Recent studies have documented an intricate, patchy mosaic of tactile receptive fields (fractured somatotopy) in the granule and Purkinje cells layers of the mammalian cerebellar cortex. Yet, little is known of the anatomical substrates for cerebellar somatotopy. A research program is proposed that will employ modern anatomical and physiological tools to elucidate the projection patterns of cerebellar afferent inputs in order to begin to fill this void. The experiments will focus on physiologically characterized inputs from the trigeminal brainstem complex, in particular those associated with the mystacial vibrissae (whiskers). Five hypotheses will be tested in normal adult rats: 1: Mossy fibers originating in the trigeminal brainstem complex have predictable projections in multiple regions of cerebellar cortex. Anterograde and retrograde bulk-labeling experiments will determine the projection patterns of mossy fibers arising from the three trigeminal brainstem subnuclei known to have significant cerebellar projections. 2: Functionally distinct mossy fiber projections are spatially segregated in the granule cell layer. Anterograde labeling, monoclonal antibody- revealed reference landmarks, and computer-assisted reconstruction methods will permit quantitative study of the somatotopic organization of mossy fibers originating in specified components of the whisker map in trigeminal subnucleus interpolaris. The homeomorphic relationship between the whiskers and the fiber/cell aggregates in interpolaris will be exploited to compare the projections of groups of cells subserving different whishers. 3: The projections and morphologies of single mossy fibers can be predicted based upon their receptive field location and size, and these projections are somatotopic. This study offers a third level of inquiry into mossy fiber somatotopy and structure-function relationships. Intra- axonal recording and labeling methods will be applied to single mossy fibers of trigeminal brainstem origin. The spatial proximity of the trigeminal brainstem complex to the cerebellum and the use of a novel long- range intracellular marker will also permit analysis of relationships between the termination patterns of individual mossy fibers and the morphology of their cells of origin in the medulla and pons. 4: The termination patterns of functionally identified mossy fibers conform to the fractured somatotopy of their target. Receptive field micromapping in the granule cell layer will be followed by intra-axonal recording and staining of two mossy fibers with receptive fields that correspond to marked cerebellar patches. These studies will again focus on the trigeminal projection to crus I-II and uvular cortex where the whiskers are heavily represented. 5: Connections between granule and Purkinje cells are more frequent within, as opposed to between, functional columns. An anatomical substrate for the vertical congruence of fractured somatotopy between the Purkinje and underlying granule cell layers will be pursued. Physiologically characterized granule cell axons will be stained in vitro and in vivo to determine whether there are more contacts onto Purinje cells via the ascending and within-path segments of granule cell axons than via their extra-patch parallel fiber segments, as suggested by Llinas (1982).

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
Project #
Application #
Study Section
Neurology B Subcommittee 2 (NEUB)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Saint Louis University
Schools of Medicine
Saint Louis
United States
Zip Code
Jacquin, Mark F; Arends, Joop J A; Renehan, William E et al. (2015) Whisker-related circuitry in the trigeminal nucleus principalis: Topographic precision. Somatosens Mot Res 32:8-20
Mosconi, Tony; Arends, J J; Jacquin, Mark F (2013) Null mutations of NT-3 and Bax affect trigeminal ganglion cell number but not brainstem barrelette pattern formation. Somatosens Mot Res 30:114-9
Mosconi, Tony; Woolsey, Thomas A; Jacquin, Mark F (2010) Passive vs. active touch-induced activity in the developing whisker pathway. Eur J Neurosci 32:1354-63
Williams, M N; Zahm, D S; Jacquin, M F (1994) Differential foci and synaptic organization of the principal and spinal trigeminal projections to the thalamus in the rat. Eur J Neurosci 6:429-53
Jacquin, M F; McCasland, J S; Henderson, T A et al. (1993) 2-DG uptake patterns related to single vibrissae during exploratory behaviors in the hamster trigeminal system. J Comp Neurol 332:38-58
Arends, J J; Jacquin, M F (1993) Lucifer Yellow staining in fixed brain slices: optimal methods and compatibility with somatotopic markers in neonatal brain. J Neurosci Methods 50:321-39
Jacquin, M F; Beinfeld, M C; Chiaia, N L et al. (1992) Cholecystokinin concentrations and peptide immunoreactivity in the intact and deafferented medullary dorsal horn of the rat. J Comp Neurol 326:22-43
Jacquin, M F; Hu, J W; Sessle, B J et al. (1992) Intra-axonal Neurobiotin injection rapidly stains the long-range projections of identified trigeminal primary afferents in vivo: comparisons with HRP and PHA-L. J Neurosci Methods 45:71-86
Waite, P M; Jacquin, M F (1992) Dual innervation of the rat vibrissa: responses of trigeminal ganglion cells projecting through deep or superficial nerves. J Comp Neurol 322:233-45