Effective Connectivity between Ventral Occipito-Temporal and Ventral Inferior Frontal Cortex during Lexico-Semantic Processing. A Dynamic Causal Modeling Study

Abstract

It has been suggested that dorsal and ventral pathways support distinct aspects of language processing. Yet, the full extent of their involvement and their inter-regional connectivity in visual word recognition is still unknown. Studies suggest that they might reflect the dual-route model of reading, with the dorsal pathway more involved in grapho-phonological conversion during phonological tasks, and the ventral pathway performing lexico-semantic access during semantic tasks. Furthermore, this subdivision is also suggested at the level of the inferior frontal cortex, involving ventral and dorsal parts for lexico-semantic and phonological processing, respectively. In the present study, we assessed inter-regional brain connectivity and task-induced modulations of brain activity during a phoneme detection and semantic categorization tasks, using fMRI in healthy subject. We used a dynamic causal modeling approach to assess inter-regional connectivity and task demand modulation within the dorsal and ventral pathways, including the following network components: the ventral occipito-temporal cortex (vOTC; dorsal and ventral), the superior temporal gyrus (STG; dorsal), the dorsal inferior frontal gyrus (dIFG; dorsal), and the ventral IFG (vIFG; ventral). We report three distinct inter-regional interactions supporting orthographic information transfer from vOTC to other language regions (vOTC -> STG, vOTC -> vIFG and vOTC -> dIFG) regardless of task demands. Moreover, we found that (a) during semantic processing (direct ventral pathway) the vOTC -> vIFG connection strength specifically increased and (b) a lack of modulation of the vOTC -> dIFG connection strength by the task that could suggest a more general involvement of the dorsal pathway during visual word recognition. Results are discussed in terms of anatomo-functional connectivity of visual word recognition network.

Probabilistic mapping of language networks from high frequency activity induced by direct electrical stimulation

“…We also showed a more extended number of regions with less probability results, including parietal and medial temporal regions. Taken together, the IFG responses shown in the present study are in line with previous findings suggesting that the IFG may represent a supramodal hierarchical processor (Tate, Herbet, Moritz‐Gasser, Tate, & Duffau, 2014; Tettamanti & Weniger, 2006) involved in specific language information processing (Bookheimer, 2002; Perrone‐Bertolotti, Kauffmann, Pichat, Vidal, & Baciu, 2017) and in a cognitive control during language tasks.…”

Dissociating the functions of superior and inferior parts of the left ventral occipito-temporal cortex during visual word and object processing

“…Our findings of a dissociation in activation and connectivity in superior and inferior vOT regions have implications for research into the interaction between left vOT and brain regions subserving higher order language function (Price and Devlin, 2011; Woodhead et al., 2013; Perrone-Bertolotti et al., 2017). More specifically, our results lead us to predict that superior and inferior vOT subregions might be differentially sensitive to top down interactions from higher order language and attention areas (Gilbert and Li, 2013).…”

Connectivity Gradient in the Human Left Inferior Frontal Gyrus: Intraoperative Cortico-Cortical Evoked Potential Study

“…The posterior fusiform gyrus, which is one of the posterior terminations of the IFOF, is known as the visual word form area. A role for the IFOF in semantic processing is further supported by dynamic causality modeling of blood oxygenation level dependent signals that showed effective connectivity from the fusiform gyrus to the anterior IFG during a semantic judgment task ( Perrone-Bertolotti et al 2017 ). These lines of evidence suggest that the superficial component of the IFOF has a semantic function.…”