Parallel and serial processes of the prefrontal and cingulate cortical systems during behavioral learning.
Multiple unit activity of the prefrontal cortex (PFC) and the mediodorsal (MD) nucleus of the thalamus was recorded during differential conditioning of a locomotory (wheel-rotation) avoidance response. The positive and negative conditional stimuli (CS+ and CS-) were pure tones (l kHz and 8 kHz), and the unconditional stimulus was a footshock (1.5-2.0 mA) delivered through the grid floor of the wheel apparatus. A principal objective was to compare the development during training of CS-related neuronal activity in the PFC and MD nucleus, to that obtained in past studies of the adjacent limbic mesocorticothalamic system (the cingulate cortex and the anteroventral (AV) thalamic nucleus). The results indicated that these systems perform associative processing of task-related stimuli in parallel: as in the cingulate cortex, discriminative neuronal discharges (greater discharges to the CS+ than to the CS-) developed in the PFC in the earliest training stage, before incipient discriminative behavior, and as in the AV nucleus, discriminative discharges in the MD nucleus developed in a later training stage. Nevertheless the possibilities of serial processing and intercausality in these systems was suggested by the finding that discriminative activity in the PFC and MD nucleus developed at briefer latencies and earlier in the course of trials than in the cingulate cortex and the AV nucleus.
D000818:Animals; D001362:Avoidance Learning; D002540:Cerebral Cortex / Q000502:physiology*; D004192:Discrimination, Psychological; D005071:Evoked Potentials; D006179:Gyrus Cinguli / Q000502:physiology*; D009043:Motor Activity; D009474:Neurons / Q000502:physiology; D011817:Rabbits; D013788:Thalamus / Q000502:physiology*