Biopsychology: Localisation Of Function Flashcards
Define Localisation of function.
The theory that different areas of the brain are responsible for different behaviours, processes or activities.
Describe the Motor Cortex
- Located in both hemispheres of the frontal lobe, along the precentral gyrus.
- Responsible for voluntary movement.
- Each hemisphere is responsible for controlling movement in the opposite side of the body.
- Regions are arranged logically ( eg the area that controls the hand is beside the wrist ).
Describe the Somatosensory cortex
- Located in both hemispheres of the occipital lobe.
- Receives sensory information from various parts of the body and processes this to give it the conscious perception of various sensations.
- The cortex in the left hemisphere controls interprets sensory information from the right side of the body.
- Regions are arranged logically.
Describe the visual cortex.
- Located in both hemispheres of the occipital lobe.
- It receives sensory information from the eyes via the optic nerve and processes this so that the person can
consciously perceive visual features. - The cortex in the left hemisphere receives information from the right-hand side of the visual field
Describe the auditory cortex
- It is located within the temporal lobes on both sides of the brain
- It receives auditory information from the ears and then processes this to give the conscious perception of the different types of acoustic information
- The cortex in the left hemisphere primarily receives information from the right ear
Describe Wernicke’s area.
- Located within the left hemisphere’s temporal lobe
- Responsible for language comprehension (understanding speech)
- People with a lesion (damage) to this area may experience a disorder Wernicke’s aphasia. People with
this disorder struggle to understand language (including written). They speak with regular rhythm and grammar, but their words don’t make sense. What’s more, they don’t realize that what they’re saying is nonsense.
Describe Broca’s area.
- Located within the left hemisphere’s frontal lobe
- Primarily responsible for language production.
- People with a lesion (damage) to this area may develop a condition called Broca’s aphasia, leaving them with problems producing language. For example, a person with Broca’s aphasia may say something like,
“Drive, store. Mom.” meaning to say, “My mom drove me to the store today.” Therefore, the content of the
information is correct, but the grammar and fluidity of the sentence is missing.
What research has challenged the theory of localisation of function.
Sur “rewired” the brains of ferrets so that signals from their eyes fed into the auditory cortex instead of the visual cortex. Sur found that the newly rewired auditory cortex was able to process information from the ferrets eyes. As the ferret’s auditory cortex was able to process visual information, this finding challenges the idea that
specific functions are necessarily localised to specific areas of the brain. If the theory of localisation of function were correct, we would expect areas of the brain with specific functions would be unable to take on unrelated functions. However, it didn’t process the visual information nearly as effectively as their visual cortex. Arguably, it provided support for the theory of localisation of function, as the newly recruited auditory cortex was not effective at assuming function it lacked specialisation for. It’s also worth noting that the visual cortex and the auditory cortex do both have similar functions, the both process sensory information. It’s possible that other parts of the brain with more distinctive functions, like Broca’s area, might have been completely unable to take on the function of the visual cortex, meaning some functions might not transfer to other areas of the brain. Thus further research must be done in order to investigate the extent of localisation of function.
What evidence is there to support localisation of function?
Broca’s research on Louis Leborgne demonstrates how Leborgne suffered from a strange speech impediment where he was able to understand language but whenever he tried to speak he could only say “tan”. After Leborgne’s death,a neuroscientist Paul Broca discovered damage to the Broca’s area. This supports the theory of localization of function as it demonstrates how specific functions can be localised to specific areas of the brain. In Leborgne’s case, damage to his Broca’s area prevented him from producing speech, suggesting speech production is localized to this area of the brain. Furthermore, Leborgne was still able to understand language. According to localization of function, this suggested that speech comprehension was localized to another undamaged area of the brain. This was supported by Carl Wernicke. However, it’s important to be cautious about this evidence as it comes from a single case study. Single cases, especially those with atypical conditions, like Leborgne’s, should not be assumed to be representative of the general population
What is an issue with the theory of localisation of function?
It is a reductionist theory meaning it explains complex phenomena such as language purely in terms of the functioning of specific regions of the brain, like Broca’s area. It reduces the complexity of the brain to a series of constituent parts. However, it has been argued that some complex brain functions, like
consciousness, cannot be easily reduced to the functions of individual parts of the brain. In the case of
consciousness, it has been suggested that it may be an emergent property, that only emerges from the brain as a whole system, meaning it cannot be explained by reducing the brain down to a simple set of constituent parts, as
localisation of function appears to do. Nonetheless, if this criticism only applies to complex brain functions, like
consciousness, then it doesn’t entirely undermine the theory of localisation of function, but it does suggest it may
offer a limited explanation of the brin, appropriate only to some functions.
