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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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General relationship between motion discrimination and perceptual awareness.Black symbols: mean proportion of correct responses (chance level  = 0.5) at each PA score. The grey histogram represents the frequency distribution of PA scores. Data are collapsed over urgency and coherence (excluding coherence  = 0%). Bars: ± S.E.M. across subjects.
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pone-0017079-g002: General relationship between motion discrimination and perceptual awareness.Black symbols: mean proportion of correct responses (chance level  = 0.5) at each PA score. The grey histogram represents the frequency distribution of PA scores. Data are collapsed over urgency and coherence (excluding coherence  = 0%). Bars: ± S.E.M. across subjects.

Mentions: Overall, the discrimination rate was positively correlated with the PA score (τ = 0.342, p<0.001, Figure 2). Observers discriminated motion direction rather well (between 87.1% and 98.8% across subjects, excluding stimuli with coherence  = 0%), even at PA = 0, where the average discrimination rate was 68% (with no significant difference between saccadic and verbal response trials, 64% and 71%, respectively). The latter values were significantly higher than chance (p<0.001), suggesting that motion could be processed to a considerable degree even when its direction was subjectively invisible. The significantly better-than-chance performance at PA = 0 held true in 7 out of 8 participants, with discrimination rates comprised between 57% and 87%.


Delayed perceptual awareness in rapid perceptual decisions.

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

General relationship between motion discrimination and perceptual awareness.Black symbols: mean proportion of correct responses (chance level  = 0.5) at each PA score. The grey histogram represents the frequency distribution of PA scores. Data are collapsed over urgency and coherence (excluding coherence  = 0%). Bars: ± S.E.M. across subjects.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0017079-g002: General relationship between motion discrimination and perceptual awareness.Black symbols: mean proportion of correct responses (chance level  = 0.5) at each PA score. The grey histogram represents the frequency distribution of PA scores. Data are collapsed over urgency and coherence (excluding coherence  = 0%). Bars: ± S.E.M. across subjects.
Mentions: Overall, the discrimination rate was positively correlated with the PA score (τ = 0.342, p<0.001, Figure 2). Observers discriminated motion direction rather well (between 87.1% and 98.8% across subjects, excluding stimuli with coherence  = 0%), even at PA = 0, where the average discrimination rate was 68% (with no significant difference between saccadic and verbal response trials, 64% and 71%, respectively). The latter values were significantly higher than chance (p<0.001), suggesting that motion could be processed to a considerable degree even when its direction was subjectively invisible. The significantly better-than-chance performance at PA = 0 held true in 7 out of 8 participants, with discrimination rates comprised between 57% and 87%.

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