Reduction of Pain Sensitivity after Somatosensory Therapy in Children with Autism Spectrum Disorders

Children with autism spectrum disorders (ASD) often present with somatosensory dysfunction including an abnormal reactivity to tactile stimuli and altered pain perception. A therapy based on somatosensory stimuli has shown effectiveness in reducing pain sensitivity among adults with cerebral palsy. The present study aims at exploring the influence of somatosensory therapy on somatosensory parameters in children with ASD. Children with high-functioning ASD were randomly assigned to either the intervention (n?=?29) or the control group (n?=?30). The intervention group received a somatosensory therapy consisting of four types of exercises (touch, proprioception, vibration, stereognosis). Somatosensory function (pressure pain thresholds, tactile thresholds, stereognosis, proprioception) was assessed before and immediately after the therapy. Children in the intervention group showed a significant reduction of pain sensitivity and increase of tactile sensitivity after treatment, whereas children in the control group displayed increased pain sensitivity in the absence of changes of tactile sensitivity. No changes were observed for proprioception or stereognosis. The repetitive somatosensory stimulation therapy led to a decrease of pain sensitivity and an increase of tactile sensitivity. These findings may have important research and clinical implications, as promoting early tactile interventions in children with ASD may lead to a more adequate development of somatosensory processing and less somatosensory abnormalities upon adult life.     

Category-level contributions to the alphanumeric category effect in visual search

Do letter and digit recognition depend on the same or different cognitive mechanisms? Letters are detected more quickly among digits than among letters; likewise, digit search is facilitated when distractors are letters, as opposed to digits. This effect suggests that different mechanisms underlie recognition of these two categories. There are, however, systematic physical differences between letters and digits that might account for the effect. We used target and distractor stimuli that facilitated within-category search when inverted, and category identity was, thereby, attenuated. However, in conditions of upright search, in which category identity was more salient, between-category search was more efficient for the same stimuli. These findings suggest that letter and digit recognition are, at least to a degree, functionally independent.     

Part‐based representations of the body in early childhood: evidence from perceived distortions of tactile space across limb boundaries

Studies show that touch in adults is referenced to a representation of the body that is structured topologically according to body parts; the perceived distance between two stimuli crossing over a body part boundary is elongated relative to the perceived distance between two stimuli presented within one body part category. Here we investigate this influence of body parts on tactile space perception in children of 5, 6 and 7 years of age. We presented children with pairs of tactile stimuli on the left hand/arm, either within the hand, within the forearm, or over the wrist. With their eyes closed children were asked to adjust the distance between the thumb and forefinger of their right hand to represent the felt distance between the two tactile stimuli. Like adults, the children perceived the distance between two stimuli that cross the body part boundary to be further apart than those that were presented within the hand or arm. They also perceive tactile distance to be greater on the hand than the arm which is the first observation of Weber's illusion in young children. We propose that a topological mode of body representation is particularly advantageous during early life given that body part categories remain constant while the metric proportions of the body change substantially as the child grows.     

Tactile retention: Reading with the skin

In four experiments, subjects were required to identify sequences of random digits, letters, or words drawn on the skin. The passive tactile digit span was determined to be three items when the digits were drawn with an interstimulus interval of 1 sec. Identification was significantly better for words than for random letter sequences. Slower rates of presentation produced better tactile retention. The deficiencies in passive retention were ascribed to two processes, the generation of aftersensations and a difficulty in the generation of a unitary percept. Perceptual activity may normally act to inhibit aftersensations and facilitate the construction of a unitary percept The results supported the notion that the tactile span of immediate memory is labile and may be limited by passivity.     

The role of transparency in perceptual grouping and pattern recognition.

The shortest stimulus exposure time for which transparency can be seen was examined. In the first experiment, overlapping digits were presented for 120 ms and the luminance in the overlapping regions was varied. Subjects reported, in separate blocks of trials, either the apparent transparency of the digits or the identity of the digits. When the luminance was set so that one set of digits appeared to be seen through the other, recognition of the digits was high. When the luminance in the overlapping regions did not produce impressions of transparency, digit recognition was low. In the second experiment, digit identification at several stimulus durations was compared between stimuli that had luminance that was valid for transparency and stimuli that had invalid luminance. Performance was found to be higher in the valid luminance condition than in the invalid condition after as little as 60 ms exposure duration. This result suggests that the impression of transparency requires only relatively short exposure durations.     

Tactile sensitivity of children: effects of frequency, masking, and the non-Pacinian I psychophysical channel

Tactile perception depends on the contributions of four psychophysical tactile channels mediated by four corresponding receptor systems. The sensitivity of the tactile channels is determined by detection thresholds that vary as a function of the stimulus frequency. It has been widely reported that tactile thresholds increase (i.e., sensitivity decreases) as a function of age. However, there is controversial evidence with regard to the progressive loss of sensitivity starting from childhood. In this study, the tactile thresholds of children (n=9, ages 7-11 years) were measured and compared with the thresholds of young adults (n=11, ages 21-27 years). The stimuli consisted of sinusoidal bursts of mechanical displacements, which were applied to the left index fingertips of the participants by using a cylindrical probe (base area=0.126 cm2) without a contactor surround. Absolute thresholds were measured at frequencies of 2, 10, 40, 100, 250, and 500 Hz without masking. The absolute thresholds decreased at high frequencies and were similar to data from the literature except for some discrepancy because of methodological differences. In addition, the threshold of the non-Pacinian I channel was measured at 40 Hz by elevating the thresholds of the Pacinian channel by forward masking. The effects of forward masking in children were similar to results in young adults. In conclusion, there were no significant differences between the tactile thresholds of children and those of young adults at key frequencies: 40 Hz for the Pacinian and non-Pacinian I channels and 250 Hz for the Pacinian channel. These findings contradict the hypothesis that there is gradual loss of tactile sensitivity starting from childhood to early adulthood. The loss of sensitivity due to aging probably is more abrupt and occurs at a later age.     

Interactive effects of numerical surface form and operand parity in cognitive arithmetic

In Experiment 1, adults (n = 48) performed simple addition, multiplication, and parity (i.e., odd-even) comparisons on pairs of Arabic digits or English number words. For addition and comparison, but not multiplication, response time increased with the number of odd operands. For addition, but not comparison, this parity effect was greater for words than for digits. In Experiment 2, adults (n = 50) solved simple addition problems in digit and word format and reported their strategies (i.e., retrieval or procedures). Procedural strategies were used more for odd than even addends and much more for word than digit problems. The results indicate that problem encoding and answer retrieval processes for cognitive arithmetic are interactive rather than strictly additive stages.     

汉语发展性阅读障碍儿童的不同视野注意能力

以某城市小学三至五年级的学生为研究对象,筛选出发展性阅读障碍和同年龄对照组两组儿童,采用不同视角的刺激探测任务初步探查了汉语发展性阅读障碍儿童的不同视野注意能力及特点。研究使用圆点、数字和汉字三种刺激类型并设置了3°,12°,17°三种视角条件。结果发现,在数字和汉字条件下,汉语发展性阅读障碍儿童对刺激探测的反应时显著长于同年龄对照组儿童,说明在加工复杂刺激时,汉语发展性阅读障碍儿童可能存在知觉加工迟缓的缺陷。但是,汉语发展性阅读障碍儿童并没有表现出扩散的视觉空间注意模式,即更多地注意外侧视野的信息。汉语发展性阅读障碍儿童的视觉空间注意模式与正常儿童相似,表现为随着视角的增加,正确率降低,反应时延长。     

Display vs. memory search for digits and faces among mentally handicapped and MA-matched non-handicapped youngsters

This experiment was designed to explore possible explanations for handicapped individuals' characteristically poor performance on memory scanning tasks. Independent variables included group (mentally handicapped vs. non-handicapped), type of search (display vs. memory), type of stimuli (digits vs. pictures of unfamiliar boys' faces), and load (2, 3, or 4 items to be searched). Results indicated that handicapped and non-handicapped groups did not differ when searching displays but did when searching memory, which suggested that the handicapped group's most significant impairment was specific to some aspect of memory search. Handicapped youngsters were also hindered by increasing loads more than control youngsters were. This result as well as impairment in memory search may have been due to handicapped youngsters' relatively short visual spans. The groups did not differ in their response to the two types of stimuli, faces and digits. Facial search was a considerably more demanding task than digit search for handicapped and normal children.     

Locus and persistence of capacity limitations in visual information processing

Although there is considerable evidence that stimuli such as digits and letters are extensively processed in parallel and without capacity limitations, recent data suggest that only the features of stimuli are processed in parallel. In an attempt to reconcile this discrepancy, we used the simultaneous/successive detection paradigm with stimuli from experiments indicating parallel processing and with stimuli from experiments indicating that only features can be processed in parallel. In Experiment 1, large differences between simultaneous and successive presentations were obtained with an R target among P and Q distractors and among P and B distractors, but not with digit targets among letter distractors. As predicted by the feature integration theory of attention, false-alarm rates in the simultaneous condition were much higher than in the successive condition with the R/PQ stimuli. In Experiment 2, the possibility that attention is required for any difficult discrimination was ruled out as an explanation of the discrepancy between the digit/letter results and the R/PQ and R/PB results. Experiment 3A replicated the R/PQ and R/PB results of Experiment 1, and Experiment 3B extended these findings to a new set of stimuli. In Experiment 4, we found that large amounts of consistent practice did not generally eliminate capacity limitations. From this series of experiments we strongly conclude that the notion of capacity-free letter perception has limited generality.     

The interaction between time and number in a temporal bisection task: a reply to Vicario (2011)

Abstract. We discuss the results of Vicario (2011, Perception 40 23-29), in the light of an experiment designed to bypass some of the limits of that study. There, participants were asked to perform a temporal bisection on numerical stimuli (small or large digits) presented either for 700/900 ms or 2000/2200 ms. For the two longest durations only, bisections of larger digits occurred later than those of smaller digits. Here, subjects judged the temporal position of a flick occurring during the visual presentation of a digit (1, 5, or 9) which lasted on the screen for either 700 ms or 2000 ms. Results revealed no difference in the perceived temporal midpoints of large compared to small digits. In contrast, they showed a response bias: only with the shortest-duration stimuli the digit's magnitude affected the subject's response.     

Finger–digit compatibility in Arabic numeral processing

Finger–digit response compatibility was tested by asking participants to identify Arabic digits by pressing 1 of 10 keys with all 10 fingers. The direction of the finger–digit mapping was varied by manipulating the global direction of the hand–digit mapping as well as the direction of the finger–digit mapping within each hand (in each case, from small to large digits, or the reverse). The hypothesis of a left-to-right mental number line predicted that a complete left-to-right mapping should be easier whereas the hypothesis of a representation based on finger counting predicted that a counting-congruent mapping should be easier. The results show that when all 10 fingers are used to answer, a mapping congruent with the prototypical finger-counting strategy reported by the participants leads to better performance than does a mapping congruent with a left-to-right oriented mental number line, both in palm-down and palm-up postures of the hands, and they demonstrate that finger-counting strategies influence the way that numerical information is mentally represented and processed.     

Roughness perception across the hands

It has previously been shown that the perceived roughness of a surface touched by one digit is influenced by the roughness of a different surface touched simultaneously by another digit on the same hand. The present study was designed to examine whether this is the case when surfaces of varying roughness are touched using digits on separate hands. Participants touched pairs of sandpaper surfaces, in sequence, using the same digit, and identified which of the two was rougher. Roughness discrimination was measured in the presence of distractor surfaces touched simultaneously with the target surface, but using a different digit either on the same or on the other hand. The overall perception of roughness of the attended surfaces was better on the left than on the right hand. Perceived roughness also varied systematically with the roughness of the distractor surfaces. Attended surfaces were more likely to be perceived as smoother when they were paired with smooth rather than rough distractors. Likewise, attended surfaces tended to be perceived as rougher with rough distractors. This pattern of results occurred whether the attended and distractor digits were on the same hand or different hands. These data confirm that it is difficult to restrict tactile attention for roughness to a single digit and show that this difficulty extends to restricting attention to a single hand. Furthermore, the effect of a stimulus at an unattended body location was not simply to impair perception in general, but to bias it in the roughness direction of the distractor surface.     

Dichhaptic hand-order effects with verbal and nonverbal tactile stimulation

The palms of normal right-handed subjects were stimulated dichhaptically, i.e., with competing, bimanually presented tactile stimuli consisting of pairs of letters, pairs of digits, or pairs of line orientations. The subjects were required to identify both stimuli in a particular order, and order of report was compared between hands and across stimulus materials. Results indicated right-hand superiority for letters and left-hand superiority for lines; no hand differences occurred for digits. However, observed differences between hands appeared with second reports only, suggesting that measures of tactile storage are more sensitive to laterality differences than measures closer in time to actual stimulation.     

Do developmental changes in digit span result from acquisition strategies?

This study tested the theoretical proposition that the developmental increase in memory span results from a corresponding increase in the use of grouping strategies. With slow presentation, experimenter-provided grouping eliminated the span differences between sixth graders and adults but, while grouping helped first graders more than adults, a sizable difference in digit span remained. With fast presentation, grouping increased the adults' performance more than the childrens'. Another finding was that both groups of children had greater digit spans with fast presentation than with slow. For adults, the reverse was true.     

Does number data entry rely on the phonological loop?

Two experiments investigated effects of articulatory processing on number data entry. Participants entered four‐digit numbers presented as either words or numerals on a keyboard, either under an articulatory condition or in silence. In Experiment 1, the articulatory condition was articulatory suppression; in Experiment 2, it was vocalisation. In Experiment 1, the articulatory suppression group typed initial digits faster than the silent group, but for subsequent digits, the opposite pattern occurred at least with word stimuli. In Experiment 2, the silent group typed initial digits faster but typed subsequent digits somewhat slower than the vocalisation group. Thus, articulation of numbers, which promotes entry into the phonological loop of working memory, retards processing of initial digits but enhances processing of subsequent digits.     

Musicians' working memory for tones,words, and pseudowords

Studies investigating factors that influence tone recognition generally use recognition tests, whereas the majority of the studies on verbal material use self-generated responses in the form of serial recall tests. In the present study we intended to investigate whether tonal and verbal materials share the same cognitive mechanisms, by presenting an experimental instrument that evaluates short-term and working memories for tones, using self-generated sung responses that may be compared to verbal tests. This paradigm was designed according to the same structure of the forward and backward digit span tests, but using digits, pseudowords, and tones as stimuli. The profile of amateur singers and professional singers in these tests was compared in forward and backward digit, pseudoword, tone, and contour spans. In addition, an absolute pitch experimental group was included, in order to observe the possible use of verbal labels in tone memorization tasks. In general, we observed that musical schooling has a slight positive influence on the recall of tones, as opposed to verbal material, which is not influenced by musical schooling. Furthermore, the ability to reproduce melodic contours (up and down patterns) is generally higher than the ability to reproduce exact tone sequences. However, backward spans were lower than forward spans for all stimuli (digits, pseudowords, tones, contour). Curiously, backward spans were disproportionately lower for tones than for verbal material—that is, the requirement to recall sequences in backward rather than forward order seems to differentially affect tonal stimuli. This difference does not vary according to musical expertise.     

Using both an auditory and a visual short-term store to increase digit span

Can digit span be increased by storing digits nonredundantly in both an auditory short-term store and a visual short-term store (dual storage)? In Experiment 1, when four digits were presented visually and then the remaining digits were presented auditorily, digit span increased three digits over a baseline measurement, but only when the auditorily presented digits were reported first (inverted response). Normal order of response for this presentation was not as effective. Possible reasons for the advantage of inverted response are suggested, based upon dual storage. For all-auditory and all-visual presentations that controlled for parsing, digit span increased only 1 to 1.5 digits over baseline, and inverted and normal order of response did not differ. Experiment 2 demonstrated that an improvement for dual storage could occur when the type of presentation was held constant and the order of response was normal rather than inverted. The results are consistent with the idea of separate auditory and visual short-term stores.     

Musicians' working memory for tones, words, and pseudowords

Studies investigating factors that influence tone recognition generally use recognition tests, whereas the majority of the studies on verbal material use self-generated responses in the form of serial recall tests. In the present study we intended to investigate whether tonal and verbal materials share the same cognitive mechanisms, by presenting an experimental instrument that evaluates short-term and working memories for tones, using self-generated sung responses that may be compared to verbal tests. This paradigm was designed according to the same structure of the forward and backward digit span tests, but using digits, pseudowords, and tones as stimuli. The profile of amateur singers and professional singers in these tests was compared in forward and backward digit, pseudoword, tone, and contour spans. In addition, an absolute pitch experimental group was included, in order to observe the possible use of verbal labels in tone memorization tasks. In general, we observed that musical schooling has a slight positive influence on the recall of tones, as opposed to verbal material, which is not influenced by musical schooling. Furthermore, the ability to reproduce melodic contours (up and down patterns) is generally higher than the ability to reproduce exact tone sequences. However, backward spans were lower than forward spans for all stimuli (digits, pseudowords, tones, contour). Curiously, backward spans were disproportionately lower for tones than for verbal material-that is, the requirement to recall sequences in backward rather than forward order seems to differentially affect tonal stimuli. This difference does not vary according to musical expertise.     

视空间和听觉数字记忆的混合广度

Ｆｒｉｃｋ成功地增加了混合通道的广度,其必要条件是同时呈现视觉刺激和反序报告。该文采用干扰更少的Ｃｏｒｓｉ视空间测验,即序列呈现视觉刺激,并用正序报告,进行混合广度的新实验。发现在分离通道报告的条件下其混合广度都明显地高于单一通道的广度,因此Ｆｒｉｃｋ的两个必要条件不总是必需的。这种新的混合广度实验可能对研究工作记忆的中央执行系统有益。比较了刺激呈现模式和被试反应方式对混合广度的影响