The human amygdala is sensitive to the valence of pictures and sounds irrespective of arousal: an fMRI study

With the advent of studies showing that amygdala responses are not limited to fear-related or highly unpleasant stimuli, studies began to focus on stimulus valence and stimulus-related arousal as predictors of amygdala activity. Recent studies in the chemosensory domain found amygdala activity to increase with the intensity of negative and positive chemosensory stimuli. This has led to the proposal that amygdala activity might be an indicator of emotional arousal, at least in the chemosensory domain. The present study investigated amygdala activity in response to visual and auditory stimuli. By selecting stimuli based on individual valence and arousal ratings, we were able to dissociate stimulus valence and stimulus-related arousal, both on the verbal and the peripheral physiological level. We found that the amygdala was sensitive to stimulus valence even when arousal was controlled for, and that increased amygdala activity was better explained by valence than by arousal. The proposed difference in the relation between amygdala activity and stimulus-related arousal between the chemosensory and the audiovisual domain is discussed in terms of the amygdala’s embedding within these sensory systems and the processes by which emotional meaning is derived.

FM3 Literature Claustrum, #Paper

Annotations

(27/12/2023, 18:09:13 )

Here: “Amygdala activity in response to visual and auditory stimuli.” (Anders et al., 2008, p. 233)

CLA method: Stimuli were presented and rated outside the scanner using CLA SAM

“After the scanning procedure, all stimuli were presented in a second pass outside the scanner and subjects were asked to rate how pleasant or unpleasant and how arousing they had experienced each stimulus during scanning on scales ranging from unpleasant (1) to pleasant (9) and non-arousing (1) to arousing (9) on a paper-and-pencil version of the self-assessment manikin (SAM; Lang, 1980; Bradley and Lang, 1994).” (Anders et al., 2008, p. 234)

“Verbal recordings of experienced valence and arousal after scanning have been shown to reliably represent emotional experiences during scanning (Phan et al., 2004)” (Anders et al., 2008, p. 235)

“no significant effect of startle probe and no significant interaction between startle probe and stimulus valence or arousal on either valence or arousal ratings” (Anders et al., 2008, p. 235)

Stimuli were ordered and divided into groups

“Based on these ratings, stimuli were rankordered, separately for each subject, and stimuli representing six subdivisions of the emotional space (negative nonarousing, negative arousing, neutral non-arousing, neutral arousing, positive non-arousing and positive arousing) were selected.” (Anders et al., 2008, p. 234)

Using quartiles for ratings

“In the visual domain, a stimulus was defined as negative (positive) when it fell into the lower (upper) quartile of valence ratings of a given subject.” (Anders et al., 2008, p. 234)

“a stimulus was defined as non-arousing (arousing) when it fell into the lower (upper) quartile of arousal ratings of a given subject” (Anders et al., 2008, p. 234)

Here: also skin conductance

“The eyeblink component of the startle response (Vrana et al., 1988) was recorded at 1000 Hz using infrared oculography (Anders et al., 2004c). Skin conductance was recorded at 16 Hz with commercial ecording equipment” (Anders et al., 2008, p. 234)

“In both modalities, valence categories accounted for >60% of the variance in valence ratings, and for <3% of the variance in arousal ratings” (Anders et al., 2008, p. 236)

“Interestingly, subjects showed a higher agreement on valence ratings for a given stimulus than on arousal ratings (visual stimuli; n ¼ 40 stimuli; average s.d. across stimuli, valence ¼ 1.3, arousal ¼ 1.5, Wilcoxon Z ¼ 3.0, P < 0.005; auditory stimuli, n ¼ 40 stimuli, average s.d. across stimuli, valence ¼ 1.4, arousal ¼ 1.7, Wilcoxon Z ¼ 4.7, P < 0.001).” (Anders et al., 2008, p. 236)

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“(i) the amygdala is sensitive to valence of emotional stimuli equated for arousal” (Anders et al., 2008, p. 240)

“(ii) that increased amygdala activity in response to emotional stimuli is better explained by valence than by arousal” (Anders et al., 2008, p. 240)

“Moreover, increasing amygdala activity in response to emotional pictures was better explained by valence than by arousal.” (Anders et al., 2008, p. 240)

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