Trigeminocerebellar mossy fiber branching to granule cell layer patches in the rat cerebellum.
Recent micromapping studies of tactile areas in rat cerebellum have revealed a spatially precise mosaic of granule cell layer areas termed 'patches', with multiple patches on several folia resulting in multiple representations of the same body part. The research reported in the present paper tested the hypothesis that trigeminocerebellar mossy fiber branching is patch-related, so that collaterals terminate only within the boundaries of one or more of the tiny (often less than 1 sq. mm) patches having similar receptive fields. This hypothesis was supported by 3 separate series of electrophysiological experiments: (1) electrical stimulation in a patch resulted in short latency, low threshold responses confined within the boundaries of a second patch having a similar receptive field; (2) antidromic collison tests demonstrated that collaterals of axons originating in nucleus interpolaris reach pairs of patches with similar receptive fields; and (3) micromapping of the area from which a particular interpolaris neuron could be antidromically activated revealed that local terminal branching of a given mossy fiber axon appeared to be confined within the boundaries of a single patch. Together these results indicate that trigeminocerebellar mossy fiber branching is related to the fractured somatotopical organization of the granule cell layer. Possible functional implications of such mossy fiber branching are discussed.
D000818:Animals; D001369:Axons / Q000502:physiology; D001931:Brain Mapping; D002531:Cerebellum / Q000502:physiology*; D004558:Electric Stimulation; D005071:Evoked Potentials; D005145:Face / Q000294:innervation; D005260:Female; D008465:Mechanoreceptors / Q000502:physiology; D009412:Nerve Fibers / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D051381:Rats; D012032:Refractory Period, Electrophysiological; D014110:Touch / Q000502:physiology; D014276:Trigeminal Nerve / Q000502:physiology*; D014278:Trigeminal Nuclei / Q000502:physiology*