Pyramidal neurons in layer 5 of the rat visual cortex. I. Correlation among cell morphology, intrinsic electrophysiological properties, and axon targets

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

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Detail(s)

Original languageEnglish
Pages (from-to)459-474
Journal / PublicationJournal of Comparative Neurology
Volume339
Issue number4
Publication statusPublished - 22 Jan 1994
Externally publishedYes

Abstract

Previous work has established two structure/function correlations for pyramidal neurons of layer 5 of the primary visual cortex of the rat. First, cells projecting to the superior colliculus have thick apical dendrites with a florid terminal arborization in layer 1, whereas those projecting to the visual cortex of the opposite hemisphere have thinner apical dendrites that terminate below layer 1, without a terminal tuft (e.g., Hallman et al.: J Comp Neurol 272:149, '90). Second, intracellular recording combined with dye injection has revealed two classes of cells: the first has a thick, tufted apical dendrite and fires a distinctive initial burst of two or more impulses, of virtually fixed, short interspike interval, in response to current injection; and the other, with a slender apical dendrite lacking a terminal tuft, tends to have a longer membrane time constant and higher input resistance, and does not fire characteristic bursts (e.g., Larkman and Mason: J Neurosci 10:1407, '90). The present study combined intracellular recording in isolated slices of rat visual cortex and injection of carboxyfluorescein, to reveal soma‐dendritic morphology, with prior injection of rhodamine‐conjugated microspheres into the superior colliculus or contralateral visual cortex to label neurons according to the target of the superior colliculus or contralateral visual cortex to label neurons according to the target of their axons. This permitted a complete correlation of morphology, intrinsic electrophysiological properties, and identity of the projection target for individual pyramidal cells. Neurons retrogradely labeled from the opposite visual cortex were found in all layers except layer 1 while those labeled from the superior colliculus lay exclusively in layer 5. Within layer 5 interhemispheric cells were more concentrated in the lower half of the layer but extensively overlapped the distribution of corticotectal cells. Every cell studied that projected to the superior colliculus was of the bursting type and had a thick apical dendrite with a terminal tuft. Every cell in this study projecting to the opposite visual cortex was a “nonburster” and had a slender apical dendrite with fewer oblique branches that ended without a terminal tuft, usually in the upper part of layer 2/3. Interhemispheric cells also had rounder, less conical somata and generally had fewer basal dendrites than corticotectal neurons. Many cells with the physiological and morphological characteristics of interhemispheric cells were not back‐labeled from the opposite visual cortex, implying that pyramidal cells of this type can have other projection targets (e.g., other cortical sites in the ipsilateral hemisphere). On the other hand, few cells of the “thick/tufted,” bursting class were found that were not back‐labeled from the superior colliculus, implying that the majority of such cells project to that target. © 1994 Wiley‐Liss, Inc. Copyright © 1994 Wiley‐Liss, Inc.

Research Area(s)

  • burst‐firing neurons, corticotectal, interhemispheric neurons, intracellular injection, neurons, regular‐spiking neurons

Bibliographic Note

Publication information for this record has been verified with the author(s) concerned.

Citation Format(s)

Pyramidal neurons in layer 5 of the rat visual cortex. I. Correlation among cell morphology, intrinsic electrophysiological properties, and axon targets. / Kasper, Ekkehard M.; Larkman, Alan U.; Lübke, Joachim et al.
In: Journal of Comparative Neurology, Vol. 339, No. 4, 22.01.1994, p. 459-474.

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review