Sensory temporal processing in adults with early hearing loss.

This study examined tactile and visual temporal processing in adults with early loss of hearing. The tactile task consisted of punctate stimulations that were delivered to one or both hands by a mechanical tactile stimulator. Pairs of light emitting diodes were presented on a display for visual stimulation. Responses consisted of YES or NO judgments as to whether the onset of the pairs of stimuli was perceived simultaneously or non-simultaneously. Tactile and visual temporal thresholds were significantly higher for the deaf group when compared to controls. In contrast to controls, tactile and visual temporal thresholds for the deaf group did not differ when presentation locations were examined. Overall findings of this study support the notion that temporal processing is compromised following early deafness regardless of the spatial location in which the stimuli are presented.

Temporal judgments, hemispheric equivalence, and interhemispheric transfer in adolescents with attention deficit hyperactivity disorder.

This study investigated temporal processing abilities, hemispheric asymmetry, interhemispheric transfer, and stimulant medication effects in adolescents with attention deficit hyperactivity disorder (ADHD). Pairs of light emitting diodes in a visual half-field display (i.e., bilateral and unilateral presentations) were presented to examine medication effects, temporal judgments, hemispheric asymmetry, and interhemispheric transfer in male adolescents with ADHD and matched controls on age and gender. Participants responded (YES/NO) whether pairs of spatially separated diodes were illuminated simultaneously. Stimulant medication did not have an affect on temporal judgments, hemispheric equivalence, or interhemispheric transfer. No group differences in temporal judgments in any of the paired conditions were revealed. Both the ADHD and control groups demonstrated hemispheric equivalence for temporal judgments. Unexpectedly, the ADHD group demonstrated significantly faster interhemispheric transfer times when compared to the control group. The overall findings indicate that the reported deficit in time perception among individuals with ADHD may be restricted to tasks that involve response inhibition, reaction time, and/or motor movements (e.g., replicate durations of stimuli by pressing a lever).

Sensory temporal thresholds and interhemispheric transfer times in multiple sclerosis: a preliminary study of a new outcome measure.

This preliminary study investigated the potential of a cerebral lateralization technique that measures both, temporal judgements to sensory stimuli and interhemispheric transfer time (IHTT), as an outcome measure in multiple sclerosis (MS). Tactile stimulation was delivered to one or both hands by mechanical tactile stimulators. Pairs of light emitting diodes were presented to hemifields for visual stimulation. Response consisted of a binary forced-choice (YES/NO) judgement as to the simultaneity of the onset of pairs of stimuli. Both tactile and visual temporal thresholds were significantly higher in MS patients than controls in every presentation condition. IHTT estimates (threshold differences between unilateral and bilateral presentations) for the tactile and visual tasks were also significantly longer in patients than controls. Age correlated with sensory temporal thresholds for the control group only. These findings suggest that this technique may be a useful outcome measure in MS. We hypothesize that myelin injury slows central conduction therefore impairing the ability to judge the onset of sensory stimuli and increasing IHTTs.

Age- and sex-related differences in temporal judgments to visual stimuli: support for hemispheric equivalence.

Light-emitting diodes in avisual half-field display were employed to examine hemispheric asymmetries in temporal resolution among young and older adults. Participants judged whether pairs of spatially separated diodes were illuminated simultaneously. No visual field threshold differences emerged for either age group, thus supporting hemispheric equivalence. Older adults had significantly higher thresholds than did younger adults, regardless of spatial location. The results further revealed that older females had significantly higher thresholds than did older males, younger males, and younger females. The results further revealed sex differences, favoring females, when interhemispheric transfer times (IHTTs) were examined for a central bilateral presentation. However, sex effects were not revealed when IHTTs were examined for a peripheral bilatepresentation, indicating a disadvantage forolder females.

Gaze pursuit and arm control of adolescent males diagnosed with attention deficit hyperactivity disorder (ADHD) and normal controls: evidence of a dissociation in processing visual information of short and long duration.

Three-dimensional kinematic analysis of line of gaze, arm and ball was used to describe the visual and motor behaviour of male adolescents diagnosed with attention deficit hyperactivity disorder (ADHD). The ADHD participants were tested when both on (ADHD-On) and off (ADHD-Off) their medication and compared to age-matched normal controls in a modified table tennis task that required tracking the ball and hitting to cued right and left targets. Long-duration information was provided by a pre-cue, in which the target was illuminated approximately 2 s before the serve, and short-duration information by an early-cue illuminated about 350 ms after the serve, leaving approximately 500 ms to select the target and perform the action. The ADHD groups differed significantly from the control group in both the pre-cue and early-cue conditions in being less accurate, in having a later onset and duration of pursuit tracking, and a higher frequency of gaze on and off the ball. The use of medication significantly reduced the gaze frequency of the ADHD participants, but surprisingly this did not lead to an increase in pursuit tracking, suggesting a barrier was reached beyond which ball flight information could not be processed. The control and ADHD groups did not differ in arm movement onset, duration and velocity in the short-duration early-cue condition; in the long-duration pre-cue condition, however, the ADHD group's movement time onset and arm velocity differed significantly from controls. The results show that the ADHD groups were able to process short-duration information without experiencing adverse effects on their motor behaviour; however, long-duration information contributed to irregular movement control.

ADHD comorbidity findings from the MTA study: comparing comorbid subgroups.

OBJECTIVES: Previous research has been inconclusive whether attention-deficit/hyperactivity disorder (ADHD), when comorbid with disruptive disorders (oppositional defiant disorder [ODD] or conduct disorder [CD]), with the internalizing disorders (anxiety and/or depression), or with both, should constitute separate clinical entities. Determination of the clinical significance of potential ADHD + internalizing disorder or ADHD + ODD/CD syndromes could yield better diagnostic decision-making, treatment planning, and treatment outcomes. METHOD: Drawing upon cross-sectional and longitudinal information from 579 children (aged 7-9.9 years) with ADHD participating in the NIMH Collaborative Multisite Multimodal Treatment Study of Children With Attention-Deficit/Hyperactivity Disorder (MTA), investigators applied validational criteria to compare ADHD subjects with and without comorbid internalizing disorders and ODD/CD. RESULTS: Substantial evidence of main effects of internalizing and externalizing comorbid disorders was found. Moderate evidence of interactions of parent-reported anxiety and ODD/CD status were noted on response to treatment, indicating that children with ADHD and anxiety disorders (but no ODD/CD) were likely to respond equally well to the MTA behavioral and medication treatments. Children with ADHD-only or ADHD with ODD/CD (but without anxiety disorders) responded best to MTA medication treatments (with or without behavioral treatments), while children with multiple comorbid disorders (anxiety and ODD/CD) responded optimally to combined (medication and behavioral) treatments. CONCLUSIONS: Findings indicate that three clinical profiles, ADHD co-occurring with internalizing disorders (principally parent-reported anxiety disorders) absent any concurrent disruptive disorder (ADHD + ANX), ADHD co-occurring with ODD/CD but no anxiety (ADHD + ODD/CD), and ADHD with both anxiety and ODD/CD (ADHD + ANX + ODD/CD) may be sufficiently distinct to warrant classification as ADHD subtypes different from "pure" ADHD with neither comorbidity. Future clinical, etiological, and genetics research should explore the merits of these three ADHD classification options.