Heterogenous Change in Neuronal Bursts Following Recovery from Activity Silencing

Abstract

Silencing of activity in hippocampal neuronal cultures was used to study how dynamic neuronal activity achieves a state of homeostasis, using calcium imaging to detect neuronal firing patterns. Recovering cultures were found to display abnormal activity patterns after 48hrs of exposure to tetrodotoxin, as indicated by paradoxical spike and correlation statistics. It was found that the cultures recovering from activity silencing did not resemble a neuronal system with enhanced excitation, but differed significantly from control experiments. Using a newly developed measure of homogeneity it was found that activity patterns in cultures recovering from silencing were more heterogeneous during bursts, which is in contrast to the current perception that bursting activity is a homogeneous event. It was also observed that there were more active neurons during the recovery period. It is hypothesized that these changes in neuronal system dynamics are brought about due to the insertion and heterogenous manipulation of silent synapses. Results suggest a mechanism through which the interplay between homeostatic scaling, silent synapses and bursting behavior could mediate neuronal network homeostasis.