Difference in Cortical Relay Time Between Intrinsic Muscles of Dominant and Nondominant Hands

The authors aimed to calculate and compare cortical relay time (CRT) between intrinsic hand muscles and between homonymous muscles of dominant and nondominant hands. The participants comprised 22 healthy volunteers. The CRT for long-latency reflexes (LLRs) was calculated by subtracting the peak latency of somatosensory evoked potentials of component N20 and the onset latency of motor evoked potentials from the onset latency of LLRs. CRT was significantly shorter for the first dorsal interosseous muscle than for the abductor pollicis brevis muscle, regardless of hand dominance. CRT for the abductor pollicis brevis muscle was significantly shorter in the dominant hand than in the nondominant hand. Evaluation of CRT for intrinsic muscles might be beneficial in the understanding of individuated finger functions.     

Coherent modulation of stimulus colour can affect visually induced self-motion perception

The effects of dynamic colour modulation on vection were investigated to examine whether perceived variation of illumination affects self-motion perception. Participants observed expanding optic flow which simulated their forward self-motion. Onset latency, accumulated duration, and estimated magnitude of the self-motion were measured as indices of vection strength. Colour of the dots in the visual stimulus was modulated between white and red (experiment 1), white and grey (experiment 2), and grey and red (experiment 3). The results indicated that coherent colour oscillation in the visual stimulus significantly suppressed the strength of vection, whereas incoherent or static colour modulation did not affect vection. There was no effect of the types of the colour modulation; both achromatic and chromatic modulations turned out to be effective in inhibiting self-motion perception. Moreover, in a situation where the simulated direction of a spotlight was manipulated dynamically, vection strength was also suppressed (experiment 4). These results suggest that observer's perception of illumination is critical for self-motion perception, and rapid variation of perceived illumination would impair the reliabilities of visual information in determining self-motion.     

Shrinkage in the perceived duration of speech and tone by acoustic replacement1

Abstract: To investigate mechanisms for perceiving the duration of an auditory event, an effect of perceptual grouping upon perceived duration was studied psychophysically. In the first experiment, the perceived duration of a spoken word was measured under three conditions of acoustic continuity (i.e., (a) intact, (b) noise‐replaced, and (c) gap‐replaced) as a function of the duration of the target stimulus. Under the noise‐replaced condition, a portion of the target stimulus was physically replaced with a noise burst. Under the gap‐replaced condition, the replacement was made with a gap. The gap‐replacement resulted in a prominent shrinkage of the perceived duration. In the case of noise‐replacement, the amount of shrinkage was moderate but highly significant, although the word employed was perceived to be phonetically intact. Independent of this effect of replacement, the amount of shrinkage was also affected by the physical duration of the target stimulus. The second experiment tested an effect of noise replacement on the perceived duration of a tone burst. In this case, the noise replacement also shrunk the perceived duration of the non‐speech stimulus. This noise‐induced shrinkage could be regarded as being general for the auditory duration. The phenomenon is discussed in relation to a revised model for perceived duration.     

Cognitively active externalization for situated reflection

This paper offers an explanation of how collaboration leads to abstract and flexible problem solving. We asked the individual and paired subjects to indicate 3/4 of 2/3 of the area of a square sheet of paper and found that (1) they primarily folded or partitioned the paper rather than algorithmically calculating the answer, (2) they strongly tendened to backtrack and confirm their proto‐plans on externalized traces such as creases on the paper, and (3) only the paired subjects shifted to the mathematical strategy in their second trials. Based on these results, we propose that two factors, individuals' activeness in choosing and confirming the initial strategies and the frequent role exchange between task‐doing and monitoring in collaborative situations, interact in collaboration to generate various solutions differing in the degree of abstraction, which are then reflected upon by the participants to lead them to abstraction.     

The prototype effect in face recognition: Extension and limits

The prototype effect in face recognition refers to a tendency to recognize the face corresponding to the central value of a series of seen faces, even when this central value or prototype has not been seen. Five experiments investigated the extension and limits of this phenomenon. In all the experiments, participants saw a series of faces, each one in two or more different versions or exemplars, and then performed a recognition test, including seen and unseen exemplars and the unseen prototype face. In Experiment 1, a strong prototype effect for variations in feature location was demonstrated in oldness ratings and in a standard old/new recognition test. Experiments 2A and 2B compared the prototype effect for variations in feature location and variations in head angle and showed that, for the latter, the prototype effect was weaker and more dependent on similarity than for the former. These results suggest that recognition across feature variations is based on an averaging mechanism, whereas recognition across viewpoint variations is based on an approximation mechanism. Experiments 3A and 3B examined the limits of the prototype effect using a face morphing technique that allows a systematic manipulation of face similarity. The results indicated that, as the similarity between face exemplars decreases to the level of similarity between the faces of different individuals, the prototype effect starts to disappear. At the same time, the prototype effect may originate false memories of faces that were never seen.     

Effects of psychoactive agents on the conditioning of the microcirculation in the rat

Normal vascular tonus and permeability of the microcirculatory network is mediated by catecholamines, histamine and serotonin. Following electroconvulsive treatment (ECT), histamine did not provoke local vasodilatation. The inhibition was further potentiated by drugs which prevent the enzymatic or physical inactivarion of free catecholamines and by locally administered norepinephrine. This system became conditioned to a visual stimulus when rats were presented in six consecutive occasions with the visual stimulus preceedingly coincided with the administration of ECT. In the conditioned rats, light alone inhibited the histamine-induced vasodilatation, and this inhibition was potentiated by sub-effective doses of injected norepinephrine and by drugs which prevent the enzymatic or physical inactivation of catecholamines. Sedatives, antidepressants, MAO inhibitors and the chlorpromazine-type agents as well as the psychotomimetic drugs characteristically influence either the acquisition or the extinction of the conditioned reflex. Results suggest that the obtained conditioning of the microcirculatory functions are mediated by tie centrally released catecholamines.     

上海博物馆藏战国楚竹书《周易》的"首符"与"尾符"

楚竹书《周易》首符、尾符所使用的方形结构,由内、中、外三层构成.依此三层结构进行分类,首、尾符号可以分为九种.将这九种符号和今本《周易》卦序非覆即变三十六卦图相对应,我们发现正好可以按四卦画一组,分为九组或九宫.假定楚竹书《周易》卦序确由九宫构成,则其与今本《周易》卦序有着密切的继承关系,但也有重要区别,其分宫法与一般以八经卦为基础的分宫法也不相同.楚竹书首、尾符号的设置,还反映出这样一种认识或意识,即一个卦,是由"卦画、卦名"和"卦辞、爻辞"两个部分构成的.     

The effects of trial repetition and individual characteristics on decision making under uncertainty

The authors examined participants' preferences between certain and uncertain outcomes in a multistage gambling task and the effects of individual difference characteristics on those preferences. In Study 1, 144 participants made choices in single-stage gambles under gain and loss conditions and replicated the certainty effect in a previous study (D. Kahneman & A. Tversky, 1979). In Study 2, 94 participants engaged in a multistage gambling task using the same decision problems as those in Study 1. They also answered a questionnaire consisting of the Japanese version (M. Kamahara, K. Higuchi, & N. Shimizu, 2001) of the Locus of Control Scale (J. B. Rotter, 1966), the Reflection-Impulsivity Scale (K. Takigiku & A. Sakamoto, 2001), and a Japanese version (M. Terasaki, K. Shiomi, Y. Kishimoto, & K. Hiraoka, 1987) of the Sensation-Seeking Scale (M. Zuckerman, 1994). The results indicated that the certainty effect (Kahneman & Tversky) disappears in multistage gambling tasks and that differences in reflection-impulsivity and in gender influence the process of decision making under gain conditions. These results are discussed in terms of the decision strategies and cognitive biases involved in the multistage gambling task.     

Remembering a nuclear accident in Japan: did it trigger flashbulb memories?

Flashbulb memories are vivid memories of the details surrounding the discovery of an emotional event. We investigated whether the nuclear accident that occurred in Japan in 1999 produced flashbulb memories among people who lived near the accident site. A questionnaire was distributed twice (approximately 3 weeks after the accident and 1 year later) to (1) the residents of the communities surrounding the accident site, (2) the students at a university near the accident site, and (3) the students at two universities far away from the accident site. Flashbulb memory holders were defined as those individuals who showed consistent memories between test and retest. The results indicated that only a small percentage of participants formed flashbulb memories. Further, no age-related decline was found. Flashbulb memories were distinguished by perfect or near perfect scores on four attributes: source, place, activity, and people. The results also indicated that the ratings on emotional reactions, personal consequentiality, and surprise did not differentiate between the flashbulb and non-flashbulb memory holders. In contrast, the flashbulb memory holders reported rehearsing more than the non-flashbulb memory holders. These results supported the notion that flashbulb memories are formed through rehearsal rather than at encoding. However, it is also possible that rehearsal was a result of the flashbulb memory.     

Involvement of IP3 receptors in LTP and LTD induction in guinea pig hippocampal CA1 neurons

The role of inositol 1, 4, 5-trisphosphate receptors (IP3Rs) in long-term potentiation (LTP) and long-term depression (LTD) was studied in CA1 neurons in guinea pig hippocampal slices. In standard solution, short tetanic stimulation consisting of 15 pulses at 100 Hz induced LTP, while three short trains of low-frequency stimulation (LFS; 200 pulses at 1 Hz) at 18-min intervals or one long train of LFS (1000 pulses at 1 Hz) induced stable LTD in both the slope of the field EPSP (S-EPSP) and the amplitude of the population spike (A-PS). Bath application of 2-aminoethoxydiphenyl borate (2-APB), an IP3R antagonist, or of alpha-methyl-4-carboxyphenylglycine (MCPG), a wide-spectrum metabotropic glutamate receptor antagonist, during weak tetanic stimulation significantly increased the magnitude of the LTP in both the S-EPSP and A-PS. Three short trains of LFS or one long train of LFS delivered in the presence of 2-APB or MCPG did not induce LTD, but elicited LTP. Based on these results, we conclude that, in hippocampal CA1 neurons, IP3Rs play an important role in synaptic plasticity by attenuating LTP and facilitating LTD.