PMC

Cortical orientation tuning remains contrast invariant in β2−/− mice. A, Normalized response at 50% contrast in WT and β2−/− mice. B, Tuning width at 50% (x-axis) and 100% (y-axis) contrast of individual neurons, with most points lying next to the unity line (the dotted line).

Drifting grating-evoked responses of a direction-selective neuron in the SC. A, Spike rasters in response to drifting sinusoidal gratings of 12 directions and 6 spatial frequencies. Each column contains raster plots at one spatial frequency along 12 different directions. This neuron preferred upward moving (90°) gratings of 0.08 and 0.16 cpd. B, Direction tuning curve of this cell demonstrates its high selectivity for moving direction. C, Spatial frequency tuning curve of the same cell.

Normal cortical responses to drifting gratings in β2−/− mice. A, Tuning curve of an orientation-selective neuron in the V1 of a β2−/− mouse. B, Spatial frequency tuning curve of the same cell. C, D, Mean OSI (C) and DSI (D) of V1 neurons in control and mutant mice, for all cells (left of each panel), cells with the preferred direction along the horizontal axis (middle), or along the vertical axis (right). E, Tuning width of control and β2−/− mice. F, Cumulative distribution of F₁/F₀ ratio of responses to drifting gratings for both control (black) and β2−/− (dotted gray line). G, H, Distribution of the preferred spatial frequency of V1 neurons in control (G) and β2−/− (H) mice. Error bars represent SEM.

Abnormal receptive field structure of SC but not V1 neurons in β2−/− mice. A, Receptive field of a representative SC neuron in WT. The color scale represents the neuron's firing rate (spikes/s) in response to light squares flashing in the visual field. B, An example of enlarged receptive fields in the SC of β2−/− mutants. C, Quantification of receptive field size of SC neurons among different genotypes. The receptive fields in β2−/− mutants were enlarged along both azimuth (p < 0.001) and elevation (p < 0.001) axes compared with WT and β2+/− controls. No difference between WT and β2+/− mice was observed along either axis (p > 0.05). D–F, Examples (D, E) and quantification (F) of V1 receptive fields in WT (D) and β2−/− (E) mice. No difference of receptive field size was observed (p > 0.05). Error bars represent SEM.

Direction-specific disruption of a subcortical visual behavior in β2−/− mice. A, A top-view diagram of the testing apparatus used in this study. B, β2−/− mice failed to track horizontally drifting vertical grating (p < 0.0001 compared with controls). No significant difference was observed between the two groups in the tracking of vertically drifting horizontal gratings (p = 0.27). C, Diagram of the visual water task, in which mice were trained to swim toward a grating-displaying monitor. D, β2−/− mice had normal visual acuity as tested in the visual water task for both vertical (p = 0.51) and horizontal (p = 0.92) grating stimuli. E, F, Contrast sensitivity of β2−/− (red) and control (black) mice for both vertical (E) and horizontal (F) gratings. Error bars represent SEM.

Abnormal responses to sweeping bars in the SC, but not V1, of β2−/− mice. A, Direction selectivity of SC and V1 neurons were studied with full-length bars drifting perpendicular to their orientations. B, Peristimulus time histograms of a SC neuron in response to long bars drifting along different directions. C, Direction tuning curve of the same cell, showing high selectivity. D, Cumulative distributions of the DSI of SC neurons. The distributions are similar between β2−/− (red) and control (black) mice (p = 0.28). E, F, DSI cumulative distributions for SC neurons with peak responses along the horizontal axis (E, p < 0.05 comparing β2−/− and control mice), or along the vertical axis (F, p = 0.49). G–I, Cumulative distributions of the DSI in V1, for all recorded neurons (G), neurons with peak responses along the horizontal axis (H), or along the vertical axis (I). No significant difference between β2−/− (red) and controls (black) was seen in any comparison.

Disruption of direction and orientation selectivity along the azimuth axis in the SC of β2−/− mice. A, B, Polar plots of direction selectivity index (DSI, radii from the origin) and preferred direction (angles) of SC neurons in control (β2 +/±, in A) and β2−/− (B) mice. The outer circles in both plots represent DSI value of 1, and the inner circles of 0.33. C, Percentage of direction selective cells (DSI >0.33) preferring either horizontally (left) or vertically (right) moving gratings. D, Mean DSI of SC neurons in control and β2−/− mice, for all cells (left), cells with peak responses to horizontally moving gratings (middle), or to vertically moving gratings (right). E, Tuning curve of an orientation-selective SC neuron. F, Mean orientation selectivity index (OSI) of SC neurons in control and mutant mice, with cells grouped the same way as in (D). G, H, Distribution of the preferred spatial frequency (SF) of SC neurons in control (G) and β2−/− (H) mice. All error bars represent SEM.