Functional Considerations of the Operation of GABAergic Inhibitory Processes in the Visual Cortex

Sillito, Adam M.

doi:10.1007/978-1-4615-6610-6_4

Cited by 210 publications

(133 citation statements)

References 71 publications

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“…This would, to take just one example, be an expected feature of inhibitory interneurones associated with the generation of orientation selectivity in the surrounding cells (Sillito, 1975(Sillito, , 1979(Sillito, , 1984Sillito, Kemp, Milson & Berardi, 1980). If this were so, then a column could perhaps appear continuous or discontinuous, according to the sampling characteristics ofthe micro-electrode used.…”

Section: Discussionmentioning

confidence: 99%

Continuity of orientation columns between superficial and deep laminae of the cat primary visual cortex.

Murphy¹,

Sillito²

1986

The Journal of Physiology

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SUMMARY1. Recent reports of a marked and consistent dislocation between orientation columns in the superficial and deep layers of cat striate cortex (Bauer, 1982(Bauer, , 1983 directly contradict the traditional view of the system (Hubel & Wiesel, 1962). This has considerable implications for our current understanding of cortical organization, and in order to clarify the issue we have carried out experiments to test the continuity of the columnar system with depth, in central regions of area 17.2. In twenty-four penetrations, eighteen of which were placed as perpendicular as possible to the surface of the cortex, orientation preference was assessed at regular intervals both qualitatively and using a randomly interleaved quantitative technique. The distribution of preferred orientations was analysed with reference to a detailed histological reconstruction of the electrode track, including the location of laminar boundaries and the course of radial tiers of cells and capillaries.3. From a further series of eighteen near-perpendicular penetrations, the change in average orientation between one superficial and one deep layer recording site was compared with the deviation of the track from perpendicular to the surface and hence parallel to the orientation columns.4. In penetrations perpendicular to the surface ofthe cortex, orientation preference showed little variation between superficial and deep laminae. In oblique penetrations, preferred orientation generally changed according to a single, smooth trend. Those irregularities that were encountered were confined to oblique penetrations, and were distributed throughout the cortical laminae.5. In conclusion, our evidence does not support the presence of a systematic discontinuity with depth within the orientation columnar system. It is therefore entirely consistent with earlier evidence on the subject.

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Section: Discussionmentioning

confidence: 99%

Continuity of orientation columns between superficial and deep laminae of the cat primary visual cortex.

Murphy¹,

Sillito²

1986

The Journal of Physiology

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“…Growing evidence supports the hypothesis that cortical interneurons can influence the discriminative responses of pyramidal neurons. For example, in the visual system, GABAergic interneurons play a key role in modulating the activity of geniculate inputs to the primary visual cortex and defining the orientation selectivity of its neurons (Sillito 1975(Sillito , 1984Tsumoto et al 1979). Support for a role of interneurons in shaping of receptor fields has been extended to other cortical areas such as the somatosensory cortex (Alloway et al 1989;Alloway and Burton 1991;Wilson et al 1994;Kyriazi et al 1996).…”

Section: Functions Of Gabaergic Interneurons In the Cortex And In Thementioning

confidence: 99%

GABAergic Interneurons Implications for Understanding Schizophrenia and Bipolar Disorder

Beneš

Berretta

2001

Neuropsychopharmacology

988

643

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Neurons that express the compound, ␥ -aminobutyric acid (GABA), are broadly present throughout the central nervous system, although telencephalic structures, such as the cerebral cortex, show the most abundant quantities of this neurotransmitter (Jones 1987). In the discussion that follows, the anatomy and physiology of various types of GABAergic interneurons in the cortex and hippocampus will be discussed and related to recent postmortem studies implicating this transmitter system in the pathophysiology of schizophrenia and bi- 25 , NO . 1 polar disorder and their treatment with neuroleptic drugs (for more comprehensive reviews on cortical and hippocampal neurons see: Hof et al. 1993;Freund and Buzsaki 1996;Somogyi et al. 1998). NEUROBIOLOGY OF GABAERGIC INTERNEURONSBased on Golgi-impregnation studies, Ramon y Cajal provided the first descriptions of several different morphological subtypes of interneurons in the cerebral cortex and hippocampus (Ramon y Cajal 1893, 1911. In more recent years, it has been shown that, with some overlap, different morphological subtypes also have distinct distributions, connectivity, neurochemistry, and electrophysiological properties (for reviews see Hof et al. 1993;Freund and Buzsaki 1996). It is interesting to note that every segment of a pyramidal neuron, such as the soma, dendritic branches and spines, and the initial axonal segment, receives dense GABAergic synaptic innervation (O'Kusky and Colonnier 1982;Hendry et al. 1983;Houser et al. 1983; Beaulieu et al. 1992; for reviews see Jones 1993;Freund and Buzsaki 1996). Even more interestingly, each of these segments appears to be innervated by distinct GABAergic neuronal subtypes (see below).These differences strongly suggest that each of these subtypes plays a fundamentally different role in physiological and pathological mechanisms. In the discussion that follows, cortical interneurons will be described first, since our most basic understanding of GABAergic cells is derived from these populations. In more recent years, however, similar characterizations of interneurons in hippocampus have emerged. Although these cells show some striking similarities to their cortical counterparts, there are also some unique features that distinguish them. For this reason, interneurons in the hippocampus are discussed separately. Cortex Neuroanatomical Studies of Cortical Interneurons.Various types of GABAergic neurons can be categorized according to the type of synaptic profiles they are associated with, as this has direct implications for understanding the physiological role of these cells in cortical circuits. These categories are discussed below.A XO -S OMATIC I NHIBITORY S YNAPSES (B ASKET C ELLS ). The most commonly encountered interneurons ( Figure 1A) are multipolar in shape, i.e., they may have three or more primary dendritic branches emanating from their cell bodies, some having somata that are as large as those of pyramidal neurons (Jones and Hendry 1984). Using immunocytochemistry to localize the enzyme ). These cells also ...

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“…For instance, there is evidence that directional selectivity is dependent on intracortical inhibitory mechanisms (Tsumoto et al, 1979;Sillito, 1984;Livingstone, 1998). Perhaps the blockage of inhibitory mechanisms reduces directional selectivity by affecting the push-pull mechanisms of simple cells (Hubel and Wiesel, 1962;Palmer and Davis, 1981;Ferster, 1988;Hirsch et al, 1998).…”

Section: Multiple Derivations Of Directional Selectivitymentioning

confidence: 99%

The Derivation of Direction Selectivity in the Striate Cortex

Peterson

Li²,

Freeman³

2004

J. Neurosci.

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In the central visual pathway of binocular animals, the property of directional selectivity (DS) is first exhibited in striate cortex. In this study, we sought to determine the neural circuitry underlying the transformation from non-DS neurons to DS cortical cells. In a well established model, DS receptive fields (RFs) are derived from the sum of two non-DS inputs with 90°(quadrature) spatiotemporal phase differences. We explored possible input sources for this model, which include non-DS simple cells and lateral geniculate nucleus (LGN) neurons, by examination of spatiotemporal RFs of single cells and of pairs of cells. We find that distributions of non-DS simple RFs do not match the temporal predictions of the quadrature model because of a lack of long-latency responses. The long-latency inputs could potentially arise from lagged LGN afferents. However, analysis of cell pairs indicates that DS cells receive cortical input from non-DS simple cells for both short-and long-latency components, with temporal phase differences typically Ͻ90°. Furthermore, the distribution of minimum phase differences needed to generate DS cells overlaps that exhibited by non-DS simple cells. Considered together, these results are consistent with a linear model whereby DS simple cells are formed from simple-cell inputs, with temporal phase differences often less than quadrature.

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Functional Considerations of the Operation of GABAergic Inhibitory Processes in the Visual Cortex

Cited by 210 publications

References 71 publications

Continuity of orientation columns between superficial and deep laminae of the cat primary visual cortex.

Continuity of orientation columns between superficial and deep laminae of the cat primary visual cortex.

GABAergic Interneurons Implications for Understanding Schizophrenia and Bipolar Disorder

The Derivation of Direction Selectivity in the Striate Cortex

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