Linking Neuronal and Behavioral Performance in a Reaction-Time Visual Detection Task

Abstract

Perceptual decisions are likely to be based on signals that are provided by populations of neurons in early sensory cortical areas. How these neural responses are combined across neurons and over time to mediate behavior is unknown. To study the link between neural responses and perceptual decisions, we recorded the activity of single units (SU) and multiple units (MU) in the primary visual cortex (V1) of monkeys while they performed a reaction-time visual detection task. We then determined how well the target could be detected from these neural signals. We found that, on average, the detection sensitivities supported by SU and MU in V1 are comparable with the detection sensitivity of the monkey even when considering neural responses during brief temporal intervals (median duration, 137 ms) that ended shortly before the monkey's reaction time. However, we observed systematic differences between the overall shape of the neurometric functions and the monkey's psychometric functions. We also examined the quantitative relationship between SU and MU activity and found that MU responses are consistent with the sum of the responses of multiple SU, most of which have low stimulus selectivity. Finally, we found weak but significant trial-to-trial covariations between V1 activity and behavioral choices, demonstrating for the first time that choice probability can be observed at the earliest stages of cortical sensory processing. Together, these results suggest that the activity of a large population of V1 neurons is combined suboptimally by subsequent processing stages to mediate behavioral performance in visual detection tasks.

The functional asymmetry of ON and OFF channels in the perception of contrast

“…Using spike count measurements, previous studies have reported significant choice-related activities in many cortical areas during a variety of behavioral tasks (Bosking and Maunsell 2011;Britten et al 1996;Cook and Maunsell 2002;Dodd et al 2001;Grunewald et al 2002;Liu and Newsome 2005;Nienborg and Cumming 2006;Palmer et al 2007;Parker et al 2002;Price and Born 2010;Purushothaman and Bradley 2005;Uka and DeAngelis 2004;Uka et al 2005). Similarly, our previous study reported above chance choice probabilities for both P and M LGN neurons (Jiang et al 2015b).…”

“…Basic procedures in computing choice probabilities were similar to those described in previous studies Jiang et al 2015a,b;Palmer et al 2007). When using spike count distributions, the proportions of choice-inside-receptive-field trials (i.e., trials in which the monkey made a saccade towards the receptive field location) were plotted against the proportions of choice-outside-receptive-field trials that exceeded all the possible spike count criteria (in number of spikes), and the area under the ROC curve was taken as the choice probability value for that contrast level.…”

Detection of Tones and Their Modification by Noise in Nonhuman Primates

“…after the analyses of Britten et al (1992) and Palmer et al (2007), where x is sound pressure level, and λ and k represent the threshold and slope parameter. However, since the monkeys' false alarm rates influenced both the maximum performance and the estimate of chance performance at sound levels below threshold, these probabilities were allowed to be free parameters in our fitting method.…”

Psychophysically measured task strategy for disparity discrimination is reflected in V2 neurons

“…One method that has been widely used to suggest that signals from particular neurons contribute to a given perceptual decision combines threshold psychophysics with single-unit recordings. A trialto-trial correlation between neuronal activity and perceptual judgment, which cannot be explained by the visual stimulus, is taken as evidence that neuronal signals contribute to a decision [1][2][3][4][5][6][7] . Such correlation, often quantified by 'choice probability', should then also depend on the task strategy employed by the subject 6 .…”