Aberrant Neuronal Synchronization Associated with Cognitive Deficits in a Rodent Model of Childhood Cranial Irradiation

Abstract

Cranial radiation can be a life-saving intervention in pediatric brain cancer therapy but often results in debilitating cognitive decline. To clarify the underlying mechanisms of these side-effects we have here recorded neurophysiological activity in distributed brain networks involved in decision-making and memory functions in adult rats exposed to cranial irradiation on postnatal day 21. Multi-structure local field potential (LFP) recordings revealed decreased power in irradiated animals in the 4-9 Hz frequency band. Additionally, a distinct slowing of the oscillatory activity was observed preceding erroneous choice in a decision-making task. Moreover, irradiated rats showed reduced dynamics and a fragmented pattern of inter-structural coherence across different phases of the task. Our results suggest that the cognitive deficits and reduced processing speed following irradiation of the juvenile brain arise as a consequence of changes in long-range functional connectivity, including thalamocortical circuits, causing abnormally slow and spatially fractionated patterns of coordinating LFP activity.