Practice-Related Improvements in Somatosensory Interval Discrimination Are Temporally Specific But Generalize across Skin Location, Hemisphere, and Modality

Abstract

This paper concerns the characterization of performance and perceptual learning of somatosensory interval discrimination. The purposes of this study were to define (1) the performance characteristics for interval discrimination in the somatosensory system by naive adult humans, (2) the normal capacities for improvement in somatosensory interval discrimination, and (3) the extent of generalization of interval discrimination learning. In a two-alternative forced choice procedure, subjects were presented with two pairs of vibratory pulses. One pair was separated in time by a fixed base interval; a second pair was separated by a target interval that was always longer than the base interval. Subjects indicated which pair was separated by the target interval. The length of the target interval was varied adaptively to determine discrimination thresholds. After initial determination of naive abilities, subjects were trained for 900 trials per day at base intervals of either 75 or 125 msec for 10-15 d. Significant improvements in thresholds resulted from training. Learning at the trained base interval generalized completely across untrained skin locations on the trained hand and to the corresponding untrained skin location in the contralateral hand. The learning partially generalized to untrained base intervals similar to the trained one, but not to more distant base intervals. Learning with somatosensory stimuli generalized to auditory stimuli presented at comparable base intervals. These results demonstrate temporal specificity in somatosensory interval discrimination learning that generalizes across skin location, hemisphere, and modality.

Perceptual learning in auditory temporal discrimination: No evidence for a cross-modal transfer to the visual modality

“…This is consistent with Karmarkar and Buonomano's hypothesis that nontemporal features of the auditory signal do not influence transfer effects within the auditory modality within the same interval duration. This finding also agrees with the other reports of transfer effects across different auditory frequencies (for auditory training, see Karmarkar & Buonomano, 2003;Wright et al, 1997) and across different skin locations (for somatosensory training, see Nagarajan et al, 1998). Second, and in contrast to previous findings (Karmarkar & Buonomano, 2003;Wright et al, 1997), our subjects also exhibited an improvement of temporal discrimination in the untrained AE500 condition.…”

“…The procedure was similar to that in previous perceptual learning studies on temporal discrimination (Karmarkar & Buonomano, 2003;Nagarajan et al, 1998;Wright et al, 1997). On each trial, two stimuli of the same type were presented successively.…”

“…In another study on temporal perceptual learning (Nagarajan, Blake, Wright, Byl, & Merzenich, 1998), subjects performed a 2AFC task on tactile stimuli presented to one of their hands during the training phase. For one group, the duration of the training stimulus was 75 msec, and it was 125 msec for the other group.…”

“…Furthermore, they employed a pretest session before the training phase and a posttest session after the training phase to assess whether this learning would generalize to intervals empty interval of 100 msec, with visual markers (VE100). Similar to the design of previous studies (Karmarkar & Buonomano, 2003;Nagarajan et al, 1998;Wright et al, 1997), potential transfer effects of perceptual learning were assessed by a standard pretest-training-posttest design.…”

Auditory Cortical Plasticity in Learning to Discriminate Modulation Rate

“…For instance, training on a pitch/frequency discrimination task leads to rapid and robust learning (Demany, 1985;Irvine et al, 1985;Moore et al, 2003;Hawkey et al, 2004), although optimal learning may depend on task difficulty (Amitay et al, 2006). In contrast, recent studies show that the discrimination of time intervals is enhanced in the auditory and somatosensory modalities only after intensive training (Wright et al, 1997;Nagarajan et al, 1998;Karmarkar and Buonomano, 2003). To date, very few studies have addressed the neural mechanisms underlying auditory perceptual learning, and virtually none have specifically focused on the time dimension despite its fundamental role in the perceptual categorization of acoustic events.…”