Voluntary head stabilization in space during oscillatory trunk movements in the frontal plane performed in weightlessness

 The ability voluntarily to stabilize the head in space during lateral rhythmic oscillations (0.59±0.09 Hz) of the trunk has been investigated during microgravity (μG) and normal gravity (nG) conditions (parabolic flights). Five healthy young subjects, who gave informed consent, were examined. The movements were performed with eyes open or eyes closed, during phases of either μG or nG. The main result was that head orientation with respect to vertical may be stabilized about the roll axis under μG with, as well as without vision, despite the reduction in vestibular afferent and muscle proprioceptive inputs. Moreover, the absence of head stabilization about the yaw axis confirms that the degrees of freedom of the neck can be independently controlled, as was previously reported. These results seem to indicate that voluntary head stabilization does not depend crucially upon static vestibular afferents. Head stabilization in space may in fact be organized on the basis of either dynamic vestibular afferents or a short-term memorized postural body schema. Received: 4 October 1995 / Accepted: 30 September 1996     

Effectiveness of a meditation-based stress reduction program in the treatment of anxiety disorders.

OBJECTIVE: This study was designed to determine the effectiveness of a group stress reduction program based on mindfulness meditation for patients with anxiety disorders. METHOD: The 22 study participants were screened with a structured clinical interview and found to meet the DSM-III-R criteria for generalized anxiety disorder or panic disorder with or without agoraphobia. Assessments, including self-ratings and therapists' ratings, were obtained weekly before and during the meditation-based stress reduction and relaxation program and monthly during the 3-month follow-up period. RESULTS: Repeated measures analyses of variance documented significant reductions in anxiety and depression scores after treatment for 20 of the subjects--changes that were maintained at follow-up. The number of subjects experiencing panic symptoms was also substantially reduced. A comparison of the study subjects with a group of nonstudy participants in the program who met the initial screening criteria for entry into the study showed that both groups achieved similar reductions in anxiety scores on the SCL-90-R and on the Medical Symptom Checklist, suggesting generalizability of the study findings. CONCLUSIONS: A group mindfulness meditation training program can effectively reduce symptoms of anxiety and panic and can help maintain these reductions in patients with generalized anxiety disorder, panic disorder, or panic disorder with agoraphobia.     

Kinematic synergy adaptation to microgravity during forward trunk movement

The aim of the present investigation was to see whether the kinematic synergy responsible for equilibrium control during upper trunk movement was preserved in absence of gravity constraints. In this context, forward trunk movements were studied during both straight-and-level flights (earth-normal gravity condition: normogravity) and periods of weightlessness in parabolic flights (microgravity). Five standing adult subjects had their feet attached to a platform, their eyes were open, and their hands were clasped behind their back. They were instructed to bend the trunk (the head and the trunk together) forward by approximately 35 degrees with respect to the vertical in the sagittal plane as fast as possible in response to a tone, and then to hold the final position for 3 s. The initial and final anteroposterior center of mass (CM) positions (i.e., 200 ms before the onset of the movement and 400 ms after the offset of the movement, respectively), the time course of the anteroposterior CM shift during the movement, and the electromyographic (EMG) pattern of the main muscles involved in the movement were studied under both normo- and microgravity. The kinematic synergy was quantified by performing a principal components analysis on the hip, knee, and ankle angle changes occurring during the movement. The results indicate that 1) the anteroposterior position of the CM remains minimized during performance of forward trunk movement in microgravity, in spite of the absence of equilibrium constraints; 2) the strong joint coupling between hip, knee, and ankle, which characterizes the kinematic synergy in normogravity and which is responsible for the minimization of the CM shift during movement, is preserved in microgravity. It represents an invariant parameter controlled by the CNS. 3) The EMG pattern underlying the kinematic synergy is deeply reorganized. This is in contrast with the invariance of the kinematic synergy. It is concluded that during short-term microgravity episodes, the kinematic synergy that minimizes the anteroposterior CM shift is surprisingly preserved due to fast adaptation of the muscle forces to the new constraint.     

Performance of a bimanual load-lifting task by parkinsonian patients.

Normal subjects and Parkinsonian patients performed a bimanual load lifting task. In this task, one "postural" forearm, held in a horizontal position while supporting a 1 kg weight, was unloaded either by the experimenter's hand (imposed unloading) or by the subject's other hand in response to a tone burst (voluntary unloading). The variables recorded were reaction time (RT: time interval between the tone and beginning of unloading) and movement time (MT: duration of the change in force measured by a force platform on the "postural" forearm). Elbow angle changes were also measured with a potentiometer. The EMG activity from brachioradialis of the "postural" arm and that from the biceps of the "active" arm were recorded. The Parkinsonian patients showed an increase in both RT and MT and an impairment of the co-ordination between movement and posture which was reflected in an increase in amplitude of the elbow rotation after voluntary unloading. Moreover, the decrease in EMG activity in the brachioradialis of the postural arm during unloading was less in Parkinsonian patients than in the normal group. This disorder of postural command was often accompanied by a lack of anticipatory EMG changes. Comparison between treated and non-treated patients showed that dopamine agonists brought about recovery of both RT and MT but did not improve postural co-ordination. The co-ordination was less impaired when the voluntary unloading was performed by the preferred hand. Several hypotheses are discussed concerning the mechanism underlying this impaired co-ordination.     

The thalamus: motor functions

Thalamic nuclei constitute the diencephalic relay system between different afferent systems and the telencephalon. The "motor" thalamus links cerebellar and pallidal afferents with the motor and pre-motor cortical regions. Separation of pallido-thalamo-cortical and cerebello-thalamo-cortical pathways is relatively complete: afferents of pallidal origin are relayed by thalamic nuclei VA, VLo and VLm and are projected onto prefrontal and supplementary motor areas whereas afferents of cerebellar origin are relayed in the VL and VPLo and then projected onto motor areas 4.6 and parietal areas 5 and 7. This report is concerned mainly with the analysis of the motor thalamus as a relay system for afferents of cerebellar origin. The anatomofunctional organization of the cerebello-thalamo-cortical tract possesses a topographic arrangement and also wide convergences and appears able to participate in the realization, through the motor cortex, of motor synergies and of co-ordinating postures and movements. The cerebello-cortical tract apparently plays a different role during learning of a movement and executing an automatized movement. For the latter, it is involved in their onset and in their completion. Its contribution to fine control of temporal parameters of motor commands or control of peripheral afferent messages is not decisive. During learning of a movement the cerebello-cortical tract plays a predominant role. According to Ito, the cerebellum is involved in the process of automatization of a movement, organized initially entirely by the cortex and then becoming progressively subcortical. Plasticity of cerebellar microcircuits could be the basis for these automatization processes expressed through the cerebello-thalamo-cortical tract.     

Remission and relapse in subjects with panic disorder and panic with agoraphobia: a prospective short-interval naturalistic follow-up

This article reports on the course of uncomplicated panic disorder and panic with agoraphobia on 309 patients participating in the Harvard/Brown Anxiety Research Project, a prospective longitudinal study of patients with DSM-III-R-defined anxiety disorders. At 1 year, there was a .39 probability of full remission for uncomplicated panic disorder and a .17 probability of full remission for panic disorder with agoraphobia Similar differences in time to remission for these syndromes were still found when criteria for remission were made less stringent. However, even requiring less improvement for remission left a large percentage of subjects in an episode, and for those that remitted, relapse occurred quickly, indicating a chronic and recurrent course of illness. This is the first longitudinal, prospective, naturalistic study on a large cohort of subjects with anxiety disorders to have regular, structured, short-interval follow-up. Our results are consistent with the view that panic disorder has a chronic course with high rates of relapse after remission and longer episodes when agoraphobia is a part of the constellation of symptoms.