RESEARCH ARTICLE Brain-to-brain interface technology: A brief history, current state, and future goals Pouya Vakilipour 1,2 | Saba Fekrvand 2,3 1 Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran 2 Universal Scientific Education and Research Network (USERN), Tehran, Iran 3 Brain and Spinal Cord Injury Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran Correspondence Pouya Vakilipour, Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran. Email: vakili.pouya1377@gmail.com Funding information: The authors did not receive support from any organization for the submitted work. Abstract A brain-to-brain interface (BBI), defined as a combination of neuroimaging and neurostimulation methods to extract and deliver information between brains directly without the need for the peripheral nervous system, is a bud- ding communication technique. A BBI system is made up of two parts known as the brain–computer interface part, which reads a sender’s brain activity and digitalizes it, and the computer–brain interface part, which writes the deliv- ered brain activity to a receiving brain. As with other technologies, BBI sys- tems have gone through an evolutionary process since they first appeared. The BBI systems have been employed for numerous purposes, including rehabilita- tion for post-stroke patients, communicating with patients suffering from amyotrophic lateral sclerosis, locked-in syndrome and speech problems follow- ing stroke. Also, it has been proposed that a BBI system could play an impor- tant role on future battlefields. This technology was not only employed for communicating between two human brains but also for making a direct com- munication path among different species through which motor or sensory commands could be sent and received. However, the application of BBI sys- tems has provoked significant challenges to human rights principles due to their ability to access and manipulate human brain information. In this study, we aimed to review the brain–computer interface and computer–brain inter- face technologies as components of BBI systems, the development of BBI sys- tems, applications of this technology, arising ethical issues and expectations for future use. KEYWORDS brain–computer interface, brain-to-brain interface, computer–brain interface Abbreviations: BBI, brain-to-brain interface; BCI, brain–computer interface; BMI, brain–machine interface; CBI, computer–brain interface; DBS, deep brain stimulation; EEG, electroencephalography; EMG, electromyography; FES, functional electrical stimulation; MMI, muscle-to-muscle interface; SSVEP, steady-state visual-evoked potentials; TMS, transcranial magnetic stimulation. Following our search strategy on Pubmed, Medline, Scopus, and Google Scholar databases, some 300 papers were found that were related to BBI technology, from which we included original papers in this review. Addi- tionally, we searched the databases mentioned before to find papers about BCI and CBI technologies, as compo- nents of BBI, to complete related parts. Received: 29 November 2023 Revised: 5 April 2024 Accepted: 18 April 2024 DOI: 10.1002/jdn.10334 Int J Dev Neurosci. 2024;1–17. wileyonlinelibrary.com/journal/jdn © 2024 International Society for Developmental Neuroscience. 1