Abstract

The amygdala is highly implicated in an array of psychiatric disorders but is not accessible using currently available non-invasive neuromodulatory techniques. Low-intensity transcranial focused ultrasound (TFUS) is a neuromodulatory technique that is capable of reaching subcortical regions non-invasively. Healthy older adult participants (n = 21; ages 48-79) received TFUS targeting the right amygdala and the left entorhinal cortex (active control region) in a two-visit within-participant crossover design. Before and after TFUS, behavioral measures were collected via the State-Trait Anxiety Inventory (STAI) and an emotional reactivity and regulation task (ERRT) utilizing neutral and negatively valenced images from the International Affective Pictures Set (IAPS). Heart rate and self-reported emotional valence and arousal were measured during the ERRT in order to investigate subjective and physiological responses to the task. Significant increases in both self-reported arousal in response to negative images and heart rate during the ERRT inter-trial intervals were observed when TFUS targeted the amygdala; these changes were not evident when the entorhinal cortex was targeted. No significant changes were found for state anxiety, self-reported valence to the negative images, cardiac response to the negative images, or emotion regulation. The results of this study provide preliminary evidence that a single session of TFUS targeting the amygdala may alter psychophysiological and subjective emotional responses, indicating some potential for future neuropsychiatric applications. However, further work on TFUS parameters and targeting optimization is necessary to determine how to elicit changes in a more clinically advantageous direction.