Multifunctional bioelectronics for brain–body circuits

The brain continuously receives, integrates and responds to an influx of sensory signals emerging from the internal organs. This is mediated not only through direct neuronal connections defined by the peripheral nervous system, but also endocrine, humoral, metabolic and immune pathways. This complex, mostly imperceptible brain–body crosstalk is essential to maintaining physiological homeostasis. It has a critical role in cognitive and behavioural functions as well as in disorders of the nervous system. The functional and anatomical diversity of brain–body pathways means that multifunctional implantable neurotechnologies must be developed to facilitate causal studies during behaviour. Although ubiquitous in studies of brain function, the electrical, optical and chemical interrogation of organ–brain circuits remains a challenge. In this Review, we discuss recent developments in multifunctional implantable neurotechnologies with the goal of enabling long-term studies of brain–body signalling. We highlight the material selection, device architectures, integration challenges and power and data transfer approaches necessary to establish robust bioelectronic interfaces between the brain and the peripheral organs. The brain continuously receives, integrates and responds to an influx of sensory signals emerging from the internal organs; this crosstalk is difficult to interrogate causally. In this Review, we discuss developments in multifunctional implantable neurotechnologies aimed at establishing robust bioelectronic interfaces between the brain and the peripheral organs suitable for long-term studies of brain–body signalling.