Acquisition of conditional discriminations in hippocampal lesioned and decorticated rats: Evidence for learning that is separate from both simple classical conditioning and configural learning.

Abstract

This study examined whether hippocampal or neocortical lesions would impair acquisition of a discrimination task using taste aversions. Rats were injected with a drug 15 min before a flavored solution-lithium chloride pairing. On alternate days, vehicle injections preceded and followed access to the same flavored solution. Rats learned to consume significantly more of the flavored solution after vehicle injections than after drug injections. Rats with hippocampal lesions or neonatal decortication performed as well as controls. Rats with hippocampal lesions also learned a similar task in which visual and textural cues predicted whether access to a flavored solution would be followed by an injection of lithium chloride or vehicle. However, these hippocampal lesions did impair performance in the Morris water task. Occasion setting may involve a type of learning dissociated from both simple classical conditioning and configural learning.

Hippocampus, Temporal Context and Taste Memories

“…In all, the results demonstrate a hippocampal role in the temporal context-dependency of LI, but not in conditional learning using taste recognition memory tasks. This is consistent with evidence obtained using other learning tasks showing a similar hippocampal role in the external context-dependency of LI (Honey and Good, 1993) and no role of the hippocampus nor amygdala in conditional learning using places as contexts (Skinner et al, 1994(Skinner et al, , 2000.…”

Environmental complexity affects contextual fear conditioning following hippocampal lesions in rats

“…Interestingly, parallel results of intact contextual learning in a relatively simple environment, following HPC lesions, have been obtained in nonaversive tasks. (Hirsh, 1974;Winocur and Olds, 1978;Skinner et al, 1994).It is widely held that the hippocampus plays a crucial role in integrating and forming relationships among multiple stimulus elements for purposes of guiding appropriate behavior (e.g., Cohen and Eichenbaum, 1993;Rudy and Sutherland, 1995;Nadel and Moscovitch, 1997;Fanselow, 1999;Rosenbaum et al, 2001;Moses and Ryan, 2006). By this view, the hippocampus is not considered to be involved in forming direct associations between specific stimuli and unconditioned responses, and it follows that HPC lesions should have limited effects on CFC in a relatively uniform environment where discrete background cues can become directly associated with the fear response.…”

A Receptor Tyrosine Kinase Plays Separate Roles in Sensory Integration and Associative Learning inC. elegans

“…In worms, if associations can be formed independently of sensory integration, then there must be a difference in how a memory is represented versus how integrated stimuli are represented within the worm nervous system, much like the differential processing of contextual cues in mammals (Skinner et al, 1994; Good et al, 1998). One possibility is that sensory integration leads to a blending of two stimuli in a single representation that leads to an appropriate motor response, whereas associative learning encodes an association between the separate representations of two stimuli.…”