Localisation of Function in the Brain and Hemispheric Lateralisation:
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Frontal Lobes:
- Involved in the executive functions of the brain, which are higher level cognitive processes. This control process is involved in coordination, planning and organising of actions towards an individuals goals.
- Contributes to: Behaviour, language, reasoning.
- Prefrontal cortex: This region controls the executive processes, such as planning, decision making, error correction, assisting in overcoming habitual responses.
- Used PET and fMRI scans to further support functional specialisation of the frontal cortex.
- Lesion studies support these findings where left frontal lobe patients exhibited problems in controlling executive functions such as creating strategies.
The Left and Right Hemispheres:
- Both hemispheres have a motor cortex and a somatosensory cortex. They each receive information from the opposite side of the body.
Somatosensory Cortex:
- Main sensory receptive area for the sense of touch. It detects sensory events from different areas of the body.
- Located in the Parietal Lobe, along a region called the Postcentral Gyrus.
- Information from skin produces sensations of: touch, pain, pressure, temperature. These sensations are then localised to specific bodily areas.
- Region of the cerebral cortex involved in: planning, control, execution of voluntary movements.
- An area of the frontal lobe located immediately anterior to the central sulcus.
- Used a common 1930s procedure to examine epileptic patients who were undergoing brain surgery.
- Patients were given a local anaesthetic and their skulls were opened to expose the brain.
- Electrical stimulation was applied to the surface of the brain to map out the areas of speech.
- This allowed the surgeon to avoid any damage to speech circuitry.
- The brain focus of the epilepsy could then be surgically removed.
Temporal Lobes:
- Contains the auditory area of the brain, which analyses speech-based information.
- Both Broca's and Wernicke's area are found in the left temporal lobe.
- Damage may produce partial hearing loss. The bigger the damage, the bigger the loss.
- Damage to Wernicke's area may affect the ability to comprehend language.
- Language is restricted to the left side of the brain (for most people).
- Broca's Area is responsible for speech production, and Wernicke's Area is responsible for language comprehension.