Automatic Semantic Facilitation in Anterior Temporal Cortex Revealed through Multimodal Neuroimaging

Abstract

A core property of human semantic processing is the rapid, facilitatory influence of prior input on extracting the meaning of what comes next, even under conditions of minimal awareness. Previous work has shown a number of neurophysiological indices of this facilitation, but the mapping between time course and localization-critical for separating automatic semantic facilitation from other mechanisms-has thus far been unclear. In the current study, we used a multimodal imaging approach to isolate early, bottom-up effects of context on semantic memory, acquiring a combination of electroencephalography (EEG), magnetoencephalography (MEG), and functional magnetic resonance imaging (fMRI) measurements in the same individuals with a masked semantic priming paradigm. Across techniques, the results provide a strikingly convergent picture of early automatic semantic facilitation. Event-related potentials demonstrated early sensitivity to semantic association between 300 and 500 ms; MEG localized the differential neural response within this time window to the left anterior temporal cortex, and fMRI localized the effect more precisely to the left anterior superior temporal gyrus, a region previously implicated in semantic associative processing. However, fMRI diverged from early EEG/MEG measures in revealing semantic enhancement effects within frontal and parietal regions, perhaps reflecting downstream attempts to consciously access the semantic features of the masked prime. Together, these results provide strong evidence that automatic associative semantic facilitation is realized as reduced activity within the left anterior superior temporal cortex between 300 and 500 ms after a word is presented, and emphasize the importance of multimodal neuroimaging approaches in distinguishing the contributions of multiple regions to semantic processing.

Brain structure in autism: a voxel-based morphometry analysis of the Autism Brain Imaging Database Exchange (ABIDE)

“…They did, however, find increased cortical thickness in several ROIs, including the left STG. The anterior region of the left STG we identified in the larger sample is associated with semantic language comprehension (Lau et al 2013) and response selectivity for human speech sounds (DeWitt and Rauschecker 2012), corroborating previous findings that the structure of the STG impacts aberrant language and communication development in ASD (Bigler et al 2007). …”

The LATL as locus of composition: MEG evidence from English and Arabic

“…This kind of hypothesis is also supported by a recent MEG investigation of noun phrase production, where adjectival modification (blue cups) but not numeral quantification (two cups) engaged the LATL, the former involving conceptual combination and the latter arguably not (Del Prato & Pylkkanen, 2014). Relatedly, activity in left anterior temporal cortex has shown both N400-type semantic effects (Halgren et al, 2002;Lau, Gramfort, Hämäläinen, & Kuperberg, 2013;Nobre & McCarthy, 1995) as well as increased amplitudes for conceptually contentful as opposed to grammatical words (Nobre & Mccarthy, 1995). Further, neuropsychological data show that neither semantic dementia patients with LATL atrophy nor patients with LATL resections exhibit profound grammatical deficits (Gorno-Tempini et al, 2004;Hodges, Patterson, Oxbury, & Funnell, 1992;Kho et al, 2008;Noppeney, Price, Duncan, & Koepp, 2005;Wilson, Galantucci, Tartaglia, & Gorno-Tempini, 2012), conforming to the hypothesis that the LATL is responsible for more conceptual as opposed to grammatical aspects of composition.…”

Combinatorial semantics strengthens angular-anterior temporal coupling

“…This left perisylvian region is a critical relay for combinatorial processing of abstract conceptual linguistic representations (BornkesselSchlesewsky & Schlesewsky, 2013). Importantly, these effects have also been observed in research examining different levels of semantic relations using word pairs (Baron & Osherson, 2011;Bemis & Pylkkanen, 2013;Lau, Gramfort, Hamalainen, & Kuperberg, 2013). Moreover, neuropsychological evidence from bilateral ATC atrophy patients presenting semantic dementia showed that these clinical populations present strong difficulties in generalizing between similar concepts with different semantic attributes (e.g., scallop vs prawn; Patterson et al, 2007;Visser et al, 2010).…”