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Figure 12.5. Development of the receptive field (RF) properties of V1 neurons in macaques (from Movshon et al., 1999, 2000). Each panel of the plot represents the development of a particular receptive field property in a study of 453 V1 neurons representing the central 5° of the visual field, recorded from 11 animals at the indicated ages. Each point represents the mean or the geometric mean, as appropriate, of the values measured for all neurons recorded at a particular age; the error bars indicate ±1 SD to convey a sense of the span of the underlying distribution. In sequence from the top, the parameters displayed are receptive field size, defined as the size of an otherwise optimal patch of grating that elicited at least 95% of the maximum response (Cavanaugh et al., 2002); spatial resolution, defined as the highest spatial frequency at which the cell gave a response of at least 10% of its maximum; spatial bandwidth, defined as the ratio between the highest and lowest spatial frequencies giving at least half-maximal response, expressed in octaves; orientation tuning, defined as the change in orientation from the peak that causes the response to fall by one half; direction index, defined as 1-np/p, where p is the response to an optimal grating moving in the preferred direction and np is the response to the same grating moving 180° from the preferred; surround suppression, defined as the fractional reduction in response resulting from the enlargement of an optimal-size patch of grating to cover the full screen (Cavanaugh et al., 2002).

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