Browsing by Author "Gogulski, Juha"
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- Automatic quantification of individual MEG signal timing during a naming task
Sähkötekniikan korkeakoulu | Bachelor's thesis(2024-12-13) Kekäläinen, AadaSpeech production is a highly complex and coordinated cognitive function that involves multiple brain regions. Precisely locating speech-critical areas is especially important in preoperative mapping to provide surgeons with critical information, enabling them to avoid these areas. Currently, preoperative speech mapping is performed using transcranial magnetic stimulation (TMS). In this procedure, the patient is asked to name objects, while TMS pulses are being delivered across multiple brain regions. TMS helps to identify areas crucial for speech by producing naming errors. However, optimal timing of TMS pulses after picture onset in each individual is unknown. The goal of this thesis was to quantify the onset of speech-related cortical activity using MEG, as individualized timing could potentially improve mapping accuracy. In the analysis, I identified the time point for each participant when the activation of non-visual areas was greatest compared to the activation in the primary visual cortex. This time likely corresponds to a moment when activation in speech-critical areas is also high, indicating the optimal timing for delivering TMS pulses after picture onset. Across individuals, these times ranged between 230–500 ms. The results highlight the importance of determining individual timing, as significant differences were observed between participants. Individualized timing could enhance the accuracy of non-invasive speech mapping, reduce false negative findings, and optimize surgical planning, thereby supporting the preservation of speech functions post-surgery. - Neural Substrate for Metacognitive Accuracy of Tactile Working Memory
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2017-11) Gogulski, Juha; Zetter, Rasmus; Nyrhinen, Mikko; Pertovaara, Antti; Carlson, SynnoveThe human prefrontal cortex (PFC) has been shown to be important for metacognition, the capacity to monitor and control one's own cognitive processes. Here we dissected the neural architecture of somatosensory metacognition using navigated single-pulse transcranial magnetic stimulation (TMS) to modulate tactile working memory (WM) processing. We asked subjects to perform tactile WM tasks and to give a confidence rating for their performance after each trial. We circumvented the challenge of interindividual variability in functional brain anatomy by applying TMS to two PFC areas that, according to tractography, were neurally connected with the primary somatosensory cortex (S1): one area in the superior frontal gyrus (SFG), another in the middle frontal gyrus (MFG). These two PFC locations and a control cortical area were stimulated during both spatial and temporal tactile WM tasks. We found that tractography-guided TMS of the SFG area selectively enhanced metacognitive accuracy of tactile temporal, but not spatial WM. Stimulation of the MFG area that was also neurally connected with the S1 had no such effect on metacognitive accuracy of either the temporal or spatial tactile WM. Our findings provide causal evidence that the PFC contains distinct neuroanatomical substrates for introspective accuracy of tactile WM.