The need for top-down attentional selection due to the competition between multiple stimulus dimensions (for discussion, see Desimone and Duncan 1995) and the lack of relevant visual information in our experiment have likely emphasized the tuning effect of top-down linguistic focus.
Moreover, the simple discrimination tasks employed so far do not explicitly control processing demands, thus task difficulty and degree of top-down linguistic focus might vary drastically between the 2 conditions, which, in turn, would affect the profile of cortical responses before versus after the subjects' switch to speech mode.
A natural follow-up of this work will hence be to explore how the intrinsic dynamics of theta and gamma activity interact not only with sensory input but also with linguistic top-down signals, e.g., word, sentence level predictions (Gagnepain et al., 2012), and even cross-modal predictions (Arnal et al., 2009).
Either way, it was worth tuning in just to see Andrew Marr discussing "the tramp stamp on the muffin top on the chav" – linguistic (and stylistic) hallmark of the decade, apparently.
The central aim of the present study is to differentiate the cortical effects of top-down attention to linguistic versus equally challenging nonlinguistic aspects of auditory input.
Finally, the inherently unidirectional nature of the debriefing procedure (from nonspeech to speech) restricts this approach in its utility as a tool for investigating top-down attention to linguistic content via repeated, within-subject measures using functional magnetic resonance imaging (fMRI).
The present study seeks to isolate top-down focus on linguistic aspects of auditory words by controlling for confounding factors (stimulation type and differences in the overall level of attentional demands) in order to test the hypothesis that selective auditory attention to language modulates responses in cortical regions involved in speech processing.
These mild difficulties could reflect problems in using information from linguistic context and top-down vocabulary knowledge to infer word identities (Nation & Snowling, 2004).
Thus, in the Supplementary Material, we also report results from within lateral prefrontal recruitment in linguistic tasks (phonological, top-down semantic, and sentence-level tasks), and the recruitment of posterior temporal areas by top-down semantics and tool-related tasks.
