Elsevier

Experimental Neurology

Volume 42, Issue 3, March 1974, Pages 566-573
Experimental Neurology

Ontogeny of levels of neural organization: The righting reflex as a model

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Abstract

The hierarchy of neural control of a reflex pattern was examined by determining the effect on the righting reflex of transections of the brain stem at various times during emergence of the response shortly after birth in the rat. It was found that the reflex was not visibly impaired with transections as low as middle of the medulla, provided that the cuts were made early in its emergent phase, i.e., 3–4 days after birth. As the reflex developed toward perfection during the next 3–4 days, the cuts had to be made progressively more rostrally to avoid severe impairment, until by 8–10 days righting attempts were rendered ineffective by any cut caudal to the inferior colliculus. In contrast, if the animals were kept alive for 3–4 days after postcollicular transection in the early emergent stage, the reflex activity progressed to nearly normal effectiveness by age 7–8 days. The combined data are interpreted as indicating that the “center” of organization of the reflex emerges a few days postnatally in low pons and medulla, and during development it becomes dependent upon but not replaced by more rostral systems such as the mesencephalic righting center.

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1

This research was supported by Grants 05713 and 17998 from the National Institute of Neurological Diseases and Stroke. The assistance of Joyce Palmer in performing the experiments and preparing the manuscript is gratefully acknowledged.

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