Madhusoothanan Bhagavathi Perumal, UQ. "Organisation of a reverberating cell assembly in the basolateral amygdala"

Speaker: 

Madhusoothanan Bhagavathi Perumal (PhD Exit Seminar)

Queensland Brain Institute, University of Queensland

Title:  Organization of a reverberating cell assembly in the basolateral amygdala

Abstract:

One of the most remarkable features of the brain is its intrinsic disposition to generate oscillatory network activity even in the absence of sensory inputs. Synchronized activity in neurons is readily observed extracellularly as electrical field potential oscillations. These network oscillations are hypothesised to perform many functions, one of which is to facilitate memory consolidation processes. Hebb’s cell assembly hypothesis is one important conceptual framework to correlate network activity and memory. Hebb postulated that neurons with recurrent connections among themselves generate a reverberating activity within a specific temporal window to encode memory traces. This form of temporally organized neural circuit can form a functional unit called a cell assembly. However, what types of neurons are present in a cell assembly and how they are organized to generate reverberating activity are not known.

We investigated how the organization of neurons in the basolateral amygdala (BLA), a key structure for emotional memory consolidation, generates network oscillations. In our preparation, BLA networks spontaneously generated widespread synchronized activity as Sharp Wave oscillations (SWs), a distinct network activity associated with memory consolidation processes. During SWs, stereotypical multi-synaptic events occurred simultaneously in widespread BLA neurons. These SWs could be initiated by a rare and special subset of GABAergic interneuron, the Chandelier neuron (Chn). Simultaneous recordings from pairs of neurons showed the presence of strong glutamatergic and GABAergic feedforward and feedback circuits in the BLA to facilitate reverberating activity. These results provide a novel circuit model for the organization of neurons in Hebb’s reverberating cell assembly for generation of SW oscillations in the BLA.