Localisation

• Localisation of function - Theory that diff areas of brain are responsible for diff behaviors, processes or activities such as movement, speech and memory.
• Motor area - Back of the frontal lobe involved in regulating movement.
• Somotasensory area - Front of the parietal lobe that processes sensory info such as touch.
• Visual area - A part of the occipital lobe that receives and processes visual info.
• Auditory area - Top of temporal lobe and concerned with speech-based info.
• Broca's area - Area of frontal lobe of brain in LH responsible for speech production.
• Wernicke's area - Area of temporal lobe of brain in LH responsible for lang comprehension.
• Historically, scientists supported holistic theory of brain. All parts involved in processing thoughts and action.
• During 19th century, B after Tan and W discovered specific parts of brain were associate with specific physical and psychological functioning, arguing functions are localized - cortical specialization.
• Generally, LH dominates control over right side of body and vice versa.
• Outer layer in brain is cerebral cortex which is highly developed in human. Cortex is subdivided into four lobes - grey matter
• Central succus separates motor cortex and somatosensory cortex
• Somatosensory area is where sensory info from skin is represented. Amount of SS taken up is reflective of body parts sensitivity. e.g. receptors for face and hands takes up over half area.
• Visual area is in occipital lobe. Each eye sends visual info from right visual field (contralateral) to left visual cortex and vice versa. E.g. damage to LH produces blindness in part of right visual field of both eyes.(cortical blindness)
• Auditory areas - Found in top of temporal lobe which analyse speech-based info. Damage may result in hearing loss.
• Somatosensory homunculus is a strange image of a distorted man/woman.The more sensory info a body part sends to CNS, the bigger the body parts representation in homunculus.
• Damage to Broca's area = Broca's aphasia characterized by slow laborious speech, lacking in fluency, short sentences and problems with words such as "and", "the".
• Damage to Wernicke's area = problems understanding speech. Often produce neologisms in content of speech.
• Peterson et al using brain scans, showed how W's area was active during a listening task but B' area was active during a reading task. Areas of brain have diff functions.
• Long term study of memory by Tulving et al showed that semantic and episodic memories reside in diff parts of prefrontal cortex.
• What type of neurosurgical procedure supports the idea that behaviors and symptoms are localized?


  Cingulotomy
• What did Dougherty et al (2002) report about OCD patients who underwent cingulotomy?


  After 32 weeks, a third met the criteria for a successful response to the surgery. This suggests that the effectiveness of cingulotomy depends on the precise location of lesioning within the brain, supporting the idea that specific brain regions are responsible for specific functions, such as those related to OCD
• What percentage of OCD patients experienced a partial response after cingulotomy according to Dougherty et al (2002)?


  14%
• How does the case of Phineas Gage support the localization theory?


  His personality changed dramatically after a pole damaged his frontal lobe.
• What caused the injury to Phineas Gage's brain?


  A metre-length pole passed through his left cheek and exited from the top of his head.
• What part of Phineas Gage's brain was primarily affected by the accident?


  Most of the frontal lobe.
• What behavioral changes did Phineas Gage exhibit after his accident?


  He became quick-tempered, rude, and lost his language skills.
• What does the change in temperament of Phineas Gage suggest about the frontal lobe?


  It may be responsible for regulating mood.
• What are the key findings from the case of Phineas Gage regarding brain localization?


  • Injury to the frontal lobe led to significant personality changes.
  • Supports the idea that specific brain areas are linked to specific behaviors.
  • Highlights the role of the frontal lobe in mood regulation.
• W - Lashley (1950) suggests processes such as learning are distributed holistically in the brain. He removed between 10-50% of the cortex of rats that were learning a maze. No single area was found to be more Important than any other, to learn the maze, and the learning process appeared to need every part. This suggests learning is too complex to be localised and needs the whole brain to be involved. Although, humans are physiologically dissimilar to rats in behaviourism e.g. Rats don't problem solve they really only have survival instincts.
• When the brain has become damaged through illness or accident, and a particular function has deteriorated or been lost, the rest of the brain reorganises itself to recover the lost function. Lashley called this the 'law of equipotentiality' - positing that all areas of the brain are equally able to perform a task so surviving brain circuits 'chip in' so the same neurological action can be achieved. This may not always happen but many stroke victims have recovered lost abilities.
• Motor, somatosensory and auditory cortices are in both hemispheres.
• Broca and Wernicke' area are only in the left hemisphere - hemispherically lateralised
• Damage to motor area = loss of muscle function in opposite side of the body
• Damage to somatosensory cortex = loss of sensation in opposite side of body, could also lead to neglect syndrome where areas of the body are ignored.