Absence of antibody production in patients treated with botulinum A toxin

To test the possibility of the formation of an antibody to botulinum A toxin after multiple injections of this potent neurotoxin, we collected serum samples from 28 patients who received 57 doses. These injections over a nine-month period with as much as 50 units per injection formed no detectable antibody.     

Transcutaneous electrical stimulation and vibration of neck muscles in neglect

Four neglect patients without visual field defects, one with a lesion of the right basal ganglia and three with a right, predominantly parietal lesion, were examined with a cancellation and a copying task before, during and after neck muscle vibration, during transcutaneous electrical stimulation of neck muscles and during vibration of hand muscles on the left side. In all patients, neck muscle vibration improved task performance, while transcutaneous electrical stimulation and hand vibration had little or no effect. The present results demonstrate that the effect of neck muscle vibration cannot be explained as arousal and activation due to unspecific sensory stimulation on the contralesional side of the body. They rather argue for the assumption that the compensatory effect of neck muscle vibration on neglect is an effect induced by the predominant activation of afferent Ia nerve fibres and their specific contribution to the central representation of egocentric space.     

Predictive value and reward in implicit classification learning

Learning efficacy depends on its emotional context. The contents learned and the feedback received during training tinges this context. The objective here was to investigate the influence of content and feedback on the efficacy of implicit learning and to explore using functional imaging how these factors are processed in the brain. Twenty-one participants completed 150 trials of a probabilistic classification task (predicting sun or rain based on combinations of playing cards). Smileys or frowneys were presented as feedback. In 10 of these subjects, the task was performed during functional magnetic resonance imaging. Card combinations predicting sun were remembered better than those predicting rain. Similarly, positive feedback fortified learning more than negative feedback. The presentation of smileys recruited bilateral nucleus accumbens, sensorimotor cortex, and posterior cingulum more than negative feedback did. The higher the predictive value of a card combination, the more activation was found in the lateral cerebellum. Both context and feedback influence implicit classification learning. Similar to motor skill acquisition, positive feedback during classification learning is processed in part within the sensorimotor cortex, potentially reflecting the activation of a dopaminergic projection to motor cortex (Hosp et al., 2011). Activation of the lateral cerebellum during learning of combinations with high predictive value may reflect the formation of an internal model.     

The effect of whole-body tilt on sound lateralization

The effect of passive whole-body tilt in the frontal plane on the lateralization of dichotic sound was investigated in human subjects. Pure-tone pulses (1 kHz, 100 ms duration) with various interaural time differences were presented via headphones while the subject was in an upright position or tilted 45 degrees or 90 degrees to the left or right. Subjects made two-alternative forced-choice (left/right) judgements on the intracranial sound image. During body tilt, the auditory median plane of the head, computed from the resulting psychometric functions, was always shifted to the upward ear, indicating a shift of the auditory percept to the downward ear, that is, in the direction of gravitational linear acceleration. The mean maximum magnitude of the auditory shift obtained with 90 degrees body tilt was 25 micro s. On the one hand, these findings suggest a certain influence of the otolith information about body position relative to the direction of gravity on the representation of auditory space. However, in partial contradiction to previous work, which had assumed existence of a significant 'audiogravic illusion', the very slight magnitude of the present effect rather reflects the excellent stability in the neural processing of auditory spatial cues in humans. Thus, it might be misleading to use the term 'illusion' for this quite marginal effect.     

Pressure support ventilation combined with volume guarantee versus synchronized intermittent mandatory ventilation: a pilot crossover trial in premature infants in their weaning phase.

OBJECTIVE: To compare pressure support ventilation combined with volume guarantee (PSV-VG) to synchronized intermittent mandatory ventilation (SIMV) regarding safety, course of blood gases, and infant-ventilator interaction in premature infants. DESIGN: Prospective, two-treatment, crossover pilot study. SETTING: Tertiary care neonatal unit. PATIENTS: Twenty-five ventilated premature infants: median (range) gestational age 26.1 wks (23.1-35.7), birth weight 765 g (450-3170), age at study 5 days (2-27), in their weaning phase. INTERVENTIONS: Infants were studied for three 30-min periods, starting from SIMV, followed by PSV-VG, and back again to SIMV. After concluding the last period, all infants were switched back to PSV-VG. On the next day, infants were studied in the opposite direction. During each period, vital parameters, ventilation parameters, degree of physical activity, duration of rhythmic breathing, and the number of vital signs monitor alarms were recorded. MEASUREMENTS AND MAIN RESULTS: Nineteen infants (84%) could be successfully ventilated with PSV-VG till the next day. PSV-VG achieved a similar oxygenation level as SIMV but with significantly lower ventilation pressures. Comparable ventilation was achieved, but infants with strong respiratory drive were more liable to hyperventilation episodes during PSV-VG. Although infants breathed more rhythmically during PSV-VG, suggesting better infant-ventilator synchrony, the infants' behavioral state and the fluctuations in blood gases did not differ. CONCLUSIONS: The potentials of PSV-VG to improve infant-ventilator synchrony and to decrease pressure needed to ventilate premature lungs are promising, even though the changes were small. However, its benefits during acute illness and on the final outcome remain to be proven.     

The anatomy of spatial neglect based on voxelwise statistical analysis: a study of 140 patients

A major challenge for any anatomical study of spatial neglect in neurological patients is that human lesions vary tremendously in extent and location between individuals. Approaches to this problem used in previous studies were to focus on subgroups of patients that are more homogeneous either with respect to the branch territory affected by the stroke or with respect to existing additional neurological symptoms (e.g. additional visual field defects). It could be argued that such strategies might bias the conclusions on the critical substrate associated with spatial neglect. The present study thus addressed the high variability inherent in naturally occurring lesions by using an unselected, but very large sample size and by comparing a neglect group with a non-neglect group using voxelwise statistical testing. We investigated an unselected 7 year sample of 140 consecutively admitted patients with right hemisphere strokes. Seventy-eight had spatial neglect, 62 did not show the disorder. The incidence of visual field defects was comparable in both groups. For assessing lesion location, in a first step, we used conventional lesion density plots together with subtraction analysis. Moreover, due to the large size of the sample voxelwise statistical testing was possible to objectively estimate which brain regions are more frequently compromised in neglect patients relative to patients without neglect. The results demonstrate that the right superior temporal cortex, the insula and subcortically putamen and caudate nucleus are the neural structures damaged significantly more often in patients with spatial neglect.     

Shutter-glasses haploscope with eye-tracking control for fusion therapy

BACKGROUND: Common haploscopes require a manual input of the presented disparity and particularly prepared images; moreover, they can be used predominantly by orthoptists. We developed a device that makes possible a haploscope on the basis of a computer monitor with shutter-glasses. The presented disparity is determined with help of an eye-tracker. MATERIALS AND METHODS: A patient looks at a monitor through shutter-glasses, the eyes being recorded by a camera. An eye-tracking software determines the fixation points and the angle of strabismus. Images are presented at the monitor with a disparity that is regulated according to these measurements. This is controlled by means of a software so that the disparity is gradually decreased according to the patients abilities. Diagnostic data are recorded permanently. RESULTS: Any monitor contents, such as videos, TV or computer applications, can be used for fusion training or diagnostic purposes with the new apparatus. Initial investigations of patients with heterophoria or intermittent exophoria indicate a decrease of the subjective angle of strabismus by compensation and an increase of the fusional range. CONCLUSIONS: The developed shutter-glass-haploscope with eye-tracking control provides several methods for diagnosis. The appliance provides automated fusion training adapted to the patient that can be done at the working place or at home.     

The cortical substrate of visual extinction

Neuroimaging studies investigated the attentional systems of the human brain revealing two networks, one for voluntary allocation of attention and another for stimulus-driven attentional processes. Whereas lesions of the latter system were supposed to lead to spatial neglect, we show that such lesions rather are typical for the occurrence of visual extinction. Extinction describes the inability of brain-damaged patients to detect a contralesional target in the presence of a competing ipsilesional stimulus. In a sample of consecutively admitted patients with right hemisphere stroke, we found dissociable cortical substrates for spatial neglect and visual extinction. There was a surprising congruency between the typical lesion site in patients with extinction and the activation clusters found in previous neuroimaging studies of healthy subjects. The results show that the temporo-parietal junction (TPJ), considered to be a crucial part of the stimulus-driven attentional network, is the neural substrate of visual extinction.     

Severity of neglect predicts accuracy of imitation in patients with right hemisphere lesions

Goldenberg [Goldenberg, G. (1996). Defective imitation of gestures in patients with damage in the left or right hemisphere. Journal of Neurology, Neurosurgery, and Psychiatry, 61, 176–180] proposed that the vulnerability of the imitation of meaningless gestures to right or left brain damage depends on the body parts that are involved in the gestures. Whereas imitation of hand postures was disturbed only in patients with left brain damage, imitation of finger postures was affected to similar degrees in left and right brain damage. Subsequent studies confirmed the selective vulnerability of hand postures to LBD but failed to replicate the severe disturbance of finger postures in RBD. In contrast to Goldenberg's studies, these studies excluded RBD patients with neglect. The present investigation aimed to explore the relationship between spatial neglect and imitation of finger postures in RBD patients.Presence and severity of spatial neglect and accuracy of imitation of hand and finger postures were tested in 50 RBD patients. Disturbance of imitation was much more severe for finger than hand postures and was tightly correlated with severity of neglect. The number of errors was higher for fingers which from the patient's perspective were located on the left side of the examiner's demonstrating hand but this spatial bias was not sufficient to explain all errors. Possible causes for non-lateralized errors could be a general narrowing of the focus of attention and reduced capacity for processing of visual information which have been postulated to be regular companions of the lateral displacement of attention in spatial neglect.