scholarly journals Space-Time Maps and Two-Bar Interactions of Different Classes of Direction-Selective Cells in Macaque V-1

2003 ◽  
Vol 89 (5) ◽  
pp. 2726-2742 ◽  
Author(s):  
Bevil R. Conway ◽  
Margaret S. Livingstone
Keyword(s):  
Principal Components Analysis ◽  
Principal Components ◽  
Space Time ◽  
Simple Cell ◽  
Simple Cells ◽  
Complex Cells ◽  
Preferred Direction ◽  
Components Analysis ◽  
Simple And Complex Cells ◽  
Simple And Complex Cell

We used one-dimensional sparse noise stimuli to generate first-order spatiotemporal maps and second-order two-bar interaction maps for 65 simple and 124 complex direction-selective cells in alert macaque V1. Spatial and temporal phase differences between light and dark space-time maps clearly distinguished simple and complex cell populations. Complex cells usually showed similar direction preferences to light and dark bars, but many of the directional simple cells were much more direction selective to one sign of contrast than the reverse. We show that this is predicted by a simple energy model. Some of the direction-selective simple cells showed multiple space-time-slanted subregions, but others (previously described as S1 cells) had space-time maps that looked like just one subregion of an ordinary simple cell. Both simple and complex cells showed directional interactions (nonlinearities) to pairs of flashed bars (a 2-bar apparent-motion stimulus). The space-time slant of the simple cells correlated with the optimum d X/d T (velocity) of the paired-bar interactions. Some complex cells also showed a space-time slant; the direction of the slant usually correlated with the preferred direction of motion, but the degree of slant correlated with the inferred velocity tuning only when measured by a weighted-centroid calculation. Principal components analysis of the simple-cell space-time maps yielded one fast temporally biphasic component and a slower temporally monophasic component. We saw no consistent pattern for the spatial phase of the components, unlike previous reports; however, we show that principal components analysis may not distinguish between spatial offsets and phase offsets.

scholarly journals Substructure of Direction-Selective Receptive Fields in Macaque V1

2003 ◽  
Vol 89 (5) ◽  
pp. 2743-2759 ◽  
Author(s):  
Margaret S. Livingstone ◽  
Bevil R. Conway
Keyword(s):  
Receptive Fields ◽  
Direction Selectivity ◽  
Positive Interactions ◽  
Null Direction ◽  
Simple Cells ◽  
Complex Cells ◽  
Preferred Direction ◽  
Orientation Axis ◽  
Interaction Regions ◽  
Simple And Complex Cells

We used two-dimensional (2-D) sparse noise to map simultaneous and sequential two-spot interactions in simple and complex direction-selective cells in macaque V1. Sequential-interaction maps for both simple and complex cells showed preferred-direction facilitation and null-direction suppression for same-contrast stimulus sequences and the reverse for inverting-contrast sequences, although the magnitudes of the interactions were weaker for the simple cells. Contrast-sign selectivity in complex cells indicates that direction-selective interactions in these cells must occur in antecedent simple cells or in simple-cell-like dendritic compartments. Our maps suggest that direction selectivity, and on andoff segregation perpendicular to the orientation axis, can occur prior to receptive-field elongation along the orientation axis. 2-D interaction maps for some complex cells showed elongated alternating facilitatory and suppressive interactions as predicted if their inputs were orientation-selective simple cells. The negative interactions, however, were less elongated than the positive interactions, and there was an inflection at the origin in the positive interactions, so the interactions were chevron-shaped rather than band-like. Other complex cells showed only two round interaction regions, one negative and one positive. Several explanations for the map shapes are considered, including the possibility that directional interactions are generated directly from unoriented inputs.

Cone Inputs to Simple and Complex Cells in V1 of Awake Macaque

2007 ◽  
Vol 97 (4) ◽  
pp. 3070-3081 ◽  
Author(s):  
Gregory D. Horwitz ◽  
E. J. Chichilnisky ◽  
Thomas D. Albright
Keyword(s):  
Linear Models ◽  
Noise Analysis ◽  
Receptive Fields ◽  
Light Responses ◽  
Simple Cells ◽  
Complex Cells ◽  
V1 Neurons ◽  
Spike Triggered Averaging ◽  
Simple And Complex Cells ◽  
Simple And Complex Cell

Rules by which V1 neurons combine signals originating in the cone photoreceptors are poorly understood. We measured cone inputs to V1 neurons in awake, fixating monkeys with white-noise analysis techniques that reveal properties of light responses not revealed by purely linear models used in previous studies. Simple cells were studied by spike-triggered averaging that is robust to static nonlinearities in spike generation. This analysis revealed, among heterogeneously tuned neurons, two relatively discrete categories: one with opponent L- and M-cone weights and another with nonopponent cone weights. Complex cells were studied by spike-triggered covariance, which identifies features in the stimulus sequence that trigger spikes in neurons with receptive fields containing multiple linear subunits that combine nonlinearly. All complex cells responded to nonopponent stimulus modulations. Although some complex cells responded to cone-opponent stimulus modulations too, none exhibited the pure opponent sensitivity observed in many simple cells. These results extend the findings on distinctions between simple and complex cell chromatic tuning observed in previous studies in anesthetized monkeys.

The time course of direction-selective adaptation in simple and complex cells in cat striate cortex

1993 ◽  
Vol 70 (5) ◽  
pp. 2024-2034 ◽  
Author(s):  
D. Giaschi ◽  
R. Douglas ◽  
S. Marlin ◽  
M. Cynader
Keyword(s):  
Time Constant ◽  
Cortical Neurons ◽  
Time Course ◽  
Adaptation Period ◽  
Simple Cells ◽  
Complex Cells ◽  
Prolonged Stimulation ◽  
Preferred Direction ◽  
Simple And Complex Cells ◽  
Exponential Change

1. Responses of single cortical neurons in area 17 of anesthetized cats were recorded in response to prolonged stimulation with a patch of drifting square-wave grating. 2. During adaptation in the preferred direction, all neurons showed some reduction in response to motion in the stimulated direction and most showed some reduction in the opposite, nonstimulated direction. 3. For complex cells, the time course of response decrement in both the stimulated and nonstimulated directions was exponential, with an average time constant of 5 s. Response recovery was also exponential but significantly slower, with time constants of 8 and 13 s in the stimulated and nonstimulated directions, respectively. 4. For simple cells the dynamics of the adaptation effect depended on the direction of testing. In the nonstimulated direction the time course of the change in sensitivity was similar to that of complex cells. In the stimulated direction during both the adaptation and recovery periods, simple cells showed an initial rapid exponential change on the order of a few seconds that was followed by a more gradual exponential change. 5. During prolonged stimulation in the nonpreferred direction, there was less overall change in sensitivity. For some neurons the change in sensitivity during adaptation and recovery was exponential, with a short time constant for both simple and complex cells and for stimulated and nonstimulated directions. Other neurons showed no change in sensitivity in either direction and a few neurons showed facilitation during the adaptation period. 6. There appears to be a rapid general or nonspecific process, which may be related to contrast gain control, underlying motion adaptation in striate cortical neurons. An additional slow, direction-selective process is revealed when simple but not complex cells are stimulated in the preferred direction. We suggest that this latter type of adaptation is a key feature underlying the perceptual motion aftereffect.

Direction-selective adaptation in simple and complex cells in cat striate cortex

1988 ◽  
Vol 59 (4) ◽  
pp. 1314-1330 ◽  
Author(s):  
S. G. Marlin ◽  
S. J. Hasan ◽  
M. S. Cynader
Keyword(s):  
Cortical Neurons ◽  
Striate Cortex ◽  
Selective Adaptation ◽  
Direction Selectivity ◽  
Simple Cells ◽  
Complex Cells ◽  
Preferred Direction ◽  
Directional Preference ◽  
Simple And Complex Cells ◽  
Cat Striate Cortex

1. The selectivity of adaptation to unidirectional motion was examined in neurons of the cat striate cortex. Following prolonged stimulation with a unidirectional high-contrast grating, the responsivity of cortical neurons was reduced. In many units this decrease was restricted to the direction of prior stimulation. This selective adaptation produced changes in the degree of direction selectivity of the cortical units (as measured by the ratio of the response to motion in the preferred direction to that in the nonpreferred direction). 2. The initial strength of the directional preference of a given cortical unit did not determine the degree of direction-selective adaptation. Indeed, even non-direction-selective units could exhibit pronounced direction-selective adaptation. The degree of direction-selective adaptation was also independent of the overall decrease in responsivity during adaptation. 3. There was no difference between simple and complex cells in the total amount of adaptation observed. The selectivity of the adaptation, however, did differ between these two cell types. As a group, simple cells showed significant direction-selective adaptation, whereas complex cells did not. The directional preference of most simple cells decreased following preferred direction adaptation and many highly direction selective simple cells became non-direction selective. In addition, simple cells became significantly more direction selective following nonpreferred direction adaptation. 4. Some complex cells also demonstrated direction-selective adaptation. There was, however, much more variability among complex cells than simple cells. Some complex cells actually increased direction selectivity following preferred direction adaptation. These differences between simple and complex cells suggest that changes in direction selectivity following unidirectional adaptation are not due to simple neuronal fatigue of the unit being recorded, but depend on selective adaptation of afferent inputs to the unit. 5. The spontaneous activity of many cortical neurons decreased following preferred direction adaptation but increased following adaptation in the nonpreferred direction. The response to a stationary grating also decreased following preferred direction adaptation. However, there was very little change in the response to a stationary grating following adaptation in the nonpreferred direction.

Diagnoses Generated by Numerical Taxonomic Methods Applied to Standard Blood Variables

1980 ◽  
Vol 19 (04) ◽  
pp. 205-209
Author(s):  
L. A. Abbott ◽  
J. B. Mitton
Keyword(s):  
Liver Cirrhosis ◽  
Renal Disease ◽  
Principal Components Analysis ◽  
Discriminant Function ◽  
Principal Components ◽  
Discriminant Function Analysis ◽  
Chronic Renal Disease ◽  
Function Analysis ◽  
Infectious Hepatitis ◽  
Components Analysis

Data taken from the blood of 262 patients diagnosed for malabsorption, elective cholecystectomy, acute cholecystitis, infectious hepatitis, liver cirrhosis, or chronic renal disease were analyzed with three numerical taxonomy (NT) methods : cluster analysis, principal components analysis, and discriminant function analysis. Principal components analysis revealed discrete clusters of patients suffering from chronic renal disease, liver cirrhosis, and infectious hepatitis, which could be displayed by NT clustering as well as by plotting, but other disease groups were poorly defined. Sharper resolution of the same disease groups was attained by discriminant function analysis.

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