基底核
Basal Ganglia
O1-9-5-1
外側毛帯による嚥下運動の調節機構
Contribution of the lateral lemniscus to the control of swallowing in decerebrate cats

○高草木薫1,2, 太田亮3
○Kaoru Takakusaki1,2, Ryo Ohta3
旭川医大・医・脳機能医工学研究センター1, 東京大院・工・精密工学2, 旭川医大・医・頭頸部外科学講座3
Reserach Center for Brain Function and Medical Engineering, Asahikawa Med. Univ. Asahikawa1, Dept Precision Eng. Univ. Tokyo, Tokyo2, Dept Head & Neck Surg, Asahikawa Med Univ, Asahikawa3

The present study was designed to test following two hypotheses;1) whether neurons in dorsal nucleus of the lateral lemniscus (LLD), a relay nucleus of auditory sensation in the brainstem, contributed to the control of swallowing, and 2) whether GABAergic projection from the substantia nigra pars reticulata (SNr), a basal ganglia output nucleus, to the LLD modulated swallowing. In acutely decerebrated cats (n=14), swallowing was induced by electrical stimulation (20-80 μA at 10 Hz for 20 s) delivered to the superior laryngeal nerve (SLN). Electrical stimulation (30-50 μA at 50 Hz for 10-20 s) applied to the LLD increased the frequency and reduced the latency to the onset of the SLN-induced swallowing. Microinjections of NMDA (0.1-0.15 μl, 5.0-10 mM) into the LLD through a stereotaxically placed glass micropipette facilitated the SLN-induced swallowing, i.e., frequency was increased and the latency to the onset of the swallowing was decreased. We also injected muscimol, a GABAA receptor agonist, bicuculline, a GABAA receptor antagonist, and baclofen, a GABAB receptor agonist, into the LLD (0.1-0.15 μl, 5.0 mM for each). It was observed that injections of muscimol suppressed the SLN-induced swallowing. While injections of bicuculline facilitated the swallowing, injections of baclofen did not alter the swallowing. On the other hand, repetitive electrical stimulation (20-60 μA at 50-100Hz) applied to the dorsolateral part of the SNr suppressed the SLN-induced swallowing. The suppressive effects were prevented by injections of bicuculline into the LLD. These results suggest that glutamatergic and GABAergic receptors on LLD neurons are involved in the modulation of swallowing. Moreover GABAergic basal ganglia efferents to the LLD may contribute to the audiomotor control of swallowing. Because GABAergic output from the SNr is considered to be overactive in Parkinson's disease, the present findings are discussed in relation to the pathogenesis of dysphagia in this disease.
O1-9-5-2
ジュウシマツのさえずりの時間構造とその制御メカニズム
Control mechanism of temporal pattern in birdsong of Bengalese finch (Lonchura striata var. domestica)

○橘亮輔1, , 岡ノ谷一夫1
○Ryosuke O. Tachibana1, Neal Hessler1, Kazuo Okanoya1
東京大院・総合文化1
Dept Life Sci, Univ of Tokyo, Tokyo1

Learning and maintenance of songbird vocalizations requires precise control of both spectral and temporal structure. It has been previously demonstrated that the anterior forebrain pathway (AFP), which is a homolog of mammalian cortico-basal ganglia circuits, is critical for juvenile learning and adult maintenance of spectral features of song, such as fundamental frequency and spectral entropy. Here we examined the capability of adult Bengalese finches (Lonchura striata var. domestica) for adaptive adjustment of song temporal structure, and the contribution of the AFP in such plasticity. We have developed a real-time processing system to detect specific syllables in ongoing song using a digital signal processor. The processor evaluates acoustic features of ongoing song in 2-ms windows and detects a targeted syllable by a template matching algorithm based on cepstral coefficients. Inter-syllable gaps were calculated with 1-ms temporal resolution. During the noise-avoidance experiment a brief noise burst was presented to birds immediately after detection of target syllable when the gap duration between target and preceding syllables was longer (or shorter) than a threshold level. Preliminary results showed that birds could modify these gap durations to avoid aversive noise stimuli. Destructions of AFP disabled such adaptive control of gap duration. These results suggest that a capacity for active maintenance of local temporal structures is retained in adult songbirds, and depends on input from the AFP.
O1-9-5-3
ラット線条体における発火の延長の維持
Sustainment of Prolonged Firing in Rat Striatum

○太田宏之1, 山口良哉2, 佐藤義明3, 西田育弘1
○Hiroyuki Ohta1, Yoshiya Yamaguchi2, Yoshiaki Sato3, Yasuhiro Nishida1
防衛医科大学校生理学講座1, 玉川大学脳情報研究科2, 帝京平成大学3
Dept Physiol, National Defense Medical College, Saitama1, Tamagawa Univ, Tokyo2, Teikyo Heisei Univ. Tokyo3

The cortico-basal ganglia networks are considered to be important for reward-based action selection and learning. Although many neurophysiological studies suggested that neurons localized in the basal ganglia are involved in these processes, how the neural system reflects the reward outcome to the chosen action is poorly understood. In reward-based learning, reward signal is significantly delayed after the action occurs. To associate action with reward, the neural system needs to use the sustained neural activities. Here, we focus on the striatum, the major input structure of the basal ganglia, and show sustained firing and its time development. We employed the acute slice of the Wistar Thy-1.2 promoter ChannelRhodopsin-2 Venus Rat and LED based local photostimulation techniques. We recorded from striatal neurons by a tetrode with photostimulation of the striatum. Striatal neurons that responded to photostimulation showed residual firings after the end of 1 sec-long photostimulation. Furthermore, the onset and the offset of the sustained firings were accelerated and prolonged, respectively, during repetitive stimulations. The speed of time development of the acceleration and the prolongation strongly correlated with the frequency of the repetitive stimulations. The developed prolongation was carried over during tens of seconds of intermission. These phenomena indicate that the neurons in the striatum can mediate their input sensitivity over time.

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