Inhibition of return in children with Tourette's syndrome and comorbid forms: a preliminary study.

BACKGROUND: This study investigated the nature and functioning of the visual-spatial inhibition of return (IOR) phenomenon in children with "pure" Tourette's syndrome (TS), and those with comorbid forms of TS. METHOD: Children with TS-only and "TS + comorbid" (TS + ADHD +/- OCD) and matched controls performed the inhibition of return (IOR) task, which involved responding to left and right visual targets appearing on a computer screen that were preceded by congruent or incongruent exogenous visual cues. RESULTS: The TS-only group performed similarly on the IOR task to the controls. When the TS-only group was subdivided into children with mild and severe TS symptoms, a post hoc comparison between the controls and severe TS symptom children revealed that these TS children had a reduced magnitude of IOR for targets appearing in the right visual field. The comparison between the TS + comorbid and controls revealed an atypical IOR pattern for the TS + comorbid group. They displayed a loss of normal facilitatory and inhibitory effects for right visual field targets. CONCLUSIONS: The findings suggest abnormalities in attentional "disengage" and "move" mechanisms in TS when directing attention to the right visual field, which may reflect left posterior parietal, superior colliculus, and midbrain pathology.     

Perfectionism, academic motivation, and psychological adjustment: an integrative model

The purpose of this article was to propose and test an integrative model on the role of perfectionism, academic motivation, and psychological adjustment difficulties in undergraduate students. The model posits that self-oriented perfectionism facilitates self-determined academic motivation, whereas socially prescribed perfectionism enhances non-self-determined academic motivation. In turn, self-determined and non-self-determined academic motivations, respectively, lead to lower and higher levels of psychological adjustment difficulties. Results from two studies using structural equation modeling analyses provided support for the model.     

Categorization and abstraction abilities in 3-year-old children: a comparison with monkey data

Three-year-old children were tested on three categorization tasks of increasing levels of abstraction (used with adult baboons in an earlier study): the first was a conceptual categorization task (food vs toys), the second a perceptual matching task (same vs different objects), and the third a relational matching task in which the children had to sort pairs according to whether or not the two items belonged to the same or different categories. The children were tested using two different procedures, the first a replication of the procedure used with the baboons (pulling one rope for a category or a relationship between two objects, and another rope for the other category or relationship), the second a task based upon childrens prior experiences with sorting objects (putting in the same box objects belonging to the same category or a pair of objects exemplifying the same relation). The children were able to solve the first task (conceptual categorization) when tested with the sorting into boxes procedure, and the second task (perceptual matching) when tested with both procedures. The children were able to master the third task (relational matching) only when the rules were clearly explained to them, but not when they could only watch sorting examples. In fact, the relational matching task without explanation requires analogy abilities that do not seem to be fully developed at 3 years of age. The discrepancies in performances between children tested with the two procedures, with the task explained or not, and the discrepancies observed between children and baboons are discussed in relation to differences between species and/or problem-solving strategies.     

Text cohesion and metacomprehension: Immediate and delayed judgments

In three experiments, we examined comprehension judgments made after a piece of text had been read. We propose that such metacognitive judgments are based on the content of working memory at the exact moment of assessment. Generally speaking, this working metacognition hypothesis is in agreement with Koriat's cue utilization approach, which implies that different elements of information will be available (and used) depending on the moment at which a judgment is made. More specifically, our hypothesis focuses on the management of working memory during reading as a cause for cue (un)availability. In support of these views, the results of Experiment 1 showed that a cohesion manipulation affecting the comprehension of specific paragraphs influences judgments only on these paragraphs, and not on judgments on the whole text. In Experiment 2, we showed that an interfering task that takes place just before this paragraph judgment is made wipes out this cohesion effect. Experiment 3 showed, on the other hand, that the whole-text judgment may, nevertheless, be affected by text cohesion, provided that the readers keep an access to the text when the judgment is made. These results support the idea that working memory management makes different cues available for metacognitive ratings at different delays.     

Stabilization and destabilization of perception--action patterns influence the self-organized recruitment of degrees of freedom

The recruitment of an additional biomechanical degree of freedom in a unimanual rhythmic task was explored. Subjects were asked to synchronize adduction or abduction of their right index finger with a metronome, the frequency of which was increased systematically. In addition, haptic contact on or off the metronome beat was provided. Results showed that the pattern exhibiting the highest intrinsic stability recruited the vertical plane more than did the less stable one. Moreover, presence and location of haptic contact modulated coordination stability and therefore induced changes in the recruitment of the vertical plane. Thus, a trade-off was shown between coordination stability on the horizontal plane and recruitment of the vertical one. These findings suggest that recruitment of degrees of freedom is governed by general principles of coordination dynamics.     

Processing reduced word forms: the suffix restoration effect

Listeners cannot recognize highly reduced word forms in isolation, but they can do so when these forms are presented in context (Ernestus, Baayen, & Schreuder, 2002). This suggests that not all possible surface forms of words have equal status in the mental lexicon. The present study shows that the reduced forms are linked to the canonical representations in the mental lexicon, and that these latter representations induce reconstruction processes. Listeners restore suffixes that are partly or completely missing in reduced word forms. A series of phoneme-monitoring experiments reveals the nature of this restoration: the basis for suffix restoration is mainly phonological in nature, but orthography has an influence as well.     

On discontinuities in motor learning: a longitudinal study of complex skill acquisition on a ski-simulator

The qualitative behavioral reorganizations that occurred during the acquisition of a complex motor skill were examined. Five novice participants practiced for 39 sessions of ten 1-min trials on a modified version of the ski-simulator. Analyses focused on the motion of the apparatus platform, modeled as a self-sustained oscillator. At the beginning of the experiment, all participants adopted a behavior that could be modeled with a highly nonlinear stiffness function and a Rayleigh damping function. The behavior in the final part of the experiment was captured by a qualitatively different model, with a linear stiffness function and a van der Pol damping behavior. The transition from the initial to the final model was gradual and was marked in most cases by an abrupt increase of oscillation frequency. During the transition stage, the 2 damping behaviors seemed alternately exploited within each trial. The results are discussed in the framework of the dynamical systems approach to motor coordination and learning, considering motor skill acquisition as a phase transition.     

Modulation of tremor amplitude during deep brain stimulation at different frequencies

Rest tremor was quantified in the index finger tip of 16 patients with Parkinson's disease (PD) receiving deep brain stimulation (DBS) of the ventro-intermediate nucleus (Vim) of the thalamus, the subthalamic nucleus (STN), or the internal part of the globus pallidus (GPi) while being off L-dopa for 12h. Clinically, without DBS, tremor amplitude varied from absent to high. Tremor was recorded continuously for about 5 min under three conditions of DBS repeated twice, namely, effective frequency (E), ineffective frequency (I), and no DBS (O). No changes in tremor were observed across conditions in subjects with little or no tremor. However, in subjects with moderate to large amplitude tremor, DBS decreased tremor amplitude to near normal values within a few seconds. Generally, transitions were progressive and occurred with a varying time delay. Occasionally, tremor escaped from control regardless of the stimulation condition considered. In some cases tremor amplitude in one condition appeared to depend on the preceding condition. Finally, the results were reproducible on two consecutive days. We conclude that tremor control with DBS follows specific dynamical rules, which must be compatible with the hypotheses proposed regarding the underlying mechanisms of DBS.     

Neuropsychological Characteristics of Adolescents With Conduct Disorder: Association With Attention-Deficit–Hyperactivity and Aggression

The purpose of this study was to determine whether an association exists between neuropsychological deficits and conduct disorder (CD) with and without concurrent attention-deficit–hyperactivity disorder (ADHD). In addition, we explored the differential neuropsychological performance of aggressive and nonaggressive CD adolescents and the combined effect of this behavioral status and ADHD on performance. Fifty-nine adolescents (mean age of 15.4 years) who met the criteria for CD were compared with 29 controls comparable in age, gender, and socioeconomic status. A neuropsychological battery of current tests measuring executive functions and a battery of language tests were used in the study. Multivariate analyses showed that, compared with controls, CD adolescents had significantly lower verbal skills but did not differ on executive function measures. However, the lower verbal performance of CD adolescents is not explained by the existence of a CD subgroup with concomitant ADHD or aggressiveness. The study confirms with a sample of CD adolescents the association between verbal deficits and antisocial behavior when socioeconomic status is controlled. Our results also demonstrate that CD per se can be a sufficient condition for such deficits.