The Structure of Primary Visual Cortex Neuron Responses and its Interaction with the Dynamics of the Preferred Orientation

AbstractWe have employed the tetrode technique, which allows accurate discrimination of individual neuronal spike trains from multiunit recordings, in order to examine the variation of orientation selectivity among local groups of neurons. We recorded a total of 321 cells from 62 sites in area 17 of halothane-anesthetized cats; each site contained between three to ten neurons that were estimated to be less than 65 μm away from the tetrode tip. For each cell, we determined the orientation tuning in response to moving bars. Of the cells tested, 8.4% were unresponsive, 22.7% had no preferential response to any particular orientation, while 68.8% were tuned. The average difference in preferred orientation between cell pairs recorded at the same site was 10.7 deg, but the variance in preferred orientation differences differed significantly among sites. Some clusters of cells exhibited the same or nearly the same orientation preference, while others had orientation preferences that differed by as much as 90 deg. Our data demonstrate that the tuning for orientation is more heterogeneously distributed at a local level than previous studies have suggested.

Download Full-text

Orientation specificity of contrast adaptation in mouse primary visual cortex

Journal of Neurophysiology ◽

10.1152/jn.01148.2011 ◽

2012 ◽

Vol 108 (5) ◽

pp. 1381-1391 ◽

Cited By ~ 10

Author(s):

Aaron C. Stroud ◽

Emily E. LeDue ◽

Nathan A. Crowder

Keyword(s):

Visual Cortex ◽

Primary Visual Cortex ◽

Visual Processing ◽

Prolonged Exposure ◽

Quantitative Description ◽

Preferred Orientation ◽

Local Network ◽

Cortical Networks ◽

Contrast Adaptation ◽

Orientation Specificity

Contrast adaptation is a commonly studied phenomenon in vision, where prolonged exposure to spatial contrast alters perceived stimulus contrast and produces characteristic shifts in the contrast response functions of primary visual cortex neurons in cats and primates. In this study we investigated contrast adaptation in mouse primary visual cortex with two goals in mind. First, we sought to establish a quantitative description of contrast adaptation in an animal model, where genetic tools are more readily applicable to this phenomenon. Second, the orientation specificity of contrast adaptation was studied to comparatively assess the possible role of local cortical networks in contrast adaptation. In cats and primates, predictable differences in visual processing across the cortical surface are thought to be caused by inhomogeneous local network membership that arises from the pinwheel organization of orientation columns. Because mice lack this pinwheel organization, we predicted that local cortical networks would have access to a broad spectrum of orientation signals, and contrast adaptation in mice would not be specific to the recorded cell's preferred orientation. We found that most mouse V1 neurons showed contrast adaptation that was robust regardless of whether the adapting stimulus matched the cell's preferred orientation or was orthogonal to it.

Download Full-text