“Efeito da emoção no planejamento de ações”

Abstract

The aim of this study was to examine by means of Transcranial Magnetic Stimulation (TMS) if the corticospinal excitability (CSE) is affected by the emotional valence of the stimulus which with one is about to grab. We also examined if effect of emotional modulation upon CSE is specific to the muscle directly enrolled in the task. Ten participants were instructed to perform a task with two experimental conditions: to grasp (ACTION condition) or just to look (NO-ACTION condition) at objects with different valences (pleasant, neutral and unpleasant). Conditions and valence order were randomly presented within four blocks. Objects were balanced in weight and placed inside transparent cups to prompt a similar grip among trials. Trials began with the stimulus presentation. After stimulus presentation, a go signal was turned on 3 s later indicating that the participant should move or just observe, depending on the experimental condition. TMS was applied over the participant primary motor cortex at 500 or 250 ms before the go signal, randomly. Motor evoked potentials (MEP) were measured by recording the electromyographic signal from first dorsalis interosseous - FDI and abductor digiti minimi - ADM muscles. Tree-way ANOVA was conducted to evaluate the emotional effect for each muscle. In ACTION condition, the ANOVA revealed a condition x valence interaction (p = 0.003) for FDI. The MEP was larger for unpleasant compared to neutral and pleasant category. Also, MEP amplitude for pleasant was lower than neutral category. There was no significant effect for FDI in NO-ACTION condition. Furthermore, a significant valence effect across conditions (ACTION and NO-ACTION) was also found: higher MEP amplitudes were found for the unpleasant category in ACTION condition as compared to NON-ACTION condition. The reverse was true for the pleasant category: lower MEP amplitudes were found in the ACTION as compared to NON-ACTION condition. For the ADM, there was neither a significant effect among emotional categories nor across conditions (p = 0.76). In conclusion, we showed here that the preparatory activity preceding the grasping of a stimulus, as measured by corticospinal excitability, is affected by its emotional value. In other words, our findings show a muscle specific modulation of corticospinal excitability during motor preparation depending on the valence of the stimuli to be grasped.