Notes

Britten, Kenneth H., et al. "The analysis of visual motion: a comparison of neuronal and psychophysical performance." Journal of Neuroscience 12.12 (1992): 4745-4765.

brittenAnalysisVisualMotion

An enduring problem for neuroscience is understanding the relationship between neuronal activity and psychophysical judgement. For instance, how is the psychophysical sensitivity of animal observers related to the sensitivity of individual cortical neurons? Previous analyses have reported sensitivities of cortical neu- rons that fell considerably short of psychophysical sensitivity. Such studies have been hampered because neuronal and perceptual data were not obtained under the same conditions. In this work, we compare the capacity of single cortical neurons for signalling motion direction with the ability of three trained rhesus monkeys to discriminate the direction of near-threshold motion signals in a stochastic visual display. Unlike previous studies, we have recorded the responses of directionally selective neurons and the psychophysical performance of monkeys under identical conditions – the same animal, sets of trials and visual display. In addition, we matched the visual display to each neuron’s preferences in terms of size, speed and direction of motion. Under these conditions, the sensitivity of most MT neurons is remarkably similar to the animal psychophysical sensitivity. The responses of single neurons provide a satisfactory account for the absolute psychophysical threshold and the shape of the psychometric function that relates stimulus strength to visual performance. Our results suggest that perceptual judgements in the psychophysical task are likely based on a relatively small number of independent neural signals present in the response of MT neurons. However, we argue that the size of the neuronal pool carrying these signals is likely dependent upon the degree of intercorrelated firing among the pooled cells.