Investigating the potential of non-invasive brain stimulation to augment cognitive functioning

Purpose: Non-invasive brain stimulation can be used to influence neural activity by applying electrical currents, magnetic fields, or ultrasound waves to the central nervous system. Here we investigated how various brain stimulation technologies can be used to augment cognitive functioning to benefit human performance in a military context. Methods: We performed a literature review focusing on the potential for improving cognitive functioning of the following non-invasive brain stimulation techniques: transcranial magnetic stimulation (TMS), transcranial electrical stimulation (tES), peripheral nerve stimulation (PNS), and focused ultrasound stimulation (FUS). Based on this literature review we selected peripheral nerve stimulation to do an experiment to evaluate performance on various cognitive tasks. Results: We found that the most promising type of non-invasive brain stimulation for cognitive augmentation is peripheral nerve stimulation, particularly stimulation of the vagus nerve. This method shows effects on boosting alertness, attention, mood, wakefulness, as well as increasing neuroplasticity to benefit learning and memory. Both transcranial electrical stimulation and TMS also show promising avenues for boosting cognition. However, high variability in results across studies as well as high inter-individual variability make these methods less attractive for cognition augmentation applications at this moment. FUS is a nascent methodology that is not sufficiently researched yet for its potential in cognitive augmentation. However, FUS can target deep brain structures whereas TMS and tES only target superficial sites, and therefore is a technology worth monitoring.
Conclusions: Vagus nerve stimulation seems to be the most promising non-invasive brain stimulation method for the augmentation of cognition. Its effects on cognitive functioning has the potential to improve operational performance, its application is straightforward, and has minimal side effects. Compared to other non-invasive brain stimulation methods, Vagus nerve stimulation appears to show the most robust response and is easiest to implement. Military impact: Non-invasive brain stimulation has the potential to improve cognitive performance, with applications in learning, attention, alertness, wakefulness, and mood. This method can be used to improve performance of human operators in a wide variety of applications within the military.