Physiology of Eating - L6

1. major determinant of palatability  -> rewarding effect of food 

2. BUT: palatability is not inherent feature of food -> related to learning, upbringing, culture -> ppl eat food because tthey get used to like what they eat 

can partly be explained by sheer physiology: 

1. D-glucose preferred fuel for neurons 

2. low storage capacity for glucose

3. specialized sugar (=sweet) receptors 

4. physiologically useful = high rewarding value 

human bitter receptors not expressed in mice and planted them in mice 

1. control mice did not differ between water and bitter substance acting on this receptor

2. mice with bitter receptor in bitter cells -> low preference for bitter substance

3. mice with bitter receptor in sweet cells -> high preference for bitter substance 

-> stimuli of sweet receptor cell produced preference behavior (its half-wired)

Liking: generated by small set of hedonic hotspots 

Wanting: generated by large and distributed systems

unexpected reward: increase DA neuron activity after cue

expected reward: increased DA neuron activity simultaneously to cue 

negative prediction error: no reward occurs -> increased DA neuron activity simultaneously to cue -> afterwards, weakening of positive association 

1. Taste + oral somatosensation + retronasal olfaction

2. Subliminal reward signals generated during nutrient metabolism in gut 

-> sweet (1) and sugar (2)

1. repeated consumption of palatable foods (usually with high energy content) has features of addictive behavior 

2. some evidence suggests that eating addiction may be associated with overweight/obesity -> but causality not unequivocally established yet

- inhibitory signals act later -> later ending of the meal 

1. our ancestors with no nutritional knowledge were dependent on mechanisms like this to survive (get enough nutrients)

2. variety in diet can also increase body weight 

3. environment we're exposed to (continuous availability of palatable, energy dense foods) is problematic 

neural stimulus (conditioned) paired with another stimulus (unconditioned) -> produces automatic response -> after repeated pairing, CS elicits response similar to unconditioned response 

adaptive change in behavior that results from experience -> conditioning is a very simple form of learing 

Eating can be elicited in satiated rats & humans by conditioned stimulus (expected reward) -> we are exposed to MANY stimuli that can condition eating -> overweight/obestiy epidemic 

hedonic experience is associated with the sensory properties of food -> influences food selection and appearance 

-> positive effects that influence experience: pleasant surroundings, memories, satiating effects

-> negative effects that influence experience: unpleasant memories, diseases, stressors 

-> sensory properties of food will then act as conditioned stimuli 

1. try modify behavior where possible (energy density, portion size, snacks, exercise)

2. no rigid control (-> counterregulation)

3. flexible control 

4. less behaviora control & more situational prevention