Temporal dynamics of perisylvian activation during language processing in children and adults

Abstract

The perisylvian region of the human cortex is known to play a major role in language processing. Especially the superior temporal cortex (STC) and the inferior frontal cortex (IFC) have been investigated with respect to their particular involvement in language comprehension. In the present research, the timing of recruitment of these language-related brain areas in both hemispheres was examined as a function of age using functional imaging data of 6-year-old children and adults with a special focus on blood oxygenation level dependent (BOLD) response time courses. The results show that children's activation time courses differ from that of adults. First, children show an overall later peak of BOLD responses. Second, children's IFC responds much later than their STC, while in adults the difference between both regions is less pronounced. Within the STC, both groups show similar regionally U-shaped activation patterns with fastest peaks in voxels at the STC's mid-portion around Heschl's gyrus and longer latencies in anterior and posterior directions, suggesting a coarsely similar information flow in adults and children in the temporal region. Finally, children in contrast to adults, display a temporal primacy of right over left hemispheric activation. The observed overall latency differences between children and adults are in line with the assumption of ongoing maturation in perisylvian brain regions and the connections between them. A functional perspective on BOLD timing argues for a developmental change from higher processing costs in children compared to adults due to slower and less automatic language processes, in particular those located in the IFC. The observed hemispheric differences are discussed in the context of developmental models assuming a high reliance on right-hemisphere-based suprasegmental information processing during language comprehension in childhood.

Neural language networks at birth

“…It may well be that the more clearly expressed left hemispheric involvement in 2-mo-old infants compared with newborns is due to developmental age. An increase in language lateralization toward the left hemisphere as a function of age from childhood to adolescence has been also reported in earlier studies (35,(37)(38)(39).…”

A Temporal Bottleneck in the Language Comprehension Network

“…Our findings confirm that fMRI can have a high temporal resolution (Menon et al, 1998;Sigman et al, 2007;Sigman and Dehaene, 2008). Sensory areas showed the fastest BOLD response to language, followed by left superior temporal sulcus and inferior frontal regions, replicating earlier observations (Dehaene-Lambertz et al, 2006;Brauer et al, 2008;Pallier et al, 2011). Importantly, these delays cannot be solely due to inflexible hemodynamics, as they vary with sentence repetition (Dehaene-Lambertz et al, 2006), syntactic complexity (Pallier et al, 2011), and word rate (present study).…”

“…Although fMRI has a low temporal resolution compared with electrophysiological methods, it can detect activation delays and duration changes of ϳ200 ms (Menon et al, 1998;Sigman et al, 2007;Sigman and Dehaene, 2008). In response to a single sentence, language areas show a systematic temporal organization, with increasingly delayed responses as one moves either posterior or anterior to primary auditory cortex, the slowest response being observed in left inferior frontal gyrus (DehaeneLambertz et al, 2006;Brauer et al, 2008;Pallier et al, 2011). This temporal gradient of activation might result from a succession of processes that integrate over increasingly larger, and possibly more abstract, linguistic units, therefore requiring longer processing time or more sustained activity (see also Hasson et al, 2008;Lerner et al, 2011;Brennan et al, 2012).…”

Fronto-temporal mapping and connectivity using NIRS for language-related paradigms

“…Similar activation findings have been reported by other groups using a verbal fluency (or word generation) stimuli in the fronto-temporal regions of the brain using NIRS (Cannestra et al, 2003;Ehlis et al, 2007;Herrmann et al, 2003;Kuwabara et al, 2006;Schecklmann et al, 2008;Watanabe et al, 1998), intra-operative intrinsic signals (Cannestra et al, 2000), and Positron emission tomography (PET) (Frith, Friston, Liddle, & Frackowiak, 1991), as well as fMRI (Brauer et al, 2008;Huang, Carr, & Cao, 2001). Fig.…”