Western diet and the weakening of the interoceptive stimulus control of appetitive behavior

Abstract

In obesogenic environments food-related external cues are thought to overwhelm internal cues that normally regulate energy intake. We investigated how this shift from external to internal stimulus control might occur. Experiment 1 showed that rats could use stimuli arising from 0 and 4h food deprivation to predict sucrose delivery. Experiment 2 then examined (a) the ability of these deprivation cues to compete with external cues and (b) how consuming a Western-style diet (WD) affects that competition. Rats were trained to use both their deprivation cues and external cues as compound discriminative stimuli. Half of the rats were then placed on WD while the others remained on chow, and external cues were removed to assess learning about deprivation state cues. When tested with external cues removed, chow-fed rats continued to discriminate using only deprivation cues, while WD-fed rats did not. The WD-fed group performed similarly to control groups trained with a noncontingent relationship between deprivation cues and sucrose reinforcement. Previous studies provided evidence that discrimination based on interoceptive deprivation cues depends on the hippocampus and that WD intake could interfere with hippocampal functioning. A third experiment assessed the effects of neurotoxic hippocampal lesions on weight gain and on sensitivity to the appetite-suppressing effects of the satiety hormone cholecystokinin (CCK). Relative to controls, hippocampal-lesioned rats gained more weight and showed reduced sensitivity to a 1.0 ug but not 2.0 or 4.0 ug CCK doses. These findings suggest that WD intake reduces utilization of interoceptive energy state signals to regulate appetitive behavior via a mechanism that involves the hippocampus.

Extinction of instrumental (operant) learning: interference, varieties of context, and mechanisms of contextual control

“…Deprivation level was also still an effective cue when the rats had no food in the home cage before either reinforced or nonreinforced sessions (they discriminated between 2-hr and 23-hr deprivation conditions). The findings add to many results reported by Davidson and colleagues which suggest that hunger and satiety states can provide discriminative cues for Pavlovian conditioned responding (e.g., Davidson, 1993; Davidson, Kanoski, Tracy, Walls, Clegg, & Benoit, 2005; Kanoski, Walls, & Davidson, 2007; Sample, Jones, Hargrave, Jarrard, & Davidson, 2016). Motivational states may function as contexts.…”

Effects of Sweet-Liking on Body Composition Depend on Age and Lifestyle: A Challenge to the Simple Sweet-Liking—Obesity Hypothesis

“…Critically, for hedonic responses to sweetness to represent the internal need state of the body, efficient interoceptive mechanisms need to be in place. Growing evidence suggests an association between Western lifestyle and poor interoceptive abilities [91,92]. While we did not obtain any objective measure of interoception here, in those with shorter exposure to the obesogenic environment (i.e., our younger group), positive hedonic responses to high sweetness (as alliesthesia would dictate) could be interpreted as a reflection of the internal state of the body.…”

Hippocampal-dependent appetitive control is impaired by experimental exposure to a Western-style diet

“…In the other account, modulation occurred via state-dependent inhibition of associative networks connected with obtaining a food (e.g. [3,12,13]). While the data from our study suggests that the hippocampus is involved in modulation, we did not set out to contrast these models.…”

“…As hippocampal-related roles in reward value are generally not to the fore when considering self-control, the findings here and from animal studies (e.g. [3,12,13,62,63]) would suggest that they may be worthy of further consideration.…”