The Identity of Inhibitory Interneurons Driving Gamma Oscillations in the Brain

The neural circuit underlying fast spike interneuron enhanced gamma band oscillations (30-100 Hertz) has been relatively well defined. The fast spiking inhibitory interneurons release GABA onto GABA-A receptors on regular spiking pyramidal neurons. The time constant of GABA-A synaptic inhibition is a key factor controlling gamma rhythmicity. Nevertheless, there is more than one type of fast spiking interneuron in the brain that are often difficult to distinguish. In the recent paper “Parvalbumin-Containing Fast-Spiking Basket Cells Generate the Field Potential Oscillations Induced by Cholinergic Receptor Activation in the Hippocampus” (published November 10, 2010 in the Journal of Neuroscience) the authors set out to establish the identity of inhibitory interneurons responsible for helping to generate gamma oscillations.

In this paper the authors identified and focused on three types of interneurons. Two were parvalbumin containing fast spiking interneurons: fast spiking basket cells and axoaxonic cells (also known as chandelier cells). The other type of interneuron was the regular spiking basket cells. The data presented by the authors lead to the conclusion that fast spiking basket cells help generate gamma oscillations in the brain whereas axoaxonic cells and regular spiking basket cells do not. They presented the following evidence:

These data add more evidence for a key role of fast spiking interneurons in the generation of gamma oscillations. More specifically, these data identify fast spiking basket cells as the drivers of gamma oscillations.

The data in this paper were obtained in hippocampal slices kept at room temperature. Therefore the observed oscillations were slower than gamma oscillations. Also, the activation of acetylcholine receptors was carried out using carbachol, which is a cholinergic agonist that induces oscillatory activity. Nevertheless, these data move us closer to establishing the detailed circuits and mechanisms underlying gamma oscillations in the brain.

Other related blog posts:

Brain Modeling Using NEURON, Interneurons, and Resonant Circuits

Brain Modeling Using NEURON: Superficial Pyramidal, Deep Pyramidal, Aspiny, and Stellate Neurons