The specific role of the amygdala remains controversial even though the development of functional imaging techniques has established its implication in the emotional process. The aim of this study was to highlight the sensitivity of the amygdala to emotional intensity (arousal). We conducted an analysis of the modulation of amygdala activation according to variation in emotional intensity via an fMRI event-related protocol. Monitoring of electrodermal activity, a marker of psychophysiological emotional perception and a reflection of the activation of the autonomic nervous system, was carried out concurrently. Eighteen subjects (10 men; aged from 22 to 29 years) looked at emotionally positive photographs. We demonstrated that the left and right amygdalae were sensitive to changes in emotional intensity, activating more in response to stimuli with higher intensity. Furthermore, electrodermal responses were more frequent for the most intense stimuli, demonstrating the concomitant activation of the autonomic nervous system. These results highlight the sensitivity of the amygdala to the intensity of positively valenced visual stimuli, and in conjunction with results in the literature on negative emotions, reinforce the role of the amygdala in the perception of intensity.

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(28/12/2023, 09:44:13 )

Here: International Aﬀective Picture System (IAPS)

“In regard to visual emotional stimulation, the most widely used stimuli are images from the . Each of these images is provided with a normalized value of valence (from 1, very pleasant to 9, very unpleasant, with 5, neutral) and intensity (from 1, very calm to 9, very excited).” (Bonnet et al., 2015, p. 2)

Positively valenced stimuli

“Stimuli were 75 positively valenced (IAPS ratings >4.6; mean = 5.90 ± 0.49) colored visual stimuli selected from the IAPS (Lang et al., 2008)” (Bonnet et al., 2015, p. 3)

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“The ratings of intensity and valence were normally distributed, according to a Shapiro-Wilk test, but there was no equality of variances across the means of intensity of our three groups (Bartlett test). We performed a Kruskall-Wallis test to search for diﬀerences between our three groups using the means of intensity (subjects’ ratings) and valence (norms from the IAPS) for each stimulus.” (Bonnet et al., 2015, p. 5)

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Only positive emotional stimuli

“That is why we chose to use only positive emotional stimuli in this study, to avoid the bias linked to valence.” (Bonnet et al., 2015, p. 7)

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The role of the amygdala in the perception of positive emotions: an “intensity detector”

Annotations

Here: International Aﬀective Picture System (IAPS)

Positively valenced stimuli

Checked assumptions

Only positive emotional stimuli