Spatiotemporal Dissociation of Human Amygdala Response to Negative Affect

The amygdala plays a crucial role in processing negative emotions, serving as a key target for top-down regulation. However, the temporal aspects of its response to such stimuli have not been thoroughly examined. Most functional magnetic resonance imaging (fMRI) studies approach this issue by employing a standard hemodynamic response function and averaging activity across the amygdala, which may overlook important variations in both time and space.

To address this limitation, researchers utilized finite impulse response (FIR) modeling in two distinct datasets, which together included 358 participants. This approach aimed to discern the blood oxygenation level-dependent (BOLD) responses during the viewing of negative images and cognitive reappraisal tasks, while also employing a data-driven clustering of voxel-wise time courses.

Across two probabilistic atlases, six out of the seven amygdala subregions exhibited prolonged activation in response to negative stimuli, yet these subregions varied in their temporal patterns. Specifically, the centromedial amygdala demonstrated persistent activation that extended beyond the immediate post-stimulus rating period.

In contrast, the laterobasal and superficial subregions reached their peak activation earlier during the presentation of the stimulus. Moreover, cognitive reappraisal, which is often employed as a strategy to regulate emotional responses, did not significantly modify either the magnitude or the temporal shape of the amygdala's response, suggesting that such downregulation is not a reliable outcome when relying on instructed regulation under these specific conditions.

By employing a data-driven analysis, the study identified four clusters of amygdala subregions, each displaying unique temporal profiles. These clusters corresponded to the laterobasal, lateral, superficial, and centromedial territories of the amygdala. This finding aligns with existing anatomical parcellations while also challenging some of the conventional boundaries within the amygdala.

The findings of this FIR modeling endeavor reveal a nuanced temporal architecture in the amygdala's response to negative affective stimuli. The pattern is characterized by an initial response from the laterobasal and superficial subregions, followed by a sustained activity in the centromedial region. This temporal organization provides valuable insights into the dynamics of the amygdala's involvement in processing negative emotions, highlighting the importance of considering both time and space when investigating its functional dynamics.