In-human evidence for temporal interference neuromodulation

A new electrical stimulation method called Temporal Interference (TI) stimulation has been introduced recently. By its concept, it can non-invasively stimulate deep brain targets.TI stimulation delivers alternating high-frequency currents (e.g., >1 kHz) to multiple electrode pairs with slightly different frequencies, with the differential frequency typically in the range of brain oscillations (between 10 and 70 Hz). The superposition of these currents generates an electric field that oscillates at a high frequency, with an envelope amplitude modulated at the difference frequency. Since its introduction, interest in and research on the effectiveness and working mechanisms of TI stimulation have grown, particularly in animal studies that primarily involved rodents. These studies have demonstrated promising effects on neural firing and modulation of brain activity. However, further investigation is necessary to assess the impact of TI stimulation in the human brain and explore its potential for neuroscience and therapeutic applications.
To address this gap and to offer insights for future human studies, we systematically reviewed the published literature, focusing on in-vivo studies examining the effects of TI stimulation in the human brain. Our review indicates both positive and negative outcomes. A total of 10 studies met the inclusion criteria: four investigated the effects of TI stimulation on the primary motor cortex, three focused on the occipito-parietal and frontoparietal regions, and three targeted deeper brain structures.
Overall, these studies provide evidence of behavioral impacts and modulation of neural activity induced by TI stimulation, as measured by changes in functional connectivity, motor cortex excitability, frequency band power, and long-term potentiation-like plasticity. We also analyzed key aspects of the studies, including stimulation parameters, study designs, comparator conditions, computational modeling, side effects, and readout methods. Based on this, we identified limitations, areas for improvement, and gaps in the current research, offering insights for future human studies.