Cerebral Bases of Subliminal and Supraliminal Priming during Reading

Kouider, Sid and Dehaene, Stanislas and Jobert, Antoinette and Le Bihan, Denis (2007) Cerebral Bases of Subliminal and Supraliminal Priming during Reading. Cerebral Cortex, 17 (9). pp. 2019-2029.

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Official URL: http://cercor.oxfordjournals.org/cgi/content/abstract/17/9/2019

Abstract

Several studies have investigated the neural correlates of conscious perception by contrasting functional magnetic resonance imaging (fMRI) activation to conscious and nonconscious visual stimuli. The results often reveal an amplification of posterior occipito-temporal activation and its extension into a parieto-frontal network. However, some of these effects might be due to a greater deployment of attentional or strategical processes in the conscious condition. Here, we examined the brain activity evoked by visible and invisible stimuli, both of which were irrelevant to the task. We collected fMRI data in a masking paradigm in which subliminal versus supraliminal letter strings were presented as primes while subjects focused attention on another subsequent, highly visible target word. Under those conditions, prime visibility was associated with greater activity confined to bilateral posterior occipito-temporal cortices, without extension into frontal and parietal cortices. However, supraliminal primes, compared with subliminal primes, evoked more extensive repetition suppression in a widely distributed set of parieto-frontal areas. Furthermore, only supraliminal primes caused phonological repetition enhancement in left inferior frontal and anterior insular cortex. Those results suggest a 2-stage view of conscious access: Relative to masked stimuli, unmasked stimuli elicit increased occipito-temporal activity, thus allowing them to compete for global conscious access and to induce priming in multiple distant areas. In the absence of attention, however, their access to a second stage of distributed parieto-frontal processing may remain blocked.

Comments/Discussion

The fourth William James Prize for Contributions to the Study of Consciousness was awarded to Sid Kouider in Las Vegas Nevada at the 11th Annual Meeting of ASSC. Sid's publication, Cerebral bases of subliminal and supraliminal priming during reading (Cerebral Cortex, 2007, 17, 2019-2029) was selected as the winning nomination from the 18 nominations received for consideration. The research described in the publication examined brain activity evoked by visible and invisible stimuli, both of which were irrelevant to the task so as to minimize the involvement of attentional or strategic processes. Under these conditions, prime visibility was associated with greater activity in the bilateral posterior occipito-temporal cortices, without extension into frontal and parietal cortices. These findings suggest that there is an intermediate level of conscious processing between subliminal perception and conscious access.

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