Functional mapping of the inner speech brain related areas: from syllable to sentence
Year: 2020
Type: dissertation
Abstract: Introduction: Inner speech can be defined as the act of talking silently with ourselves. Recent studies in this area were dedicated to understanding the brain networks that underlie this process and how it is related to speech organisation and language. The problem: Despite the recent breakthroughs, knowledge is incomplete and some results are contradictory or lack confirmation due to limitations in experimental control. Knowledge is scarce regarding language dependency, and the non-inclusion of control conditions in several studies raises concerns about the neural correlates of inner speech performance. Method: Aiming at studying the neural correlates of inner speech in the Portuguese language, a three-step approach was employed: (1) development of a controlled paradigm; (2) acquisition of a functional Magnetic Resonance Imaging (fMRI) database for Portuguese native speakers with rich verbal content; (3) General Linear Model analyses. Results: The database, the first for inner speech studies in European Portuguese, contains acquisitions of twenty-two healthy participants of vowels, syllables, words and sentences presented visually both for inner and overt speech. The analyses identified several brain areas such as the left inferior frontal gyrus, including Broca’s area; supplementary motor area; precentral gyrus and left and right middle temporal gyrus, including Wernicke’s area. Results revealed similar regional activation for inner and overt speech and strong bilateral brain activation for the overt speech condition when compared to inner speech condition. Significant statistical differences when both conditions were compared rely on the motor component responsible for speech vocalisation. The parametric level of difficulty analysis performed for the inner speech condition shows stronger activations for complex and longer sequences than for more simple and shorter stimuli. Conclusion: In general, results obtained confirm the outcomes reported for other languages, but with subtle and relevant distinctions, contributing to diminish the knowledge gap concerning language dependency. Nevertheless, some novel activation was identified, such as in Intrapariental Sulcus (IPS); activation that can be explained by its possible involvement in working memory and attentional control during language processing.
Author: Carlos Ferreira
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W3171587517