Decision-Related Activity in Sensory Neurons May Depend on the Columnar Architecture of Cerebral Cortex

Abstract

Many studies have reported correlations between the activity of sensory neurons and animals' judgments in discrimination tasks. Here, we suggest that such neuron-behavior correlations may require a cortical map for the task relevant features. This would explain why studies using discrimination tasks based on disparity in area V1 have not found these correlations: V1 contains no map for disparity. This scheme predicts that activity of V1 neurons correlates with decisions in an orientation-discrimination task. To test this prediction, we trained two macaque monkeys in a coarse orientation discrimination task using band-pass-filtered dynamic noise. The two orientations were always 90°a part and task difficulty was controlled by varying the orientation bandwidth of the filter. While the trained animals performed this task, we recorded from orientation-selective V1 neurons (n ϭ 82, n ϭ 31 for Monkey 1, n ϭ 51 for Monkey 2). For both monkeys, we observed significant correlation (quantified as "choice probabilities") of the V1 activity with the monkeys' perceptual judgments (mean choice probability 0.54, p ϭ 10 Ϫ5). In one of these animals, we had previously measured choice probabilities in a disparity discrimination task in V1, which had been at chance (0.49, not significantly different from 0.5). The choice probabilities in this monkey for the orientation discrimination task were significantly larger than those for the disparity discrimination task (p ϭ 0.032). These results are predicted by our suggestion that choice probabilities are only observed for cortical sensory neurons that are organized in maps for the task-relevant feature.

Binocular depth processing in the ventral visual pathway

“…The view that V1 neurons act as local absolute disparity filters that convey information that is still too far-removed from global depth perception is further supported by the fact that the activity of V1 neurons does not correlate with monkeys' perceptual reports during a depth-discrimination task [48] (but see [49] for an alternative explanation and [50] for a discussion). Nevertheless, and as expected from the resulting cortical blindness, lesioning V1 in macaques dramatically impairs stereoacuity [51].…”

Belief states as a framework to explain extra-retinal influences in visual cortex

“…For example, if neurons tuned to vertical were more active, the monkey was more likely to choose the vertical orientation. Thus, V1 neurons carried signals related to the animal's choice.Reproduced with permission from [53 ].…”

“…These correlations are frequently referred to as 'choice-probabilities' and occur in many perceptual tasks and in many visual areas [47][48][49][50][51][52]. Figure 1d shows recent results of a study reporting choice probabilities in V1 for an orientation discrimination task [53 ]. The animal's task was to discriminate between two orientations 90 degrees apart in a noisy stimulus (orientation bandpass filtered noise).…”

Dissecting neural circuits for multisensory integration and crossmodal processing

“…For example, trial-by-trial correlations of the responses of sensory neurons with perceptual decisions have been used to probe for functional roles in perception [1,2]. However, a crucial test of any model relating neural activity to behaviour involves interrogating how behaviour changes upon causal manipulation of these networks.…”