Spatiotemporal Convergence of Semantic Processing in Reading and Speech Perception

Abstract

Retrieval of word meaning from the semantic system and its integration with context are often assumed to be shared by spoken and written words. How is modality-independent semantic processing manifested in the brain, spatially and temporally? Time-sensitive neuroimaging allows tracking of neural activation sequences. Use of semantically related versus unrelated word pairs or sentences ending with a semantically highly or less plausible word, in separate studies of the auditory and visual modality, has associated lexicalsemantic analysis with sustained activation at ϳ200 -800 ms. Magnetoencephalography (MEG) studies have further identified the superior temporal cortex as a main locus of the semantic effect. Nevertheless, a direct comparison of the spatiotemporal neural correlates of visual and auditory word comprehension in the same brain is lacking. We used MEG to compare lexical-semantic analysis in the visual and auditory domain in the same individuals, and contrasted it with phonological analysis that, according to models of language perception, should occur at a different time with respect to semantic analysis in reading and speech perception. The stimuli were lists of four words that were either semantically or phonologically related, or with the final word unrelated to the preceding context. Superior temporal activation reflecting semantic processing occurred similarly in the two modalities, left-lateralized at 300 -450 ms and thereafter bilaterally, generated in close-by areas. Effect of phonology preceded the semantic effect in speech perception but not in reading. The present data indicate involvement of the middle superior temporal cortex in semantic processing from ϳ300 ms onwards, regardless of input modality.

Ventral and dorsal pathways of speech perception: An intracerebral ERP study

“…Trébuchon et al / Brain & Language xxx (2013) xxx-xxx 7 temporal window (Trébuchon-Da Fonseca et al, 2009). These results are in line with MEG studies in which were compared the patterns of activation evoked by either visually presented or spoken words and were shown that the source of semantic processing, at 400 ms converged along the caudo-rostral axis of the temporal lobe (Marinkovic et al, 2003;Vartiainen, Parviainen, & Salmelin, 2009) especially in the middle part of the STG. Unfortunately, because of the clinical sampling used in these recordings, we have no data recorded in the anterior STG.…”

Functional Magnetic Resonance Imaging Blood Oxygenation Level-Dependent Signal and Magnetoencephalography Evoked Responses Yield Different Neural Functionality in Reading

“…For an initial overview of the data, areal mean signals were calculated over 10 regions: occipital, parietal, and the left and right frontal, rolandic, temporal, and occipitotemporal regions (Vartiainen et al, 2009a). The individual areal mean signals were characterized by measuring the mean amplitude in four time windows: 70 -130 ms, 115-150 ms, 130 -250 ms, and 300 -500 ms, that were selected on the basis of the grand-mean and individual signals.…”

“…With the increasing number of studies, apparent differences between MEG and fMRI views of reading have started to form a systematic pattern. Although both methods show involvement of the occipital, occipitotemporal, and temporal cortex in reading, the resulting views of those areas' functional roles are partly inconsistent (e.g., Jobard et al, 2003;Vartiainen et al, 2009a).…”

Differential Phonological and Semantic Modulation of Neurophysiological Responses to Visual Word Recognition

“…Similarly, other MEG studies have identified the middle part of the temporal cortex to be involved in semantic processing [40,41,42]. For example, Vartiainen et al [42] identified the middle superior temporal cortex to be active when presented with lists of semantically similar items, while Helenius et al [40] identified activity in this region in response to sentences with semantically incongruous endings. As with the early N400 literature, these studies do not differentiate responses to familiarity from semantic processing.…”

“…A number of other studies have suggested that semantic processing is localised to the superior temporal gyrus [40,41,42]. Recent studies of coherent networks also identified differential semantic and phonological networks during word recognition [18,43].…”