Impaired stimulus-outcome but preserved stimulus-response shifting in young substance-dependent individuals.

Substance dependency has been related to an impairment in executive functions and to a dysfunction of the frontal cortex. In this study we developed two experimental tasks, which are physically identical, to analyze whether substance-dependent individuals are impaired in shifting response patterns (stimulus response links) or preferences (stimulus outcome links). To increase the specificity of the dependent variable, we also used two control tasks to analyze for unspecific performance deficits. We included 35 young subjects with polysubstance abuse (International Classification of Diseases, F19.2 ICD 10 diagnosis, mean age of 22 years, maximum age < 27 years) and 18 normal controls, but for a first step focused on only 22 patients and 15 age-matched controls, because we excluded all patients with an IQ below 100. The results show that the substance-dependent individuals are selectively impaired in shifting object preference (stimulus-outcome links) and not in shifting response patterns. They moreover show a higher general impulsivity as reflected in their faster responses than controls on all tasks except the stimulus-outcome task. In a second step we replicated these results by analyzing the original groups of 35 patients and 18 controls. We argue that substance-dependent subjects show an impairment only on specific executive tasks, and these tasks concern stimulus-outcome link shifting, which has been associated with the functioning of the orbitofrontal cortex, not of the lateral prefrontal cortex.

Disturbed egocentric space representation in cervical dystonia.

In addition to visual spatial input, vestibular and proprioceptive signals are used in judging the egocentric space. We asked whether the abnormal head posture of patients with cervical dystonia (CD) is associated with distortions of their internal spatial reference frame. The perception of subjective straight-ahead (SSA) was tested under various conditions in 28 CD patients and in matched controls. They were asked to direct a laser pointer to the position that they believed to be "straight ahead" relative to their bodies' orientation (body-centered spatial perception). Body-independent visual spatial perception was assessed with different neuropsychological tests. CD patients had a greater deviation of the subjective straight ahead, indicating body-centered visual spatial perception, than controls. No effects were seen in body-independent visual spatial perception. Patients with CD are impaired in body-centered, egocentric spatial perception, but not in body-independent, allocentric spatial perception.

Anxiety in musicians with focal dystonia and those with chronic pain.

Psychological conditions were studied in 20 musicians with focal dystonia and compared with 20 musicians with chronic pain and 30 healthy musicians using the Freiburg Personality Inventory and the Questionnaire for Competence and Control Orientations. Additional questionnaires focused on perfectionism and anxiety particularly with regard to the dynamics of these psychological features. Musicians with focal dystonia and those with chronic pain more often displayed anxiety than controls. In both patient groups, anxiety was present before onset of the playing-related disorder. Dystonic musicians additionally showed higher levels of perfectionism than controls, which was not observed in musicians with chronic pain.

Disturbance of "extrinsic alertness" in Huntington's disease.

Neuropsychological deficits are a main feature of Huntington's disease (HD) with previous data suggesting involvement of attentional functions. Attention can be divided into several different dimensions: intensity, selectivity and supervisory attentional control. These different aspects of attention were investigated in a group of 13 patients with HD and 13 healthy matched control subjects. HD patients were impaired mostly for the intensity dimension: contrary to controls, and like other neurological patient groups, they were not able to speed up their reaction times when an auditory warning stimulus preceded a visual target which suggests a deficit in 'extrinsic alertness.' In addition less severe impairments were found in the dimensions selectivity and supervisory attentional control.

The effects of proprioceptive stimulation on cognitive processes in patients after traumatic brain injury.

OBJECTIVE: To investigate the hypothesis that proprioceptive stimulation may be effective in the treatment of brain injury, using neurophysiologic and neuropsychologic measures. DESIGN: Cohort analytic study. SETTING: Patients recovering from traumatic brain injury (TBI) in a neurologic rehabilitation hospital were examined. PARTICIPANTS: Eleven patients with TBI (Glasgow Coma Scale score > 3) and 11 healthy control subjects matched for age and education. INTERVENTIONS: Subjects were examined with the event-related potential (ERP) technique during a computerized choice-reaction-time task, in which they had to discriminate between even and odd digits. There were experimental runs with and without vibratory stimuli applied to the left forearm serving as proprioceptive stimulation. In addition, ERPs were recorded to vibratory stimuli without any additional task. MAIN OUTCOME MEASURES: Outcome measures included latencies and amplitudes of the P300 ERP component and of the late negative component. RESULTS: In the passive vibration condition, both groups showed the same ERP distribution. In the choice-reaction-time task, latencies and amplitudes of the P300 differed between the 2 groups. The patient group showed longer P300 latencies, which were shortened by vibratory stimuli. In contrast, the control subjects were not affected by vibratory stimuli. CONCLUSION: Our findings support the hypothesis that pathologic cognitive processes after TBI can be improved by proprioceptive stimulation. Muscle vibration has positive effects on pathologically slowed cognitive processes but not in healthy subjects.