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Title: Raw MEG signal correlates of the decision when to act
Authors: Σμύρνης, Νικόλαος Π.
Σιέττος, Κωνσταντίνος Ι.
Βεντούρας, Ερρίκος Μ.
Κτώνας, Περικλής Υ.
Rezaie, R.
Contributors: Παπανικολάου, Ανδρέας
Ευδοκιμίδης, Ιωάννης
Μυλωνάς, Δημήτρης Σ.
Item type: Conference publication
Conference Item Type: Full Paper
Keywords: Signal;Triangular-shaped signal;Σήμα;Τριγωνικού σχήματος σήμα
Subjects: Medicine
Medical technology
Ιατρικά όργανα και εξοπλισμός
Issue Date: 5-Feb-2015
Publisher: Society for Neuroscience
Abstract: Reaction times for simple actions such as pressing a button in response to a stimulus are characterized by a large variability that cannot be explained by physiological processes such as synaptic delays and conduction velocities. It has been hypothesized that such a stimulus response sequence involves a decision process that evolves over time and the rate of this evolution varies for each occurrence of the sequence thus producing the large variability of sensorimotor reaction times. In this experiment we explored the neural events during the reaction time when human subjects had to respond to the presentation of a salient visual stimulus (checkerboard flushing on a screen) by squeezing a ball with their right arm. Each one of 8 subjects performed a series of 120 squeeze movements while magnetoencephalographic signals were recorded. Visualizing the series of raw MEG data for different recording sites with the use of color coding of MEG magnitude revealed the presence of a response aligned signal that could be observed before the onset of the squeeze for most trials in the left central and frontal areas as well as in the middle and right central and frontal areas for all subjects. Then a cross-correlation analysis (CCA) between the temporal MEG signal for each trial and a triangular-shaped signal, of appropriate width, which served as a template function was performed in order to produce an estimate of the time of onset of this activity before the onset of the squeeze. The recording sites for which the CCA coefficient was significant for at least 70 of the 120 trials were selected and these sites corresponded nicely to the sites that were identified by the previous visualization method to have a signal before the squeeze movement onset. Then a correlation was performed at each of these recording sites between the onset of activity and the RT for all trials. A significant correlation was observed in a subset of these recording sites suggesting the presence of a linear relation between the onset of activity and RT as predicted by the decision signal hypothesis. The topography of this decision related signal was variable from subject to subject with the tendency to be more central and ipsilateral to the moving arm suggesting that its origin is not in the contralateral to the moving arm motor cortex.
Language: English
Citation: Smyrnis, N., Siettos, C., Ventouras, E., Ktonas, P., Rezaie, R., et al. (2010). Raw MEG signal correlates of the decision when to act. In the 2010 Annual Meeting of the Society for Neuroscience, Program No. 83.12/XX19, 2010 Neuroscience Meeting Planner. Society for Neuroscience: San Diego, 2010. (Online)
Conference: Annual Meeting of the Society for Neuroscience, Program No. 83.12/XX19, 2010 Neuroscience Meeting Planner
Access scheme: Embargo
License: Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 3.0 Ηνωμένες Πολιτείες
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