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- P-ISSN1226-9654
- E-ISSN2733-466X
- KCI
ISSN : 1226-9654
Vol.10 No.1
Abstract
The Korean language has many words whose pronunciations are identical to their spellings. Since each phoneme in these words can be converted from their spellings, the naming responses to these words don't seem to require lexical access. Generally, the degree of lexical access in word recognition depends on orthographic depth, or correspondence between letters and phonemes. On the other hand, some studies that have dealt with Korean word recognition have consistently observed significant frequency effect. This effect may be regarded as the result of lexical access. To explain this conflicting phenomenon, this study attempted to clarify the effect of processing resource in addition to orthographic depth. This study consisted of two experiments. Experiment 1 employed as stimuli single-syllable words that end with Korean 'seven final consonants' in order to secure shallow orthographic depth. The naming process with these words simply convert letters into phonemes one by one and thus save processing resource. Therefore, It was assumed that frequency effect might appear, because left-over processing resource could be used for lexical access. The frequency effect almost disappeared when interfering tasks were employed to minimize processing resource. Experiment 2 employed as stimuli simple two-syllable words to generalize the findings of Experiment 1. In conclusion, This study manipulated interfering tasks to impinge on processing resource, with the result that the degree of lexical access was determined by processing resource as well as orthographic depth.
Abstract
This study investigated the effects of alcohol and diazepam on conditioned fear and extinction in Sprague-Dawley male rats. Fear was conditioned by pairing an experimental chamber with footshock and was assessed by observing freezing. During extinction session, rats were exposed to the chamber without shocks. In Experiment 1, the effects of ethanol and diazepam on fear acquisition and retention were examined. The interaction between ethanol and diazepam on conditioned freezing was also tested. Diazepam 5.0mg/kg and ethanol 1.2g/kg decreased freezing response immediately following the shocks and in retention test. Diazepam 1.0mg/kg interacted synergistically ethanol 1.2g/kg to reduce conditioned freezing. These results demonstrate a significant dose-dependent anxiolytic effect due to the combined treatment of ethanol and diazepam. Experiment 2 investigated whether fear extinction conducted under the influence of ethanol and diazepam transfer to the undrugged state. The groups that received extinction with either ethanol 1.2g/kg or diazepam 5.0mg/kg showed significantly more freezing than the saline control during undrugged test but those with either ethanol 0.6g/kg or diazepam 2.0mg/kg did not. These result suggest that ethanol and diazepam produce state-dependent fear extinction in dose-related manner as indicated by renewed fear during undrugged test. The practical implications for both the behavioral interaction effect between ethanol and diazepam and the state-dependent extinction with ethanol and diazepam are noted.
Abstract
Two experiments were conducted to investigate whether phonological information was activated during semantic processing of hanja. In these experiments, both using a semantic categorization task, the performance of skilled hanja readers were compared with that of less-skilled hanja readers. The less-skilled hanja readers were found to produce more false positive categorization errors on homophone foils, as well as on graphically similar foils, than the errors on their controls. Thus phonological and visual information appear to affect the semantic task. However, skilled hanja readers were found to produce no phonological effect and no visual similarity effect. This indicates that phonological and visual information do not seem to affect the semantic task. Therefore, the present results suggest that the use of phonological and visual information depends on reading proficiency. Phonological activation appears to be an optional rather than obligatory process.
Abstract
Neuropathic pain produced by nerve injury is very intolerable and uncontrollable. It is also resistant to analgesics including opioids. Until now the mechanism of neuropathic pain symptoms has been unknown at least in part because there is no reasonable and reliable animal model. Recently we developed new animal model of neuropathic pain in which the tibial and sural nerves of the sciatic nerve branches were injured and the common peroneal nerve was left intact. The present study was conducted to determine whether this animal model of neuropathic pain represent sympathetically maintained or independent pain. Under halothane anesthesia, rats were subjected to neuropathic surgery by cutting the tibial and sural nerves, leaving the common peroneal nerve intact. Two weeks after neuropathic surgery, the animals were anesthetized with urethane for electrophysiological experiments. Almost all the nerve fibers of L4 or L5 dorsal root, regardless whose peripheral axons were injured or not, did not respond to adrenergic drugs. These results suggest that this new animal model of neuropathic pain produced by the injury of the tibial and sural nerves, leaving the common peroneal nerve intact, may represent sympathetically independent pain.
Abstract
Long-term potentiation (LTP) of hippocampal synapses has been suggested to be a cellular mechanism for the learning and memory. However, few studies have reported a relationship between LTP and the behavioral index and the results have often been inconsistent with each other. The present study was conducted to see: 1) if LTP develops in the hippocampal dentate gyrus during classical conditioning of rabbit's nictitating membrane response (NMR) and 2) if stimulation of the medial septum, which is known to be an afferent structure, affects the induction of the LTP and the classical conditioning. Animals were pseudorandomlyassigned to one of four following experimental conditions: 1) CS(conditioned stimulus)-US(unconditioned stimulus), 2) CS-US with the electrical stimulation of medial septum, 3) unpaired presentation of CS and US 4) CS-US without test pulse to the perforant path. The results revealed that the three paired groups showed the robust acquisition compared with the unpaired group. The amplitude of evoked potential at hippocampal dentate gyrus to the test pulse of the perforant path during the acquisition was significantly increased in two paired groups with the test pulse, but not in the unpaired group. The electrical stimulation of the medial septum facilitated the behavioral acquisition without a change in evoked potential of dentate gyrus. The results of this study suggest that learning-related information from the enthorhinal cortex carried via perforant path induces LTP at hippocampus, and information to hippocampus carried via the medial septum modulates acquisition in conditioning of NMR, which can be independent of the induction mechanism of LTP.
Abstract
This study carried out to implement the Guided Search Model (GSM; Wolfe, Cave, and Franzel, 1989) in visual search using a neural network modeling technique. In Study 1, effects of noise on visual search were examined by adding noise in two different layers: the input layer and the activation map layer. When the noise was inserted in the input layer, the search performance for the feature search condition showed a linearly increasing function, whereas no such pattern was observed in the activation map layer-noise condition. In Study 2, we compared the simulation results of this model with those of the previous studies in order to show the validity and the generalizability of the model. The results were consistent with those of Wolfe et al.(1989) in most of the tasks employed. The simulation results were then compared with the results of other previous studies. In general, out simulation results were found to be compatible with the predictions of GSM.
Abstract
This study investigated the role of infralimbic(IL) and prelimbic(PL) areas of medial prefrontal cortex on the acquisition and extinction of conditioned fear response in rats using Pavlovian conditioning paradigm. Conditioned fear behavior(freezing response) was measured during both the acquisition and extinction phases of the task. Conditioned fear was measured both to the conditioned stimulus(CS) and to the contextual stimuli during both phases. IL lesion group, PL lesion group, and sham operated group showed similar conditioned fear to the contextual stimuli during acquisition. IL lesion and PL lesion enhanced conditioned fear to the CS in 2nd conditioning day. IL lesion prolonged conditioned fear to the CS(but not to the context) during extinction. PL lesion prolonged conditioned fear both to the CS and to the context during extinction. These results suggest that IL and PL are involved in emotion, especially fear, and that they are important in inhibition of conditioned fear.
Abstract
Two experiments were performed to test Johnson-Laird et al.'s naive probability theory. Experiment 1 replicated Johnson-Laird & Savary's(1996) fording of the illusory inferences of relative probability. Participants were asked to write down true cases and false cases for the two premises prior to estimating probability of two events in Experiment 2 to test two principles of naive probability theory: The truth principle of representation and the proportionality principle of probability estimation. The truth principle was supported, but the proportionality principle for probability estimation was not supported in Experiment 2.
Abstract
This study was conducted to examine the effects of kainic acid lesion of the red nucleus (RN) on the learning-related neuronal activities of the cerebellar interpositus nucleus(INT) and the dorsal accessory inferior olive (DAO). Kainic acid(2mg/㎖, 0.4㎕) was injected to RN after the animals reached a criterion of acquisition in delay conditioning(300msec ISI). Behavioral CRs were severely impaired by the lesion with decreased amplitude and increased latency. The amplitude and the latency of UR were also affected by the lesion. However, the reflex facilitation of UR by CS-US pairing was maintained after RN lesion. The lesion of RN reduced the conditioning-related activities of INT throughout sessions. However, the patterns of the neuronal responses in CR/noCR trials, when analyzed separately, revealed that INT robustly showed the neuronal model of behavioral response in a few remaining CR trials with the RN lesion. DAO continued to show conditioning-related activities in both CR and noCR trials after the lesion. The results suggest that the lesion of RN does not simply block the performance of CRs, but results in a systematic alteration of the neural network including the cerebellum and the brain stem, which can establish the neuronal plasticity for the development and maintenance of CR.
Abstract
Three experiments were conducted to explore the internal structure of Korean syllables. A phoneme substitution task with aurally presented stimuli was used. In Experiment 1 with monosyllables as stimuli, the coda was substituted faster than the nucleus, and the nucleus was substituted faster than the onset. The performance to open syllables was roughly the same as that to closed syllables. In Experiment 2 in which the phoneme to substitute and the position of substitution were fixed in a session, similar results as in Experiment 1 was obtained. In experiment 3 disyllabic words were used as stimuli to test the effect of syllable structure and word structure and the results suggesting only the effect of syllable structure were obtained. All the results from the three experiments indicated that the internal structure of Korean syllables is the body structure.
Abstract
The superior colliculus (SC) has been known as a critical neural structure in controlling saccadic (rapid) eye movements. The locations of visual stimuli, common targets of saccadic eye movements, are registered in place code by the retina and by various areas of the visual cortex. Motor commands to acquire these targets by reorienting the gaze line, on the other hand, are represented in the temporal pattern of neural discharges. Thus, the neural signal is thought to undergo a spatial-to-temporal transformation, and the SC is considered to play a critical roles for this transformation. Despite the intensive neurophysiological and pharmacological studies, roles of collicular neurons are not fully understood in relation to this transformation, and a few computational models appeared trying to make sense out of these incomplete biological data. We reviewed key aspects of the patterns of neural discharges of various saccade-related neurons of the SC and of brain stem areas that are known to be involved in generation of saccades, focusing on the spatial-to-temporal transformation. We also reviewed various models of saccade generation, and proposed further studies to better understand neural mechanisms for saccade generation.
Abstract
This study was planned to improve the same-different categorization task(Lee, 1996) by modifying several procedural problems of it, and to investigate, by manipulating factors such as learning experiences or stimulus types, whether the task could reflect the effects of rules and similarities on categorization. Experiment 1 examined relative effects of rule and similarity on categorization by changing learning experiences, the results showed that learning experiences had an effect on rule effects only. In Experiment 2, the same results as that of experiment 1 were found in the high cohesive condition, but a trade off between rule effect and similarity effect was found in the low cohesive condition. In Experiment 3, two stimulus were presented two stimulus concurrently or successively to investigate the extent the presentation procedure of the same-different categorization task had any relation to similarity effects. There was no statistically significant effect of learning experiences in the concurrent presentation condition, but a trade off between similarity effect and rule effect was found in the successive presentation condition. These results suggest that categorization processes cannot be explained by rule or similarity alone, and that the same-different categorization task can be regarded as a promising task for analyzing relative effects of rule and similarity on categorization.
Abstract
People tend to perceive a vertical line to be longer than the same size of horizontal line (the horizontal-vertical illusion; HVI). We asked whether the configuration of a form could have an effect on HVI, using the method of adjustment where participants adjusted the length of one (horizontal or vertical) line to be equal to that of the other line. In the first experiment, when '⊥' -like and 'ㅏ' -like figures with varying division positions were introduced, the total amount of HVI changed with the division position (so-called bisection effect; BE). The amount of pure HVI (with BE subtracted) was less in the '⊥' type figures than in the 'ㅏ' type figures. Trend analysis on the HVI of '⊥' type figures showed that BE had a quadratic component, which we thought was a reflection of configural effect of a whole form. In the second experiment with a rectangular or a cross, HVI was less in these good configurations than in the 'ㄴ' type figures. In the third experiment, we divided each of the above good configurations into two separate 'ㄴ' type figures and observed less HVI with the divided patterns than with the 'ㄴ' figure. But the effect size was small. It was concluded that configuration could have an effect on HVI and some of its effect could result from the multiple comparison pairs belonging to the configuration. Configurational aspects and anchorage effect in size judgment were discussed.