Abstract
Over the last 20 years, major advances in cognitive neuroscience have clearly shown that the language function is not restricted into the classical language areas but it involves brain regions, which had never previously considered. Indeed, recent lines of evidence have suggested that the processing of words associated to motor schemata, such as action verbs, modulates the activity of the sensorimotor cortex, which, in turn, facilitates its retrieval. To date, no studies have investigated whether the spinal cord, which is functionally connected to the sensorimotor system, might also work as an auxiliary support for language processing. We explored the combined effect of transcutaneous spinal direct current stimulation (tsDCS) and language treatment in a randomized double-blind design for the recovery of verbs and nouns in 14 chronic aphasics. During each treatment, each subject received tsDCS (20 min, 2 mA) over the thoracic vertebrae (10th vertebra) in three different conditions: (1) anodic, (2) cathodic and (3) sham, while performing a verb and noun naming tasks. Each experimental condition was run in five consecutive daily sessions over 3 weeks. Overall, a significant greater improvement in verb naming was found during the anodic condition with respect to the other two conditions, which persisted at 1 week after the end of the treatment. No significant differences were present for noun naming among the three conditions. The hypothesis is advanced that anodic tsDCS might have influenced activity along the ascending somatosensory pathways, ultimately eliciting neurophysiological changes into the sensorimotor areas which, in turn, supported the retrieval of verbs. These results further support the evidence that action words, due to their sensorimotor semantic properties, are partly represented into the sensorimotor cortex. Moreover, they also document, for the first time, that tsDCS enhances verb recovery in chronic aphasia and it may represent a promising new tool for language treatment.
Highlights
Since the late nineteenth century, it has long been assumed that the language function is hierarchically organized into specific cortical areas, the Broca’s and Wernicke’s areas [1]
Over the past decades, several lines of evidence have shown that the language faculty engages a number of cortical and subcortical regions that extend far beyond the classical areas [for reviews, transcutaneous spinal direct current stimulation (tsDCS) for Language Recovery in Aphasia see for example [2, 3]] but it is represented within regions that had never been considered before to support language [for review see Ref. [4]]
This study assessed whether tsDCS coupled with language treatment improves word retrieval in persons with chronic non-fluent aphasia
Summary
Since the late nineteenth century, it has long been assumed that the language function is hierarchically organized into specific cortical areas, the Broca’s and Wernicke’s areas [1]. The hypothesis has been advanced that action verbs are mentally represented in different semantic representations among which the sensorimotor features to perform the action [10,11,12]. This implies that the sensory–motor regions of the brain may process action concepts. Several lines of evidence have already suggested that the sensorimotor cortex takes part in language processing, at least when speech is translated into sensorimotor acts [10, 13, 14] Much of this evidence comes from studies that used action verbs (individually presented or embedded in sentences) as stimuli [e.g., Ref. Slower hand motor responses have been shown during processing of nouns referring to hand-related objects [(11, 12); see Ref. [18]]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
