体性感覚 Somatosensory System
O3-9-4-1 マウスバレル野第2/3層におけるスパースで不均一な感覚シナプス入力分布 Sparse and heterogeneous organization of sensory inputs in layer 2/3 of mouse barrel cortex ○喜多村和郎1, 狩野方伸1 ○Kazuo Kitamura1, Masanobu Kano1 東京大学大学院　医学系研究科　神経生理学1, 科学技術振興機構　さきがけ2 Dept Neurophys, Univ of Tokyo, Tokyo1, PRESTO, JST, Japan2 Neurons integrate thousands of synaptic inputs in a highly nonlinear manner and generate distinct patterns of spike output depending on the spatiotemporal input sequences. To understand the mechanism and physiological relevance of single neuronal computation, it is critical to uncover the spatiotemporal patterns of individual synaptic inputs in the intact brain. Recent advances in imaging and recording techniques in the intact rodents can facilitate the analysis for the spatiotemporal patterns of synaptic inputs in vivo (Jia et al., 2010; Chen et al., 2011; Varga et al., 2011; Takahashi et al, 2012; Xu et al, 2012). We used whole-cell patch-clamp recordings in combination with in vivo two-photon calcium imaging to visualize individual sensory synaptic inputs to layer 2/3 neurons in the barrel cortex of mouse. Both spontaneous and sensory-evoked synaptic inputs were very sparse, consistent with very low firing rate in layer 4 and 2/3 neurons in the barrel cortex (Brecht and Sakmann, 2002; Brecht et al., 2003). We found that the spatiotemporal patterns of synaptic inputs were highly heterogeneous. Both spontaneous and sensory-evoked inputs were locally clustered, and vast majority of sensory inputs were directed to a small subset of spines. The results indicate that functionally coupled neurons, which may be synaptically connected or receive common inputs, tend to innervate nearby spines of layer 2/3 neurons. Co-activation of nearby spines might be an efficient way for integrating synaptic inputs elicited by a given sensory stimulus and thus it can enhance the computation of sensory information within a single neuron.	O3-9-4-2 随意運動中の末梢感覚神経集団による運動キネマティクス情報の表現 Population coding of forelimb kinematics in primary sensory afferents during voluntary movements of monkeys ○梅田達也1, 佐藤雅昭2, 川人光男2, 伊佐正1,3, 西村幸男1,3,4 ○Tatsuya Umeda1, Masa-aki Sato2, Mitsuo Kawato2, Tadashi Isa1,3, Yukio Nishimura1,3,4 生理研・認知行動発達1, 国際電気通信基礎技術研究所・脳情報通信総合研究所2, 総研大3, さきがけ4 Dept. of Dev. Neurophysiol. NIPS1, BCI, ATR, Kyoto2, Grad. Univ. Adv. Studies (SOKENDAI)3, PRESTO, JST4 It is well known that the activity of a single peripheral afferent is correlated with joint kinematics of the extremity. Recently, we have shown that the joint kinematics of a passively moved forelimb could be reconstructed from temporal firing pattern of ensembles of dorsal root ganglion (DRG) neurons recorded from anesthetized monkeys. In this study, we investigated whether population of DRG neurons could encode forelimb joint kinematics of behaving monkeys. Two multi-electrode arrays (each array containing 48 channels) were chronically implanted in the DRGs at the level of C7 and C8 spinal segments of two monkeys. Neuronal responses to reaching and grasping movements were simultaneously recorded and 3-D trajectories of hand/arm movements were tracked by using an optical motion capture system. 14 and 25 neurons were recorded in monkey 1 and 2, respectively. The DRG ensemble included muscle spindle, cutaneous and joint receptors. Using a sparse linear regression analysis, forelimb joint kinematics could be reconstructed from the temporal firing pattern of a subset of DRG ensembles (R=0.8 for elbow joint angle, 0.6 for elbow joint angle velocity). Furthermore, we could classify 3 objects with different shapes which a monkey grasped from the activity of DRG ensemble (more than 95% correct). The results indicated that ensemble of peripheral afferents precisely coded forelimb joint kinematics and grasping shape during the voluntary reaching and grasping behavior of monkeys.
O3-9-4-3 Differences in projections from the primary and secondary somatosensory cortex to the trigeminal sensory nuclear complex in the rat ○Md. Haque1, Fumihiko Sato1, Ayaka Oka1, Rieko Takeda1, Fatema Akhter Mst.1, Makoto Higashiyama1, Takafumi Kato1, Atsushi Yoshida1 Department of Oral Anatomy and Neurobiology,Graduate School of Dentistry, Osaka University1 Little is known about projections from orofacial areas of the S1 and S2 to the brain stem including the second-order somatosensory neuron pools. To address this in rats, we first examined the distribution of S1 and S2 neurons projecting to the trigeminal principal nucleus (Vp) or oral subnucleus (Vo) of the trigeminal sensory nuclear complex (TSNC) after injections of a retrograde tracer, Fluorogold (FG), into five regions in the Vp/Vo which were responsive to stimulation of trigeminal nerves innervating the orofacial tissues. A large number of FG-labeled neurons were seen in the S1 and S2 with a contralateral predominance, in a somatotopic manner. This somatotopic arrangement in the orofacial S1 and S2 was shown to closely match that of the orofacial afferent inputs by recording cortical surface potentials evoked by stimulation of trigeminal nerves. We then examined the morphology of descending projections from the defined areas of orofacial S1 and S2 to the brain stem after injections of an anterograde tracer, biotinylated dextranamine (BDA), into the areas. BDA-labeled axon fibers and terminals were seen in the second-order somatosensory neuron pools, most notably in all levels of the contralateral TSNC. Both orofacial S1 and S2 projections terminated somatotopically and both termination patterns were very similar except for the fact that S2 projection did not terminate in the trigeminal interpolar subnucleus. They also showed dorsoventral and mediolateral somatotopy within almost all rostrocaudal TSNC levels. In the Vp or Vo of TSNC, BDA-labeled axon terminals showed a somatotopic arrangement closely matched to that of the electrophysiologically defined projection sites of orofacial primary afferents. The present results suggest that the orofacial S1 and S2 project to the trigeminal second-order somatosensory neuron pools, and the projections may allow the orofacial S1 and S2 to accurately modulate orofacial somatosensory transmission to higher brain centers.	O3-9-4-4 Neuronal basis of target-specific information transfer from primary sensory cortex ○Takayuki Yamashita1, Carl C.H. Petersen1 Laboratory of Sensory Processing, Brain Mind Institute, Faculty of Life Sciences, Swiss Federal Institute of Technology, Lausanne, Switzerland1 Sensory information arriving at primary sensory cortex is discriminated and transmitted to other brain regions according to its features. However, its underlying neuronal mechanisms are unknown. By combining retrograde tracer labeling with in vivo targeted whole-cell recordings we here demonstrate that membrane potential dynamics of layer 2/3 long-range projection neurons in primary somatosensory barrel cortex of awake mice markedly varies with respect to their intracortical axonal targets. The neurons projecting to motor cortex had distinct intrinsic membrane properties and received synaptic inputs with different somatic impacts as compared to those projecting to secondary somatosensory cortex residing in the same barrel column. Furthermore, by integrating kinetics of postsynaptic potentials and internal brain states, these neurons computed a target-specific firing pattern in response to passive and active tactile sensation. Our findings thus reveal distinct subcolumnar neural networks mediating cortico-cortical transfer of tuned information, and provide novel cellular and synaptic mechanisms for sensory discrimination.

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