RESUMEN
As the speech apparatus is also involved in producing non-speech movements, understanding whether speech and non-speech planning are controlled by the same brain mechanisms is central to the comprehension of motor speech planning. A crucial issue is whether a specialized motor planning/control system is dedicated to speech or if the motor planning/control system is shared across oromotor behaviors. We investigated the EEG/ERP spatio-temporal dynamics of the motor planning processes preceding articulation by comparing the production of non-speech gestures matched to monosyllabic words and non-words. To isolate motor from pre-motor planning, we used a delayed production task combined with an articulatory suppression task. Results suggest that the planning processes preceding articulation for non-speech, words and non-words recruit the same neural networks but with different involvement for non-speech and speech. The results support the idea of shared motor planning/control systems for speech and non-speech but with different dynamics for each oromotor behavior.
Asunto(s)
Encéfalo/fisiología , Gestos , Habla , Adulto , Comprensión , Potenciales Evocados , Femenino , Humanos , Masculino , Desempeño PsicomotorRESUMEN
Understanding events requires interplaying cognitive processes arising in neural networks whose organisation and connectivity remain subjects of controversy in humans. In the present study, by combining diffusion tensor imaging and functional interaction analysis, we aim to provide new insights on the organisation of the structural and functional pathways connecting the multiple nodes of the identified semantic system -shared by vision and language (Jouen et al., 2015). We investigated a group of 19 healthy human subjects during experimental tasks of reading sentences or seeing pictures. The structural connectivity was realised by deterministic tractography using an algorithm to extract white matter fibers terminating in the selected regions of interest (ROIs) and the functional connectivity by independent component analysis to measure correlated activities among these ROIs. The major connections link ventral neural stuctures including the parietal and temporal cortices through inferior and middle longitudinal fasciculi, the retrosplenial and parahippocampal cortices through the cingulate bundle, and the temporal and prefrontal structures through the uncinate fasciculus. The imageability score provided when the subject was reading a sentence was significantly correlated with the factor of anisotropy of the left parieto-temporal connections of the middle longitudinal fasciculus. A large part of this ventrally localised structural connectivity corresponds to functional interactions between the main parietal, temporal and frontal nodes. More precisely, the strong coactivation both in the anterior temporal pole and in the region of the temporo-parietal cortex suggests dual and cooperating roles for these areas within the semantic system. These findings are discussed in terms of two semantics-related sub-systems responsible for conceptual representation.
Asunto(s)
Corteza Cerebral , Comprensión/fisiología , Conectoma/métodos , Imagen de Difusión Tensora/métodos , Red Nerviosa , Reconocimiento Visual de Modelos/fisiología , Lectura , Sustancia Blanca , Adolescente , Adulto , Corteza Cerebral/anatomía & histología , Corteza Cerebral/diagnóstico por imagen , Corteza Cerebral/fisiología , Femenino , Humanos , Masculino , Red Nerviosa/anatomía & histología , Red Nerviosa/diagnóstico por imagen , Red Nerviosa/fisiología , Vías Nerviosas/anatomía & histología , Vías Nerviosas/diagnóstico por imagen , Vías Nerviosas/fisiología , Semántica , Sustancia Blanca/anatomía & histología , Sustancia Blanca/diagnóstico por imagen , Sustancia Blanca/fisiología , Adulto JovenRESUMEN
This research tests the hypothesis that comprehension of human events will engage an extended semantic representation system, independent of the input modality (sentence vs. picture). To investigate this, we examined brain activation and connectivity in 19 subjects who read sentences and viewed pictures depicting everyday events, in a combined fMRI and DTI study. Conjunction of activity in understanding sentences and pictures revealed a common fronto-temporo-parietal network that included the middle and inferior frontal gyri, the parahippocampal-retrosplenial complex, the anterior and middle temporal gyri, the inferior parietal lobe in particular the temporo-parietal cortex. DTI tractography seeded from this temporo-parietal cortex hub revealed a multi-component network reaching into the temporal pole, the ventral frontal pole and premotor cortex. A significant correlation was found between the relative pathway density issued from the temporo-parietal cortex and the imageability of sentences for individual subjects, suggesting a potential functional link between comprehension and the temporo-parietal connectivity strength. These data help to define a "meaning" network that includes components of recently characterized systems for semantic memory, embodied simulation, and visuo-spatial scene representation. The network substantially overlaps with the "default mode" network implicated as part of a core network of semantic representation, along with brain systems related to the formation of mental models, and reasoning. These data are consistent with a model of real-world situational understanding that is highly embodied. Crucially, the neural basis of this embodied understanding is not limited to sensorimotor systems, but extends to the highest levels of cognition, including autobiographical memory, scene analysis, mental model formation, reasoning and theory of mind.