sensory integration and perception

• What is the thickness of the cortex in humans?


  1. 4 mm thick
• What type of cells are pyramidal cells and what is their function?


  Pyramidal cells are excitatory and project out of the cortex
• From which layer does sensory input come into the cortex?

  Sensory input comes into layer 4 from the thalamus
• Where does motor output leave the cortex?


  Motor output leaves layer 5 to the sub-cortex
• What is the function of layer 6 in the cortex?


  Layer 6 is involved in descending control to the thalamus and cortex
• What are Brodmann's areas and how many are there?


  • Mapped 52 areas through Nissl staining
  • Area 17 = primary visual cortex
  • Area 22 = primary auditory cortex
• Which areas correspond to the primary somatosensory cortex?


  • Areas 1, 2, 3a, 3b
• What are the implications of Penfield's homunculus being based on white males?


  • Women are 50% more likely to have heart attacks misdiagnosed
  • Oximeters are less effective with darker skin tones
• What did Mountcastle’s micromapping reveal about cortical neuron populations?


  • Defined modalities and adaptation rates
  • Identified columnar organization of the cortex
• What is a column in the context of the cortex?


  • The functional unit of informational processing
  • Detects information and passes it to the next column
• How does information from specific places in the cortex remain separate?


  • Information from each finger is processed in slightly different places in the cortex
• What is the sequence of information processing in Brodmann’s areas 1, 2, 3a, and 3b?


  • Skin = 3b → 1 → association areas
  • Joints and muscles = 3a → 2 → association
• What is asterognosis?

  Asterognosis is the inability to recognize an everyday object by touch
• What types of information do feature detecting neurons process?


  • Textural information is processed by area 1
  • Shape and size information is processed by area 2
• How do feature detecting neurons rely on convergence?


  • They require information from multiple neighboring sensory receptors
• What does the pattern of a primary neuron’s activity depend on?

  The pattern depends on orientation and direction
• What is the role of association areas in somatosensory perception?


  • Integrate information from multiple brain regions
  • Allow sensory stimuli to be recognized and assigned meaning
• What percentage of the human brain is made up of association areas?


  80%
• What do somatosensory association areas allow for?


  • Multisensory understanding of the world
  • Predicting the future
• What are the connections of somatosensory association areas related to?


  • Strong connections to the hippocampus and amygdala (emotion + memory component)
• What happens when there is damage to the primary somatosensory region?


  • Loss of ability to detect sensory stimuli
  • Cannot recognize a key with eyes closed, but visual field remains fine
• What are the effects of damage to association areas?


  • Issues around recognition and perception
  • Important for integration of sensory information with body image and other senses
• What can damage to association areas cause?


  It can cause asterognosis and hemineglect
• What can happen after a small stroke affecting body image?


  • The individual may feel as if their leg has been removed from their body image
  • Often ends in voluntary amputation
• What happens when there is damage to alpha neurons related to proprioception?


  • The individual has to learn how to move based on vision
• What is the effect of dramatic parietal damage on perception?


  It can cause an inability to perceive the left-hand side of the world
• Which side of the brain is typically damaged to cause an inability to perceive the left-hand side of the world?


  The right side of the brain is typically damaged