External and Self-Regulation Modalities for Cognitive Improvement: Non-Invasive Mechanical and Electromagnetic Approaches

Cognitive functions are cerebral activities leading to attainment of information and subsequently knowledge. Memory, attention, and language are the main cognitive functions. Each cognitive function is regulated by modulatory process. Preclinical and clinical evidence has demonstrated that cognitive functions can be modulated by self-regulation techniques as well as external regulation modalities. Some of these techniques are currently under development as therapeutic approaches for healthy individuals and cognitive impaired patients.

Neuromodulation is the alteration of neural activities in a specific site or distant regions with a targeted delivery of a stimulus, such as mechanical, electrical stimulation or chemical agents. Learned self-regulation based modalities such as neurofeedback training (NFT) has reportedly shown beneficial effects for different disorders such as attention deficit disorder, attention deficit hyperactivity disorder (ADHD), Autism Spectrum Disorder (ASD), addiction, depression, and post-traumatic stress disorder (PTSD). In addition the cognitive impaired patients, NFT has shown beneficial effects in healthy individuals so that it is currently used in artists, athletes and other occupations to improve the performance. In line with technical and engineering advancements, non-invasive brain stimulation techniques with good spatiotemporal resolution have been developed. These external neural regulating modalities such repetitive magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS) have shown therapeutic outcomes in impaired cognitive functions as well as healthy individuals. Transcranial ultrasound stimulation (TUS) is a new modality that can mechanically stimulate neural circuit with high focality (1-2 mm) and depth (>2cm). These techniques can induce transient and persistent changes in different neural interfaces and pathways, neurotransmitters and neurochemical markers resulting in physiological and behavioral modulations.

These techniques are safe and cost-effective modalities that can alter neural activities that can last beyond the intervention period. Initial preclinical and clinical studies have shown therapeutic efficacies of rTMS, tDCS, and NFT alone or in combinations with other modalities for different disorders with cognitive impairments. TUS has also shown promising outcomes in neurorehabilitation due to its high spatiotemporal resolution. To reach routine clinical protocols based on these external or self-regulation modalities for neuropsychiatric disorders, further studies are needed to determine exact dose-response and the mechanisms of actions of the modalities.

In this Research Topic, we aim to review the recent advances in the use of self-regulation modality such as NFT and stimulating self-regulation techniques such as rTMS, tDCS, and TUS in cognitive impaired disorders. Moreover, preclinical and clinical applications of these techniques alone or in combinations, particularly combination of tDCS, rTMS, or TUS with NFT, for cognitive enhancement in healthy individuals are reviewed. The original and review papers are welcome on the use of rTMS, tDCS, TUS or NFT for improvement of cognitive functions in different neuropsychiatric disorders such as ADHD, PTSD, ASD, addiction, depression, anxiety, and also in healthy individuals. The papers focusing on the mechanisms of actions of the above mentioned modalities are also encouraged.