Subcortical origin of visuomotor apraxia.

Visuomotor apraxia (VMA) is a clinical syndrome characterized by a failure to make use of visual information when performing a target-directed movement. Visuomotor apraxia has traditionally been assumed to result from a disconnection of cortico-cortical fibres between visual and motor areas following occipito-parietal lesions. We describe a patient who developed a permanent contralesional and a temporary ipsilesional visuomotor apraxia as part of a complex neurological syndrome after a right [corrected] thalamic haemorrhage. MRI showed that the suprathalamic white matter was not involved but the most caudal fibres of the internal capsule appeared to be interrupted. To our knowledge this is the first case of a VMA with a lesion restricted to a deep subcortical area indicating that VMA can result from damage to subcortical projections rather than interruption of cortico-cortical fibres.

Learning "what" and "how" in a human motor task.

We studied the development of implicit and of verbally declared knowledge for normal human subjects who learned an unfamiliar motor task in one learning session. The exploratory nature of motor learning and a special period for optimizing skill were followed in real time. Subjects understood the goal for task success, but they had to learn a motor strategy of what pattern of serial movements to make and the tactics of how much to scale their amplitudes and timing. We compared the time course for acquiring tactical skill with that for acquiring knowledge of strategy and of tactics, and their necessary cues. Implicit and declarative knowledge were distinguished from one another by correlating subjects' verbal self-reports with movement kinematics and their results. Implicit generation of the correct strategy and of the tactics developed in an exploratory manner from the beginning of the learning session. Implicit strategy learning soon gave way to conscious efforts, but tactical learning remained implicit until its first unambiguous verbal declaration (with one exception). First strategy declarations were voiced before those for tactics, during trial-and-error learning that did not require task success, and referred to reversing the direction of hand movements (one exception). In contrast, first declarations of tactics almost always required actual or imminent success, referred to when direction was to be reversed, and it was achieved near the top of a sigmoid learning curve that rose to tactical skill (with one exception). During the sigmoid rise, movement amplitudes and timing were optimized in a distinct manner, although tactics usually adapted thereafter to movements of more moderate speed that could still be successful.

Motor analysis predicts progression in HIV-associated brain disease.

One hundred HIV-positive individuals without clinically evident central nervous system (CNS) deficits entered this follow-up study and were examined clinically and with a well-defined motor test battery every 3 months over 2 years or until they decreased. They underwent magnetic resonance tomography once a year. None received any form of therapy at onset of the study. Three groups were analyzed: (A) patients without electrophysiologically detectable motor impairment (n = 23), (B) patients with electrophysiologically detectable motor impairment but no virostatic medication (n = 33), and (C) patients with motor deficits undergoing AZT treatment (n = 44) after study onset. Group A patients, although slightly deteriorating over time, had the best clinical and electrophysiological outcome compared to the other groups, whereas group B patients deteriorated markedly in both clinical and electrophysiological tests, even though the majority did not develop cerebral complications during the observation period. Those group C patients belonging to early CDC stages (II and III) improved electrophysiologically under AZT therapy, while 76% of the patients in more advanced stages (CDC IVA-D) died of cerebral AIDS manifestations. Four patients of this group, being alive at the end of the study, were completely demented. It is suggested that early detectable motor impairment predicts future cerebral involvement in AIDS. Late onset of virostatic treatment did not influence the clinical outcome.

Age-dependent decline in cognitive information processing of HIV-positive individuals detected by event-related potential recordings.

Cognitive event-related potentials (ERP) were recorded in 100 HIV-positive patients of all CDC stages without clinical CNS deficits with an auditory oddball paradigm. Four latency peaks and three amplitudes were evaluated (N1, P2, N2 and P3 latencies, N1-P2, P2-N2 and N2-P3 amplitudes). In contrast to an age-matched control group of comparable education and social environment, a statistically significant N2-P3 amplitude reduction was found in the patient group deteriorating with the CDC stages. The physiological N2-P3 amplitude reduction with age in normals was found to be twice as fast in HIV-positive individuals. No group-statistically relevant EEG abnormalities were found in the patient group. In psychometric testing, there was no marked depressive syndrome in the HIV-positive individuals, but a mild slowing of speed-dependent abilities.

Improvement of motor performance of HIV-positive patients under AZT therapy.

We performed motor tests (most rapid alternating movements [MRAMs] of index fingers and most rapid contractions [MRCs] of voluntary isometric index finger extensions) in HIV-positive patients with (group 1) and without (group 2) AZT treatment over a 6-month period. Whereas MRAMs remained uninfluenced, MRCs showed a clear improvement in the treated group and a decline in the nontreated group, according to the T helper cell counts. MRCs were not only a sensitive test procedure for detecting subclinical lesions in HIV-positive patients, but also a reliable therapy control measurement.