title: Interaction of inhibitory and facilitatory effects of conditioning trials on long-term memory formation.
abstract: Animals learn through experience and consolidate the memories into long-time storage. Conditioning parameters to induce protein synthesis-dependent long-term memory (LTM) have been the subject of extensive studies in many animals. Here we found a case in which a conditioning trial inhibits or facilitates LTM formation depending on the intervals from preceding trials. We studied the effects of conditioning parameters on LTM formation in olfactory conditioning of maxillary-palpi extension response with sucrose reward in the cockroach Periplaneta americana We found, at first, that translation- and transcription-dependent LTM forms 1 h after training, the fastest so far reported in insects. Second, we observed that multiple-trial training with an intertrial interval (ITI) of 20 or 30 sec, often called massed training, is more effective than spaced training for LTM formation, an observation that differs from the results of most studies in other animals. Third, we found that a conditioning trial inhibits LTM formation when the intervals from preceding trials were in the range of 10-16 min. This inhibitory effect is pairing-specific and is not due to decreased motivation for learning (overtraining effect). To our knowledge, no similar inhibition of LTM formation by a conditioning trial has been reported in any animals. We propose a model to account for the effects of trial number and ITIs on LTM formation. Olfactory conditioning in cockroaches should provide pertinent materials in which to study neuronal and molecular mechanisms underlying the inhibitory and facilitatory processes for LTM formation.
authors.affiliation: Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan.|Graduate School of Agriculture, Tamagawa University, Machida 194-8610, Japan.
authors.forename: Shouhei
authors.initials: S
authors.lastname: Hosono
authors.affiliation: Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.|Faculty of Liberal Arts, Tokyo Medical and Dental University, Ichikawa 272-0827, Japan.
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Matsumoto
authors.affiliation: Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan mizunami@sci.hokudai.ac.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Mizunami
mesh_terms: D000818:Animals; D003213:Conditioning, Psychological / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D008297:Male; D057567:Memory, Long-Term / Q000187:drug effects; D008570:Memory, Short-Term / Q000187:drug effects; D008960:Models, Psychological; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D055696:Olfactory Perception / Q000187:drug effects; D010526:Periplaneta; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D013997:Time Factors
chemical_list: D019384:Nucleic Acid Synthesis Inhibitors; D011500:Protein Synthesis Inhibitors; D003609:Dactinomycin; D003513:Cycloheximide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester