The premotor theory of attention and the Simon effect

In the paper by Hommel (2011-this issue), the roles of the theory of event coding (TEC) and the premotor theory of attention (PMTA) for the Simon effect were considered. PMTA was treated by Hommel in terms of the proposal that attentional orienting can be viewed as the preparation of a saccade towards a certain location, and was dismissed as providing no useful contribution for an attentional explanation of the Simon effect. Here we considered a more recent and broader conception of the PMTA, compared this approach with TEC, and confronted both approaches with a few studies focusing on the role of spatial attention for the Simon effect. It was argued that PMTA may account more easily for various studies examining the influence of spatial attention on the Simon effect. We concluded our paper by listing some elements that an overall encompassing theory on the Simon effect should contai

Does transcranial direct current stimulation affect the learning of a fine sequential hand motor skill with motor imagery?

Learning a fine sequential hand motor skill, comparable to playing the piano or learning to type, improves not only due to physical practice, but also due to motor imagery. Previous studies revealed that transcranial direct current stimulation (tDCS) and motor imagery independently affect motor learning. Other studies showed that training with motor imagery combined with anodal tDCS might generally enhance motor performance. In the present study, we investigated whether tDCS combined with motor imagery above the primary motor cortex influences sequence-specific learning of a fine hand motor skill. Four groups of participants were involved: an anodal, cathodal, and sham stimulation group, and a control group without stimulation. A modified discrete sequence production (DSP) task was employed: the Go/NoGo DSP task. After a sequence of spatial cues, a response sequence had to be either executed, imagined or withheld. The task allows to estimate general learning effects in a practice phase, and sequence-specific learning effects in a test phase by comparing the execution of unfamiliar sequences, familiar imagined sequences, familiar withheld and familiar executed sequences. Results showed that the effects of anodal tDCS were already developing during the practice phase, while no sequence-specific effects were visible during the test phase. These findings confirm that anodal tDCS affects motor performance but they also reveal that it does not facilitate the influence of motor imagery on sequence learning

Spatial Tapping Interferes With the Processing of Linguistic Spatial Relations

Simple spatial relations may be represented either in a propositional format that is dependent on verbal rehearsal or in a picture-like format that is maintained by visual-spatial rehearsal. In sentence-picture and picture-picture verification tasks, we examined the effect of an articulatory suppression and a spatial tapping dual task on the encoding of simple spatial relations (e.g., triangle left of circle). Articulatory suppression did not interfere, while spatial tapping lowered performance in both tasks. Apparently, both linguistic and perceptual inputs of simple spatial relations engaged the visual-spatial working memory. In the sentence-picture verification experiments, spatial tapping only hampered performance of participants who were classified on the basis of their RT patterns as having used a visual-spatial strategy, while it had no effect for those who were classified as having applied a verbal strategy. Therefore, this study provides converging evidence, using a dual-task methodology, that both separate verbal and visual-spatial strategies exist for the processing of simple spatial sentences

Qualitative Differences Between Conscious and Nonconscious Processing? On Inverse Priming Induced by Masked Arrows

In general, both consciously and unconsciously perceived stimuli facilitate responses to following similar stimuli. However, masked arrows delay responses to following arrows. This inverse priming has been ascribed to inhibition of premature motor activation, more recently even to special processing of nonconsciously perceived material. Here, inverse priming depended on particular masks, was insensitive to contextual requirements for increased inhibition, and was constant across response speeds. Putative signs of motor inhibition in the electroencephalogram may as well reflect activation of the opposite response. Consequently, rather than profiting from inhibition of primed responses, the alternative response is directly primed by perceptual interactions of primes and masks. Thus there is no need to assume separate pathways for nonconscious and conscious processing

Modality-specific involvement of occipital cortex in Early Blind?

What happens in occipital cortex when neuronal activity is no longer evoked by regular visual stimulation? Studying brain activity induced by tactile and auditory stimuli in the blind may provide an answer. Several studies indicate that occipital cortex in the blind is recruited in simple tasks, like auditory localization, and complex tasks, involving verbal memory. The goal of the current study was to establish whether or not this occipital recruitment is modality-specific when highly comparable tactile and auditory tasks are carried out. Early-blind subjects performed auditory and tactile duration discrimination tasks while their EEG was being measured. Source localization on secondary activity, after about 250 ms, revealed an occipito-parietal and occipito-temporal locus in case of auditory and tactile stimuli, respectively. This modality-specific result was underlined by a correlation between right occipital activity and performance on auditory targets. These findings suggest that specific parts of occipital cortex are more suitable for the takeover of modality-specific functions, which may possibly be related to the distinction between dorsal and ventral visual pathways