Abstract
Priming occurs when one stimulus (i.e., the prime) influences the processing of a subsequently presented stimulus (i.e., the target), even when the first stimulus remains unconscious. Although examples of unconscious shape priming have been extensively documented, whether such processing requires primary visual cortex (V1) has not been established. In the current study, we used transcranial magnetic stimulation (TMS) of V1 at varying temporal intervals to suppress the visibility of preceding shape primes while the interval between primes and targets was kept constant. On each trial, we measured reaction times to targets (priming) as well as prime visibility (awareness). Our results show that although conscious perception requires V1, unconscious priming can occur without V1 at intermediate temporal intervals but not at early or later stages of processing. This phasic TMS suppression of priming suggests that there may be visual information processing cycles during which only certain phases robustly represent information within V1. Because the later time window of priming suppression (85 - 105 ms) has been proposed to interfere with feedback processing, our results further suggest that feedback processing is also essential for unconscious priming and may not necessarily be a signature of conscious vision.
Meeting abstract presented at VSS 2012