View source for FEB 12

==8. FEB 12==

===Assigned Work===
:*Gordon Shepherd, ''Neurogastronomy'' Chapters 11, 18, 19, (22)

===In Class===

===Gordon Shepherd, Neurogastronomy Chapters 11, 18, 19===

:C11 Creating, Learning, and Remembering Smell

:*lateral olfactory tract — context output from the bulb to the olfactory cortex in the brain.  Long in humans.  What is its role?  
:*importance of pyramidal cells.  100: capable of feedback excitation to stimulating cells.  Thought important to memory.  Damaged in dimentia patients. 
:*101: Olfactory cortex “serves as content-addressable memory for association of odor stimuli with memory traces of odors.  “.  Structures that support this claim.  Herb rule - identifies activity that suggest memory and learning.  Interesting parallels between odor recognition and face recognition.  
:*103: summary of functions of olfactory cortex.  Not clear if perception of smell itself arises in ol. Cortex.  Some research suggesting that it can detect the absence of the essential amino acids.

:*key ideas: knowledge of mechanisms for understanding memory and flavor; learning mechanism, may even detect amino acids.

:*[Point: Reinforcement learning takes place immediately in the olfactory cortex.  Our experience of food is not a “passive awareness”.  Because food is essential to survival, and omnivores have complex food / memory needs, learning and memory processes are crucial.  The reward structure of the brain is involved.  The olfactory cortex is smart.]


:C18 Putting it all Together: The Human Brain Flavor System

:*Opening summary of the "human brain flavor system."  
:*Reference and quote from Brillat-Savarin, the first “gastronome” .  Nice continuity between early language and neurogastronomy.   “The human brain has specific capabilities that makes the appreciation of flavor of unique importance to humans.”
:*Sensory system vs action system
:*Sensory system:
::*Flavor also produced by smell, taste, mouth-sense, sight, sound. Not just “volatile molecules reaching the olfactory bulb. 
::*Multi-sensory integration, or “Supra-addivtivity” involves congruent repetition of combinations of stimuli.  “internal brain image” of the flavor object.
::*read summary sentence, p. 160: “A consensus is emerging that simultaneous activation by a food of a common set of regions, including the orbitofrontal cortex, anterior insula and operculum, frontal operculum, and anterior cingulate Byrd’s, constitutes the distributed representation in our minds of a flavor object”  [Think about this a minute....]
:*Flavor-action system
::*Chart on p. 161 matching brain structures to aspects of flavor perception and desire, motivation, and action.  The action system includes emotional response, memory, decision making, plasticity (how the activity of the body/brain — in this case eating— changes the brain) Language, consciousness.  (Each treated in next section.  We sample the chapter on emotions.)

:C19: Flavor and Emotions

:*emotions moves us toward action, but also reflect our internal state of desiring and wanting.  What is diff between want and craving? 

:*research from Monell Chemical Senses Institute.  Cravings implicated in eating disorders.  Dull diets stimulate craving.  Marcia Pelchat and colleagues looked at parallels between food cravings and drug craving.  In a study, one group of test subjects were on a monotonous diet and another on a normal diet.   In brain imaging, the monotonous eaters produced strong activation when asked to imagine a favorite food.  Supports hypothesis that there is a common circuitry to natural and pathological rewards (food and drugs).   168ff: discussion of brain structures implicated in the study.  Hippocampus, insula, caudate nucleus.  Caudate includes high concentration of dopamine.  Also part of the striatum, which involves habits (which probably involve dopamine).  When we are hungry, we can activate food memories and emotional responses in anticipation of the food.  

:*[An implication of this for eating is that hunger plays a key role in satisfaction.  The hungrier eater produces stronger anticipatory activation.  “Hunger is the best relish.”  “Images of desire” maybe be important to satisfaction.  But also, this research suggests that an '''unsatisfied brain''' (one on a dull diet) is more likely to produce cravings .  In a sense the brain demands satisfaction.  read at 168. Digression on question: Does the industrial diet produce real satisfactions? Mixed evidence.  ]

:*chocolate-satiety study (Dana Small) — test subjects eat chocolate to satiety while in imaging.  Difference in activation can be thought of as a change in the flavor image (for chocolate) under conditions of craving and satisfaction.   Mentions concept of “reward value” current in brain research.  cool idea here is that our flavor images change with our hunger states.