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The Journal of Neuroscience, November 15, 1998, 18(22):9354-9364
Development of Functional Topography in the Corticorubral Projection: An In Vivo Assessment Using Synaptic Potentials Recorded from Fetal and Newborn Cats
Wen-Jie Song and Fujio Murakami Division of Biophysical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560, Japan
In mammals, topographic maps emerge from initially diffuse projections during development. To gain insight into the mechanisms governing the transition from a diffuse projection to a topographic map, we studied topographic specificity of functional connections during development, using the cat corticorubral system as a model. In the adult cat, rubrospinal neurons in the dorsomedial part of the red nucleus (RN) receive input primarily from the forelimb area of the sensorimotor cortex, whereas those in the ventrolateral part receive input primarily from the hindlimb area. During development, axons from the sensorimotor cortex arrive in the RN at embryonic day 50 (E50) () and are diffusely distributed in the RN until postnatal day 13 (P13) (). Here, we studied the development of the pattern of functional cortical inputs to individual rubrospinal neurons, using synaptic potentials recorded in vivo. The functional topography in each rubrospinal neuron in developing cats was examined and classified either as adult-like or nonadult-like by comparison with the adult pattern. In preterm kittens from E61 to E65, only about half of the recorded neurons (41%; n = 22) showed adult-like functional topography. This percentage, however, increased to 82% (n = 56) in P1-P8 kittens and to 93% (n = 42) in P13-P28 kittens. These results, in conjunction with the above mentioned anatomical observations, suggest that corticorubral axons make functional synapses nonselectively with rubrospinal neurons before birth. Furthermore, the functional topographic map developed earlier than the anatomical map (<P8 vs >P13), suggesting that there is a developmental step of selective promotion of synapse formation and/or selective enhancement of synaptic efficacy in topographically appropriate regions in the RN, before the emergence of the mature anatomical map.
Key words: topographic map; sensorimotor cortex; red nucleus; rubrospinal neuron; immature synapse; intracellular recording
Copyright © 1998 Society for Neuroscience 0270-6474/98/18229354-11$05.00/0
This article has been cited by other articles:
W.-J. Song, H. Kawaguchi, S. Totoki, Y. Inoue, T. Katura, S. Maeda, S. Inagaki, H. Shirasawa, and M. Nishimura
Cortical Intrinsic Circuits Can Support Activity Propagation through an Isofrequency Strip of the Guinea Pig Primary Auditory Cortex
Cereb Cortex, May 1, 2006; 16(5): 718 - 729.
[Abstract] [Full Text] [PDF]
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