A reassessment of the forms of nonpyramidal neurons in area 17 of cat visual cortex

Abstract

The nonpyramidal neurons in area 17 of cat visual cortex have been examined in Golgi preparations. From their dendritic patterns, neurons are classified as being multipolar, bitufted, or bipolar, and on the basis of the abundance of dendritic spines as spinous, sparsely spinous, or smooth. When neurons are so classified seven different types of nonpyramidal neurons are encountered in layers I1 through V.Three of the types of multipolar neurons in layers I1 through V have spherical dendritic trees. The small multipolar cells have smooth dendrites and are the smallest neurons in the cortex. They have short dendrites and dense local axonal plexuses and occur throughout layers I1 to V. The sparsely spinous stellate cells have longer dendrites, are confined to layer II/III, and have local axonal arborizations, whereas the spinous stellate cells are limited to layer IV. A fourth type of multipolar neuron in layers I1 through V is the basket cell. Such neurons have elongate dendritic trees and either smooth or sparsely spinous dendrites. Depending upon the orientation of the neurons in the sections, their axons appear to form arcades or long, horizontally extended branches, or a mixture of these two axonal patterns. The terminal portions of the axons of these basket cells pass around the cell bodies of adjacent neurons.The two types of bitufted neurons in layers I1 through V have vertically oriented dendritic trees. One type, the chandelier cell, has smooth dendrites and a characteristic axon forming vertical strings of terminals. The other sparsely spinous bitufted neurons have axons producing vertically oriented plexuses. The remaining type of neuron encountered in layers I1 through V is a bipolar cell. The bipolar cell has a single major dendritic trunk arising from each pole of the cell body, and each of these gives rise to a very narrow, long, and vertically oriented dendritic tree. The axon usually takes origin from one of the primary dendrites.In layer I are horizontally oriented, bitufted cells with smooth dendrites. The s o n s of these horizontal cells of layer Z arise from one of the primary dendritic trunks and appear to form a plexus confined to layer I. Horizontally oriented neurons are also present in deep layer VI, but the horizontal cells of layer VZ are bipolar. The other two neuronal types in layer VI are multipolar cells with sparsely spinous dendrites. The larger of these two types resembles the basket cells in layers I1 through V, the only important difference between them being that in addition to the long horizontal branches, the axons of the basket cells of layer VZ have a long ascending branch which reaches at least as far as layer 1V. The other sparsely spinous cells of layer VZ are medium sized. Their axons take a descending and oblique course before elaborating a locally distributed plexus.The various types of neurons defined in this study are compared with neurons described by previous authors who have examined the populations of nonpyramidal cells in area 17 of cat visual cortex an...

A Quantitative Map of the Circuit of Cat Primary Visual Cortex

“…Thalamic afferents, which form the major extra-striate source of asymmetric synapses in layer 4 (Ahmed et al, 1994), are also included. Anatomical studies of cortical smooth neurons indicate that, like spiny neurons, a variety of types exist (Peters and Regidor, 1981). For one of the most prominent, the basket cells, we have samples from layer 2/3, 4, and 5.…”

“…Although chandelier cells are located primarily in layer 2/3 (Fairen and Valverde, 1980;Somogyi et al, 1982), where they form ϳ3.4% of the GABAergic neurons (see Materials and Methods), Martinotti cells and neurogliaform cells are located principally outside layer 2/3 (Peters and Regidor, 1981;Wahle, 1993). We therefore assumed that the PV-IR neurons in layer 4 and 5 are basket cells, and the CB-IR neurons in layer 2/3 are the double bouquet cells.…”

Glutamic acid decarboxylase in the striate cortex of normal and monocularly deprived kittens

“…However, it is clear that all of the GAD-positive cells in kitten striate cortex fall into the broad category of nonpyramidal neurons with aspinous or sparsely spinous dendrites. Golgi staining (O'Leary, 1941;Lund et al, 1979;Peters and Regidor, 1981) and, recently, intracellular filling with horseradish peroxidase (HRP) (Gilbert and Wiesel, 1979;Freund et al, 1983;Martin et al, 1983) have revealed the morphological heterogeneity of cells in this category. O'Leary (1941) split this group into two divisions: those cells with locally arborizing axons, usually confined within a single layer, and those cells with widely ramifying axons.…”

Actions of Propofol on Neurons in the Cerebral Cortex

“…In the primary sensory cortex, glutamatergic neurons are classified into pyramidal cells located in layers II, III, V, and VI, and spiny stellate cells located in layer IV. GABAergic neurons are classified into more than ten subtypes, depending on their firing and morphological properties (Peters and Regidor, 1981). We must understand the effects of general anesthetics on the cortical local circuit that involves both glutamatergic and GABAergic neurons to elucidate the mechanism for the induction of unconsciousness by general anesthetics.…”