| Inhibitory contributions to spatiotemporal receptive-field structure and direction selectivity in simple cells of cat area 17. | |
| | |
MedLine Citation:
|
PMID: 10085348 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
|
Intracortical inhibition contributes to direction selectivity in primary visual cortex, but how it acts has been unclear. We investigated this problem in simple cells of cat area 17 by taking advantage of the link between spatiotemporal (S-T) receptive-field structure and direction selectivity. Most cells in layer 4 have S-T-oriented receptive fields in which gradients of response timing across the field confer a preferred direction of motion. Linear summation of responses across the receptive field, followed by a static nonlinear amplification, has been shown previously to account for directional tuning in layer 4. We tested the hypotheses that inhibition acts by altering S-T structure or the static nonlinearity or both. Drifting and counterphasing sine wave gratings were used to measure direction selectivity and S-T structure, respectively, in 17 layer 4 simple cells before and during iontophoresis of bicuculline methiodide (BMI), a GABAA antagonist. S-T orientation was quantified from fits to response temporal phase versus stimulus spatial phase data. Bicuculline reduced direction selectivity and S-T orientation in nearly all cells, and reductions in the two measures were well correlated (r = 0.81) and reversible. Using conventional linear predictions based on response phase and amplitude, we found that BMI-induced changes in S-T structure also accounted well for absolute changes in the amplitude and phase of responses to gratings drifting in the preferred and nonpreferred direction. For each cell we also calculated an exponent used to estimate the static nonlinearity. Bicuculline reduced the exponent in most cells, but the changes were not correlated with reductions in direction selectivity. We conclude that GABAA-mediated inhibition influences directional tuning in layer 4 primarily by sculpting S-T receptive-field structure. The source of the inhibition is likely to be other simple cells with certain spatiotemporal relationships to their target. Despite reductions in the two measures, most receptive fields maintained some directional tuning and S-T orientation during BMI. This suggests that their excitatory inputs, arising from the lateral geniculate nucleus and within area 17, are sufficient to create some S-T orientation and that inhibition accentuates it. Finally, BMI also reduced direction selectivity in 8 of 10 simple cells tested in layer 6, but the reductions were not accompanied by systematic changes in S-T structure. This reflects the fact that S-T orientation, as revealed by our first-order measures of the receptive field, is weak there normally. Inhibition likely affects layer 6 cells via more complex, nonlinear interactions. |
| | |
Authors:
|
A Murthy; A L Humphrey |
Related Documents
:
|
1869908 - Selectivity for relative motion in the monkey superior colliculus. 12826108 - Speed tuning of direction repulsion describes an inverted u-function. 2017888 - Using metamers to explore motion perception. 12670428 - Directional anisotropies reveal a functional segregation of visual motion processing fo... 871178 - Scalar perceptions of distance in simple binocular configurations. 21199878 - Stoichiometric relationship among clock proteins determines robustness of circadian rhy... |
Publication Detail:
|
Type: Journal Article; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
|
Title: Journal of neurophysiology Volume: 81 ISSN: 0022-3077 ISO Abbreviation: J. Neurophysiol. Publication Date: 1999 Mar |
Date Detail:
|
Created Date: 1999-05-06 Completed Date: 1999-05-06 Revised Date: 2007-11-14 |
Medline Journal Info:
|
Nlm Unique ID: 0375404 Medline TA: J Neurophysiol Country: UNITED STATES |
Other Details:
|
Languages: eng Pagination: 1212-24 Citation Subset: IM |
Affiliation:
|
Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA. |
Export Citation:
|
APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
|
Animals Bicuculline / analogs & derivatives, pharmacology Brain Mapping* Cats GABA Antagonists / pharmacology Iontophoresis Membrane Potentials / physiology Neural Inhibition* Nonlinear Dynamics Photic Stimulation Time Factors Visual Cortex / cytology, physiology* Visual Fields / physiology* |
| Grant Support | |
ID/Acronym/Agency:
|
EY-06459/EY/NEI NIH HHS; EY-08098/EY/NEI NIH HHS |
| Chemical | |
Reg. No./Substance:
|
0/GABA Antagonists; 40709-69-1/bicuculline methiodide; 485-49-4/Bicuculline |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
Previous Document: Projections and firing properties of down eye-movement neurons in the interstitial nucleus of Cajal ...
Next Document: Role of presynaptic L-type Ca2+ channels in GABAergic synaptic transmission in cultured hippocampal ...