F. Nottebohm et al., THE LIFE-SPAN OF NEW NEURONS IN A SONG CONTROL NUCLEUS OF THE ADULT CANARY BRAIN DEPENDS ON TIME OF YEAR WHEN THESE CELLS ARE BORN, Proceedings of the National Academy of Sciences of the United Statesof America, 91(17), 1994, pp. 7849-7853
The number of high vocal center (HVC) neurons labeled in adult male ca
naries by systemic injections of [H-3]thymidine depended on season and
survival time. This was true for HVC neurons projecting to the robust
nucleus of the archistriatum and for other HVC neurons that could not
be retrogradely filled from the robust nucleus of the archistriatum.
Birds injected in October and killed 40 days later had twice as many l
abeled HVC neurons as birds injected in May and killed 40 days later.
However, this difference became much larger (5 times) when the birds w
ere allowed to survive for 4 months. Whereas more than half of the spr
ing-born neurons disappeared between 40 days and 4 months, there was n
o reduction in the number of fall-born neurons present at the 4-month
survival point. We infer that seasonal variables affect the life span
of HVC neurons born in adulthood.