Title - Feature Finding
Featured Finding Figure
In primates, little is known about intrinsic electrophysiological properties of neocortical neurons and their morphological correlates. To classify inhibitory interneurons in layers 2-3 of monkey dorsolateral prefrontal cortex, we employed whole cell voltage recordings and intracellular labeling in slice preparations with subsequent morphological reconstructions. Regular-spiking pyramidal cells were also included in the sample. As shown in the Figure, regular-spiking neurons (RSN) display low input resistance and require the largest amplitude of depolarization current to reach action potential threshold. In contrast, intermediate-spiking neurons (ISN) have the largest input resistance and require the lowest amplitude of depolarization current to reach action potential threshold. Fast-spiking neurons (FSN) display properties intermediate between RSN and ISN. As shown in panel D, monoexponential curve fittings to the first hyperpolarizing sweeps demonstrate longest, intermediate and shortest time constant in the RSN, ISN and FSN, respectively. Using cluster analysis as a multivariate exploratory technique, morphological types of neurons were mapped on these physiological clusters. The cluster of RSN contained all pyramidal cells, whereas the ISN and FSN clusters consisted exclusively of interneurons. The cluster of FSN contained all of the chandelier cells and the majority of local, medium and wide arbor (basket) interneurons. The cluster of ISN predominantly consisted of cells with the morphology of neurogliaform or vertically oriented (double bouquet) interneurons. Thus, a quantitative approach enabled us to demonstrate that intrinsic electrophysiological properties of neurons in the monkey prefrontal cortex define distinct cell types, which also display distinct morphologies.
Krimer LS, Zaitsev AV, Czanner G, Kröner S, González-Burgos G, Povysheva NV, Iyengar S, Barrionuevo G and Lewis DA: Cluster analysis-based physiological classification and morphological properties of inhibitory neurons in layers 2-3 of monkey dorsolateral prefrontal cortex. J. Neurophysiol 94: 3009-3022, 2005.

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David A. Lewis, M.D. | Department of Psychiatry | University of Pittsburgh
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