A gradient of plasticity in the amygdala revealed by cortical and subcortical stimulation, in vivo

Projections to the amygdala from various cortical and subcortical areas ter minate in different nuclei. In the present study we examined long-term pote ntiation of synaptic transmission in the lateral or the basal amygdaloid nu clei by theta burst stimulation of thalamic vs. cortical sensory projection s in the anesthetized rat. Although both the medial geniculate nucleus and the dorsal perirhinal cortex have direct projections to lateral nucleus. on ly the thalamic stimulation induced long-term potentiation of field potenti als recorded in the lateral nucleus. In contrast. cortical (ventral perirhi nal cortex) but not thalamic stimulation induced long-term potentiation in the basal nucleus. Since the thalamic pathway is believed to process simpie/unimodal stimulus features, and the perirhinal cortex complex/polymodal sensory representatio ns, the dissociation of long-term potentiation in lateral and basal nuclei suggests that the basal nucleus may serve as an amygdaloid sensory interfac e for complex stimulus information similar to the role of the lateral nucle us in relation to relatively simple representations. Thus plasticity of sim ple and complex representations may involve different amygdala inputs and c ircuits. (C) 2001 IBRO, Published by Elsevier Science Ltd, All rights reser ved.