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- P-ISSN1226-9654
- E-ISSN2733-466X
- KCI
ISSN : 1226-9654
Vol.7 No.1
Abstract
Two experiments were performed to exploit the hemispheric characteristics in processing Hangul word and the color. The stimuli were presented bilaterally in a button-pressing version of the Stroop-like task Subjects were asked to choose which alternative was in accord with the standard stimulus in a given response criterion(color/word), when they were presented on both side of fixational point. The results showed that there was no hemispheric difference in case of the color-unrelated word as the word dimension(Experiment 1), but when color-related words(color names) were used as the word dimension(Experiment 2), RTs were significantly faster for the stimulus presented in the right visual field than for that presented in the left visual field. This implies that the hemispheric difference can be easily detected when the task poses difficulty in information processing. In comparision of the two response criteria, responses to the color criterion were faster than those to the word and the interference of color with the word was greater than the opposite condition, which is contrary to the results of the conventional Stroop tasks. The results indicate that word responses require more processing load than the color responses.
Abstract
This review paper has been divided into two parts, the first dealing with components that have short latencies and brief durations, and the second dealing with components that occur late in time and have long durations. This was a convenient way of dividing the material covered and fits most ERP investigators' notions of these being two discrete domains of research. Indeed, most investigations of short-latency components have usually paid little attention to slow waves and vice versa. The early latency components(e.g., MMN, P300, Nd, etc.) have a very large range of durations that actually overlap with those of the slow waves. A selctive attention effect with auditory stimuli lasted for only 20 msec (from about 30- to 50 msec latency), whereas selective attention effects associated with spatial selection of visual stimuli typically last for about 100 msec (i.e., the duration of the P1 and N1 components). The MMN usually lasts for about 200 msec. The P300 component can last for 500 or more msec., and the Nd can persist for many hundreds of msec. It is clear that the strategies subjects use to perform different tasks will alter the pattern of ERP results obtained. Initially, it was thought that there is one slow wave, being positive in posterior regions and negative frontally. Since the slow wave occurred after P300, and the experimental designs were such that the slow waves may have been subsequent to the processes that determined the subjects' behavior, its functional significance was conceptualized in terms of further processing associated, for example, with a re-examination of the events which had just occurred. This interpretation was applied to diverse experimental tasks, such as signal detection, discrimination between stimuli, prediction situations, etc. On two major events in slow wave research, one is that a variety of slow waves have been found which have different scalp distributions and are associated with different psychological processes. The other is that the slow waves have more recently been studied in tasks where the subject's performance depended upon very-long duration processes. Thus, these slow waves may well have been associated with processing that determined the behavioral response. Consequently, the features that used to separate the two domains of research are not as relevant as they once were. Moreover, the division of components into those of short-and long-lasting durations has become arbitrary.
Abstract
Simple reaction time to a luminance target may be lengthened when the target is preceded by a noninformative cue at the same location. This is known as inhibition of return, because attention is inhibited from returning to the locus of the first stimulus. Three experiments were carried to test several alternative explanations of inhibition of return. Using vertical stimulus arrays in Experiment 1 and employing a voice key in Experiment 2, we failed to obtain evidence for a motor explanation of the inhibition effect. Experiment 3 used response accuracy as a dependent measure and failed to obtain an inhibition effect. In conclusion, 1) eye movements and motor interference are not responsible fa inhibition of return; 2) since inhibition of return is obtained only in a speeded RT task, a peripheral-sensory interference is not the cause of the inhibition effect. To accommodate these results, a revised model of inhibition of return was proposed.
Abstract
Three experiments examined the influences of word fragment exposure time and completion time on the availability of perceptual and conceptual processes in word fragment completion priming. In Experiment 1, with visual words and auditory words as primes, word fragment exposure time and completion time were manipulated as follows: 500 ms - 2 s, 500 ms - 4 s, 500 ms - 8 s, 2 s - 2 s, and 8 s - 8 s. Cross-modal priming was not obtained only at the short exposure and completion time(500 ms - 2 s). In Experiment 2, with physically processed words and semantically processed words as primes, effects of level of processing was not obtained at the same short exposure and completion time, but was obtained at the long exposure and completion time(8 s - 8 s). In Experiment 3, with read words and generated words as primes, read words produced more priming than generated words at the short exposure and completion time, but the advantage of read words was not obtained at the long exposure and completion time. At the short exposure and completion time, only perceptual information was available, and conceptual information became available at the longer exposure and completion time. These results suggest that relative contributions of perceptual and conceptual processes are influenced by the retrieval manipulation both of fragment exposure time and completion time(cf. Weldon, 1993).
Abstract
Nucleus accumbens receives afferents from the hippocampus, the amygdala and the prefrontal cortex and projects to the several motor structures such as the globus pallidus and the substantia nigra. The dopaminergic(DA) system of the ventral tegmental area innervates the hippocampus, the amygdala and the prefrontal cortex as well as the nucleus accumbens. So the limbiccotical afferents and the DA terminals arising in the vental tegmental area are overlapped in the nucleus accumbens. Several hypothses of the behavioral function of the mesoaccumbens DA system were proposed. Wise(1982) and Bozarth(1991) proposed that the DA system is activated by rewards. By their reward hypotheses, mesoaccumbens DA system is involved in the rewarding effects of electrical brain stimulation, psychomotor stimulants and opiates as well as the natural rewards such as feeding, drinking, and sexual behavior. Reward hypothesis has undergone revision. The revised reward hypotheses propose that mesoaccubens DA system is activeted by conditined incentive stimuli as well as the primary reinfocers after conditioned stimuli are associated with primary stimuli. Phillips et al.(1991) argued that the system is not activated by rewards, but rather by the stimuli that precede and predict the delivery of rewards. And they proposed the system is involved in the incentive learning. Hypotheses of neuromodulatory functions were proposed by Mogenson & Yim(1991), Cador et al.(1991), Salamone(1991, 1992), Scheel-Krüger & Willner(1991). They believe that the DA system plays a crucial role in the regulation of the transfer of information from its inputs to the output structures of the striatum. Schultz et al.(1993) found that midbrain DA neurons can be activated both by primary food and fluid rewards and by conditioned incentive stimuli predicting reward, so they proposed midbrain DA neurons are involved in basic attentional and motivational processes. Similarly Robinson & Berridge(1993) argued that midbrain DA projections mediate a process termed "incentive salience attribution". Many experimental results supporting several hypotheses will be considered and summarized. And the function of the mesoaccumbens DA system will be synthesized.
Abstract
Two experiments were conducted to investigate the internal structure of Korean syllables and Kulcas, the orthographic units corresponding to syllables. In experiment 1 using word game, first letters in Kulcas corresponding to initials in a syllable were substituted faster than last letters corresponding to codas. The type of Kulca didn't exert any influence on response times. In experiment 2 using phoneme shift task, the same result was obtained. But the type of Kulca influenced on the response times for mid letters which correspond to peaks. The results from experiment 1 and 2 together indicated the body/coda structure of Korean syllable. The language-specificity of syllable structure was suggested.
Abstract
A possibility of parametric elimination of the visual component from the activity of the cat superior colliculus was sought for. Form a known population distribution of spike density, trial data simulating the transient visual response of the cat superior colliculrs were derived. The onset and the peak times of the visual activity were determined with 4 methods of spike density estimation: time histogram, inverse interspike-interval histogram, fixed and adaptive kernel estimation. The results were compared and applied to 178 trial data obtained with the chronic recording from the deep layers of the cat superior colliculus. The possibility of obtaining the activity component related with saccadic eye movements without behavioral task is discussed.
Abstract
The frequency information on occurrence of a stimulus may be encoded automatically or computed at retrieval. In this study, we investigated whether the frequency information on occurrence of a superordinate category was encoded automatically or computed at retrieval. In experiment 1, manipulating attention and typicality of exemplars, we found that frequency information could be encoded only with attentional effort and computed at retrieval. In experiment 2, we asked subjects to speak of names of it's superordinate categories when exemplars were displayed. Such a manipulation to activate directly a superordinate category had influenced on the accuracy of frequency estimations in the frequency instruction condition only in which subject tried to encode frequency informations intentionally. In experiment 3, manipulating response time limit and typicality of exemplars, the effect of typicality was founded in the short response condition only. These results contradict with the view that the frequency information on occurrence of a superordinate category is encoded automatically.
Abstract
Sears et al. showed that learning-related multiple unit activity (MUA) developing in the hippocampus during the classical conditioning of nictitating membrane response depends on the intactness of the cerebellar interpositus nucleus, that was confirmed by our recent study. The cerebellar interpositus nucleus is known to be an essential neural structure for this conditioning, and a place representing time-amplitude neural model of the conditioned response(CR). Lesioning the interpositus nucleus, therefore, abolishes the learning itself and as a result, the hippocampal MUA can not develop. In case the red nucleus, the principal output pathway of the interpositus nucleus is lesioned, the learning-related MUA in the interpositus nucleus can be recorded, which is possibly interpreted as the learning is established but the performance of CR is blocked. The present study was conducted to determine if the learning-related MUA could be developed in the hippocampus after lesioning the red nucleus, the target of the interpositus nucleus. Experimental rabbits were given unilateral electrolytic lesions of the red nucleus before the conditioning sessions (CS: 550msec tone, US: 100msec air puff, ISI: 450msec). Experimenal rabbits showed less than 8% CRs by the end of the 8th session, whereas the control animals showed on the average more than 80% CRs by the 4th session (F[1,10]=187.84,p<0.01). The control group showed typical increase of hippocampal MUA in the process of learning, while the group with the red nucleus lesion did not showed the increases of hippocampal MUA in the CS period(F[1,10]=10.67,p<0.05). These results suggest that the learning-related input from the interpositus nucleus via the red nucleus may play a critical role for the normal MUA development in the hippocampus.
Abstract
This paper investigates use of rules and exemplar memories in category learning by manipulating the salience of correlational rules. The resulis of two experiments showed that salient condition was better in categorization performance than nonsalient conditions (no symmetry cue and random arrangement conditions). An interaction between the two variables of salience and category size was also found in Experiment 2. In a salient condition, categorization appeared to be better in a larger category size than in a small category size. This implies the use of abstract rules. In a no symmetry cue condition, a small category size was found to categorize better than a larger category size, suggesting the involvement of memory-based knowledge. But a random arrangement condition was not affected by category size. In addition, the two experiments were used to test the relation between categorization and recognition. Salience of rules was found to affect categorization but did not affect recognition, which suggests a dissociation of the two tasks. These findings are consistent with the implicit/explicit learning that salient conditions employ analytic and explicit rules during category learning whereas nonsalient conditions are based on exemplar memories.
Abstract
The present study was designed to examine effects of capsaicin administration on aggressive behaviors and autonomic thermoregulation in rats. In six-week-old rat, capsaicin was injected subcutaneously on 4 consecutive days in increasing doses(20mg/kg, 30mg/kg, 30mg/kg, 50mg/kg) to total of 150mg/kg of the drug. The controls were treated in the same way with vehicle alone. Two experments began six or eight weeks after the treatment. In experiment 1, isolation-induced agressive behaviors, scored a 10-min session in the dyadic situation, were significantly decreased by capsaicin pretreatment. This result was not in accord with the previous findings. In experiment 2, body temperature of the capsaicin-treated rats increased more than the control's at two amibient temperatures studied(37℃ and 40℃). Our result concerning thermoregulation supports the preceding studies that applied to the capsaicin-treated animals as neonate or adult. Thus, it is likely that the effect of capsaicin treatment on thermoregulation has nothing to do with the age of capsaicin injection. The capsaicin effects from this study were compared with hypothalamic lesion effects in the discussion part.
Abstract
We investigated the effects of capsaicin(s.c. 150mg/kg) on the open-field behaviors and the thresholds and latency of nociceptive responses in adult rats. Results are as follows. 1) Capsaicin did not affect open-field behaviors. It hints that capsaicin did not alter the emotionality and motor function of rats. 2) Whereas the threshold of jumping was elevated, those of fore and hind paw licking were not in animals treated with capsaicin. Capsaicin also enhanced hind paw licking latency to thermal stimulus over thershold in hot plate test. These results suggest that capsaicin affects the coping reaction to strong thermal stimulus, but not adaptive reaction to mild stimulus, in adult rats.