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Postle, B. R.

Publications and source records attributed to Postle, B. R..

5 recordsLinked to original sources
bioRxiv2018

Confidence boosts serial dependence in orientation estimation

In the absence of external feedback, a decision maker must rely on a subjective estimate of their decision accuracy in order to appropriately guide behavior. Normative models of perceptual decision making relate subjective estimates of internal signal quality (e.g. confidence) directly to the internal signal quality itself, thereby making it unknowable whether the subjective estimate or the underlying signal is what drives behavior. We constructed stimuli that dissociated human observers performance on a visual estimation task from their subjective estimates of confidence in their performance, thus violating normative principles. To understand whether confidence influences future decision making, we examined serial dependence in observers responses, a phenomenon whereby the estimate of a stimulus on the current trial can be biased towards the stimulus from the previous trial. We found that when decisions were made with high confidence, they conferred stronger biases upon the following trial, suggesting that confidence may enhance serial dependence. Critically, this finding was true also when confidence was experimentally dissociated from task performance, indicating that subjective confidence, independent of signal quality, can amplify serial dependence. These findings demonstrate an effect of confidence on future behavior, independent of task performance, and suggest that perceptual decisions incorporate recent history in an uncertainty-weighted manner, but where the uncertainty carried forward is a subjectively estimated and possibly suboptimal readout of objective sensory uncertainty.

neuroscience↗
bioRxiv2018

Different states of priority recruit different neural codes in visual working memory

We tracked the neural representation of the orientation and the location of stimuli held in working memory at different levels of priority (\"attended\" and \"unattended\" memory items -- AMI and UMI), using multivariate inverted encoding models of human fMRI. Although representation of the orientation of the AMI and of the UMI could be reconstructed in several brain regions, including in early visual and parietal regions, the identity of the UMI was actively represented in early visual cortex in a distinct \"reversed\" code, suggesting this region as a site of the focus of attention to nonspatial stimulus information. The location of stimuli was also broadly represented, although only in parietal cortex was the location of the UMI represented in a reversed code. Our results suggest that a common recoding operation may be engaged, across stimulus dimensions and brain areas, to retain information in working memory while outside the focus of attention.

neuroscience↗
bioRxiv2017

Correlated Individual Differences Suggest A Common Mechanism Underlying Metacognition In Visual Perception And Visual Short-Term Memory

Adaptive behavior depends on the ability to accurately introspect about ones own performance. Whether this metacognitive ability is supported by the same mechanisms across different tasks has thus far been investigated with a focus on correlating metacognitive accuracy between perception and long-term memory paradigms. Here, we investigated the relationship between metacognition of visual perception and metacognition of visual short-term memory (VSTM), a cognitive function thought to be more intimately related to visual processing. Experiments 1 and 2 required subjects to estimate the perceived or remembered orientation of a grating stimulus and rate their confidence. We observed strong positive correlations between individual differences in metacognitive accuracy between the two tasks. This relationship was not accounted for by individual differences in task performance or average confidence, and was present across two different metrics of metacognition and in both experiments. A model-based analysis of data from a third experiment showed that a cross-domain correlation only emerged when both tasks shared the same task-relevant stimulus feature. That is, metacognition for perception and VSTM were correlated when both tasks required orientation judgments, but not when the perceptual task was switched to require contrast judgments. In contrast to previous results comparing perception and long-term memory, which have largely provided evidence for domain-specific metacognitive processes, the current findings suggest that metacognition of visual perception and VSTM is supported by a domain-general metacognitive architecture, but only when both domains share the same task-relevant stimulus feature.

neuroscience↗
bioRxiv2016

Electrophysiological correlates of phosphene perception induced by stimulation of human occipital and parietal cortex

Magnetic stimulation (TMS) of human occipital and posterior parietal cortex can give rise to visual sensations called phosphenes, but neural correlates of phosphene perception preceding and succeeding stimulation of both areas are unknown. Using near-threshold TMS with concurrent electroencephalography (EEG) recordings, we uncover oscillatory brain dynamics that covary, on single trials, with the perception of phosphenes following occipital and parietal TMS. Prestimulus power and phase predominantly in the alpha-band (8-13 Hz) predicted occipital TMS phosphenes, whereas higher frequency beta-band (13-20 Hz) power (but not phase) predicted parietal TMS phosphenes. TMS evoked responses related to phosphene perception were similar across stimulation sites and were characterized by an early (200 ms) posterior negativity and a later (>300 ms) parietal positivity in the time domain and an increase in low-frequency (~5-7 Hz) power followed by a broadband decrease in alpha/beta power in the time-frequency domain. These correlates of phosphene perception closely resemble known electrophysiological correlates of conscious perception using near-threshold visual stimuli and speak to the possible early onset of visual consciousness. The differential pattern of prestimulus predictors of phosphene perception suggest that distinct frequencies reflect cortical excitability within different cortical regions, and that the alpha-band rhythm, long thought of as a general index of cortical inhibition, may not reflect excitability of posterior parietal cortex.\n\nSignificance statementAlpha-band oscillations are thought to reflect cortical excitability and are therefor suggested to play an important role in gating information transmission across cortex. We directly probe cortical excitability in human occipital and parietal cortex and observed that whereas alpha-band dynamics indeed reflect excitability of occipital areas, beta-band activity was most predictive of parietal cortex excitability. Differences in the state of cortical excitability predicted perceptual outcomes, which were manifest in both early and late patterns of evoked activity, shedding light on the neural correlates of consciousness. Our findings prompt revision of the notion that alpha activity reflects inhibition across all of cortex and suggests instead that excitability in different regions is reflected in distinct frequency bands.

neuroscience↗