Dissociating Cognitive Processes During Ambiguous Information Processing in Perceptual Decision-Making

Abstract

Decision-making requires the accumulation of sensory evidence. However, in everyday life, sensory information is often ambiguous and contains decision-irrelevant features. This means that the brain must disambiguate sensory input and extract decision-relevant features. Sensory information processing and decision-making represent two subsequent stages of the perceptual decision-making process. While sensory processing relies on occipito-parietal neuronal activity during the earlier time window, decision-making lasts for a prolonged time, involving parietal and frontal areas. Although perceptual decision-making is being actively studied, its neuronal mechanisms under ambiguous sensory evidence lack detailed consideration. Here, we analyzed the brain activity of subjects accomplishing a perceptual decision-making task involving the classification of ambiguous stimuli. We demonstrated that ambiguity induced high frontal θ-band power for 0.15 s post-stimulus onset, indicating increased reliance on top-down processes, such as expectations and memory. Ambiguous processing also caused high occipito-parietal β-band power for 0.2 s and high fronto-parietal β-power for 0.35-0.42 s post-stimulus onset. We supposed that the former component reflected the disambiguation process while the latter reflected the decision-making phase. Our findings complemented existing knowledge about ambiguous perception by providing additional information regarding the temporal discrepancy between the different cognitive processes during perceptual decision-making.

Attentional Bias for the Left Visual Field in Ambiguous Necker Cube Processing

“…On the one hand, this set could be separated into subsets of left-oriented (LO) a = {0.15, 0.25, 0.4, 0.45} and right-oriented (RO) cubes a = {0.55, 0.6, 0.75, 0.85}. On the other hand, in accordance with our previous study 14 , this set could be also divided into low-ambiguous (LA) images a = {0.15, 0.25, 0.75, 0.85}, which are easily interpreted by an observer, and high-ambiguous (HA) images a = {0.40, 0.45, 0.55, 0.60}, whose interpretations requires more effort. We also supposed that HA processing engages more top-down control.…”

“…Considering response times (RT), we found that high ambiguity increases RT, as reported in our earlier works on the Necker cube perception 14,15 . We also observed that for low ambiguity, subjects responded faster to the left-oriented than right-oriented stimuli.…”

“…Statistical analysis followed a methodology, similar to our recent works 14,15 . We performed the group-level statistics for the median reaction time (RT) and presentation time (PT) with two within-subject factors: ambiguity and orientation.…”

Effect of repetition on the behavioral and neuronal responses to ambiguous Necker cube images

“…We revealed that the subjects responded to LA stimuli faster and more correctly than to HA stimuli that coincides with our previous findings 12,26 . In the latter case, they deal with ambiguous sensory information and may increasingly rely on the top-down processes, such as expectations and memory, to make a correct decision 9,13 . When processing LA stimuli, subjects responded quicker to the left-oriented stimuli than to the right-oriented ones.…”

“…* email: maximenkovl@gmail.com Experimental procedure. We chose an ambiguous drawing of a Necker cube as a bistable visual stimulus [11][12][13] . The ambiguity, as well as the orientation of the cube's image, was determined by the balance between the brightness of the inner edges forming a left-lower ( b l = 1 − a ) and right-upper ( b r = a ) squares, where a ∈ [0, 1] was a normalized edge's luminance in a gray-scale palette.…”