Lateralized state-dependent learning produced by hippocampal kindled convulsions: effect of split-brain.
In previous experiments, it was demonstrated that convulsions kindled from a ventral hippocampal focus in rats supported state-dependent learning which tended to lateralized to, and asymmetrical in, the right hemisphere. The question of the differential contribution of the left and right hippocampus to the production of state-dependency can best be addressed through confining the seizure to one or the other hemisphere via commissurotomy. In the present investigation, then, commissurally-intact and split-brain rats were implanted with bilateral hippocampal electrodes, then a left or a right focus was kindled. Later behavioral testing in an aversive inhibitory avoidance (IA) paradigm, revealed that intact animals, both left and right kindled groups, displayed good state-dependency. Split-brain animals, however, exhibited differential state-dependent responses to convulsive stimulation. Those kindled in the left hippocampus showed good retention when the conditions of seizure during training and testing were the same (same-state conditions), while showing deficient recall in changed-state conditions (a good state-dependent profile). On the other hand, those kindled in the right hippocampus displayed good retention of the IA experience in both same- and changed-state conditions. Differential recall after a left versus a right hippocampal convulsion in split-brain animals could not be accounted for in terms of differential seizure parameters, laterality of afterdischarge, extent of extracommissural damage or the extent of the actual transection. Possible mechanisms underlying this effect were discussed.
D000818:Animals; D001362:Avoidance Learning / Q000502:physiology; D001931:Brain Mapping; D003337:Corpus Callosum / Q000503:physiopathology; D004292:Dominance, Cerebral / Q000502:physiology*; D006624:Hippocampus / Q000503:physiopathology*; D007696:Kindling, Neurologic; D008297:Male; D009433:Neural Inhibition; D009434:Neural Pathways / Q000503:physiopathology; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000502:physiology; D012640:Seizures / Q000503:physiopathology*