Biomedical subjects

G Nozawa

Publications and source records attributed to G Nozawa.

5 recordsLinked to original sources

PubMed1998

Differences in the luminance of the first and second displays affects visible persistence in opposite ways.

Visible persistence was measured using a two-frame temporal integration paradigm. Most such studies match the brightness of the two frames, and find that equal increases in the brightness of the frames impairs performance on the task. This suggests that increases in frame brightness decrease the duration of visible persistence. Little is known about what happens when the frames differ in brightness. In this study, the luminance intensities of the first and second frames were set at five different intensity levels in a factorial arrangement. Increasing the intensity of the first frame improved performance, whereas increasing the intensity of the second frame impaired performance. These results suggest, contrary to the findings with brightness-matched frames, that increasing the intensity of one frame increases the duration of visible persistence of that frame. A mathematical model supports this conclusion.

Afterimage↗

PubMed1995

Fate of neglected targets: a chronometric analysis of redundant target effects in the bisected brain.

The authors examined some of the sensorimotor effects of the split-brain operation to understand how a "dual mind" can produce unified behavior. They report psychophysical evidence of extinction to bilateral simultaneous stimulation in callosotomy patient J.W.: Although he could verbally report the occurrence of a unilateral left or right visual field target, left field report accuracy dropped by 34% when targets occurred bilaterally. Paradoxically, the same stimulus conditions produced abnormally robust redundant signal effects on simple manual and vocal reaction times, which exceeded predictions that were based on probability summation. Neural summation is often inferred from redundancy gain of this magnitude. Because this seems less likely after callosotomy, the authors suggest a model that is based on response competition between the disconnected hemispheres to account for J.W.'s redundant target effects. The dissociation between explicit report and motor performance is discussed.

Adult↗

PubMed1994

Parallel and serial processes in the human oculomotor system: bimodal integration and express saccades.

Saccadic reaction times (SRTs) were analyzed in the context of stochastic models of information processing (e.g., Townsend and Ashby 1983) to reveal the processing architecture(s) underlying integrative interactions between visual and auditory inputs and the mechanisms of express saccades. The results support the following conclusions. Bimodal (visual+auditory) targets are processed in parallel, and facilitate SRT to an extent that exceeds levels attainable by probability summation. This strongly implies neural summation between elements responding to spatially aligned visual and auditory inputs in the human oculomotor system. Second, express saccades are produced within a separable processing stage that is organized in series with that responsible for intersensory integration. A model is developed that implements this combination of parallel and serial processing. The activity in parallel input channels is summed within a sensory stage which is organized in series with a pre-motor and motor stage. The time course of each subprocess is considered a random variable, and different experimental manipulations can selectively influence different stages. Parallels between the model and physiological data are explored.

Cybernetics↗

PubMed1994

Visual-auditory interactions in sensorimotor processing: saccades versus manual responses.

Reaction times (RTs) to bimodal (visual and auditory) stimuli were examined using 3 different response systems: saccades, directed manual responses, and simple manual responses. The observed levels of intersensory facilitation exceeded race model predictions and therefore support summation (coactivation) models of bimodal processing. However, response-dependent differences suggest that the processing of bimodal targets also depends on the relevant sensorimotor pathways and requirements of the task. Coactivation of response mechanisms might account for the effects found using simple RTs. The results for saccades are consistent with known patterns of auditory-visual convergence in the oculomotor system.

Acoustic Stimulation↗

PubMed1980

Experimental studies on TDI dermatitis in mice.

Allergic contact dermatitis occurred with 2, 4-toluene diisocyanate (TDI) in BALB/c mice. The results were obtained by the measurement of the ear thickness after challenged to the ear with 1% TDI in olive oil in mice previously sensitized with 5% TDI. The ear swelling rate at 48 hr postchallenge in sensitized mice was more than twice of that in unsensitized mice. In BALB/c-nu/nu (nude) mice, delayed type hypersensitivity could not be induced even when a 30% TDI solution was applied. These results suggest that T cells may play an essential role in contact sensitivity to TDI in BALB/c mice.

Animals↗