Frontal Lobes and Voluntary Behaviour

• The brain


  A bit like a cauliflower
• The brain


  A bit like a walnut
• The normal brain's cortical surface is more symmetrical than the surface of a typical walnut

  
• The cerebral cortex


  • Divided into two separate wrinkled sheets - one on the left that forms a kind of 'skin' of the left hemisphere, and one on the right
• Lobes of the cerebral cortex


  • Temporal lobe
  • Occipital lobe
  • Parietal lobe
  • Frontal lobe
• Frontal lobes


  • Comprise a big chunk of the cerebral cortex
• Frontal cortex


  • A substantial proportion has motor-related functions (M1, PMA, SMA + FEF, SEF, Broca's area)
• Primary motor cortex (M1)


  Occupies the precentral gyrus
• Motor function of primary motor cortex (M1) was determined by direct electrical stimulation of the brain surface when the head was opened for surgery
• Motor homunculus


  Penfield's motor homunculus
• Damage to primary motor cortex


  Problems coordinating and controlling muscles in voluntary movement; tight (contracted) musculature (hypertonia)
• Damage to more rostral motor areas


  Does not affect muscle control, but has effects on planning, selecting and initiating acts and/or courses of action
• Damage to Broca's area affects a person's ability to produce comprehensible speech - speech lacks grammatical structure and other qualities that make the intended message understandable