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- P-ISSN1226-9654
- E-ISSN2733-466X
- KCI
ISSN : 1226-9654
Vol.14 No.1
Abstract
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Abstract
It is well known that in two-way active avoidance learning, animals that can avoid footshock successfully after extensive training show reduced fear or no fear at all to the stimulus (i.e., CS) used in the training. However, recent studies reported that animals with extensive avoidance training still show significant fear to the CS. The present study examined whether this discrepancy is due to context discrimination. That is, if extensively trained animals can discriminate between fear-testing and avoidance learning situations, then they would know that no shocks follow the CS in the testing situation, and consequently, show reduced fear to the CS. Flats were divided into 2 groups: A preexposure group that received 24 presentations of CS alone in fear-testing box before avoidance learning, and a non-preexposure group that received avoidance training without preexposure to the testing situation. Both groups received 15 avoidance training trials on day 1, and were trained to the criterion of 27 consecutive avoidance responses on day 2. The fear-testing results indicate that while the non-preexposure group had normal level of conditioned fear to the CS, the preexposure group showed reduced fear to the CS. These findings support the context discrimination hypothesis and suggest that extensive avoidance training does not necessarily reduce fear to the CS.
Abstract
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Abstract
This study assessed whether frontal brain asymmetry(FBA) could predict affective style and personality trait. Electroencephalographic(EEG) activity was recorded from 23 right-handed female adults participants during eight 1-min baseline resting periods. Four baselines were conducted with eyes open, and four were administered with eyes closed. Counterbalanced orders were used for the eyes-open and eyes-dosed conditions of the resting baselines. Mean alpha power asymmetry was extracted in midfrontal(F3, F4), lateral frontal(F7, F8), and anterior temporal(T3, T4) regions. For lateral frontal region, but not the midfrontal and anterior regions, there was a significant relationship between relative left hemispheric activation and extraversion. For midfrontal and lateral frontal regions, there was a significant relationship between relative right hemispheric activation and depression. Theoretical and methodological implications of these findings are discussed.
Abstract
It has been shown that nitric oxide(NO) is a mediator of nerve injury or the physiological response to injury. The present study was conducted to determine whether NO synthase(NOS) inhibitor enhances functional recovery after nerve injury or not. Under pentobarbital anesthesia, male Sprague-Dawley rats were subjected to one of four different types of sciatic nerve injury (crush, cut, ligation, and sham injury models). The rats received i.p. injections of N<sup>ω</sup>-nitro- L-arginine methyl ester(L-NAME), a NOS inhibitor, for ten days from the day of surgery. Twenty five days after injury, the rats were anaesthetized with urethane and the compound muscle action potentials(CMAPs) were recorded following sciatic nerve stimulation. L-NAME significantly shortened the latencies of the CMAPs in crush injury model compared to the vehicle treated rats. In the case of cut or ligation injury model, L-NAME tended to shorten the latencies but the differences between L-NAME and vehicle treated rats were not statistically significant. These results suggest that L-NAME facilitates functional recovery after sciatic nerve injury.
Abstract
Acidic fibroblast growth factor(aFGF) has been shown to increase regeneration across a gap between the proximal and distal stumps of a transected nerve. In the present study, we examined sensory axon regeneration using an electrophysiological technique in order to investigate the effects of aFGF on regeneration of peripheral nerve axons after injury. Under pentobarbital anesthesia, male Sprague-Dawley rats were subjected to one of three different types of injury(crush, ligation, and sham injury models). The rats received i.v. injections of aFGF for ten days from the day of surgery. Twenty five days after injury, the rats were anaesthetized with urethane and the somatosensory evoked potentials(SSEPs) were recorded following sciatic nerve stimulation. aFGF significantly shortened the latencies of the SSEPs in crush injury model compared to the vehicle treated rats. In the case of ligation injury model, aFGF tended to shorten the latencies but the differences between aFGF and vehicle treated rats were not statistically significant. These results suggest that aFGF facilitates functional recovery after sciatic nerve injury.
Abstract
It is very important to develop effective method to relieve neuropathic pain which may be produced by nerve or tissue injury. This study was conducted to determine interaction between opioid and NMDA systems in the modulation of sympathetically independent neuropathic pain. Under halothane anesthesia, the tibial and sural nerves of male Sprague-Dawley rats were ligated and cut. Fourteen days after injury, the rats were reanesthesized by urethane and subjected to iontophoretic experiment. Opioid agonists such as DAMGO (µ), DALDA (δ), and bremazocine (K) were ejected microiontophoretically. MK-801, an NMDA antagonist, was injected intravenously. Microiontophoretically ejected DAMGO more robustly inhibited the responses of dorsal horn neurons to external stimulation compared to DALDA or bremazocine. Furthermore, iontophoretically ejected DAMGO enhanced the inhibitory effects of intravenously injected MK-801. The results suggest that opioid system may interact with NMDA system in modulation of neuropathic pain, depending on receptor subtypes.
Abstract
It is well established that the neuronal plasticity in the cerebellar interpositus nucleus(INT) is essential for eyeblink classical conditioning. The current study attempted to combine INT stimulation with the occurrence of learning-related neural activity that normally precedes the behavioral conditioned response. Rabbits were trained with a trace paradigm(300ms tone-CS; 600rns ISI; 100ms air puff-US) that included extracellular stimulation of the INT. The electrical stimulation(ES; 200Hz, 0.1ms pulse width) was administered midway though the trace interval(400ms after CS onset for 50ms). Stimulation intensity was set at 25uA. Extinction training, consisting of tone+ES trials, followed acquisition. Rabbits with INT stimulation acquired conditioned response(CR) to the tone CS very quickly within the first two sessions and showed strong resistance to extinction. The timed INT activation combined with its learning plasticity facilitated learning and maintained the ability of CS to elicit CR. These results could be discussed by the association among three stimuli.
Abstract
The development of the computer technology and cell recording techniques have made possible continuous recording and sorting of extracellulary-recorded action potentials. At the same time, a reliable sorting of action potentials became a significant focus of interest. In this study, we describe and summarize a method of sorting of extracellulary-recorded spikes based on the Principal Component Analysis(PCA). In this method, a strategic number of principal components are chosen and each cell is represented in the feature space formed by the chosen components. The number of data cluster(i.e., cells) in the space is determined by the Maximum Likelihood Estimator(MLE) and the center of each cluster is determined by the Learning Vector Quantization(MLQ) method, an unsupervised learning algorithm. The distances between every cell pair and the center of each cluster are calculated. According to the Euclidean distance from the center, the data are sorted into each duster. Removing the outliers of each cluster based on the distribution of the distance completes the sorting process. A computer program, 'WAVESORTER' was written using the Matlab(The Mathworks Inc.) to realize all the phases of the sorting processes. In this paper, the logic and routines of the 'WAVESORTER' is described.