Spontaneous Activity and Rhythm Assimilation Reactions in Baby Rabbit Hippocampal Neurons During Learning: Age-Related Characteristics

The neural mechanisms of the age-related characteristics of memory formation were studied in experiments based on a model providing an analog of a conditioned reflex to time: trace assimilation of the rhythm with which neurons in hippocampal field CA1 were stimulated, in rabbits aged 1–4 weeks and 5–6 months. Stages of changes in neuron spike activity characteristic for developing animals were described. In animals studied one week after birth, there was a predominance of silent cells and cells with low spontaneous activity. At 2–3 weeks of life, the level of spontaneous neuron activity increased, reaching adult levels by 25–30 days. The dynamics of the ontogenetic development of learning ability showed a number of stages: from virtually complete inability to form and assimilate traces of the rhythm (at age 6–7 days) to the stage of good formation and rapid forgetting (8–14 days), and, finally, the development of complete memory (25–30 days). The synchronous development of plastic rearrangements and the level of spontaneous neuron activity provided evidence of the direct involvement of the mechanisms underlying the formation of spontaneous spike activity in the organization of neural processes supporting adaptive reactions in the developing animal. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 55, No. 1, pp. 52–59, January–February, 2005.