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1. In neuroanatomy, term loosely applied to a variety of stalklike connecting structures in the brain, composed either exclusively of white matter ( e.g., cerebellar p.) or of white and gray matter ( e.g., cerebral p.. 2. SYN: pedicle (2). [Mod. L. pedunculus, dim. of pes, foot]

- cerebral p. [TA] originally denoting either of the two halves of the midbrain (a relatively narrow “neck” connecting the forebrain to the hindbrain); this term has been variably used to designate only those large bundles of corticofugal fibers forming the crus cerebri or to designate the crus cerebri plus the midbrain tegmentum; this latter, more inclusive, usage (crus cerebri and midbrain tegmentum) is preferred; the substantia nigra, while a part of the base of the p. (basis pedunculi), is considered a structure separating the midbrain tegmentum from the crus cerebri. SEE ALSO: crus cerebri. SYN: pedunculus cerebri [TA].

- p. of corpus callosum SYN: subcallosal gyrus.

- p. of flocculus [TA] the bundle of afferent and efferent nerve fibers connecting the flocculus and the nodule of the cerebellum; part of its course is in the inferior medullary velum. SYN: pedunculus flocculi [TA].

- inferior cerebellar p. large paired bundles of nerve fibers that develop on the dorsolateral surfaces of the upper medulla, extend under the lateral recesses of the rhomboid fossa and curve dorsally into the cerebellum caudomedial to the middle cerebellar p.; composed of a larger (lateral) bundle, the restiform body [TA], and a small (medial) bundle, the juxtarestiform body [TA]. Fibers forming this composite bundle originate from spinal neurons and medullary relay nuclei. The largest constituent (restiform body) contains crossed fibers from the inferior olive; it also contains the dorsal spinocerebellar tract and cerebellar projections from the lateral reticular nucleus, the accessory cuneate nucleus, the paramedian reticular nuclei, the perihypoglossal nuclei, and other nuclei. Vestibulocerebellar fibers are placed medially in the inferior cerebellar p. and are separately identified as the juxtarestiform body. SYN: pedunculus cerebellaris inferior [TA].

- inferior thalamic p. a large fiber bundle emerging from the anterior part of the thalamus in the ventral direction, in part joining the medial fibers of the internal capsule, in other part curving laterally around the medial margin of the capsule into the innominate substance. Many of its fibers establish a reciprocal connection of the mediodorsal nucleus of the thalamus with the orbital gyri of the frontal lobe, but numerous other fibers constitute a conduction system from the amygdala and olfactory cortex to the mediodorsal nucleus. SEE ALSO: ansa peduncularis. SYN: inferior thalamic radiation [TA], radiatio inferior thalami [TA], pedunculus thalami inferior.

- lateral thalamic p. the massive group of fibers that emerges from the laterodorsal side of the thalamus to join the corona radiata; it reciprocally connects the lateral nucleus and the geniculate bodies of the thalamus with the corresponding regions of the cerebral cortex. SEE ALSO: central thalamic radiation. SYN: pedunculus thalami lateralis.

- p. of mammillary body a fascicle of nerve fibers passing to the mamillary body along the ventral surface of the midbrain; it consists of fibers that originate from the dorsal and ventral tegmental nuclei. SYN: fasciculus pedunculomammillaris, pedunculomammillary fasciculus, pedunculus corporis mammillaris.

- middle cerebellar p. [TA] the largest of three paired cerebellar peduncles, composed mainly of fibers that originate in the pontine nuclei, cross the midline in the basilar pons, and emerge on the opposite side as a massive bundle arching dorsally along the lateral side of the pontine tegmentum into the cerebellum; there are some uncrossed pontocerebellar fibers in this p.; its fibers are distributed chiefly to the cortex of the cerebellar hemisphere with some collateral fibers passing to the cerebellar nuclei. SYN: pedunculus cerebellaris medius [TA], brachium pontis.

- olfactory p. SYN: olfactory tract.

- superior cerebellar p. [TA] a large bundle of nerve fibers that originates from the dentate and interpositus nuclei and emerges from the cerebellum in the rostral direction, along the lateral wall of the fourth ventricle. The bundle submerges from the dorsal surface of the brainstem into the mesencephalic tegmentum, where most of its fibers cross in the massive decussation of the superior cerebellar peduncles. Part of the bundle terminates in the contralateral red nucleus; the bulk of the fibers continue rostrally to parts of the ventral intermediate nucleus of thalamus, ventral posterolateral nucleus of thalamus, and central lateral nucleus of thalamus. SYN: pedunculus cerebellaris superior [TA], brachium conjunctivum cerebelli.

- ventral thalamic p. the massive system of fiber bundles emerging through the ventral, lateral, and anterior borders of the thalamus to join the internal capsule and parts of the corona radiata; it contains the fibers reciprocally connecting the ventral thalamic nuclei with the precentral and postcentral gyri of the cerebral cortex. SYN: pedunculus thalami ventralis.

pe·dun·cle 'pē-.dəŋ-kəl, pi-' n

1) a band of white matter joining different parts of the brain see CEREBELLAR PEDUNCLE, CEREBRAL PEDUNCLE

2) a narrow stalk by which a tumor or polyp is attached

pe·dun·cu·lar pi-'dəŋ-kyə-lər adj

a narrow process or stalk-like structure, serving as a support or a connection. For example, the middle cerebellar peduncle connects the pons and cerebellum.