Functional and anatomical network linking the basal ganglia and cerebral cortex: In vivo MRI study

Abstracts / Neuroscience Research 71S (2011) e46–e107

it could also be applied for the functional electrical stimulation for restoring body movements. Research fund: JST-Presto.

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such stimulus-intensity-specific conditioning is equivalent to the endpoint variability suppression of saccades. doi:10.1016/j.neures.2011.07.382

doi:10.1016/j.neures.2011.07.380

O4-C-2-1 Expression of Foxp2 in mouse cerebellum changes from a homogeneous to a transversely oriented stripe-like pattern during development from embryo to adult Hirofumi Fujita , Izumi Sugihara Systems Neurophisiol., Grad. Sch. of Med., Tokyo Med. and Dent. Univ., Tokyo, Japan Purkinje cells (PCs) are heterogeneous in their molecular expression despite their uniform morphological and functional properties. Molecular expression in PCs differs depending on the developmental stage and on the location of PCs in the cerebellum. For example, aldolase C is expressed in a subpopulation of PCs that are arranged in ‘longitudinal’ (=parasagittal) stripes in the adult. Another molecule, calbindin-D28k, is expressed only in a subpopulation of PCs that are clustered in specific locations in embryo, although it is expressed in all PCs, and is hence a molecular marker for PCs, in the adult. FoxP2, a forkhead box transcription factor involved in vocal communication or language, is strongly expressed in PCs as well as in the forebrain. However, developmental and locational changes in its expression in PCs remain unclear. In the present study we examined Foxp2 expression in the mouse cerebellar cortex systematically by immunostaining serial sections from embryonic day 14.5 to adult. Before postnatal day 6 (P6), all PCs were almost uniformly Foxp2positive except for those in the flocculus. After P6, some populations of PCs gradually became Foxp2-negative. As a consequence, the adult cerebellar cortex displays a transverse stripe-like expression pattern. Double immunostaining for Foxp2 and aldolase C revealed little relationship between their expression patterns. Moreover, the Foxp2 expression pattern in the adult cerebellum indicates a new transverse compartmentalization that does not resemble any other molecular expression patterns so far reported. The functional significance of this transverse compartmentalization is not clear, but Foxp2 expression in the adult mouse cerebellum is not likely to be specifically related to vocal communication. On the other hand, Foxp2 may be involved in the general differentiation of PCs in embryo, and can be useful as a molecular marker for developing PCs. Research fund: KAKENHI20300137. doi:10.1016/j.neures.2011.07.381

O4-C-2-2 A unified theory of cerebellar motor learning for saccadic adaptation and eyeblink conditioning Masahiko Fujita Fac. of Sci. and Eng., Hosei Univ., Tokyo, Japan Saccades show endpoint variability even when made repetitively to the same target while random noise in motor commands and visual uncertainty of target localization seem to degrade accuracy. Cerebellar lesioning can greatly increase the endpoint variability of saccades, and also deprive the saccade system of its ability for rapid adaptation with the double-step paradigm. Since motor noise seems to occur in the upper stream during saccade command generation, feedback control may be ineffective in adjusting the trajectory. Furthermore, even if the rapid adaptation could be completed in a single trial, the reduced (or increased) gain would make a saccade more hypometric (or hypermetric) for a subsequent undersized (or oversized) command. Thus, rapid adaptation alone cannot explain the reduction of variability. This severe challenge to the traditional concepts of cerebellar function can be resolved if the cerebellum encodes noisy input variation as an internal differential representation and combines it with a motor performance result. Motor learning derived from such a causal relationship could perform adaptation and also cancel endpoint and trajectory variability. To implement this function, I have proposed a novel preprocessing step performed by a system comprising Golgi and granule cells that endows the cortex with a universal learning ability. This learning ability not only leads to successful simulations of the rapid adaptation and variability suppression of saccades but also to that of classical eyeblink conditionings. This conditioning simulation shows generalization with respect to the frequency and intensity of the conditioning stimulus and also discrimination of the frequency. Here I propose an experiment that predicts an intensity-specific eyeblink conditioning in which a weak tone will evoke eyeblink while a strong tone will not. Theoretically,

O4-C-2-3 Single-neuron tracing study of thalamocortical projections arising from the rat ventral medial nucleus by using viral vectors Eriko Kuramoto 1 , Sachi Ohno 1,2 , Fumino Fujiyama 1,3 , Takahiro Furuta 1 , Tomo Unzai 1 , Hiroyuki Hioki 1 , Yasuhiro Tanaka 1 , Takeshi Kaneko 1 1

Dept. of Morphol. Brain Sci., Grad. Sch. of Med., Kyoto Univ., Kyoto, Japan Dept. Dental Anesthesiology, Grad. Sch. of Med. and Dent., Kagoshima Univ., Kagoshima, Japan 3 JST, CREST 2

The rat motor thalamic nuclei are composed of ventral medial (VM), ventral anterior (VA) and ventral lateral nuclei (VL). The caudodorsal portion of the VA–VL receives glutamatergic afferents from the cerebellum, whereas the VM and rostroventral portion of the VA–VL receive GABAergic afferents from the basal ganglia. Previously we reported that axonal arborization was different between the rostroventral and caudodorsal VA–VL neurons by using single neuron-tracing method with Sindbis viral vector expressing membrane-targeted GFP. In the present study, the axonal arborization of single VM neurons was examined by the same method, and compared with the previous results of VA–VL neurons. When the axons exited from the thalamus, the reconstructed VM neurons always emitted axon collaterals to the thalamic reticular nucleus as VA–VL neurons. The VM neurons formed less axonal arborization in the striatum than rostrovental VA–VL neurons. In the cerebral cortex, the VM neurons sent axon fibers to more widespread cortical areas than VA–VL neurons, projecting to the primary motor, secondary motor, primary somatosensory, orbital, cingulate and insular areas. Of cortical layers, the axon fibers of VM neurons were most abundantly distributed in layer 1 (78.1 ± 5.6%), especially in the superficial part of layer 1. In comparison with the previously reported data of rostroventral (54%) and cuadodorsal VA–VL neurons (5.6%), VM neurons highly preferred layer 1 to other cortical layers. Although both the VM and rostroventral VA–VL have been reported to receive massive afferents mainly from the basal ganglia, the present results indicate that VM neurons more intensely innervate apical dendrites of pyramidal neurons in more widespread frontal/limbic areas than rostroventral VA–VL neurons. This suggests that, of motor thalamic neurons, VM neurons are most specialized to control the gain of widespread pyramidal neurons simultaneously. Research fund: KAKENHI 20020014, 22700367, 22700368, 17022020, 22300113. doi:10.1016/j.neures.2011.07.383

O4-C-2-4 Functional and anatomical network linking the basal ganglia and cerebral cortex: In vivo MRI study Nobukatsu Sawamoto 1 , Takuya Oguri 1,2 , Hayato Tabu 1 , Hidenao Fukuyama 1 1 Human Brain Research Center, Kyoto University Graduate School of Medicine, Kyoto, Japan 2 Department of Neurology & Neuroscience, Graduate School of Medical Sciences, Nagoya City University

It has been proposed that the basal ganglia, as components of multiple parallel and segregated circuits, integrate and funnels inputs only from several functionally related cortical areas, and then send back outputs to the cortical areas providing the inputs to the circuit (Alexander et al., 1986). The circuits have been proposed to exist at least five, and the corresponding cortical components are the supplementary motor area (SMA), frontal eye fields (FEF), dorsolateral prefrontal cortex (DLPFC), lateral orbitofrontal cortex (OFC) and anterior cingulate cortex (ACC). We investigated whether the proposed five circuits are parallel and segregated, or not, by examining functional and anatomical connectivity between the cortex and striatum in healthy human brain. Resting-state fMRI, diffusion weighted images (DWI) and T1 image of 20 volunteers were acquired on a 3T. With labels on cortical gyri and sulci generated by FreeSurfer and additional criteria, we created masks on the SMA (Mayka et al., 2006), FEF (Paus, 1996), DLPFC (Rajkowska et al., 1995), OFC (Petrides, 2000) and ACC (Vogt et al., 2003). Taking the preprocessed fMRI data, the major Eigen time series in each mask were identified, and the partial correlation scores were calculated for each voxel in the brain. With the preprocessed DWI data, probabilistic tractography was run from the striatum to each cortical mask. Resting-state fMRI showed that spatially restricted zones in the striatum were specifically correlated with each cortical region

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Abstracts / Neuroscience Research 71S (2011) e46–e107

(p < 0.001 uncorrected). DWI also demonstrated that spatially limited zones in the striatum sent tracts to each cortical region (>5% of the maximum probability of connectivity observed for each mask). The two results elucidated not identical but similar spatial profiles. In the overlay, distinct distribution but partial overlap was observed for the five cortical masks. The findings suggest that proposed five circuits are parallel but not completely segregated. doi:10.1016/j.neures.2011.07.384

O4-D-1-1 Maintenance of long-term memory requires persistent regulation of gene expression Yukinori Hirano , Minoru Saitoe Tokyo Metropolitan institute of Medical Science Acquisition of long-term memory (LTM) requires de novo gene expression mediated by CREB. However, the mechanism in which the acquired LTM is maintained remains elusive. We hypothesized that, similarly to LTM acquisition, LTM maintenance may also require regulation of gene expression. If this were the case, memory is not only encoded in individual synapses, so called “synaptic tag”, but also in the nucleus, which we call “memory tag”. Here we provide evidences that support “memory tag” hypothesis in Drosophila. We utilized the spatiotemporal gene expression system, which is targeted to the memory center, the mushroom bodies (MBs). We found that the expression of the dominant negative isoform of CREB in the MBs after LTM acquisition blocked LTM maintenance. Similarly, LTM maintenance was impaired by knockdown of CREB activator, TORC. Therefore, the CREB/TORC pathway is required for maintenance of LTM. The persistent regulation of gene expression may be achieved by epigenetic modulation, such as histone acetylation. In fact, expression of histone deacetylase, RPD3 in the MBs abolished maintenance of LTM. Our results suggest that the CREB/TORC pathway and histone acetylation act as a memory tag, and thus provide the model in which the regulation of gene expression is not only required for LTM acquisition, but also for LTM maintenance. Research fund: Grant-in-Aid for JSPS Fellows (KAKENHI (21-6051)). doi:10.1016/j.neures.2011.07.385

O4-D-1-2 Female-specific enhancement of fear conditioning in mice lacking the serotonin 5-HT4 receptor Kobayashi 1,2

Katsunori , Yasunori Nagahama 1 , Hidenori Suzuki 1,2

Mikahara 1 ,

Kenichirou

1

Dept. of Pharmacol., Nippon. Med. Sch., Tokyo, Japan 2 JST, CREST, Saitama, Japan The central serotonergic system is the important target for pharmacological treatments of psychiatric disorders. We have recently shown that the serotonergic antidepressant fluoxetine can reverse the state of maturation of adult hippocampal neurons and causes marked destabilization of activity levels of mice in their home cages. These effects of fluoxetine were attenuated in mutant mice lacking the serotonin 5-HT4 receptor, suggesting a possible involvement of this subtype of serotonin receptors in cellular and behavioral changes associated with psychiatric disorders. In the present study, in order to reveal the role of the 5-HT4 receptor in regulating behaviors related to psychiatric disorders, we carried out a battery of behavioral tests using 5-HT-deficient mice and their wild-type littermates. In the open-field test, light/dark transition test and elevated plus-maze test, behaviors of the mutant mice were generally intact in both males and females, except for slightly enhanced anxiety-related behavior in the male mutant in the elevated plus maze. Behavioral despair in the forced swim test was also normal However, the female, but not male, mutant mice showed a robust increase in freezing in contextual fear conditioning. The female mutant also showed impaired prepulse inhibition. These results suggest that the 5-HT4 receptor is involved in regulation of contextual fear memory and sensorimotor gating in a female-specific manner. Our finding raises the possibility that the 5-HT4 receptor contributes to emergence of gender differences in mental disorders that are characterized by altered fear memory. doi:10.1016/j.neures.2011.07.386

O4-D-1-3 Parallel gene activation and memory encoding in neocortex during hippocampus-dependent learning Tomonori Takeuchi 1 , Dorothy Tse 1 , Masaki Kakeyama 2 , Yasushi Kajii 3 , Hiroyuki Okuno 4 , Haruhiko Bito 4 , Richard Morris 1 1

Centre for Cognitive & Neural Systems, University of Edinburgh, UK Laboratory of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Japan 3 Pharmacology Research Laboratories I, Mitsubishi Tanabe Pharma Corporation, Japan 4 Department of Neurochemistry, University of Tokyo Graduate School of Medicine, Japan 2

When new learning occurs against the background of established prior knowledge, relevant new information can be readily assimilated and so expand the knowledge base. In our new approach to systems consolidation that incorporates prior knowledge, the assimilation of new paired-associate (PA) memories into existing activated cortical “schemas” proceeds very rapidly (Tse et al., Science, 2007). Learning of PAs (flavours and places) always requires the hippocampus with, for lasting memory, novelty-triggered cellular consolidation of PAs in hippocampus as an essential first step in the encoding of new information later assimilated into schemas. What remains poorly understood is whether such information is then, in a bottom-up manner, transferred to the neocortex over time (“trace transfer” hypothesis) or may be simultaneously encoded in the cortex (“parallel encoding” hypothesis) and so potentially reflect top-down influences. We now report that the hippocampal-dependent learning of new PAs is associated with a striking upregulation of 2 immediate early genes (Zif268 and Arc) in the prelimbic region of the medial prefrontal cortex that was non-monotonic with respect to the extent of learning-associated novelty. Pharmacological interruption of AMPA and NMDA receptors in prelimbic cortex during new PA encoding results in a failure of memory tested 24 h later. Furthermore, the cued-recall of both original and new PA information requires AMPA but not NMDA receptor transmission in prelimbic cortex at the time of memory trace reactivation. These findings indicate that, at least for the assimilation of rapidly acquired new PA information into existing cortically based mental schemas, there is parallel encoding of information in the cortex during rather than after hippocampal-dependent learning, and that this parallel encoding is essential for long-term memory. doi:10.1016/j.neures.2011.07.387

O4-D-1-4 Object recognition memory deficit by dyshomeostasis of synaptic zinc in the hippocampal CA1 Masatoshi Nakamura , Atushi Takeda, Shunnsuke Takada, Masaki Anndou, Naoto Oku Dept. of Med. Biochem. Grad. Sch. of Pharm. Sci., Univ. of Shizuoka, Japan Hippocampal chelatable zinc (Zn2+) signaling may participate in synaptic plasticity such as long-term potentiation (LTP) that is a cellular model for memory. Clioquinol (5-chloro-7-iodo-8-hydroxyquinoline; CQ) forms lipophilic chelates with cations such as Zn2+ and has used for selective modulation of Zn2+ pools. Acute exposure to CQ affects object recognition memory, suggesting that transient lack of Zn2+ is involved in recognition memory deficit. In contrast, excess of Zn2+ can be neurotoxic under pathological conditions. It is possible that the bidirectional actions of Zn2+ are observed in hippocampal LTP induction and recognition memory. CQ also serves as an ionophore for zinc. The present study examined an idea that a moderate increase in Zn2+ in the hippocampus transiently elicits object recognition memory deficit. It was found that Zn–CQ prepared (CQ:Zn = 2:1) is much more toxic in young rats than CQ and ZnCl2; 70% of rats i.p. injected with Zn–CQ (98.1 ␮mol/kg) was died within 24 h, suggesting that cellular uptake of excessive zinc is linked to the toxicity. To check the action of Zn–CQ in brain function, CA1 LTP was induced in hippocampal slices after i.p. injection of Zn–CQ (9.8 ␮mol/kg). CA1 LTP was significantly attenuated in hippocampal slices prepared 2 h after the injection, but not 6 h after the injection. Two hours after the injection, intracellular Zn2+ measured with ZnAF-2DA were significantly increased in the CA1 pyramidal cell layer and object recognition memory deficit was observed. Furthermore, in vivo hippocampal LTP recording indicated that CA1 LTP, unlike dentate gyrus LTP, is attenuated 2 h after the injection. Object recognition memory deficit was observed after injection of ZnCl2 and Zn–CQ into the CA1, unlike the dentate gyrus. The present study suggests that object recognition memory deficit is linked to the preferential increase in intracellular Zn2+ and/or the preferential vulnerability to Zn2+ in the CA1. doi:10.1016/j.neures.2011.07.388