Temporal and spatial integration for electrocutaneous stimulation

Tashero

1990

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Five experiments were carried out to investigate the effects of electrode size on threshold for current pulses that flowed between the ventral and dorsal sides of the right forearm. The main result was that the total current threshold decreases as the size of the cathode and anode increases at least up to 15 mm in diameter. To account for this finding, a neural summation model was proposed, assuming that the central nervous system sums up neural impulses discharged near the conduction paths under electrodes. It was also found that the current flowing from the dorsal to the ventral side provided lower thresholds and more stable localization than the opposite flow of current did. This finding suggested that current threshold and its perceived locus are determined by both the body site on which electrodes were placed and the relative polarity that was assigned to electrodes.

Section: Effect Of Electrode Configuration On Thresholdcontrasting

confidence: 71%

Electrocutaneous spatial integration at threshold: The effects of electrode size

Tashero

1990

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“…Jones (1956) and Wieland (1960) placed a large anode on the ventral surface of the forearm and a small cathode(s) on its dorsal surface. Anderson and Munson (1951), Higashiyama and Rollman (1991), and Higashiyama and Tashiro (1983) placed two same-sized electrodes side by side on the forearm. In these configurations, the distance between the electrodes usually ranges from 2 to 20 em.…”

mentioning

confidence: 99%

Localization of electrocutaneous stimuli on the fingers and forearm: Effects of electrode configuration and body axis

Hayashi

1993

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Four experiments were done on the effects of electrode configuration (concentric vs. unifocal) and body axis (longitudinal vs. transverse) on localization of electrocutaneous pulse stimuli at the fingers and forearm. Subjects pointed to the apparent location of current pulses. For the transverse placement of electrodes, pulses were localized correctly, whatever the configuration and the body site might be. In addition, intrasubject variability at the forearm was smaller for the transverse axis than for the longitudinal axis. For the longitudinal placement of electrodes, pulses were localized as a function of configuration and body site. At the fingers, concentric electrodes provided precise localization but unifocal electrodes provided a great mislocalization; and intrasubject variability ·of localization was larger for the unifocal electrodes than for the concentric electrodes. At the forearm, whatever the configuration might be, the pulses were localized more proximally than the stimulus site; and intrasubject variability of localization did not differ between the configurations. These results are related to Boring's anchor theory, apparent distance between two points, and the localization of other somatosensory stimuli.

“…A pair of rectangular silver electrodes were constructed to fit into a plastic plate (I cm wide x 2.9 cm long) that was strapped to the underside of the subject's right wrist in the vicinity of the ulnar nerve. The size of each electrode was I x .7 cm; the longer side of an electrode faced that of another electrode, with the inner edges separated laterally by a distance of 1.5 cm (for details of electrodes, see Higashiyama & Tashiro, 1983).…”

Section: Apparatusmentioning

confidence: 99%

Magnitude estimates for electrical pulses: Evidence for two neural mechanisms

Tashiro

1989

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The hypothesis that there are two neural mechanisms for electrocutaneous stimulation-one that is sensitive to low current and is adaptive to repeated stimulation and another that is responsive to high current and is less adaptive-was tested in a control and four main experiments. In the main experiments, magnitude estimates obtained for single electrical pulses (of 2-msec duration) were described by a simple power function for each combination of high-and low-current levels and 10 trial blocks. The results were: (1) The slope of the power function for low current was steeper than was that for high current; (2) for low current, the intercept of the power function decreased with increasing block, whereas for high current, it remained constant over blocks; (3) this decrease of the intercept for low current disappeared when judgmental blocks were separated by a rest period of 8 min; (4) the modulus did not affect the slope; (5) for a large modulus combined with low current, the intercept decreased rapidly over trial blocks, whereas for a small modulus combined with high current, the intercept increased over trial blocks. The fIrst four fIndings support the two-mechanism hypothesis, but the last one may also be interpretable in terms of the regression to absolute scale values.Higashiyama and Tashiro (1987) obtained free-modulus magnitude estimates for single electrical pulses as a function of stimulus current, with the parameters of trial block and current level. For the high-current level, which produced pain responses, the magnitude estimates remained constant independently of block, whereas for the low-current level, which yielded tactile sensations, they decreased as a function of block. In addition, the exponents of power functions fItted to the magnitude estimates were smaller for the high-current level (2.02) than were those for the low-current level (4.06). These fIndings have led them to suggest that there are two neural mechanisms with different adaptation processes: One is sensitive to low current and is very adaptive to repeated stimulation, and another is responsive to high current and is less adaptive.However, these outcomes also could be explained in terms of a natural absolute scale. Zwislocki and Goodman (1980) argued that subjects tend to use absolute judgments rather than ratio judgments when making magnitude estimations or productions of sensation. In usual ratio scales, the unit of measurement is arbitrary and can be changed by multiplying all scale values by a constant. In absolute scales, on the other hand, the unit is not arbitrary