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Delayed perceptual awareness in rapid perceptual decisions.

Gregori-Grgič R, Balderi M, de'Sperati C - PLoS ONE (2011)

Bottom Line: It made no difference whether motion discrimination was accomplished by saccades or verbal responses.These findings suggest that perceptual awareness emerges on the top of a developing or even mature perceptual decision.We argue that the middle temporal (MT) cortical region does not confer us the full phenomenic depth of motion perception, although it may represent a precursor stage in building our subjective sense of visual motion.

View Article: PubMed Central - PubMed

Affiliation: Visuo-Motor Functions Lab, Univeristà Vita-Salute San Raffaele, Milano, Italy.

ABSTRACT
The flourishing of studies on the neural correlates of decision-making calls for an appraisal of the relation between perceptual decisions and conscious perception. By exploiting the long integration time of noisy motion stimuli, and by forcing human observers to make difficult speeded decisions--sometimes a blind guess--about stimulus direction, we traced the temporal buildup of motion discrimination capability and perceptual awareness, as assessed trial by trial through direct rating. We found that both increased gradually with motion coherence and viewing time, but discrimination was systematically leading awareness, reaching a plateau much earlier. Sensitivity and criterion changes contributed jointly to the slow buildup of perceptual awareness. It made no difference whether motion discrimination was accomplished by saccades or verbal responses. These findings suggest that perceptual awareness emerges on the top of a developing or even mature perceptual decision. We argue that the middle temporal (MT) cortical region does not confer us the full phenomenic depth of motion perception, although it may represent a precursor stage in building our subjective sense of visual motion.

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Stimulus and motion discrimination task.See Methods for details.
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pone-0017079-g001: Stimulus and motion discrimination task.See Methods for details.

Mentions: Despite the diffusion of studies on perceptual decision-making, and the number of hypotheses on how the decision signal accumulates over time [1], [2], [3], [4], [16], the temporal relation between the objective decision performance and the associated subjective sensation has never been investigated directly, perhaps also owing to the above difficulties. Here we addressed this issue by jointly assessing how visually-guided decisions and visual awareness develop in time after stimulus onset. We took advantage of degraded motion stimuli that entail a long processing time [12], [17], and sampled the accumulation of sensory evidence by forcing participants to make speeded discrimination of motion direction, with a saccade or a verbal response, at various points in time after stimulus onset, guessing if necessary (Figure 1). In each trial, observers rated the subjective visibility of global motion direction through a perceptual awareness (PA) scale.


Delayed perceptual awareness in rapid perceptual decisions.

Gregori-Grgič R, Balderi M, de'Sperati C - PLoS ONE (2011)

Stimulus and motion discrimination task.See Methods for details.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3040746&req=5

pone-0017079-g001: Stimulus and motion discrimination task.See Methods for details.
Mentions: Despite the diffusion of studies on perceptual decision-making, and the number of hypotheses on how the decision signal accumulates over time [1], [2], [3], [4], [16], the temporal relation between the objective decision performance and the associated subjective sensation has never been investigated directly, perhaps also owing to the above difficulties. Here we addressed this issue by jointly assessing how visually-guided decisions and visual awareness develop in time after stimulus onset. We took advantage of degraded motion stimuli that entail a long processing time [12], [17], and sampled the accumulation of sensory evidence by forcing participants to make speeded discrimination of motion direction, with a saccade or a verbal response, at various points in time after stimulus onset, guessing if necessary (Figure 1). In each trial, observers rated the subjective visibility of global motion direction through a perceptual awareness (PA) scale.

Bottom Line: It made no difference whether motion discrimination was accomplished by saccades or verbal responses.These findings suggest that perceptual awareness emerges on the top of a developing or even mature perceptual decision.We argue that the middle temporal (MT) cortical region does not confer us the full phenomenic depth of motion perception, although it may represent a precursor stage in building our subjective sense of visual motion.

View Article: PubMed Central - PubMed

Affiliation: Visuo-Motor Functions Lab, Univeristà Vita-Salute San Raffaele, Milano, Italy.

ABSTRACT
The flourishing of studies on the neural correlates of decision-making calls for an appraisal of the relation between perceptual decisions and conscious perception. By exploiting the long integration time of noisy motion stimuli, and by forcing human observers to make difficult speeded decisions--sometimes a blind guess--about stimulus direction, we traced the temporal buildup of motion discrimination capability and perceptual awareness, as assessed trial by trial through direct rating. We found that both increased gradually with motion coherence and viewing time, but discrimination was systematically leading awareness, reaching a plateau much earlier. Sensitivity and criterion changes contributed jointly to the slow buildup of perceptual awareness. It made no difference whether motion discrimination was accomplished by saccades or verbal responses. These findings suggest that perceptual awareness emerges on the top of a developing or even mature perceptual decision. We argue that the middle temporal (MT) cortical region does not confer us the full phenomenic depth of motion perception, although it may represent a precursor stage in building our subjective sense of visual motion.

Show MeSH
Related in: MedlinePlus