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How quickly carry out different kinds of conceptual knowledge become available

How quickly carry out different kinds of conceptual knowledge become available following visual word perception? Resolving this question will inform neural and computational theories of visual word recognition and semantic memory use. living nonliving graspable or ungraspable ones and for all participants regardless of their response velocity. The latency of the N200 nogo effect by contrast is usually sensitive to decision velocity. We propose a tentative hypothesis of the neural mechanisms underlying semantic access and a subsequent decision process. contain an animal. This inference was questioned however as the scenes that contained animals and those that did not likely differed in low-level visual characteristics which also have been found to influence electrophysiological activity Demethoxycurcumin before 150 ms (Johnson & Olshausen 2003 In response to this concern VanRullen and Thorpe (2001) ensured that images from each category appeared equally often as targets and non-targets with the same images contributing to the average go and nogo ERPs. They found that the visual characteristics of the images affected ERPs by 80 ms but also replicated the 150 ms N200 effect. This early nogo N200 effect was obtained in studies using images. The current study used words which provide a less direct route to meaning and are less likely to engender low-level visual stimulus confounds. These differences between words and images could delay the time course of conceptual access for words relative to that for images. The above experiments involved a single decision on each trial but a handful of dual-task go/nogo ERP studies have employed a dual-task paradigm in which participants make two different decisions per item: a go/nogo decision contingent upon one kind of information available from the stimulus and a left/right hand decision on go trials contingent upon another kind of information available from the stimulus. Some dual-task studies for example used black and white line drawings where the semantic decision was whether the image depicted an animal or an object (Rodriguez-Fornells Schmitt Kutas & Munte 2002 Schmitt Munte & Kutas 2000 or whether the image depicted an object heavier or lighter than 500 grams (Schmitt Schiltz Zaake Kutas & Demethoxycurcumin Munte 2001 In all cases the nogo ERP was characterized by a larger frontal negativity starting around 200 ms post-stimulus onset than the go ERP. This is somewhat later than nogo N200 effects in the visual object categorization studies perhaps due to the use of line drawings instead of photographs the use of longer stimulus duration Tgfb2 latencies differences in instructions or some combination thereof. Two go/nogo neurophysiological studies have employed words rather than pictures or images. Müller and Hagoort (2006) conducted a dual-task go/nogo ERP study to contrast a semantic decision (e.g. buildings vs. consumables; weapons vs. clothing) with a syntactic decision; they found a significant N200 effect beginning around 300 ms after stimulus onset- substantially later than those in the implicit picture naming or the visual categorization studies.Hauk et al. (2012) used a single-task paradigm with single words presented briefly (100 ms) in order to foster rapid decision-making along the lines of Van Rullen and Thorpe (2001). They used a living/nonliving semantic decision rather than a more specific decision. In contrast to Müller and Hagoort (2006) they found that nogo and go ERPs at frontal sites significantly diverged by 168 ms for lexical decisions and by 166 ms for living/nonliving decisions. These onset latencies are very early-only slightly later than those reported in the rapid visual Demethoxycurcumin categorization studies (Thorpe Fize & Marlot 1996 VanRullen & Thorpe 2001 suggesting that people can begin to access conceptual information during visual word recognition almost as early as during visual object recognition. Several questions remain unanswered however. In particular Hauk et al’s evidence for rapid semantic access (i.e. < 200 ms) in a decision-related paradigm is an important finding that calls for greater scrutiny. The main unanswered questions are whether information besides category-related information is accessed as quickly and whether rapid semantic access can.