CONTEXT-SPECIFIC MULTISITE CINGULATE CORTICAL, LIMBIC THALAMIC AND HIPPOCAMPAL NEURONAL-ACTIVITY DURING CONCURRENT DISCRIMINATIVE APPROACH AND AVOIDANCE TRAINING IN RABBITS

This study assessed the context specificity of learning-related neuron al activity: whether the same physical stimuli would elicit different neuronal responses depending on the learning situation. Neuronal activ ity was recorded simultaneously in six limbic areas as rabbits learned to approach a spout for water reinforcement after a tone (CS+) and to ignore the spout after a different tone (CS-). The rabbits then recei ved avoidance training in which they learned to prevent a foot-shock b y stepping in an activity wheel after one tone (CS+) and to ignore a d ifferent tone (CS-). Avoidance training sessions were alternated (1 se ssion daily) with sessions in the well learned approach task. The tone assigned as the CS+ for approach training was the CS- for avoidance t raining and vice versa. The neuronal records of the anterior ventral a nd medial dorsal thalamic nuclei and the anterior and posterior cingul ate cortices showed neuronal discrimination appropriate to the approac h task during pretraining in the avoidance training apparatus with unp aired presentations of the tones and foot-shock. This finding demonstr ated that the discriminative neuronal activity for approach learning w as unaffected by a change in context in the pretraining session. Howev er, context-appropriate discrimination occurred in both tasks thereaft er, with the exception that medial dorsal thalamic neurons no longer s howed discrimination during overtraining in the approach task. Hippoca mpal area CA1 neurons showed entirely context-appropriate discriminati on in both tasks, with no carryover of the approach-relevant discrimin ation to the avoidance training apparatus. Avoidance training stage-sp ecific peaks of training-induced excitation in different brain areas w ere not elicited by the same physical stimuli during concurrent approa ch training sessions. The results are consistent with an involvement o f limbic-circuit neuronal activity in the use of context cues for mnem onic retrieval. Differential persistence of the approach-related neuro nal discrimination in anterior and posterior cingulate cortex confirme d the previously hypothesized distinct mnemonic functions of these are as.