File:Christian and Thompson Figure 5 SVG.svg

English: . The basic essential circuitry for classical eye-blink conditioning. The CS (green pathway) starts as sensory information (in this example, an auditory tone) entering via the vestibulocochlear nerve and associate with neurons in the auditory nuclei. Cells the auditory nuclei, project to the contralateral pontine nuclei where they synapse onto third order neurons that project back across midline and enter the cerebellum, send a collateral to the interpositus deep cerebellar nuclei and synapse onto granule cells. Granule cells in turn, continue to the cerebellar cortex forming parallel fibers. The US is a puff of air to the eye that enters the via the trigeminal nerve and synapses onto neurons within the trigeminal nucleus (NV). From the trigeminal complex, the first efferent pathway UR (reflex paths; orange pathway) is a direct projection to facial motoneurons controlling the orbicularis oculi muscle as well as presumably inhibition of the levator palpebrae superioris motoneurons in the caudal central subdivision of the oculomotor nucleus (peripheral and direct synapses to Motor nuclei). Additionally, the US (light blue pathway) has a second projection, with neurons projecting out of the trigeminal nucleus to the contralateral side where they synapse onto third order neurons in the dorsal accessory olive division of the inferior olivary nucleus. The third order neurons in the US pathway project back across midline, enter the cerebellum, sending an excitatory collateral to the interpositus deep cerebellar nuclei then continuing to form climbing fibers on purkinje. Pontocerebellar CS and olivocerebellar US collaterals to the interpositus nuclei initiate the CR pathway (navy blue pathway). Activated cells in the interpositus nucleus, project to neurons in the red nucleus, which then project on to pre- and motoneurons necessary for blink behavior. Purkinje are transiently activated by individual parallel fibers and largely activated by climbing fibers, when stimulated, they project down to the interpositus nuclei and have an inhibitory effect (red pathways). (Modified from Christian and Thompson, 2003; figure 5).