Long term memory, late LTP and gene expression

Abstracts neuronal representations are different in VS and DS. In this study, we recorded neuronal activity from the dorsolateral striatum (DLS), the dorsomedial striatum (DMS), and VS of rats performing a choice task in which a rat should select a left or right hole poking to obtain a pellet delivered stochastically. We found that the information of action represented before the choice behavior (action command) was higher in DS than in VS. On the other hand, the reward information represented after a tone informing reward availability was opposite, namely, higher in VS than in DS. Our findings suggest a functional dissociation in the striatum, consistent with previous imaging and lesion previous studies. doi:10.1016/j.neures.2009.09.505

P1-i04 Implication of hippocampal dopamine in the conditioning of the rewarding effect of cocaine Tomoko Tanaka 1,2 , Nobuyuki Kai 3 , Kazuto Kobayashi 3 , Naoyuki Hironaka 1 1

SHIMOJO Implicit Brain Function Project, JST, Kanagawa, Japan; 2 Section of Psychiatry and Behavioral Sciences, Tokyo Medical and Dental University Graduate School, Tokyo, Japan; 3 Department of Molecular Genetics, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima, Japan Dopamine receptors express in medial temporal lobes and midbrain regions and have important roles of contextual learning. Meanwhile, repeated intake of cocaine lead to the development of addiction. Dopamine plays a major role in the rewarding effects of cocaine. In this study, we verified that acute cocaine treatment enhanced dopamine release in hippocampus. Furthermore, we trained animals in a CPP apparatus. Animals were later tested for their place preference in a drug-free state and sacrificed to assess dopamine D1A receptor. As a result, protein and mRNA levels of dopamine D1A receptor increased at several phases of CPP. The results of these experiments demonstrated several ways in which the dopamine neuron in hippocampus is important in cocaine associated contextual learning.

S111

retrieval of information to and from the ITC and agree with previous results that showed PFC as source of top-down signal in memory retrieval. doi:10.1016/j.neures.2009.09.509

P1-i08 Abnormality in the left–right asymmetry of the brain affects spatial learning: behavioral studies in iv mice Kazuhiro Goto 1 , Ryo Kurashima 2 , Hayato Gokan 2 , Naomi Inoue 2 , Isao Ito 3 , Shigeru Watanabe 2 1

Kokoro Research Center, Kyoto Univ, Kyoto, Japan; Japan; 3 Kyushu Univ, Fukuoka, Japan

2

Keio Univ, Tokyo,

Left–right (L–R) asymmetry is a fundamental feature of higher order neural function but how it affects learning is yet unknown. We recently reported that the inversus viscerum (iv) mouse hippocampus lacks the L–R asymmetry and that it exhibits right isomerism in the synaptic distribution of NMDA receptor ␧2 (NR2B) subunits. In this study, we examined how the L–R asymmetry in hippocampus affects spatial learning using a dry maze and an operant spatial delayed nonmatching to sample (SDNMTS). In the dry maze, mice were trained to search for a baited food in the open-field and thus examining the acquisition of long-term memory. In contrast, in the SDNMTS, mice were required to remember the lever position and retrieve it after some delay intervals, thus examining the retention in short term. In both tasks, iv mice performed poorer than its control, suggesting that the L–R asymmetry in hippocampal circuitry affects both the acquisition of long-term memory and retention of short-term memory. doi:10.1016/j.neures.2009.09.510

P1-i09 Cantor coding performance of hippocampal CA1 pyramidal neurons in relation to interval of input sequence Yasuhiro Fukushima 1 , Minoru Tsukada 1 , Ichiro Tsuda 2,3 , Yutaka Yamaguti 2 , Shigeru Kuroda 2 1

doi:10.1016/j.neures.2009.09.506

P1-i05 Long term memory, late LTP and gene expression Chikafusa Bessho, Reiko Kido, Hajime Nakatsuka Department Physical Sci., Kyoto Sangyo University, Kyoto, Japan Long-term memory (LTM) is thought to require gene expression and late memory related genes in rat hippocampus in water maze learning have been identified by RNA fingerprinting and DNA microarray. Long-term potentiation (LTP) is one kind of brain plasticity and thought to be a basic mechanism of explicit memory. Late LTP (l-LTP) is dependent on mRNA and protein synthesis. In order to study the relation between l-LTP and LTM in water maze learning, l-LTP in acute brain slices of mouse was induced by 4 train tetanus stimulus (100 Hz) and recorded by multi electrode dish (MED) system and the gene expression was analyzed by RT-PCR. Ryanodine receptor type 2 (RYR2) gene strongly expressed but glutamate dehydrogenase (GDH) gene expression did not change compared to the control brain slice without tetanus stimulus. The senescence accelerated prone mouse (SAMP8) shows the learning and memory deficits and is a good model of age-related cognitive decline. SAMP8 mouse did not learn and memorize in water maze training and RGR2 gene expression in the hippocampus was not detected. We are trying to study the EPSP and LTP in the brain of SAM. doi:10.1016/j.neures.2009.09.507 doi:10.1016/j.neures.2009.09.507

P1-i07 Prefrontal neurons encode associative information in visual pair-associations Jorge M. Andreau 1 , Shintaro Funahashi 1,2 1

Kyoto Univerity, Japan;

2

Kokoro Res. Ctr., Kyoto University, Kyoto Japan

Our memories are mostly organized in an associative way. Previous studies showed that the inferotemporal cortex (ITC) participates in encoding and retrieving pairs of visual stimuli during the pair-association (PA) task. Lesion studies in monkeys showed that connections between the ITC and the prefrontal cortex (PFC) are important to perform a visual–visual association task. To understand the participation of PFC in PA, we trained two monkeys to perform a visual PA task and a familiar/nonfamiliar (FNF) task. We found that PFC neurons encode pairs of stimuli stronger than ITC neurons during PA. But, this difference was not observed during FNF. The mean response latency during the sample period was 138 ms, which was longer than the latency of the bottom-up signal but faster than the latency of the top-down signal observed in the ITC. These results indicate that PFC participates in encoding and

Brain Sci. Inst., Tamagawa University, Tokyo, Japan; 2 RIES, Hokkaido University, Hokkaido, Japan; 3 Department Sci., Hokkaido University, Hokkaido, Japan In hippocampal CA3–CA1 network, Tsuda (2001) and Tsuda and Kuroda (2001, 2004) theoretically predicted the possibility of Cantor coding. Cantor coding provides an information coding scheme for temporal sequences of events. Our previous study showed the physiological evidence of Cantor coding in rat hippocampal CA1 neurons (Fukushima et al., 2007; Kuroda et al., submitted). Recently, Yamaguti (submitted) showed that the performance of Cantor coding sensitivity is dependent on interval of input sequence in two-compartment modeled neurons. However, the sensitivity is not confirmed physiologically. In order to confirm this, we applied electrical stimulation of input sequence at several intervals, and the responses were recorded from rat hippocampal CA1 pyramidal neurons. Our results showed that self-similar property related to Cantor coding was dependent on interval of input sequence. doi:10.1016/j.neures.2009.09.511

P1-i10 Enhancement of prepulse inhibition by fear conditioning in mice Daisuke Ishii 1 , Daisuke Matsuzawa 1 , Yuko Fujita 2 , Chihiro Sutoh 1 , Kenji Hashimoto 2 , Masaomi Iyo 2 , Eiji Shimizu 1 1

Department Physiol, University of Chiba, Chiba, Japan; chiatry, University of Chiba, Chiba, Japan

2

Department Psy-

Prepulse inhibition (PPI) is one of the few and major paradigms for investigating sensorimotor gating systems in humans and rodents in similar fashion. PPI deficits are observed in patients with schizophrenia or anxiety disorders. Previous studies have shown that PPI in rats can be enhanced by auditory fear conditioning (Li et al., 2008). In this study, we evaluated the effects of contextual fear conditioning (FC) for six times a day and fear extinction (FE) for seven days on PPI in mice. C57BL/6J mice (male, 8–12 weeks) were divided into three groups; no-FC (control), FC only and FC + FE. We measured PPI at the following three time points, (1) baseline before FC, (2) after FC, and (3) after FE. The results showed that PPI increased in both groups of FC and FC + FE. No significant differences among all groups were found in the Acoustic Startle Response (ASR) without prepulse. In conclusion, it was suggested that the enhanced PPI following FC might be maintained even after FE. doi:10.1016/j.neures.2009.09.512