Where is the visual cortex
In the occipital lobe of the brain, with the visual cortex spanning both hemispheres and the fields lateralised
How does the visual cortex work
It has several areas, processing different kinds of visual information, such as colour, shape or movement.
Where does visual processing actually start
At the back of the retina, where photoreceptor cells detect light and nerve impulses are sent from the retina to the brain via the optic nerve. Some of these travel to areas of the brain involved in circadian rhythms, but most terminate at the thalamus, which acts as a relay station for the visual cortex
What is the auditory centre of the brain
The auditory cortex
Where is the auditory cortex
It lies in the temportal lobes on both sides of the brain
What is the pathway for auditory information
-Starts in the cochleas, where sound waves are converted to nerve impulses, which travel to the brainstem by the auditory nerve
-In the brainstem, basic decoding takes place, for example the duration and intensity of a sound
-Then information reaches the thalamus, which acts as a relay station and carries out further processing of auditory stimulus
-Finally signals arrive at the auditory cortex. At this stage sound is largely decoded, so the signals are recognized so a response can be given
What are the language centres of the brain
Broca’s area and Wernicke’s area
What was Broca’s big case study
Tan, who could only express the syllable Tan. Tan could understand spoken language but couldn’t speak or even express thoughts in writing.
Outside of Tan, who did Broca study
Eight patients, all of whom had similar languge deficits to Tan, along with lesions in their left frontal hemisphere. Those with damage to these areas in the right hemisphere did not have language problems
Where is Broca’s area
In the posterior portion of the frontal lobe of the left hemisphere
What have neuroscientists recently found Broca’s area does
Neuroscientists have found evidence of activity in Broca’s area when people perform cognitive tasks that have nothing to do with language. Fredorenko et al discovered two regions of Broca’s area, one selectively involved in language, the other involved in responding to demanding cognitive tasks like maths problems
Who found evidence that Broca’s area does more than just language
Fedorenko et al
Who discovered an area of the brain invloved in understanding language
Carl Wernicke
Where is Wernicke’s area
In the posterior portion of the left temporal lobe
How did wernicke discover his area
Those with a legion in the posterior portion of the left temporal lobe were able to speak but not understand language
How did Wernicke propose that language works
It involved seperate motor and sensory regions in different corticol regions. The motor region, in Broca’s area, is close to the area controlling the mouth, tounge and vocal cords. The sensory region, in Wernicke’s area, is close to the area of the brain responsible for auditory and visual input. Input from these regions is transferred to Wernicke’s area where it is recognised as language and associated with meaning
What neural loop runs between Broca’s and Wernicke’s area
The arcuate fasciculus
What areas are Broca’s area near
Areas controlling the mouth, tounge and vocal cords
What areas are Wernicke’s area near
Those responsible for auditory and visual input
How are Broca’s and Wernicke’s areas connected
Through a neural loop called the Arcuate Fasciculus
How have studies into aphasia supported the existance of Broca and Wernicke’s area
It has been discovered that damage to Broca and Wernicke’s areas cause different types of aphasia. Expressive aphasia is an impaired ability to produce language, and in most cases is caused by damage to Broca’s area. Receptive aphasia is an inability to extract meaning from spoken or written words, usually the result of damage to Wernicke’s area.
What are the different types of Aphasia
-Expressive aphasia is an impaired ability to produce language, associated with damage to Broca’s area
-Receptive aphasia is an inability to extract meaning from spoken or written words, associated with damage to Wernicke’s area
Describe how individual differences can affect localisation of function
Pattern of activation observed in response to various language activities can vary between individuals Bavelier et al found considerable variability in the patterns of activation across different individuals whilst reading, seeing activity in the right temporal, left frontal, temporal and occipital lobes. (Add gender differences)
What research has found differences in sizes of brain areas between men and women
Harasty et al found that women have proportionately larger Broca’s and Wernicke’s areas than men. These anatomical differences may explain the superior language skills often found in females
Who found different patterns of brain activation can be found between different individuals when reading
Bavelier et al
Who found gender differences in the size of Broca and Wernicke’s areas
Harasty
Why is it possible that language function is not confined to Broca’s area alone
Dronkers et al re-examined the preserved brains of Tan and Lelong (two of Broca’s patients), and used MRI imaging to identify the extent of any lesions in more detail. They revealed that other areas besides Broca’s area could have contributed to impaired speech.
Why are Dronker’s findings particularly important
Because lesions to Broca’s area alone can cause temporary speech disruption, but they don’t usually result in severe disruption of spoken language. Their work overall suggests the brain is more complicated than localised function, involving brain regions rather than localised areas
Who MRI’d up Tan and Lelong’s brain
Dronkers
Why does equipotentiality threaten a view of localisation
Put forward by Lashley who believed that basic motor and sensory functions were localized, but that higher mental functions were not. He claimed that intact areas of the brain could take over responsibility for specific cognitive functions if there was an injury. According to this point of view, effects of brain damage would be determined by extent rather than location of damage. This view has been supported by the discovery of brain plasticity
Who suggested the view of equipotentiality
Lashley
