Hiroyuki Takuwa

Effects of Self-Generated Wind on Compensational Recovery of Escape Direction in Unilaterally Cercus-Ablated Crickets, Gryllus bimaculatus

Abstract The effects of self-generated wind on the compensational recovery of escape direction were investigated in unilaterally cercus-ablated crickets, Gryllus bimaculatus. To separate walking and self-generated wind during walking, unilaterally cercus-ablated crickets were placed on a styrofoam ball that was easily rotated by leg motion during walking. The stationary walking on the ball did not produce self-generated wind, because no body motion occurred. Crickets that were trained on the ball but given no artificial air puff for 14 days after cercal ablation did not show any compensational recovery of escape direction. Therefore, spontaneous walking itself was not sufficient to compensate the wind-evoked escape direction in the crickets. Artificial air puffs from the anterior direction synchronized with the stationary walking were effective for the compensational recovery of escape direction, but those from the posterior direction were not. As most of the spontaneous walking was directed to the forward direction, only an artificial air puff from the anterior direction coincided well with actual self-generated wind occurring during the onset of normal walking. Therefore, self-generated wind during walking seems essential for the compensational recovery of escape direction in unilaterally cercus-ablated crickets. When artificial air puffs were unsynchronized with walking, no compensational recovery was observed. This result suggests that artificial air puffs should be given just after the onset of spontaneous walking. Otherwise, the artificial air puffs may not be recognized as self-generated wind.

Sensitive period in which walking affects recovery of direction of wind-evoked escape in the cricket Gryllus bimaculatus.

Abstract Unilaterally cercus-ablated crickets, Gryllus bimaculatus, were reared in an apparatus that induced walking artificially. In the crickets that experienced different distances of enforced walking per day, the directionality of escape was investigated before and 1, 4, 7, 10, 13, and 16 days after the ablation of the cercus. The crickets that walked a longer distance per day showed a quicker and a higher degree of compensational recovery of the escape direction than the crickets that walked a shorter distance per day, even after walking the same distance. Thus, the time course and amount of compensational recovery from cercal ablation depend on when crickets experience walking during the recovery period. During the recovery period, unilaterally cercus-ablated crickets were subjected to walking at different times to determine the most effective period in which walking affects the compensational recovery of escape direction. The compensational recovery of the escape direction occurred only in crickets experiencing walking in early periods after the ablation. In particular, walking experienced 2–6 days after the ablation was most effective for the compensational recovery. On the other hand, no compensational recovery occurred in crickets experiencing walking in later periods after the ablation. These results suggest that there is a sensitive or critical period in which walking affects the compensational recovery of escape direction.

Rearing Under Different Conditions Results in Different Functional Recoveries of Giant Interneurons in Unilaterally Cercus-Ablated Crickets, Gryllus bimaculatus

Abstract The effects of rearing conditions on the functional recovery of wind-sensitive giant interneurons (GIs) after unilateral cercal ablation were investigated in the cricket, Gryllus bimaculatus. Crickets were reared in a glass vials to prohibit free walking for 14 days after unilateral cercal ablation (“14-day vial” crickets). Other crickets were reared in an apparatus called a “walking inducer” (WI) to increase the walking distance during the same 14-day period (“14-day WI” crickets). In these crickets, the response properties of GIs 8-1, 9-1, 9-2, and 9-3 to air currents from various directions were investigated. From the intensity-response curves obtained, directionality curves expressed in terms of threshold velocity and response magnitude were made independently. To understand changes in the functional recovery of GIs more thoroughly, the directional characteristics of GIs in crickets 1 day after unilateral cercal ablation (“1-day free” crickets) were also compared. Between the 1-day free and 14-day vial crickets, all the GIs showed differences in both threshold velocity and response magnitude for some stimulus directions. Between the 14-day vial and 14-day WI crickets, differences in the threshold velocities of GIs 9-1, 9-2, and 9-3, and in the response magnitudes of GIs 8-1, 9-1, and 9-3 were detected. Because the rearing condition after unilateral cercal ablation largely affects the compensatory recovery in some parameters of wind-evoked escape behavior, such as relative occurrence and escape direction, we discuss the functional differences in GIs revealed here in relation to the roles of GIs in the neural system that controls escape behavior.

Effects of the Delay and Duration of Self-generated Wind on Behavioral Compensation in Unilaterally Cercus-ablated Crickets, Gryllus bimaculatus

The effects of the delay and duration of wind self-generated during walking on the compensational recovery of escape direction were investigated in unilaterally cercus-ablated crickets, Gryllus bimaculatus. Artificial self-generated winds (self-stimulations; hereafter, SSts) from a nozzle set in front of a cricket placed on a styrofoam ball for stationary walking were used for training after unilateral cercus ablation. The delay and duration of artificial SSts were separately controlled. When the stimulus duration was fixed to 100 msec, the crickets trained with artificial SSts of 1000 msec delay showed a compensational recovery of the escape direction. However, no such compensational recovery was observed in crickets trained with artificial SSts of 1200, 1500, and 2000 msec delays. The relationship between the delay and duration of artificial SSts for compensational recovery was investigated. An artificial SSt with a longer delay required a longer-duration air current to cause a recovery of the escape direction. In contrast, an artificial SSt with a shorter delay was effective even when the duration was short. On the basis of the results obtained in the present study, we propose a hypothesis to explain the initial step for the compensation, that is, how the delay and duration of SSts are traded in terms of the compensational recovery of the escape direction.

Sensitive Period for the Recovery of the Response Rate of the Wind-Evoked Escape Behavior of Unilaterally Cercus-Ablated Crickets (Gryllus bimaculatus)

We examined the compensational recovery of the response rate (relative occurrence) of the wind-evoked escape behavior in unilaterally cercus-ablated crickets (Gryllus bimaculatus) and elucidated the existence of a sensitive period for such recovery by rearing the crickets under different conditions. In one experiment, each cricket was reared in an apparatus called a walking inducer (WI) to increase the sensory input to the remaining cercus, i.e., the self-generated wind caused by walking. In another experiment, each cricket was reared in a small plastic case separate from the outside atmosphere (wind-free: WF). In this rearing condition, the cricket did not experience self-generated wind as walking was prohibited. During the recovery period after the unilateral cercus ablation, the crickets were reared under either the WI or WF condition to investigate the role of the sensory inputs on the compensational recovery of the response rate. The compensational recovery of the response rate occurred only in the crickets reared under the WI condition during the early period after the ablation. In particular, WI rearing during the first three days after the ablation resulted in the largest compensational recovery in the response rate. In contrast, no compensational recovery was observed in the crickets reared under the WF condition during the first three days. These results suggest that a sensitive period exists in which sensory inputs from the remaining cercus affect the compensational recovery of the response rate more effectively than during other periods.

Effects of Visual Information on Wind-Evoked Escape Behavior of the Cricket, Gryllus bimaculatus

We investigated the effects of visual information on wind-evoked escape behavior in the cricket, Gryllus bimaculatus. Most agitated crickets were found to retreat into a shelter made of cardboard installed in the test arena within a short time. As this behavior was thought to be a type of escape, we confirmed how a visual image of a shelter affected wind-evoked escape behavior. Irrespective of the brightness of the visual background (black or white) or the absence or presence of a shelter, escape jumps were oriented almost 180° opposite to the source of the air puff stimulus. Therefore, the direction of wind-evoked escape depends solely depended on the direction of the stimulus air puff. In contrast, the turning direction of the crickets during the escape was affected by the position of the visual image of the shelter. During the wind-evoked escape jump, most crickets turned in the direction in which a shelter was presented. This behavioral nature is presumably necessary for crickets to retreat into a shelter within a short time after their escape jump.

Cerebellar complex spikes encode movement in intrinsic coordinate frames

s / Neuroscience Research 58S (2007) S1–S244 S93 P1-e0 7 Quantitative analysis of inputs to projection neurons from the neocortex or the thalamus in the rat neostriatum Takahiro Sonomura1, Takahiro Furuta2, Keiko O. Furuta2, Tomo Unzai2, Haruki Iwai1, Masanori Uemura1, Takeshi Kaneko2,3 1 Department of Anatomy for Oral Sciences, Kagoshima University, Kagoshima, Japan; 2 Department of Morphological Brain Sciense, Kyoto University, Kyoto, Japan; 3 CERST, Japan Projection neurons in the neostriatum are composed of at least two groups: striatopallidal neuron group and striatonigral neuron group. These projection neurons resceive excitatory inputs from the neocortex and the thalamus. In this study, we quantitatively analysed the relation between the two groups of the projection neurons and two kinds of inputs in the neostriatum. Dendrites of projection neurons in the neostriatum were visualized by a recombinant virus vector which labeled the infected neurons in a Golgi stain-like fashion. Axon terminals input to projection neurons in the neostriatum from the neocortex or the thalamus were stained by the immunofluorescence method. The appositions of the dendrites to the inputs were observed three-dimensionally with a confocal laser-scanning microscope. Some appositions were examined electron-microscopically and calculated the densities of inputs. Research funds: KAKENHI (17791305) (18019017) P1-e0 8 Effects of task requirements on the brain activity in the coincident timing task Tatsuyuki Ohtsuki1, Akiko Kagajo1, Hiroshi Kadota2, Yashoichi Nakajima2, Kimitaka Nakazawa2, Kazutoshi Kudo1 1 Department of Life Sciences, University of Tokyo, Tokyo, Japan; 2 Research Institute, National Rehabilitation Center for Persons with Disabilities, Japan Subjects intercepted a moving visual target on the screen at the designated point using a cursor manipulated by handgrip force. Timingand position (= force) errors were converted to the score. Two conditions of lowand high task requirement were prepared in each block of trials to manipulate psychological pressure. In the high-requirement condition (condition P), if the subject could not obtain a preset criterion score, the total score of that block was nullified, while if he could, obtained score was doubled. In the low-requirement condition (condition C), obtained score was kept intact. Anxiety level was higher in condition P and in failed block. Timing error decreased and force error increased in condition P. An fMRI imaging revealed enhanced activity of amygdala and SMA, and depressed activity of prefrontal cortex in condition P, suggesting high psychological pressure and anxiety modifies the working memory and motor planning. Research fund: KAKENHI (16300206) P1-e0 9 Balance control of the virtual inverted pendulum: Effects of experimentally introduced time delays Hirohito Sawahata, Hitoshi Tsuzuki, Ryohei Ochiai, Takashi Yamaguchi HSAFE, Yamagata University, Yonezawa, Yamagata, Japan To understand how humans use openand closed-loop control in visually guided movement, we constructed a virtual inverted pendulum (VIP); its dynamics was simulated within a computer (its temporal characteristics could be changed), and subjects could stand it in a display by moving a mouse according to visual feedback. The present study examined effects of time delay (0–400 ms) additionally introduced between subject’s action and movement of the VIP bottom on balance control of the VIP (that was equivalent to a 1 m-rod in the gravity field of 0.2 G (G = 9.8 m/s2)). As results, (1) in control (time delay, 0 ms) subjects intermittently moved the VIP. Each action showed bell-shaped velocity profile with duration of ca. 150 ms (“go” phase). Between subsequent “go” phases a “stop” phase was intercalated, in which the VIP bottom remained still. (2) Introduction extra time delays decreased occurrence of “stop” phase. Appearance of continuous “go” without intercalated “stop” could be related to the openloop control based on the prediction of on-going planned action. P1-e10 Cerebellar complex spikes encode movement in intrinsic coordinate frames Yoshiaki Tsunoda1, Wataru Matsui1, Hiroyuki Takuwa3, Strick Peter2, Hoffman Donna2, Shinji Kakei1 1 Department of Behavioral Neuroscience, Tokyo Metropolitan Institute for Neuroscience, Japan; 2 Center for the Neural Basis of Cognition, University of Pittsburgh School of Medicine, USA; 3 Ehime University, Japan What triggers complex spikes (CS) of cerebellar Purkinje cells (PC) is a crucial issue for understanding the cerebellum. There is a well-known spiky increase of the CS discharge around onsets of visually guided forelimb movements. We examined whether the increased discharge is triggered by the visual stimulus or any other intrinsic signals, such as motor commands. We used a wrist movement task that introduced a delay between the presentation of a target and the go signal for movement initiation. The CS discharge was tightly linked to the movement onset rather than to the go signal. Furthermore, directional selectivity of the CS discharge covaried for a change in posture, indicating encoding in intrinsic coordinate frames. These results suggested that the discharge of the CS is triggered by an internal signal, such as efference copies, rather than a visual stimulus associated with the go signal. Research funds: PRESTO/JST, MESSC (SK) P1-e11 Rhythm learning in the monkey Naho Konoike, Shigehiro Miyachi, Akichika Mikami Section of Brain Research, Primate Research Institute, Kyoto University, Aichi, Japan Rhythm is a fundamental aspect of our motor behaviors. It is important not only in music, but also in any skilled behaviors. However, the neural basis of rhythm is largely to be studied. To study the neural mechanisms of rhythmic motor control, we have trained two monkeys on a rhythmic button press task. In this task, the monkeys were required to press an LED button when it flashed with or without a tone. The button flashed six times (beats) with an isochronous rhythm (inter-beat interval: 750, 1000, or 1500 ms), a complex rhythm (combination of two intervals), or random intervals. The monkeys did learn the rhythms as indicated by the shortening of the reaction time. The monkeys’ performance was compared to that of human subjects. Both monkeys and humans learned faster rhythms better. For the complex rhythms, both species performed better with the 750/1500 ms intervals (1:2 rhythm) than with the 750/1000 ms intervals (1:1.33 rhythm). These results suggest that the monkeys and humans share the basic mechanisms of rhythmic motor control. P1-e12 Continuous information flow decreases the activity of continuous information flow decreases the activity of supplementary motor area (SMA) in coincident timing task Kazutoshi Kudo1, Hiroshi Kadota2, Yashoichi Nakajima2, Kimitaka Nakazawa2, Tatsuyuki Ohtsuki1 1 Department of Life Sciences, University of Tokyo, Tokyo, Japan; 2 National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan The environment surrounding us is abundant. Therefore, different types of information can specify the same event. For example, a certain time in the future can be specified by two consecutive onsets of stimuli as well as by continuous time-to-arrival information. We investigated human brain activity in interval and interceptive timing tasks, in which discrete and continuous information specifying the same timing was provided, respectively. Brain activity was recorded by 1.5 T fMRI when participants performed the tasks. Results showed that the SMA was activated more strongly in the interval timing task than in the interceptive timing task, suggesting that different neural networks are activated for timing control depending on different information provided to specify the same timing. Research fund: KAKENHI (17500416)