Abstract:Hemispheric asymmetries for tactile simultaneity judgments were investigated in 34 dextral adults. Pairs of vibrotactile stimuli with simultaneous or successive onsets were delivered unilaterally to the left or right hand. Participants made a forced-choice, bipedal response, indicating whether a stimulus was simultaneous or successive. The effect of hemispatial attentional biases was investigated, using ipsilateral (arms uncrossed) and contralateral (arms crossed) hand placements. Trialspresented to the right … Show more
“…The performance in the 3-pin 1-finger condition dropped to 75% at 20 Hz, where the phase difference between the adjacent pins was 12.5 ms. This is close to the previously reported best performance of human temporal discrimination with single taps 23 – 27 . Figure 3 Results of asynchrony discrimination with sine waves (experiment 1A).…”
Section: Resultssupporting
confidence: 91%
“…The frequency of vibration is within the low-frequency range preferred by the non-PC channels (<40 Hz), where the information about the input waveform is well stored in the pattern of neural firings 12 , 16 – 22 . The phase difference among the low-frequency sine waves matches the behavioural effective range of tactile temporal judgments (20–100 ms) 23 – 27 . Figure 2 Stimulus arrangements and time sequence.…”
When we touch an object, the skin copies its surface shape/texture, and this deformation pattern shifts according to the objects movement. This shift pattern directly encodes spatio-temporal “motion” information of the event, and has been detected in other modalities (e.g., inter-aural time differences for audition and first-order motion for vision). Since previous studies suggested that mechanoreceptor-afferent channels with small receptive field and slow temporal characteristics contribute to tactile motion perception, we tried to tap the spatio-temporal processor using low-frequency sine-waves as primitive probes in our previous study. However, we found that asynchrony of sine-wave pair presented on adjacent fingers was difficult to detect. Here, to take advantage of the small receptive field, we investigated within-finger motion and found above threshold performance when observers touched localized sine-wave stimuli with one finger. Though observers could not perceptually discriminate rightward from leftward motion, the adaptation occurred in a direction-sensitive way: the motion/asynchronous detection was impaired by adapting to asynchronous stimuli moving in the same direction. These findings are consistent with a possibility that human can directly encode short-range spatio-temporal patterns of skin deformation by using phase-shifted low-frequency components, in addition to detecting short- and long-range motion using energy shifts of high-frequency components.
“…The performance in the 3-pin 1-finger condition dropped to 75% at 20 Hz, where the phase difference between the adjacent pins was 12.5 ms. This is close to the previously reported best performance of human temporal discrimination with single taps 23 – 27 . Figure 3 Results of asynchrony discrimination with sine waves (experiment 1A).…”
Section: Resultssupporting
confidence: 91%
“…The frequency of vibration is within the low-frequency range preferred by the non-PC channels (<40 Hz), where the information about the input waveform is well stored in the pattern of neural firings 12 , 16 – 22 . The phase difference among the low-frequency sine waves matches the behavioural effective range of tactile temporal judgments (20–100 ms) 23 – 27 . Figure 2 Stimulus arrangements and time sequence.…”
When we touch an object, the skin copies its surface shape/texture, and this deformation pattern shifts according to the objects movement. This shift pattern directly encodes spatio-temporal “motion” information of the event, and has been detected in other modalities (e.g., inter-aural time differences for audition and first-order motion for vision). Since previous studies suggested that mechanoreceptor-afferent channels with small receptive field and slow temporal characteristics contribute to tactile motion perception, we tried to tap the spatio-temporal processor using low-frequency sine-waves as primitive probes in our previous study. However, we found that asynchrony of sine-wave pair presented on adjacent fingers was difficult to detect. Here, to take advantage of the small receptive field, we investigated within-finger motion and found above threshold performance when observers touched localized sine-wave stimuli with one finger. Though observers could not perceptually discriminate rightward from leftward motion, the adaptation occurred in a direction-sensitive way: the motion/asynchronous detection was impaired by adapting to asynchronous stimuli moving in the same direction. These findings are consistent with a possibility that human can directly encode short-range spatio-temporal patterns of skin deformation by using phase-shifted low-frequency components, in addition to detecting short- and long-range motion using energy shifts of high-frequency components.
“…However, morphometric and cytoarchitectonic measurements show no lateralized differences in somatosensory cortices [79]. Psychophysical tests show no differences in spatial acuity between hands [80,81], although there does appear to be a left-hemisphere advantage for tactile processing of simultaneity judgment [82]. Furthermore, as in our study, previous somatosensory evoked potential studies show no difference in topography or response amplitude between the two hemispheres [83,84].…”
Background: Our goal was to examine the spatiotemporal integration of tactile information in the hand representation of human primary somatosensory cortex (anterior parietal somatosensory areas 3b and 1), secondary somatosensory cortex (S2), and the parietal ventral area (PV), using high-resolution whole-head magnetoencephalography (MEG). To examine representational overlap and adaptation in bilateral somatosensory cortices, we used an oddball paradigm to characterize the representation of the index finger (D2; deviant stimulus) as a function of the location of the standard stimulus in both right-and left-handed subjects.
“…Therefore, the functional asymmetry of the somatosensory cortex, separate from well documented asymmetries in the motor and language cortices, yields information about the specialized processing of somatosensory cognitive input. For example, a previous investigation has reported on a left-hemisphere temporal processing advantage, evidence that there exists a hemispheric specialization for tactile simultaneity judgments (Nicholls and Lindell, 2000).…”
Section: An Asymmetry Of Brain Function and Psychophysiologymentioning
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