Fading-figure tracing in Williams syndrome

Williams syndrome (WS) is a neurodevelopmental disorder characterized by severe impairment of visuospatial abilities. Figure-drawing abilities, which are thought to reflect visuospatial abilities, have yet to be fully investigated in WS. The purpose of the present study was to clarify whether drawing abilities differ between WS individuals and typically developing children (TD). We compared the performance of two groups of subjects (WS, mean age 16 years; TD, 5-6 years of age) using a fading-figure tracing task that requires subjects to trace a target figure that is gradually disappearing from a PC screen. Although the TD group exhibited clearly improved performance with long fading time, the WS group did not. Moreover, the TD group exhibited poor performance for figures with more than six angles, regardless of the figure type (e.g. closed or open), whereas the WS group exhibited generally poor performance for figures with more than five angles but relatively preserved performance for open figures. These findings indicate that a combination of decreased visuospatial span associated with incomplete development of visual scanning and disproportionate development of global processing may cause drawing disabilities in WS.     

Effects of sound-marker durations on rhythm perception

Our aim in this study was to examine the influence of sound-marker durations on the perception of simple rhythm patterns. These comprised three successive sounds marking two neighbouring time intervals, T1 and T2, with their onsets. We varied the durations of each of the three sound markers to make them either 20 or 60 ms. Durations of T1 and T2 were also varied, but the total duration of T1 and T2 was fixed at either 240 or 480 ms. In experiment 1, participants compared the durations of T1 and T2. In experiment 2, the subjective duration of each interval was measured separately. We found that lengthening the duration of the sound marker which terminated an interval increased the subjective duration of that interval: lengthening the duration of the second marker increased the subjective duration of T1, and lengthening the duration of the third marker increased the subjective duration of T2. Lengthening the duration of the first marker increased the subjective duration of T1 when T1 + T2 = 240 ms, especially when T1 > T2. This effect of first-marker duration, which could not be observed with single intervals used in the control conditions, seemed to enhance the contrast between T1 and T2. The effects of marker durations are associated with previous time-perception studies, in which single time intervals were used. They are discussed in the context of rhythm-perception studies, in which more complex sound patterns have been used.     

Conditioned Ethanol Aversion in Rats Induced by Voluntary Wheel Running, Forced Swimming, and Electric Shock: An Implication for Aversion Therapy of Alcoholism

This study was planned to demonstrate rats' acquisition of aversion to ethanol solution consumed before voluntary running, forced swimming, or electric shock delivery. Wistar rats under water deprivation were allotted to four groups of eight rats each, and all rats were allowed to drink 5% ethanol solution for 15 min. Immediately after the ethanol drinking, rats of Group Run were put into the individual running wheels for 15 min, those of Group Swim were put into the individual swimming pools for 15 min, those of Group Shock received electric shocks for 15 min (15 0.45-mA shocks of 0.7s with the intershock interval of 1 min) in the individual small chambers, and those of Group Control were directly returned back to the home cages. This procedure was repeated for six days, followed by a two-day choice test of ethanol aversion where a bottle containing 5% ethanol solution and a bottle of tap water were simultaneously presented for 15 min. In the test, Groups Run, Swim, and Shock drank ethanol solution significantly less than tapwater, while Group Control drank both fluids equally. The effects of running, swimming, and shock were equivalent. The successful demonstration of acquired ethanol aversion induced by exercise (running and swimming) or shock in rats suggests an avenue for clinical application of exercise and shock treatments for human alcoholics, though there are many issues to be resolved before the practical use.     

Context-dependent olfactory learning in an insect

We studied the capability of the cricket Gryllus bimaculatus to select one of a pair of odors and to avoid the other in one context and to do the opposite in another context. One group of crickets was trained to associate one of a pair of odors (conditioned stimulus, CS1) with water reward (appetitive unconditioned stimulus, US+) and another odor (CS2) with saline solution (aversive US, US-) under illumination and to associate CS1 with US- and CS2 with US+ in the dark. Another group of crickets received training of the opposite stimulus arrangement. At 1 d after the training for 3 d, the former group significantly preferred CS1 over CS2 under illumination but preferred CS2 over CS1 in the dark, and the latter group exhibited the opposite odor preference. The results of control experiments showed that the background light condition had no significant effects on memory formation or retrieval unless it was explicitly associated with US during training. Thus, the visual context affected learning performance only when crickets were requested to use it to disambiguate the meaning of CSs and to predict USs.     

Time-shrinking,its propagation,and Gestalt principles

When a relatively short empty time interval is preceded by an even shorter one, its duration can be underestimated remarkably. This phenomenon, called time-shrinking, has been investigated with patterns consisting of two time intervals. In five experiments, we investigated whether underestimation of the last interval would occur when it was preceded by two time intervals. Significant underestimations of the last interval occurred in some of those patterns. The influence of the second preceding interval was dominant, but in some patterns, the first preceding interval could shrink the subjective duration of the last time interval directly. The first interval could also affect perception of the duration of the last one indirectly by shrinking the second interval, as a result of which the latter either shrank the last interval more strongly or became too short to shrink it. There were two types of temporal patterns in which the perceived duration of the last interval could not be explained by time-shrinking or its propagation through the pattern. It seemed plausible that auditory Gestalt principles invoked strong figural organizations in these patterns, which rendered the time-shrinking mechanism inoperative.     

Assessment of weight-error derivative (WED) analysis

Often considered one of the more discriminating tests between normal and brain-damaged individuals, the Category Test has been described as a complex measure of new problem solving, logical analysis, concept formation, abstract reasoning, and mental efficiency. Since publication of a booklet format by DeFilippis and McCampbell in 1979, researchers have attempted to develop other versions to reduce time required for administration. The present study compared the sensitivity of the Short Category Test, Booklet Format with the Booklet Category Test. Subjects were 22 male veterans seen for comprehensive neuropsychological evaluation and were classified into a brain-damaged or a control group (ns =11) according to independent neurological or neuroradiological evidence. Comparison of performances based on T scores yielded no significant differences between the groups on either format. Analyses of performance based upon suggested raw score cut-offs for the tests, however, yielded a statistically meaningful difference, but caution is in order when using T scores derived from age- or education-based normative data to suggest the presence of brain dysfunction. Raw score cut-offs yielded valid differentiation of individual patients in both groups.     

Modification of depth and distance perception caused by long-term wearing of left-right reversing spectacles

For 35 to 39 days, four observers wore continuously left-right reversing spectacles which pseudoscopically reverse the order of binocular disparity and direction of convergence. In three tests, we investigated how the visual system copes with the transformation of depth and distance information due to the reversing spectacles. In stereogram observation, after a few days of wearing the spectacles. the observers sometimes perceived a depth order which was opposite to the depth order that they had perceived in the pre-spectacle-wearing period. Monocular depth cues contributed more to depth perception in the spectacle-wearing period than they did in the pre-spectacle-wearing period. While the perceived distance significantly decreased during the spectacle-wearing period, we found no evidence of adaptive change in distance perception. The results indicate that the visual system adapts itself to the transformed situation by not only changing the processing of disparity but also by changing the relative efficiency of each cue in determining apparent depth.     

Neural and behavioural effects of domoic acid, an amnesic shellfish toxin, in the rat.

To examine the neurotoxic effects of domoic acid, an amnesic shellfish toxin, electroencephalographic and behavioural experiments were conducted on 38 rats. Injection of domoic acid (0.5-1.0 mg/kg intravenously, or 0.04-0.08 microgram intraventricularly) caused seizure discharges in the hippocampus, tonic-clonic convulsions, and death within a few days. Convulsions and ensuing death were prevented by diazepam. Animals pretreated with diazepam (5 mg/kg, ip) tolerated intraventricular dose of domoic acid 0.4 microgram, but showed a loss of pyramidal neurons mainly in the CA3, CA4, and a part of CA1 areas of the dorsal hippocampus. Learning of a radial maze task was severely impaired in naive rats after intraventricular injection of domoic acid (and diazepam, ip). In the animals previously trained on the maze task, domoic acid interfered with relearning of the same task. These effects appear similar to those of kainic acid and are analogous to the symptoms observed in humans who ingested mussels tainted with domoic acid.     

Signaled reinforcement effects on fixed-interval performance of rats with lever depressing or releasing as a target response

The effect of a diffuse auditory signal filling a brief delay between a response and reinforcement depends upon the nature of the trained target response. Rats in a signaled condition responded slower than rats in an unsignaled condition if the target response was lever release. If the target response was lever depression, however, rats in the signaled condition responded faster than rats in the unsignaled condition at the end of training     

Effects of information conflict and complexity in visual figures on voluntary visual exploration, using structural information theory

This study was designed to examine the effects of information conflict and complexity on voluntary visual exploration quantitatively. 31 adults viewed each of 16 slides of geometrical figures and places for as long as they wished. The stimuli had two values of information conflict and complexity which had been calculated by means of structural information theory. Free looking times indicated that only when information conflict was low, voluntary visual exploration was positively correlated with complexity. Furthermore, voluntary visual exploration correlated positively with information conflict when complexity was low.