Bio Psych B -Hemispheres

• Localisation of Function


  The idea that certain functions (eg, language, memory, etc.) have certain locations or areas within the brain
• Brain


  Divided into two hemispheres: the left and the right
• Brain hemispheres


  • Each hemisphere is responsible for specific functions
  • Lateralisation: the dominance of one hemisphere of the brain for particular physical and physiological functions
• Activity on the left-hand side of the body


  Controlled by the right hemisphere
• Cerebral cortex


  • Outer layer of both hemispheres (like a tea cosy covering the inner parts of the brain!)
  • About 3 mm thick
  • What separates us from other animals because the human cortex is much more developed
• Locations.


  Locations of structures

  
• Left side of brain


  Responsible for speech and analytical thinking, controls the right side of the body
• Right side of the brain


  Responsible for image processing and spatial thinking, controls the left side of the body
• Primary visual cortex


  Located at the back of the brain in the occipital lobe, receives and processes visual information
• Visual information from the right hand side visual field

  Processed in the left hemisphere
• The visual cortex contains different parts that process different types of information including colour, shape or movement
• Primary auditory cortex


  Located in the temporal lobe, responsible for analysing and processing acoustic information
• Information from the left ear


  Goes primarily to the right hemisphere
• Information from the right ear


  Goes primarily to the left hemisphere
• The auditory area contains different parts and the primary auditory area is involved in processing simple features of sound, including volume, tempo and pitch
• Motor cortex


  Located in the frontal lobe, responsible for voluntary movements by sending signals to the muscles in the body
• Hitzig and Fritsch discovered that different muscle areas are coordinated by different areas of the motor cortex by electrically stimulating the motor areas of dogs resulting in muscular contractions in different areas of the body depending on where the probe was inserted
• Regions of the motor area are arranged in a logical order, for example, the region that controls finger movement is located next to the region that controls the hand/arm
• Somatosensory centres


  Located in the parietal lobe, receive incoming sensory information from the skin to produce sensations related to pressure, pain, temperature, etc.
• Different parts of the somatosensory area receive messages from different locations of the body
• robertson found that somatosensory area of the brain is highly adaptable
• Aphasia


  • An impaired ability to understand or produce speech, as a result of brain damage
• Expressive aphasia (Broca's aphasia)


  An impaired ability to produce language, usually caused by brain damage in Broca's area
• Receptive aphasia (Wernicke's aphasia)


  An impaired ability to understand language, usually the result of damage in Wernicke's area
• Idiographic studies lack population validity and are not appropriate to generalize findings to the rest of the population as some individual cases may be unique
• Broca's area

  • Located in the left posterior of the frontal lobe
  • The motor speech area
  • Helps in movements required to produce speech
• Broca's aphasia


  When there is an issue in Broca's area, a patient can understand the speech of others, but can't produce any speech him or herself
• Wernicke's area


  Located in the posterior left temporal lobe, involved in language processing/comprehension
• Wernicke's area


  • People with damage to this area struggle to comprehend language, often producing sentences that are fluent, but meaningless (Wernicke's aphasia)
• Wernicke studied a patient who had suffered a stroke


  1873
• Although the man was able to speak and his hearing was unimpaired, he could barely understand what was said to him. Nor could he understand written words
• After he died, Wernicke found a lesion in the rear parietal/temporal region of the patient's left-brain hemisphere
• Broca


  Studied the difficulties that Tan (stroke victim) had with his communication for many years
• Tan died at age

  51
• Autopsy of Tan


  • Revealed a lesion in the left frontal lobe
  • Broca concluded that parts of the left frontal lobe including the area damaged in Tan had the role of the "language centre in our brain"
• Language production may not be confined to Broca's area alone
• Broca's area


  A region of the brain associated with speech production
• Dronkers et al (2007) study

  1. Conducted an MRI scan on Tanj brain

  2. Tried to confirm Broca's findings

  3. Found a lesion in Broca's area

  4. Also found evidence to suggest other areas may have contributed to the failure in speech production
• These results suggest that Broca's area may not be the only region responsible for speech production
• The deficits found in patients with Broca's aphasia could be the result of damage to other neighbouring regions