Single trial neuronal activity dynamics of attentional intensity in monkey visual area V4

Understanding how activity of visual neurons represents distinct components of attention and their dynamics that account for improved visual performance remains elusive because single-unit experiments have not isolated the intensive aspect of attention from attentional selectivity. We isolated attentional intensity and its single trial dynamics as determined by spatially non-selective attentional performance in an orientation discrimination task while recording from neurons in monkey visual area V4. We found that attentional intensity is a distinct cognitive signal that can be distinguished from spatial selectivity, reward expectations and motor actions. V4 spiking on single trials encodes a combination of sensory and cognitive signals on different time scales. Attentional intensity and the detection of behaviorally relevant sensory signals are well represented, but immediate reward expectation and behavioral choices are poorly represented in V4 spiking. These results provide a detailed representation of perceptual and cognitive signals in V4 that are crucial for attentional performance.

Reward-Related Suppression of Neural Activity in Macaque Visual Area V4

In order for organisms to survive, they need to detect rewarding stimuli, for example, food or a mate, in a complex environment with many competing stimuli. These rewarding stimuli should be detected even if they are nonsalient or irrelevant to the current goal. The value-driven theory of attentional selection proposes that this detection takes place through reward-associated stimuli automatically engaging attentional mechanisms. But how this is achieved in the brain is not very well understood. Here, we investigate the effect of differential reward on the multiunit activity in visual area V4 of monkeys performing a perceptual judgment task. Surprisingly, instead of finding reward-related increases in neural responses to the perceptual target, we observed a large suppression at the onset of the reward indicating cues. Therefore, while previous research showed that reward increases neural activity, here we report a decrease. More suppression was caused by cues associated with higher reward than with lower reward, although neither cue was informative about the perceptually correct choice. This finding of reward-associated neural suppression further highlights normalization as a general cortical mechanism and is consistent with predictions of the value-driven attention theory.

Visual area V4 encodes history dependent attentional effort and single-trial perceptual detection

ABSTRACTIntense attentional effort improves performance. Neurons in visual area V4 exhibit changes in spike rates that are correlated with effort, selective attention and absolute reward expectation. How neuronal spikes in V4 encode attentional states and perceptual performance with reference to other task relevant motivational and decision signals is poorly understood. We recorded neuronal spikes from monkey visual area V4, and isolated attentional effort from reward expectancy and motor decisions in a visual orientation detection task using a statistical approach based on generalized linear models. We found that V4 spike responses exhibit hysteresis with reward changes. Single trial spiking activity encodes a combination of temporally overlapping sensory and cognitive signals. Neuronal spikes integrate contextual history of attentional effort on a longer time scale, and task related perceptual detection in a shorter timescale within a single trial. Notably, immediate reward expectation and behavioral choice probability are poor predictors of V4 spikes throughout the trial. Further, detection of task relevant perceptual signal is decoded from single trial population spikes with high accuracy. These results provide a detailed representation of perceptual and cognitive signals in V4 that are crucial for performance.