Figure 1. The lingual-hypoglossal reflex. This reflex has been directly analyzed by electrical stimulation of the nerve and extracellular recording from hypoglossal nerve branches. In a second approach, intracellular recordings from hypoglossal motoneurons determining excitatory (EPSP) and inhibitory (IPSP) synaptic potentials are obtained. Mechanical stimulation of the tongue will also evoke these synaptic potentials. An example of the reflex effects is given in one study in the anesthetized cat (Takata, 1981), in which a polysynaptic reflex had different proportions of excitatory and inhibitory effects, depending upon whether the motoneurons innervated the tongue-protruding or -retruding muscles. (The drawing of the dissection of the tongue muscles is adapted with permission from Fregosi and Fuller [1997].)