Ontogenetic differences in the expression of conditioned stimulus conditioning: effects of retention interval.
Preweanling 17-day-old rats were tested for retention of the conditioned emotional response after a 5-min or 24-hr retention interval. For a variety of conditioning parameters (i.e., variation in conditioned stimulus modality, unconditioned stimulus intensity, number of training trials), conditioned responding was consistently weaker after 5 min than after 24 hr. This apparent "incubation," or "hypermnesic," effect was not found in adult rats, even when comparable conditioning levels were indicated on the 24-hr test. The transient short-term retention deficit observed in 17-day-old preweanlings was alleviated by placing the pup in its home cage during the 5-min retention interval or by extending the conditioning session. Fifteen-day-old rat pups did not benefit from home cage exposure or extended training and displayed the transient short-term retention deficit regardless. The results are discussed in terms of age-related effects on time-dependent memory consolidation.
McKinzie
D L
DL
Department of Psychiatry, Indiana University School of Medicine, Indianapolis 46202, USA. DMCKINZI@IUPUI.EDU
Chen
W J
WJ
Spear
N E
NE
D000161:Acoustic Stimulation; D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000833:Animals, Suckling / Q000254:growth & development / Q000523:psychology; D003214:Conditioning, Classical / Q000502:physiology*; D003463:Cues; D004597:Electroshock; D004777:Environment; D005239:Fear / Q000502:physiology*; D005260:Female; D008297:Male; D009043:Motor Activity / Q000502:physiology; D010775:Photic Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D012153:Retention, Psychology / Q000502:physiology*; D013997:Time Factors