Brain Localisation

• Different functions are localised to different parts of the brain - Localisation of function
• What is localisation of function?

  The idea that different parts of the brain perform different functions
• The brain is divided into two halves, called hemispheres, which are divided by a small gap.
• Hemispheric lateralisation is the idea that the two hemispheres perform different functions.
• Spatial skills are hemispherically lateralised to the right hemisphere.
• Language skills are hemispherically lateralised to the left hemisphere.
• Both hemispheres are involved in controlling our movement and all five senses.
• What senses are organised contralaterally?

  Vision, Movement and Touch
• contralaterally = opposite side
• Statements needed to know on lateralisation of function?

  • Language skills are hemispherically lateralised.
  • Spatial skills are hemispherically lateralised.
  • Movement, vision and touch are organised contralaterally.
• Although hearing, smelling and taste are controlled by both hemispheres they are NOT organised contralaterally.
• How do the two hemispheres communicate with each other?

   By sending nerve impulses to each other via synapses
• The corpus callosum is a bundle of nerve axons that enables communication between the two hemispheres.
• Which two regions of the brain are involved in the fight or flight response?

  • Pituitary Gland
  • Hypothalamus
• Split brain patients:

  • Split-brain patients are patients whose corpus callosum has been cut.
  • In split-brain patients, the two hemispheres can no longer communicate with each other.
• Research that investigates split-brain patients is called split brain research, and it has enabled researchers to study hemispheric lateralisation.
• What is the process used in split-brain research?

  • The researcher presents a stimulus to either the patient’s left, or their right hemisphere.
  • Patients are asked to describe a stimulus that has been presented to them.
  • Patients are asked to respond to a stimulus that has been presented to them, by pointing at the stimulus that matches the one they were just shown.
• In split-brain research, how should the stimulus be presented to the patient?

  To just one hemisphere at a time.
• As vision is organised contralaterally, to present the image to the left hemisphere, the researcher needs to place the image on the patient’s right hand side.
• What is the consequence of a function not being hemispherically lateralised?

  The patient should be able to perform the function, regardless of whether the stimulus is presented to the right or left hemisphere.
• Sperry’s split-brain study

  • Sperry presented images to either the patient’s right or left hemisphere.
  • Sperry’s first study found that if patients were asked to point to one of four pictures to identify which matched the image, they could perform the task whether or not the image was presented to their right or left hemisphere.
  • Sperry’s second study found that if patients were asked to verbally describe the image, they could only perform this task if the image was presented to their left hemisphere.
  • Sperry concluded that language is hemispherically lateralised to the left hemisphere.
• Limitations of Split-brain Research

  • Research involves a small number of participants (lack generalisability)
  • Patients brains may function differently: seizures (confounding variable)
  • Not entirely replicated
  • There are exceptions to hemispheric lateralisation
• EB has his left hemisphere removed when he was 2.5 years old, meaning he initially lost his language skills. After rehabilitation, he regained these skills. However, nobody thought this was possible because these skills are hemispherically lateralised to the left hemisphere.
• Danelli's investigation on EB found that...

  • Conducted a case study, using verbal testing and MRI
  • Her control group were people with normal brains.
  • She found that hemispherically lateralised functions can be taken over by the other hemisphere.
• What is the cortex?

   The outer surface of the brain.
• The motor cortex controls our body movement by sending nerve impulses to motor neurons, which control the muscles in our body.
• As there is a somatosensory cortex in both hemispheres, our sense of touch is organised contralaterally.
• What does the somatosensory cortex process?

  Our feeling of touch
• The auditory cortex processes sound by receiving nerve impulses from sensory neurons that talk to sensory receptors in the ears.
• What is the auditory cortex?

  The auditory cortex is the part of the brain that processes sound. There is an auditory cortex in both hemispheres, but the auditory cortex isn’t organised contralaterally.
• If you damage one visual cortex, what could happen?

  If you damage the right visual cortex, you lose the ability to process vision and see things on your left side and vise versa.
• Information on the visual cortex

  • The visual cortex processes vision
  • Both hemispheres are involved in processing vision
  • The visual cortex receives nerve impulses from sensory neurons that talk to sensory receptors in your eyes.
  • vision is organised contralaterally.
• Broca’s area is involved in producing language, so we can say it is hemispherically lateralised to the left hemisphere.
• Information on Broca's area

  • Broca’s area is hemispherically lateralised to the left hemisphere.
  • Broca’s area is the part of the brain that enables us to produce language.
• Wernicke's area information

  • Wernicke’s area is the part of the brain that enables us to understand spoken and written language.
  • Wernicke’s area is hemispherically lateralised to the left hemisphere.
• Wernicke’s aphasia leads to the inability to understand language.
• Broca's aphasia leads to the inability to produce language.
• What is Aphasia?

  • Aphasia is when people lose the ability to understand or use language.
  • Broca’s aphasia is when Broca’s area is damaged, leading to an inability to produce language.
  • Wernicke’s aphasia is when Wernicke’s area is damaged, leading to an inability to understand language.
• A = Motor Cortex

  B = Somatosensory Cortex

  C = Broca's area

  D = Auditory Cortex

  E = Wernickle's area

  F = Visual Cortex

  
• Brain Diagram