Point 11
Intro
The
ROSTRAL portion of the solitary complex is a
component of the TASTE PATHWAY. The axons
within the rostral tractus solitarius are the central
processes of cells within THREE cranial nerve
ganglia, the GENICULATE GANGLION OF C.N. VII, the
INFERIOR GANGLION of C.N. IX and the INFERIOR
GANGLION of C.N. X. These central processes travel with
the rostral tractus solitarius terminate within the
ROSTRAL or GUSTATORY portion of the nucleus
solitarius. The peripheral processes of these neurons
innervate the TASTE BUDS of the tongue in the
following distribution:
- C.N. VII=anterior twothirds
- C.N. IX=posterior onethird
- C.N. X=taste buds on epiglottis
Like other ascending sensory pathways, taste information heads for the thalamus (the great GATEWAY to the cerebral cortex!), and in particular to the ventral posteromedial nucleus (VPM; the nucleus of the HEAD!; after all, the tongue is in the head; remember the trigeminal-VPM relationship). The third neuron in the pathway i.e., the thalamic VPM neuron, then sends its axon to the ventral lateral portion of the postcentral gyrus, areas 3, 1, and 2. UNLIKE OTHER ASCENDING SENSORY PATHWAYS THE SOLITARIOTHALAMIC TRACT (STT) IS UNCROSSED, repeat, UNCROSSED, repeat, UNCROSSED.
You should also keep in mind that the interruption of the solitariothalamic tract will not result in major problems in respiratory and cardiovascular control, since most of the pathways over which the nucleus solitarius controls these functions pass caudally in the brain stem. Let's reserve a loss of taste from the ipsilateral side of the tongue for lesions of the solitariothalamic tract. Lesions of the rostral nucleus solitarius will also result in loss of taste from the ipsilateral side of the tongue. In contrast, a lesion of the CAUDAL portion of nucleus solitarius will result in an INCREASE IN HEART RATE.