Impulsiveness as a timing disturbance: neurocognitive abnormalities in attention-deficit hyperactivity disorder during temporal processes and normalization with methylphenidate.

We argue that impulsiveness is characterized by compromised timing functions such as premature motor timing, decreased tolerance to delays, poor temporal foresight and steeper temporal discounting. A model illustration for the association between impulsiveness and timing deficits is the impulsiveness disorder of attention-deficit hyperactivity disorder (ADHD). Children with ADHD have deficits in timing processes of several temporal domains and the neural substrates of these compromised timing functions are strikingly similar to the neuropathology of ADHD. We review our published and present novel functional magnetic resonance imaging data to demonstrate that ADHD children show dysfunctions in key timing regions of prefrontal, cingulate, striatal and cerebellar location during temporal processes of several time domains including time discrimination of milliseconds, motor timing to seconds and temporal discounting of longer time intervals. Given that impulsiveness, timing abnormalities and more specifically ADHD have been related to dopamine dysregulation, we tested for and demonstrated a normalization effect of all brain dysfunctions in ADHD children during time discrimination with the dopamine agonist and treatment of choice, methylphenidate. This review together with the new empirical findings demonstrates that neurocognitive dysfunctions in temporal processes are crucial to the impulsiveness disorder of ADHD and provides first evidence for normalization with a dopamine reuptake inhibitor.

Attention disengagement in children with developmental coordination disorder

Purpose. Previous research has shown that children with Developmental Coordination Disorder (DCD) have poorly developed strategies for allocating attention. This study examines the allocation of attention and integration of visuo-spatial and motor systems in children with DCD in a motor (look+hit condition) and a motor-free (look condition) task. Method. Three groups of control children were used to compare the performance of a group of children with DCD. Children were seated in front of a central fixation point and six peripheral targets, and were asked to look at or hit targets when illuminated. Saccade/hand movement latencies were measured on gap trials (gap between fixation offset and target onset) and overlap trials (fixation offset and target onset overlapped). Results. DCD children were not slower than controls to disengage attention during the look condition. However, during the look+hit condition the DCD children showed a prolonged disengagement period, which was also seen in younger control children. Conclusions. The results suggest that DCD children may have deficits in the allocation of attention for action, in both the speed of onset of a movement and the accuracy of the movement. It is concluded that attention disengagement may contribute to problems of visuo-motor integration in DCD.

Self-esteem and coping in children with developmental coordination disorder

This study investigated self-esteem in children with developmental coordination disorder (DCD). Fifteen children between the ages of 8 and 12 years diagnosed with DCD were compared with a typically developing group comprising 30 children with average and good motor abilities, using measures of perceived competence, social support and self-esteem. The types of coping strategy generated in response to example vignettes were also compared. There was no significant difference between the groups in global self-esteem, but the children with DCD reported lower athletic and scholastic competence than their typically developing peers. No difference was found between the groups in level of perceived social support. The DCD group generated fewer coping strategies overall, but more passive and avoidant strategies than the typically developing children. The implications of the study are discussed with regard to future research directions, such as the investigation of the effects of motor skill intervention on self-esteem and the development of strategies to protect children's self-esteem.

Investigation of language and motor skills in Serbian speaking children with specific language impairment and in typically developing children

Specific language impairment (SLI) is usually defined as a developmental language disorder which does not result from a hearing loss, autism, neurological and emotional difficulties, severe social deprivation, low non-verbal abilities. Children affected with SLI typically have difficulties with the acquisition of different aspects of language and by definition, their impairment is specific to language and no other skills are affected. However, there has been a growing body of literature to suggest that children with SLI also have non-linguistic deficits, including impaired motor abilities. The aim of the current study is to investigate language and motor abilities of a group of thirty children with SLI (aged between 4 and 7) in comparison to a group of 30 typically developing children matched for chronological age. The results showed that the group of children with SLI had significantly more difficulties on the language and motor assessments compared to the control group. The SLI group also showed delayed onset in the development of all motor skills under investigation in comparison to the typically developing group. More interestingly, the two groups differed with respect to which language abilities were correlated with motor abilities, however Imitation of Complex Movements was the unique skill which reliably predicted expressive vocabulary in both typically developing children and in children with SLI.

Speech motor control in fluent and dysfluent speech production of an individual with apraxia of speech and Broca’s aphasia

Apraxia of speech (AOS) is typically described as a motor-speech disorder with clinically well-defined symptoms, but without a clear understanding of the underlying problems in motor control. A number of studies have compared the speech of subjects with AOS to the fluent speech of controls, but only a few have included speech movement data and if so, this was primarily restricted to the study of single articulators. If AOS reflects a basic neuromotor dysfunction, this should somehow be evident in the production of both dysfluent and perceptually fluent speech. The current study compared motor control strategies for the production of perceptually fluent speech between a young woman with apraxia of speech (AOS) and Broca’s aphasia and a group of age-matched control speakers using concepts and tools from articulation-based theories. In addition, to examine the potential role of specific movement variables on gestural coordination, a second part of this study involved a comparison of fluent and dysfluent speech samples from the speaker with AOS. Movement data from the lips, jaw and tongue were acquired using the AG-100 EMMA system during the reiterated production of multisyllabic nonwords. The findings indicated that although in general kinematic parameters of fluent speech were similar in the subject with AOS and Broca’s aphasia to those of the age-matched controls, speech task-related differences were observed in upper lip movements and lip coordination. The comparison between fluent and dysfluent speech characteristics suggested that fluent speech was achieved through the use of specific motor control strategies, highlighting the potential association between the stability of coordinative patterns and movement range, as described in Coordination Dynamics theory.