EFFECTS OF LESIONS OF THE MEDIAL PARABRACHIAL NUCLEUS (PBNM) - TASTE DISCRIMINATION AND LITHIUM-CHLORIDE-INDUCED AVERSION LEARNING AFTER DELAYED AND CONTIGUOUS INTERSTIMULUS INTERVALS
A. Aguero et al., EFFECTS OF LESIONS OF THE MEDIAL PARABRACHIAL NUCLEUS (PBNM) - TASTE DISCRIMINATION AND LITHIUM-CHLORIDE-INDUCED AVERSION LEARNING AFTER DELAYED AND CONTIGUOUS INTERSTIMULUS INTERVALS, Psychobiology, 24(4), 1996, pp. 265-280
This article analyzes the effects of lesions to the medial parabrachia
l nucleus (PBNm) in taste aversion learning (TAL) and taste discrimina
tion tasks (TDT). In the first experiment, control and lesioned rats w
ere presented with a delayed TAL task in which presentation of the gus
tatory stimulus was followed 15 min later by the intragastric administ
ration of LiCl. In the second experiment, ingestion of the gustatory s
timulus was followed immediately by LiCl administration. Control anima
ls successfully learned both tasks, whereas PBNm-lesioned animals lear
ned only the second task. In the third experiment, the animals were su
bjected to TDT with water, saccharine, and quinine. The lesioned anima
ls ingested significantly different amounts of stimuli from that inges
ted by control rats, showing a clear preference for high concentration
s of saccharine; the lesioned animals rejected high concentrations of
quinine to a lesser degree than did control animals. In a fourth exper
iment, PBNm-lesioned animals were able to solve a delayed TAL task whe
n discriminated gustatory stimuli were used. These results are interpr
eted as evidence that the PBNm lesion interferes with gustatory proces
sing and that the temporal demands imposed by Experiment 1 obviate the
use of exteroceptive cues.