Using rhythmic network activity to probe neural circuit function
Neural circuits are built from two basic components: excitatory glutamatergic neurons and inhibitory GABAergic interneurons. While comprising only a minority of cortical and hippocampal neurons, inhibitory interneurons are a diverse class of cells that display great physiological and morphological heterogeneity, with each subtype controlling a different aspect of neural circuit function. One of the primary roles played by interneurons in neural circuits is to synchronise the activity of large groups of neurons. This synchrony gives rise to neuronal oscillations, which are waves of electrical activity that can be detected on the scalp, in the form of the EEG, or from extracellular recordings within numerous brain regions. Neuronal oscillations are classified according to their frequency, and each class of oscillation is strongly associated with different cognitive states. For example, slow oscillations (<1 Hz) are apparent during slow wave sleep and are associated with memory consolidation, whilst faster gamma oscillations (30 – 80 Hz) occur during periods of high cognitive load, such as working memory tasks. I will discuss how neuronal oscillations can be used to probe neural circuit function in health and disease, with a particular focus on inhibitory interneurons.