Low Intensity Focused Ultrasound of Medial Temporal Lobe Regions for the Improvement of Learning and Memory / Low Intensity Focused Ultrasound as a Non-Invasive Neural Prosthetic for the Improvement of Emotion Regulation

Medial temporal lobe (MTL)-dependent memory is impacted by a wide range of psychiatric and neurologic conditions. These cognitive limitations often result in limited functional abilities for patients. Currently available pharmacologic and behavioral treatments are somewhat controversial and have minimal evidence-based effectiveness. Recently, deep brain stimulation was used to modulate MTL activity and subsequently improve memory performance. However, such implantable devices require neurosurgery with major associated health risk. At present, there are no publications reporting non-invasive neurostimulation targeting MTL regions to improve memory. The central hypothesis of this project is that non-invasive, low intensity focused ultrasound pulsation (LIFUP) can selectively increase regional MTL activity and thus be used as a cognitive neural prosthetic capable of improving memory performance. The aims of this portion of the study focus on whether LIFUP can increase blood oxygen level dependent (BOLD) activation and perfusion (measured by arterial spin labeling) in the entorhinal cortex and functionally associated regions, and whether LIFUP to the entorhinal cortex will result in improved memory.

The Amygdala is highly involved in emotional response, emotional reactivity and anxiety. Amygdala functions are therefore involved in a wide range of psychiatric disorders including generalized and social anxiety, specific phobia, obsessive compulsive disorder and posttraumatic stress disorder. Therefore, potential clinical implications of amygdala stimulation are great. However, to date, such efforts have been limited by the inability of non-invasive neuromodulation techniques (e.g. transcranial magnetic stimulation - TMS) to reach the amygdala and the highly invasive (i.e. neurosurgical) nature of methods (e.g. deep brain stimulation - DBS) which can, but to our knowledge has rarely been used, target these areas. In order to overcome these current limitations, study investigators propose the use of low intensity focused ultrasound pulsation (LIFUP) to affect amygdala activity to improve emotion regulation. The aim of this portion of the study focuses on whether LIFUP can modulate blood oxygen level dependent (BOLD) activation and perfusion (measured by arterial spin labeling) in the amygdala and functionally associated regions, and whether LIFUP to the amygdala will result in changes to anxiety levels and emotion regulation.

This study will be conducted using a crossover design in which each participant will complete two visits spaced two weeks apart. At one visit, they will receive LIFUP sonication (with parameters hypothesized to be inhibitory) to the right amygdala, and at the other, they will receive sonication (with parameters hypothesized to be excitatory) to the left entorhinal cortex. The order of conditions will be randomized and counterbalanced across participants. Participants will be blinded to condition order, and all other testing will be conducted the same at both visits. This design will allow us to test the effects of two potentially clinically-relevant targets for LIFUP, and will allow us to determine whether observed effects on brain activity, learning and memory, and emotion regulation are target-specific by comparing results between the two LIFUP paradigms.