brain localisation

• localisation: the theory that specific areas of the brain are associated with particular physical and psychological functions
• hemispheric laterialisation: the dominance of one hemisphere of the brain for particular physical and psychological functions
• left brain functions: analytic thought, logic, language, science and math
• right brain functions: holistic thought, intuition, creativity, art and music
• the human brain can be viewed as being formed of three concentric layers

  the central core

  the limbic system

  the cerebrum
• the central core

  regulates our most primitive and involuntary behaviours such as breathing sleeping or sneezing
• what is the central core also known as and what structures does it include

  also known as the brain stem

  includes hypothalamus - in the midbrain
• the central core

  regulates eating and drinking as well as regulating the endocrine system in order to maintain homeostasis
• the limbic system

  controls our emotions

  around the central core of the brain, interconnected with hypothalamus

  contains hippocampus; key roles in memory
• the cerebrum

  regulates our higher intellectual processes e.g

  language

  memory

  problem solving
• what is the outermost layer of the cerebrum called

  cerebral cortex

  appears grey (grey-matter)
• what is the cerebrum made up of

  left and right hemispheres connected by a bundle of fibres called the corpus callosum
• the cerebrum: what does the corpus callosum do?

  enables messages that enter the right hemisphere to be conveyed to the left hemisphere and vice versa
• each hemisphere is further divided into 4 lobes

  frontal lobe

  parietal lobe

  temporal lobe

  occipital lobe
• frontal lobe

  location for awareness of what we are doing within our environment (our consciousness)
• parietal lobe

  location for sensory perception
• temporal lobe

  location for the auditory ability and memory acquisition
• occipital lobe

  location for vision
• motor area

  in frontal lobe

  responsible for voluntary movements by sending signals to the muscles in the body
• motor area

  regions of motor area are arranged in a logical order e.g region that controls finger movement is located next to region that controls hand and arm and so on

  motor cortex in the left hemisphere is responsible for movement on the right hand side and vice versa
• somatosensory area

  in parietal lobe

  recieves incoming sensory information from the skin to produce sensations related to pressure, pain, temperature etc.
• visual area

  in occipital lobe

  recieves and processes visual info

  info from right-hand side visual field is processed in left hemisphere

  info from left-hand side visual field is processed in the right hemisphere
• auditory area

  in temporal lobe

  responsible for analysing and processing acoustic info

  info from left ear goes primarily to right hemisphere

  info from right ear goes primarily to left hemisphere
• broca's area

  paul broca treated a patient named leborgne, more referred to as 'Tan'

  tan could understand spoken language but was unable to produce any coherent words, could only say 'Tan'
• broca's area

  during broca's post-mortem examination on tan's brain he found a lesion (damage) in the left frontal lobe

  he concluded that area was responsible for speech production

  people with damage to this area experience broca's aphasia, results in slow and inarticulate speech
• wernicke's area

  karl wernicke identified a region in the left temporal lobe as being responsible for language comprehension which would result in wernicke's aphasia when damaged
• what happens to patients who have wernicke's aphasia

  they will often produce nonsense words as part of the content of their speech.

  speech is often fluent but meaningless
• phineas gage (strength of localisation)

  whilst working on the railroad in 1848, 25 year old phineas gage was preparing to blast a section of rock with explosives to create a new railway line

  during the process, gage dropped his tamping iron onto the rock causing the explosive to ignite

  the explosion hurled the metre-length pole through gage's left cheek, passing behind his left eye, exiting his skull from the top of his head taking a portion of his brain with it - most of his left frontal lobe
• phineas gage pt 2

  gage survived

  many people that knew him stated that he turned from someone who was calm and reserved to someone who was quick-tempered and rude
• brain scan evidence (strength of localisation)

  wealth of evidence providing support for the idea that many neurological functions are localised, particularly in relation to language and memory

  e.g peterson (1988) used brain scans to demonstrate how wernicke's area was active during a listening task and broca's area was active during a reading task, indicating the different functions of the areas
• higher cognitive functions are not localised - equipotentiality theory

  not all researchers agree with the view that cognitive functions are localised in the brain. the work of karl lashley (1950) suggests that the basic motor and sensory functions were localised, but that higher vital functions were not
• higher cognitive functions are not localised - equipotentiality theory pt 2

  lashley claimed that intact areas of the cortex could take over responsibility for specific cognitive functions following injury to the area normally responsible for that function
• higher cognitive functions are not localised - equipotentiality theory pt 3

  lashley removed parts of the brain from rats and tested their ability to run through a maze. he found that the area of brain removed did not make any difference to their ability to complete the task
• higher cognitive functions are not localised - equipotentiality theory pt 4

  according to this point of view, the effects of damage to the brain would be determined by the extent rather than the location of the damage

  this view recieved some support from the discovery that humans were able to regain some of their cognitive abilities following damage to specific areas of the brain