Vagal Input to Lateral Area 3a in Cat Cortex

Abstract

Penfield's sensory homunculus included visceral organs at its lateral extreme, and vagal input was recently identified lateral to the intraoral representation in primary somatosensory cortex (S1) of rats. We tested whether vagal input is similarly located in cats where area 3b (equivalent to S1) is clearly distinguishable from adjacent regions. Field potentials were recorded from the intact dura over the left hemisphere using electrical stimulation of the left or right cervical vagus nerve in seven cats. A surface positive-negative potential was evoked from either side in the lateral part of the sigmoid gyrus. Finer mapping made at the pial surface with a microelectrode identified a focal site anteromedial to the anterior tip of the coronal sulcus. Depth recordings demonstrated polarity reversals and multi-unit vagal responses, indicating that the potentials were generated by an afferent activation focus in the middle layers of the cortex. The S1 mechanoreceptive representation was localized by mapping multi-unit somatosensory receptive fields in the middle cortical layers near the coronal sulcus. The vagal-evoked potential site was distinctly anterior to the intraoral S1 representation and adjacent to the masseteric-nerve-evoked potential focus. Lesions made at the focal site revealed that this site is cytoarchitectonically located in area 3a not area 3b. Thus vagal input to the sensorimotor cortex in cats resembles deep rather than cutaneous somatic input, similar to the localization of nociceptive-specific input to area 3a in monkeys. The possibilities are considered that this vagal input is involved in motor control and in the sensory experience of visceral afferent activity.

Cortical visual areas process intestinal information during slow‐wave sleep

“…For somatosensory system this question is much better investigated. Vagal and splanchnic cortical projections terminated in somatosensory cortical areas were described in many studies 39–43 . It is also well known since early anatomical studies of 19th century 44 that visceral and somatosensory afferents terminate at the same neurons in spinal cord, and thus visceral information may travel to the cerebral cortex using the fibers of somatosensory columns.…”

"Pusher syndrome" following cortical lesions that spare the thalamus

“…In cats, stimulation of the renal nerve resulted in responses of neurons in the periphery of the ventral posterolateral nucleus and the dorsal and lateral posterior complex of the thalamus indicating that these sites process afferent information from the kidneys [44]. Stimulation of the vagus nerve resulted in activity modulation in the lateral primary somatosensory and insular cortices of rats and in the primary somatosensory cortex of cats [45][46][47][48]. In humans,functional imaging techniques have shown that stimulation of the vagus nerve in epileptic patients influences neural activity in the thalamus, the insular cortex and the postcentral gyrus, among other brain regions [49][50][51].…”

Basic and clinical aspects of visceral sensation: transmission in the CNS

“…Sensory input projects from the nucleus of the solitary tract via the parabrachial nucleus and ventromedial thalamus to the insular cortex caudal to the taste area 49 . A recent study suggests that vagal afferents may also project to the primary sensory cortex, lateral to the region activated by stimulation within the oral cavity 50 . Connections with hypothalamus, supraoptic nucleus, anterior cingulated cortex, amygdala and their cortical projections contribute to autonomic and emotional responses to visceral stimulation 51,52 .…”