Enhanced Episodic Memory Encoding Following Modulation of the Amygdala via Transcranial Low-intensity Focused Ultrasound.

The amygdala is considered crucial to the formation of emotional episodic memories, yet causal evidence in humans is limited due to challenges in noninvasive neuromodulation of deep brain structures. In a double-blind, sham-controlled, repeated-measures study, we tested whether transcranial low-intensity focused ultrasound (tFUS) targeting the left amygdala before encoding emotional and neutral pictures impacted memory for these pictures 24 hr later (n = 23). Using a putative inhibitory tFUS protocol previously shown to attenuate amygdala BOLD-dependent signal, we hypothesized that preencoding amygdala inhibition would impair emotional memory. Contrary to this hypothesis, active (vs. sham) sonication enhanced-or tended to enhance-memory for both neutral and emotional memory across two memory tests. As a secondary measure of amygdala modulation, participants completed a dynamic emotional facial recognition task (n = 20). Active tFUS selectively enhanced recognition of subtle fearful expressions. Computational modeling further supported tFUS-mediated memory and emotion recognition enhancements. Assuming that this tFUS protocol did indeed inhibit amygdala function, these findings suggest that rather than solely amplifying emotional salience, the amygdala may act as a filter that suppresses weaker, ambiguous signals. Inhibiting the amygdala may thus attenuate this gating function, thereby unmasking subtle affective cues and enhancing their processing into memory. Nevertheless, the purported inhibitory nature of this tFUS protocol requires further investigation. Should these findings replicate, they highlight the potential for tFUS as a translational tool to modulate affective processes for disorders such as depression and posttraumatic disorder characterized by impairments in emotional processing and memory.