Presentation
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Probing the functional relevance of pre-SMA and aIFG for controlled semantic processing with transcranial magnetic stimulation
Poster D23 in Poster Session D, Wednesday, October 25, 4:45 - 6:30 pm CEST, Espace Vieux-Port
This poster is part of the Sandbox Series.
Matteo Ferrante1, Sandra Martin1, Gesa Hartwigsen1,2; 1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 2Wilhelm-Wundt Institute for Psychology, Leipzig University, Germany
Introduction: Recent studies indicate that domain-general cognitive control areas contribute to semantic processing in the human brain. However, consensus is still lacking about the precise extent of the multiple demand network (MDN) for cognitive control, its boundaries relative to core semantic processing regions, and the nature of its involvement in semantic cognition. Meta-analytic mappings of the MDN and the semantic processing network show areas of overlap, especially by the left inferior frontal gyrus (IFG) and the pre-supplementary motor area (pre-SMA). In particular, the pre-SMA has been associated with controlled semantic processing, possibly supporting the core semantic area in left anterior IFG in the context of challenging semantic tasks. However, its relevance for domain-general and semantic operations is still unclear. Our project investigates network interactions between a core semantic area and a MDN area in the context of controlled semantic processing. To this end, we used neurostimulation to focally perturb the activity of pre-SMA and left anterior IFG and tested outcomes on semantic fluency (at high and low semantic control load demands) and non-semantic fluency performance. Methods: We performed a transcranial magnetic stimulation (TMS) experiment, based on an offline dual-site paradigm. The effects of left anterior IFG inhibition (1 Hz rTMS), left pre-SMA inhibition (1 Hz rTMS), and combined inhibition of both areas (1 Hz rTMS to aIFG followed by cTBS to pre-SMA) were tested. We additionally included a sham condition as baseline for each subject, replicating the procedures of the dual-site session. A total of 24 healthy young subjects (mean age: 30, age range: 20-40) were included and completed all four experimental sessions. Subjects first received the respective stimulation condition and subsequently completed a battery of three tasks (offline stimulation), including a semantic fluency task, a non-semantic fluency task (5-point figural fluency task), and a picture naming task. The semantic fluency task was designed to modulate the required level of semantic control, featuring low-difficulty and high-difficulty categories intermixed across trials. The figural fluency task was included as the main control task, sharing executive processes that are common to the semantic fluency task, but requiring the generation of geometrical figures, as opposed to words. The picture naming task was intended as an additional control, accounting for bottom-up semantic cognition processes, with lower control load demands compared to semantic fluency. To mitigate practice effects, novel stimuli were presented in each session for each task; stimuli sets and TMS condition orders were counterbalanced across subjects. Individual stimulation intensities were defined at the beginning of the first session via determination of the individual resting motor threshold (RMT). Repetitive TMS was delivered at 100% of RMT. Results: Accuracy scores and reaction times were extracted for each task. The analysis of the behavioural performance is ongoing. Linear mixed-effect models will be fitted for each measure to test the effects of task, semantic control load, target site, and stimulation, as well as potential interactions.
Topic Areas: Meaning: Lexical Semantics, Control, Selection, and Executive Processes