Different brain areas are involved in memory expression at different times from training.
Rats were trained in a step-down inhibitory avoidance task and tested for retention 1, 31, or 60 days later. Three to 7 days prior to testing, they were bilaterally implanted with cannulae in the CA1 region of the dorsal hippocampus and in the amygdaloid nucleus (H + A), in the entorhinal cortex (EC), and in the posterior parietal cortex (PPC). Ten minutes prior to testing, the animals received, through the cannulae, 0.5-microliter microinfusions of vehicle (20% dimethylsulfoxide in saline) or of 0.5 microgram of CNQX dissolved in the vehicle. A second test session was carried out 90 min after the first. CNQX blocked retention test performance when given into H + A 1 day after training but not later; when given into EC 1 or 31 days after training, but not later; and when given into PPC 1, 31, or 60 days after training. In all cases performance returned to normal levels in the second test session. The data suggest that H and A are involved in memory expression for only a few days after acquisition; that EC is involved in memory expression for up to 31, but less than 60, days after acquisition; and that PPC is involved in memory expression for up to at least 2 months after acquisition.
Quillfeldt
J A
JA
Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil.
Zanatta
M S
MS
Schmitz
P K
PK
Quevedo
J
J
Schaeffer
E
E
Lima
J B
JB
Medina
J H
JH
Izquierdo
I
I
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology*; D000679:Amygdala / Q000187:drug effects*; D000818:Animals; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D006624:Hippocampus / Q000187:drug effects*; D008297:Male; D008568:Memory / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione