The relationship between parameters and effects in transcranial ultrasonic stimulation

Area of Science:

• Neuroscience
• Biomedical Engineering
• Medical Physics

Background:

• Transcranial ultrasonic stimulation (TUS) is an emerging non-invasive technique for human neuromodulation.
• Establishing optimal TUS protocols is crucial for maximizing its therapeutic and research efficacy.
• Existing empirical data requires synthesis to guide protocol development.

Purpose of the Study:

• To review and synthesize empirical evidence linking tunable TUS parameters to in vitro and in vivo outcomes.
• To inform TUS researchers on optimal parameter settings for enhanced neuromodulatory efficacy.
• To identify challenges in protocol translation and parameter extrapolation for future TUS interventions.

Main Methods:

• Aggregation and examination of empirical evidence from in vitro and in vivo studies.
• Multiscale analysis of TUS parameters, including frequency, intensity, pressure, pulse duration, and pulse train duration.
• Discussion of challenges in inter-model protocol translation and TUS-brain interaction complexities.

Main Results:

• Empirical evidence suggests lower sub-MHz frequencies, higher intensities, and longer pulse durations/trains may yield larger neuromodulatory effects.
• Optimal TUS parameter settings are influenced by a complex interplay between protocol specifics and brain characteristics.
• Significant variability exists in experimental paradigms, necessitating cautious interpretation of prior work.

Conclusions:

• A synthesis of current evidence indicates specific parameter ranges (lower frequencies, higher intensities, longer durations) are promising for enhanced TUS efficacy.
• Translating TUS protocols across different models and understanding brain interactions remain critical challenges.
• Further refinement of TUS parameters for human neuromodulation requires cautious interpretation and integration of diverse empirical data.