Wednesday, 4 November 2015

Neural Mechanisms of Eating Behaviour

Homeostasis

This involves mechanisms which detect the state of the internal environment. There is a time lag between restoring equilibrium and measuring effect. 


For a hunger mechanism to be adaptive, it must anticipate and prevent energy deficits.

Dual-Process Model

Decline in glucose
              |
Activates lateral hypothalamus
              |
         Hunger
              |
Search and consume food
              |
     Glucose rises
              |
Activates ventromedial hypothalamus
              |
  Feeling of satiation
              |
  Stops further eating       

Lateral Hypothalamus
- Functions as the feeding centre, stimulating feeding in response to signals from the body.
- Damage to LH can cause aphagia. Stimulation elicits feeding behaviour.
- The view that LH serves as an 'on switch' for eating has problems - damage to LH had other behaviour deficits (thirst and sex).

Research: Sakuri (1998)

Ventromedial Hypothalamus 
- Part of the hypothalamus that functions as a satiety centre to inhibit feeding.
- Damage to the VMH caused rats to overeat - hyperphagia.
- Usually overeating only occurred when there was also damage to the paraventricular nucleus.

Research: Gold (1973)

Neuropeptide Y
- Important in turning on eating. When injected into hypothalamus of rats, it caused them to begin eating despite having eaten before.
- Obese people may have an over-production of NPY.

Research: Marie et al (2005)

Neural Control of Cognitive Factors
- The Amygdala - Thought to be primarily in the selection of foods on the basis of previous experience.
- Rolls and Rolls (1973) 

- Inferior Frontal Cortex - Thought to be linked with odours and food response. Diminished odour response decreased eating.

Research: Zald and Pardo (1997)
    

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