Climbing fibers provide excitation to the deep cerebellar nuclei and the Purkinje neurons. The climbing fibers originate from which of the following structures?
(A) inferior olivary nucleus
(B) pontine nuclei
© spinal cord
(D) superior olivary nucleus
(E) vestibular nuclei
explanation
(A) The inferior olivary nucleus in the medulla oblongata is the sole source of climbing fibers to the cerebellum. All other sources of fibers to the cerebellum such as the pontine nuclei (choice B), spinal cord (choice C), or vestibular nuclei (choice E) provide mossy fibers to the cerebellum. The superior olivary nucleus (choice D) receives auditory fibers from the cochlear nuclei and projects back to the cochlea by way of the olivocochlear bundle. It modifies the sensory input from the organ of Corti in the cochlea and is not involved with cerebellar circuitry.