High resolution

Module 10: Figure network gamma oscillations

Neuronal network gamma oscillations.

Numerous neural circuits (see inset at the bottom) consist of fast spiking inhibitory interneurons (red) and excitatory neurons (green) interacting with each other through a positive/negative-feedback loop. A unique feature of many circuits is that each interneuron controls the activity of many excitatory neurons all of which send axon collaterals back to the inhibitory interneuron. The interneuron fires an action potential on each gamma cycle (Arrow 1) and this serves to induce a hyperpolarization that occurs synchronously in all the excitatory neurons. While all the excitatory neurons participate in each gamma cycle, they fire much less frequently towards the end of the pacemaker depolarization (Arrows 2 and 3). The inhibitory interneuron registers each of these action potentials as a small excitatory postsynaptic potential (EPSP) that sum to activate the interneuron to fire an action potential to initiate another gamma oscillatory cycle.