[Development of certain innate reflex reactions in mice selected for brain weight]

The rates of functional differentiation of the CNS were studied in mice, selected for high (H-line), and low (L-line) brain weight. Four tests were used, based on most distinct reflex responses. Comparison of ages of responses accomplishment in all the tests indicates that mice from L-line meet the test criteria on average 0.5 day earlier than those from H-line. The obtained data suggest that the low adult brain weight in L-line originates from genetically controlled early CNS maturation.