Figure 1

Cranial and spinal afferent pathways provide direct inputs to neural circuits regulating psychophysiological arousal and stress responses.

The diagram illustrates trigeminal and facial nerve afferents impinging on the nucleus of the solitary tract (NTS) and trigeminal nuclei (primary sensory nucleus and spinal nucleus) in the brainstem. The NTS and trigeminal nuclei impinge on the noradrenergic locus coeruleus (LC) and other brainstem nuclei comprising a loose network of interconnected structures historically recognized as the reticular formation (RF). The major pathways and circuitry highlighted (blue) were targeted using high-frequency pulsed currents (7–11 kHz) using transdermal electrical neurosignaling (TEN) waveforms delivered to trigeminal, facial and cervical spinal (C2/C3) afferent fibers. Trigeminal and facial nerve afferents (sensory and proprioceptive) can modulate the activity of the LC and NTS to affect psychophysiolgical arousal, the activity of the sympathoadrenal medullary (SAM) axis, biochemical stress responses and the dorsal motor nucleus (DMN) of the vagus. The bottom-up neurosignaling pathways illustrated serve mechanisms for the regulation of cortical gain control and performance optimization by influencing a broad variety of neurophysiological and cognitive functions, as well as primary sympathetic responses to environmental stress^55,73.