Here we present two experiments investigating the implicit orienting of attention over time by entrainment to an auditory rhythmic stimulus. In the first experiment, participants carried out a detection and discrimination tasks with auditory and visual targets while listening to an isochronous, auditory sequence, which acted as the entraining stimulus. For the second experiment, we used musical extracts as entraining stimulus, and tested the resulting strength of entrainment with a visual discrimination task. Both experiments used reaction times as a dependent variable. By manipulating the appearance of targets across four selected metrical positions of the auditory entraining stimulus we were able to observe how entraining to a rhythm modulates behavioural responses. That our results were independent of modality gives a new insight into cross-modal interactions between auditory and visual modalities in the context of dynamic attending to auditory temporal structure.

When we direct attentional resources to a certain point in time, expectation and preparedness is heightened and behavior is, as a result, more efficient. This future-oriented attending can be guided either voluntarily, by externally defined cues, or implicitly, by perceived temporal regularities. Inspired by dynamic attending theory, our aim was to study the extent to which metrical structure, with its beats of greater or lesser relative strength, modulates attention implicitly over time and to uncover the neural circuits underlying this process of dynamic attending. We used fMRI to investigate whether auditory meter generated temporal expectancies and, consequently, how it affected processing of auditory and visual targets. Participants listened to a continuous auditory metrical sequence and pressed a button whenever an auditory or visual target was presented. The independent variable was the time of target presentation with respect to the metrical structure of the sequence. Participants' RTs to targets occurring on strong metrical positions were significantly faster than responses to events falling on weak metrical positions. Events falling on strong beats were accompanied by increased activation of the left inferior parietal cortex, a region crucial for orienting attention in time, and, by greater functional connectivity between the left inferior parietal cortex and the visual and auditory cortices, the SMA and the cerebellum. These results support the predictions of the dynamic attending theory that metrical structure with its relative strong and weak beats modulates attentional resources over time and, in turn, affects the functioning of both perceptual and motor preparatory systems.

The time-course of morphological processing during spoken word recognition was investigated using event-related brain potentials (ERPs) in an auditory lexical decision task. We compared three different types of French words: truly suffixed (e.g., pochette 'little pocket' = poche 'pocket' + diminutive suffix-ette), pseudo-suffixed (e.g., mouette 'seagull' = mou 'soft' + pseudo-suffix-ette) and non-suffixed target words (e.g., fortune 'fortune' = fort 'strong' + non-suffix-une). Suffixed (e.g., mouesse = mou + suffix-esse) and non-suffixed nonwords (e.g., mouipe = mou + non-suffix-ipe) were also tested. The behavioural results showed that participants responded more slowly to non-suffixed words than to truly suffixed and pseudo-suffixed words, but there was no difference between these two suffixed conditions. Moreover, participants made more errors rejecting pseudo-suffixed nonwords than non-suffixed nonwords. In the ERP analyses, T0 was shifted to the end of the embedded stem or pseudo-stem. The ERP results revealed enhanced N400 amplitudes for non-suffixed words compared to truly suffixed and pseudo-suffixed words. Again, there was no difference between the truly and pseudo-suffixed conditions. In addition, we found an increased N400 amplitude for both pseudo-suffixed and non-suffixed nonwords than for words. The latency of the onset of this N400 effect varied between the three experimental conditions: the wordnonword difference occurred earliest in the truly suffixed condition, slightly later in the pseudo-suffixed condition and latest in the non-suffixed condition. Both behavioural and EEG data jointly suggest that spoken words with a genuine morphological structure and words with a pseudo-morphological structure are decomposed into morphemic sub-units. Moreover, the earlier appearance of the N400 effects in the truly suffixed condition indicates that morphological information is more readily available in words with a semantically transparent morphological structure.

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