PSC 129 - Sensory Processes

Classification of tastes

• Four categories: sweet, sour, salty, bitter. (taste tetrahedron)
  
  
• Gestalt vs. perception of distinct components.
  
  
• MDS reveals more than four dimensions.
  
  
  

• Taste buds are located in papillae in the tongue (but not in center). Each taste bud contains about 50 tast receptor cells. Taste buds also located in the roof of the mouth, inside cheeks, and in the throat. (some insects have taste buds on feet)
  
  
• Humans possess on average 6000 taste buds. These are constantly degenerating and being replaced. Life expectancy is about 10 days. Not true neurons (unlike olfactory receptor cells)
  
  
• Different regions of tongue are most sensitive to different primary tastes. (but not really a “tongue map” - tastes are intermingled over the tongue)
  
  
• Center of the tongue has no taste buds and is thus “blind” to taste.
  
  
• Our perception is that taste sensations originate from entire mouth, not just the tongue.
  
  

• Taste afferents originating from taste buds run through the cranial nerves, project to the gustatory nucleus, in the medulla, and then onto thalamus (ventral posterior medial nucleus), and eventually cortex (insular cortex and postcentral gyrus). Fibers also project to limbic system, as in olfaction.
  
  
• Cross-fiber theory (aka “population coding”) states that taste quality is represented by the pattern of activity across a population of neurons.
  
  
  

• Indentification is poor near threshold sensitivity.
  
  
• Women are better than men at identification.
  
  
• Perception is modified by adaptation and by context.
  
  
• Taste identification is aided by olfaction.