c-Fos After Incentive Shifts: Expectancy, Incredulity, and Recovery.

Abstract

Rats were used in a successive negative contrast procedure to determine which brain structures were activated by sucrose concentration downshifts, and on what day this occurred. Subjects were given preshift solutions for 12 days before being shifted to their postshift concentrations. Groups included 2 unshifted controls (32%-32% and 4%-4%) and 1 shifted group (32%-4%). Half of each group was killed 1 hr after the first exposure to the shifted solution (Shift 1), and half after the second exposure (Shift 2). Brains were processed for c-Fos-like immunoreactivity (FLI). Two major patterns emerged. Terminal drinking of 32% sucrose activated minimal brainstem regions involved in palatable taste, visceral feedback, and fluid homeostasis. In contrast, shifted subjects showed extensive cortical activation with selective activation in cerebral nuclei and brainstem. Robust FLI on Shift 1 was absent on Shift 2, consistent with evidence for rapid (1-trial) changes in all major motor outputs mediated by expectancy.

Food-associated cues alter forebrain functional connectivity as assessed with immediate early gene and proenkephalin expression

“…Our gene expression results are consistent with these findings despite some methodological differences. A similar pattern of c-Fos induction to that which we observed was also evident in a recent study assessing regional gene expression in response to shifts in the incentive value of sucrose [64]. These findings suggest that the gene expression changes observed in the present study may play a role in altering the valuation of reward-paired cues used to guide behavior.…”

C-fos expression in the rat brain following lithium chloride-induced illness

“…A clear demonstration of the importance of this latter issue can be seen with regard to the neural substrates of successive negative contrast, the exaggerated underresponding to a low value reward in a situation where a high value reward was expected (Flaherty, 1996). While Pecoraro and Dallman (2005) found no evidence of c-Fos activation in the gustatory thalamus (GT; parvicellular region of the ventral posteromedial nucleus) during the reward downshift trials, neurotoxic lesions of the GT completely prevent the occurrence of successive negative contrast (Reilly & Trifunovic, 1999;.…”

Expression of Fos during sham sucrose intake in rats with central gustatory lesions

“…Thus the current experiment extends the DA dialysis data by providing clues as to where central gustatory activity is processed before it reaches nucleus accumbens. Several other studies have examined the distribution of the protein products of the immediate early gene fos during sapid sucrose stimulation, but none have done so using sham intake or central lesions (9,15,47,70).…”