The evolution of the arcuate fasciculus revealed with comparative DTI. Nat Neurosci 11: 426-428
ABSTRACT The arcuate fasciculus is a white-matter fiber tract that is involved in human language. Here we compared cortical connectivity in humans, chimpanzees and macaques (Macaca mulatta) and found a prominent temporal lobe projection of the human arcuate fasciculus that is much smaller or absent in nonhuman primates. This human specialization may be relevant to the evolution of language.
Full-textDOI: · Available from: Todd M Preuss, Aug 27, 2015
- SourceAvailable from: William D Marslen-Wilson
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- "Additional evidence that non-human primates can learn linear sequences of sounds defined by simple transitional probabilities between concatenated elements [Arnold and Zuberb€ uhler, 2006; Fitch and Friederici, 2012; Wilson et al., 2013] suggest further parallels that may underpin bihemispheric linguistic capacities in the modern human. A critical difference between the primate and the human brain is the set of LH structures and white matter connections that link posterior temporal to inferior frontal areas BA 44/45 [Rilling et al., 2008; Rolheiser et al., 2011]. In current models of language processing, these pathways are commonly associated with grammatical computations— most specifically with the processing of complex hierarchical structures and dependencies generated by supra-regular grammars [Friederici, 2011] which non-human primates are not capable of mastering [Fitch and Hauser, 2004]. "
ABSTRACT: Language processing engages large-scale functional networks in both hemispheres. Although it is widely accepted that left perisylvian regions have a key role in supporting complex grammatical compu-tations, patient data suggest that some aspects of grammatical processing could be supported bilaterally. We investigated the distribution and the nature of grammatical computations across language processing networks by comparing two types of combinatorial grammatical sequences—inflectionally complex words and minimal phrases—and contrasting them with grammatically simple words. Novel multivariate analy-ses revealed that they engage a coalition of separable subsystems: inflected forms triggered left-lateralized activation, dissociable into dorsal processes supporting morphophonological parsing and ventral, lexically driven morphosyntactic processes. In contrast, simple phrases activated a consistently bilateral pattern of temporal regions, overlapping with inflectional activations in L middle temporal gyrus. These data confirm the role of the left-lateralized frontotemporal network in supporting complex grammatical computations. Critically, they also point to the capacity of bilateral temporal regions to support simple, linear grammati-cal computations. This is consistent with a dual neurobiological framework where phylogenetically older bihemispheric systems form part of the network that supports language function in the modern human, and where significant capacities for language comprehension remain intact even following severe left hemisphere damage. Hum Brain Mapp 00:000–000, 2014. V C 2014 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.Human Brain Mapping 03/2015; DOI:10.1002/hbm.22696 · 6.92 Impact Factor
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- "Beside the right pSTG, the temporal region in the posterior fundus of the right STS (fpSTS) showed the strongest connection strength to frontal target regions, both along the right dorsal and ventral pathway. The fpSTS was the only region to target the right IFG, taking the right ventral pathway, which has been not well described in humans yet, but seems to have precursors in nonhuman primates (Ghazanfar, 2008; Rilling et al., 2008). Previously, we found that the fpSTS is active independent of the attentional focus, but exhibiting sensitivity to the features of acoustic features of affective prosody, such as pitch and intensity variations . "
ABSTRACT: Dorsal and ventral pathways for syntacto-semantic speech processing in the left hemisphere are represented in the dual-stream model of auditory processing. Here we report new findings for the right dorsal and ventral temporo-frontal pathway during processing of affectively intonated speech (i.e. affective prosody) in humans, together with several left hemispheric structural connections, partly resembling those for syntacto-semantic speech processing. We investigated white matter fiber connectivity between regions responding to affective prosody in several subregions of the bilateral superior temporal cortex (secondary and higher-level auditory cortex) and of the inferior frontal cortex (anterior and posterior inferior frontal gyrus). The fiber connectivity was investigated by using probabilistic diffusion tensor based tractography. The results underscore several so far underestimated auditory pathway connections, especially for the processing of affective prosody, such as a right ventral auditory pathway. The results also suggest the existence of a dual-stream processing in the right hemisphere, and a general predominance of the dorsal pathways in both hemispheres underlying the neural processing of affective prosody in an extended temporo-frontal network. Copyright © 2015. Published by Elsevier Inc.NeuroImage 02/2015; DOI:10.1016/j.neuroimage.2015.01.016 · 6.36 Impact Factor
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- "Inconsistencies in detecting AF's frontal lobe endpoints may be due to different tracing algorithms. In our study and in Rilling et al. (2008) the newly developed probabilistic tractography algorithm was used, designed to track through crossing fibres by also considering the secondary diffusion direction (Behrens, Berg et al. 2007). On the contrary, Bernal and Ardila (2009) used the earlier-developed deterministic tractography (Mori, Crain et al. 1999). "
ABSTRACT: Diffusion tensor imaging (DTI) and a longitudinal language learning approach were applied to investigate the relationship between the achieved second language (L2) proficiency during L2 learning and the reorganization of structural connectivity between core language areas. Language proficiency tests and DTI scans were obtained from German students before and after they completed an intensive 6-week course of the Dutch language. In the initial learning stage, with increasing L2 proficiency, the hemispheric dominance of the BA6-temporal pathway (mainly along the arcuate fasciculus) shifted from the left to the right hemisphere. With further increased proficiency, however, lateralization dominance was again found in the left BA6-temporal pathway. This result is consistent with reports in the literature that imply a stronger involvement of the right hemisphere in L2-processing especially for less proficient L2-speakers. This is the first time that a L2-proficiency-dependent laterality shift in structural connectivity of language pathways during L2 acquisition has been observed to shift from left to right, and back to left hemisphere dominance with increasing L2-proficiency. We additionally find that changes in fractional anisotropy values after the course are related to the time elapsed between the two scans. The results suggest that structural connectivity in (at least part of) the perisylvian language network may be subject to fast dynamic changes following language learning.01/2015; DOI:10.1089/brain.2013.0199