INTRODUCTION: Perceiving and immediately reacting to potential threats is critical for survival. However, previous TMS studies have failed to disclose a selective modulation of the dominant hand motor representation when seeing unpleasant stimuli (Hajcak et al., 2007; Borgomaneri et al., 2012), at least during resting conditions (see Van loon et al., 2010; Coombes et al., 2009 for investigation during action planning or execution). These studies have reported comparable motor facilitations for both emotionally positive and negative pictures in the observers’ motor system. However, in all previous studies, motor excitability was tested in a relatively late time window, i.e. at >300ms after stimulus onset. Using single-pulse TMS we tested the hypothesis that motor reactions to unpleasant visual stimuli can be detected earlier than reactions to pleasant stimuli. METHODS: MEPs to single-pulse TMS of the left motor cortex were recorded from two right hand muscles (FDI, APB) during observation and active categorization of negative, positive, and emotionally neutral scenes from the International Affective Picture System (IAPS) database (Lang et al., 1999) (32 pictures for each condition). MEPs were recorded at 150 ms and 300 ms after stimulus onset. After TMS, subjects completed the Interpersonal Reactivity Index (IRI) (Davis, 1996). RESULTS: The Muscle x Time x Stimulus ANOVA revealed a Time x Stimulus interaction (p=0.02) but no triple interaction. At 150 ms from stimulus onset, MEP amplitudes were higher for negative relative to positive and neutral images (p<0.05) which in turn did not differ from one another. IRI’s Personal Distress scores were significant predictors of this early selective motor facilitation for unpleasant stimuli (β=1.04, p<0.001). At 300 ms, MEP amplitudes were comparable for negative and positive images (p=0.15) and greater than for neutral images (p<0.05). CONCLUSIONS: Seeing unpleasant visual pictures increased motor excitability earlier than seeing pleasant pictures, supporting the view that potentially negative stimuli require processing and response resources to be more intensely and urgently mobilized to minimize negative consequences associated with the unpleasant cues (Ekman, 1992; Ohman et al., 1992). Notably, people with greater dispositional personal distress showed greater early motor facilitation when facing negative images, suggesting that interpersonal anxiety-related traits may promote valence specific fast motor reactivity. In keeping with previous research (Hajcak et al., 2007; Borgomaneri et al., 2012), at a later time (300 ms), both positive and negative stimuli elicited comparable motor facilitation relative to neutral pictures. These findings highlight the different time course of corticospinal reactivity when facing with positive and negative emotional visual stimuli.
Temporal dynamics of motor cortex excitability during perception of emotional IAPS stimuli
BORGOMANERI, SARA;AVENANTI, ALESSIO
2012
Abstract
INTRODUCTION: Perceiving and immediately reacting to potential threats is critical for survival. However, previous TMS studies have failed to disclose a selective modulation of the dominant hand motor representation when seeing unpleasant stimuli (Hajcak et al., 2007; Borgomaneri et al., 2012), at least during resting conditions (see Van loon et al., 2010; Coombes et al., 2009 for investigation during action planning or execution). These studies have reported comparable motor facilitations for both emotionally positive and negative pictures in the observers’ motor system. However, in all previous studies, motor excitability was tested in a relatively late time window, i.e. at >300ms after stimulus onset. Using single-pulse TMS we tested the hypothesis that motor reactions to unpleasant visual stimuli can be detected earlier than reactions to pleasant stimuli. METHODS: MEPs to single-pulse TMS of the left motor cortex were recorded from two right hand muscles (FDI, APB) during observation and active categorization of negative, positive, and emotionally neutral scenes from the International Affective Picture System (IAPS) database (Lang et al., 1999) (32 pictures for each condition). MEPs were recorded at 150 ms and 300 ms after stimulus onset. After TMS, subjects completed the Interpersonal Reactivity Index (IRI) (Davis, 1996). RESULTS: The Muscle x Time x Stimulus ANOVA revealed a Time x Stimulus interaction (p=0.02) but no triple interaction. At 150 ms from stimulus onset, MEP amplitudes were higher for negative relative to positive and neutral images (p<0.05) which in turn did not differ from one another. IRI’s Personal Distress scores were significant predictors of this early selective motor facilitation for unpleasant stimuli (β=1.04, p<0.001). At 300 ms, MEP amplitudes were comparable for negative and positive images (p=0.15) and greater than for neutral images (p<0.05). CONCLUSIONS: Seeing unpleasant visual pictures increased motor excitability earlier than seeing pleasant pictures, supporting the view that potentially negative stimuli require processing and response resources to be more intensely and urgently mobilized to minimize negative consequences associated with the unpleasant cues (Ekman, 1992; Ohman et al., 1992). Notably, people with greater dispositional personal distress showed greater early motor facilitation when facing negative images, suggesting that interpersonal anxiety-related traits may promote valence specific fast motor reactivity. In keeping with previous research (Hajcak et al., 2007; Borgomaneri et al., 2012), at a later time (300 ms), both positive and negative stimuli elicited comparable motor facilitation relative to neutral pictures. These findings highlight the different time course of corticospinal reactivity when facing with positive and negative emotional visual stimuli.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
