TY - JOUR
T1 - CA3 NMDA receptors are crucial for rapid and automatic representation of context memory
AU - Cravens, Catherine J.
AU - Vargas-Pinto, Noelia
AU - Christian, Kimberly M.
AU - Nakazawa, Kazu
PY - 2006/9
Y1 - 2006/9
N2 - It is argued that the hippocampus contributes to acquisition of context-specific memory although neural mechanisms have not been clarified. To evaluate the role of CA3 in context-specific memory, we developed one-trial context discrimination tasks to test acquisition and retrieval of contextual memory in CA3 pyramidal cell-restricted N-methyl-d-aspartate (NMDA) receptor knockout mice. Mutants were unable to discriminate conditioned and no-shock contexts 3 h after one-trial avoidance training. These phenotypes were not evident 24 h after one-trial training or 3 h after multi-trial training. Following one-trial contextual fear conditioning, mutants showed a selective deficit in context discrimination during a retention test 3 h after acquisition, although overall freezing levels were similar to those of the control mice. As in the avoidance task, this context discrimination impairment was not observed 24 h after initial conditioning. Interestingly, extending the post-shock period to 3 min during the one-trial fear conditioning task eliminated the discrimination deficit observed at the 3 h retention interval. These results suggest that: (i) impaired rapid context discrimination during the recall test is dependent on the duration of post-shock period during conditioning; (ii) CA3 NMDA receptors are critically involved in rapid and automatic formation of a unified context memory representation from the sensory information; (iii) CA3 NMDA receptors support contextual pattern separation; (iv) fear memory to foot-shock is acquired without CA3 NMDA receptors. It appears that rapid and automatic context memory representations from one-time experience are mediated, at least in part, by CA3 NMDA receptors.
AB - It is argued that the hippocampus contributes to acquisition of context-specific memory although neural mechanisms have not been clarified. To evaluate the role of CA3 in context-specific memory, we developed one-trial context discrimination tasks to test acquisition and retrieval of contextual memory in CA3 pyramidal cell-restricted N-methyl-d-aspartate (NMDA) receptor knockout mice. Mutants were unable to discriminate conditioned and no-shock contexts 3 h after one-trial avoidance training. These phenotypes were not evident 24 h after one-trial training or 3 h after multi-trial training. Following one-trial contextual fear conditioning, mutants showed a selective deficit in context discrimination during a retention test 3 h after acquisition, although overall freezing levels were similar to those of the control mice. As in the avoidance task, this context discrimination impairment was not observed 24 h after initial conditioning. Interestingly, extending the post-shock period to 3 min during the one-trial fear conditioning task eliminated the discrimination deficit observed at the 3 h retention interval. These results suggest that: (i) impaired rapid context discrimination during the recall test is dependent on the duration of post-shock period during conditioning; (ii) CA3 NMDA receptors are critically involved in rapid and automatic formation of a unified context memory representation from the sensory information; (iii) CA3 NMDA receptors support contextual pattern separation; (iv) fear memory to foot-shock is acquired without CA3 NMDA receptors. It appears that rapid and automatic context memory representations from one-time experience are mediated, at least in part, by CA3 NMDA receptors.
KW - Avoidance learning
KW - Conditioning
KW - Fear
KW - Hippocampus
KW - Knockout mouse
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U2 - 10.1111/j.1460-9568.2006.05044.x
DO - 10.1111/j.1460-9568.2006.05044.x
M3 - Article
C2 - 17004940
AN - SCOPUS:33748914830
SN - 0953-816X
VL - 24
SP - 1771
EP - 1780
JO - European Journal of Neuroscience
JF - European Journal of Neuroscience
IS - 6
ER -