Abstract

Feedback projections from upstream targets and neuromodulatory systems provide real time regulation of information processing. In the olfactory pathway, sensory neurons establish synapses with principal neurons of the olfactory bulb (OB), where the earliest stages of odor processing occur. Unlike other sensory systems, output neurons in the OB project to the olfactory cortex bypassing the thalamus. Therefore, neural circuits in the OB, and odor processing, are tightly regulated by several top-down mechanisms. A large source of modulatory signals to the OB arises from neurons of the basal forebrain, most importantly from clusters of cholinergic and GABAergic neurons. While cholinergic modulation of the OB circuit is thought to be critical in olfactory processing, including odor discrimination and perceptual learning, the role of the inhibitory GABAergic input from the basal forebrain is poorly understood. Here we describe an experimental approach that uses virus-mediated expression of Designer Receptor Exclusively Activated by Designer Drugs (DREADDs) in basal forebrain GABAergic neurons, and behavioral tests, to examine how this inhibitory modulation contributes to olfactory processing.