Citizen seismology helps decipher the 2021 Haiti earthquake.

On 14 August 2021, the moment magnitude (Mw) 7.2 Nippes earthquake in Haiti occurred within the same fault zone as its devastating 2010 Mw 7.0 predecessor, but struck the country when field access was limited by insecurity and conventional seismometers from the national network were inoperative. A network of citizen seismometers installed in 2019 provided near-field data critical to rapidly understand the mechanism of the mainshock and monitor its aftershock sequence. Their real-time data defined two aftershock clusters that coincide with two areas of coseismic slip derived from inversions of conventional seismological and geodetic data. Machine learning applied to data from the citizen seismometer closest to the mainshock allows us to forecast aftershocks as accurately as with the network-derived catalog. This shows the utility of citizen science contributing to our understanding of a major earthquake.

Effect of prism adaptation on left dichotic listening deficit in neglect patients: glasses to hear better?

Unilateral neglect is a disabling syndrome frequently observed following right hemisphere brain damage. Symptoms range from visuo-motor impairments through to deficient visuo-spatial imagery, but impairment can also affect the auditory modality. A short period of adaptation to a rightward prismatic shift of the visual field is known to improve a wide range of hemispatial neglect symptoms, including visuo-manual tasks, mental imagery, postural imbalance, visuo-verbal measures and number bisection. The aim of the present study was to assess whether the beneficial effects of prism adaptation may generalize to auditory manifestations of neglect. Auditory extinction, whose clinical manifestations are independent of the sensory modalities engaged in visuo-manual adaptation, was examined in neglect patients before and after prism adaptation. Two separate groups of neglect patients (all of whom exhibited left auditory extinction) underwent prism adaptation: one group (n = 6) received a classical prism treatment ('Prism' group), the other group (n = 6) was submitted to the same procedure, but wore neutral glasses creating no optical shift (placebo 'Control' group). Auditory extinction was assessed by means of a dichotic listening task performed three times: prior to prism exposure (pre-test), upon prism removal (0 h post-test) and 2 h later (2 h post-test). The total number of correct responses, the lateralization index (detection asymmetry between the two ears) and the number of left-right fusion errors were analysed. Our results demonstrate that prism adaptation can improve left auditory extinction, thus revealing transfer of benefit to a sensory modality that is orthogonal to the visual, proprioceptive and motor modalities directly implicated in the visuo-motor adaptive process. The observed benefit was specific to the detection asymmetry between the two ears and did not affect the total number of responses. This indicates a specific effect of prism adaptation on lateralized processes rather than on general arousal. Our results suggest that the effects of prism adaptation can extend to unexposed sensory systems. The bottom-up approach of visuo-motor adaptation appears to interact with higher order brain functions related to multisensory integration and can have beneficial effects on sensory processing in different modalities. These findings should stimulate the development of therapeutic approaches aimed at bypassing the affected sensory processing modality by adapting other sensory modalities.

Parietal damage dissociates saccade planning from presaccadic perceptual facilitation.

A well-known theory in the field of attention today is the premotor theory of attention which suggests that the mechanisms involved in eye movements are the same as those for spatial attention shifts. We tested a parietal damaged patient with unilateral optic ataxia and 4 controls on a dual saccade/attentional task and show a dissociation between saccadic eye movements and presaccadic perceptual enhancement at the saccade goal. Remarkably, though the patient was able to make the appropriate saccades to the left, impaired visual field (undistinguishable from saccades to his right, intact visual field), he was unable to discriminate the letter at the saccade goal (whereas his performance was like controls for letter discrimination in his right visual field). This suggests that saccade planning and presaccadic perceptual facilitation are separable--planning a saccade to a location does not necessitate that the processing of this location is enhanced. Based on these results, we suggest that the parietal cortex is necessary for the coupling between saccade planning and presaccadic perceptual facilitation.

Optic ataxia errors depend on remapped, not viewed, target location.

Optic ataxia is a disorder associated with posterior parietal lobe lesions, in which visually guided reaching errors typically occur for peripheral targets. It has been assumed that these errors are related to a faulty sensorimotor transformation of inputs from the 'ataxic visual field'. However, we show here that the errors observed in the contralesional field in optic ataxia depend on a dynamic gaze-centered internal representation of reach space.

An 'automatic pilot' for the hand in human posterior parietal cortex: toward reinterpreting optic ataxia.

We designed a protocol distinguishing between automatic and intentional motor reactions to changes in target location triggered at movement onset. In response to target jumps, but not to a similar change cued by a color switch, normal subjects often could not avoid automatically correcting fast aiming movements. This suggests that an 'automatic pilot' relying on spatial vision drives fast corrective arm movements that can escape intentional control. In a patient with a bilateral posterior parietal cortex (PPC) lesion, motor corrections could only be slow and deliberate. We propose that 'on-line' control is the most specific function of the PPC and that optic ataxia could result from a disruption of automatic hand guidance.

[Deep brain stimulation and Parkinson's disease]. / Stimulation cérébrale profonde et maladie de Parkinson.

Ten years after the therapeutic revolution that emerged from the discovery of l-dopa, some pioneer teams led the rebirth of a new nonablative stereotaxical surgical treatment, which came from the interest of high frequency stimulation. Three targets were retained as the main location of a reversible functional inhibition: Vim, GPI and STN. The unilateral or bilateral stimulation, adjustable and possibly reversible, led to an exceptional medicosurgical collaboration, within expert dedicated places, based on the control of the Parkinson's disease's (PD) triad. The stimulation was initially applied to the most advanced forms of PD, after the medical control period of the motor performance, when the pejorative effects of the evolution settled and/or when side effects of the treatment appeared. Subsequently, the research of selection criterions and the strict control of the stereotaxical procedure during the per- and postoperatory period, with the collaboration of the patient and his family, progressively brought different teams to an earlier indication of this new treatment option, up to now reserved for fully medicosurgical concerted cases. Apparition of cognitive and postural decline as well as the known resistance stage to l-dopa tend to become a real contra-indication. Despite the initial relative weakness of controlled studies with limited number of patients, the multiplication of follow-up studies among high quality multicentric cohorts enabled the validation of practices respecting the differences related to the initial background of each different team. In Europe first, the prevalence of the subthalamic target is now to be generally admitted. A new objective is now imposing itself: trying to maintain the patient's quality of life, beyond the only motor benefit. The social adaptation of a young patient is now also taken into account. If this exemplary clinical research approach, efficient for a few highly selected patients, has not transformed the long-term prognostic of the PD, it will continue to improve the comprehension of this degenerative pathology and its extension. It still remains hopeful for the future in the actual constant technological progress, and that probably beyond the only PD.

Prism adaptation to rightward optical deviation improves postural imbalance in left-hemiparetic patients.

Left-hemiparetic patients show predominant postural imbalance as compared to right-hemiparetic patients. The right hemisphere is crucial for generating internal maps used for perceptual and premotor processing of spatial information. Predominant postural imbalance with right-brain damage could thus result from a distortion of an internal postural map. Well-known manifestations of distorted internal maps due to right-hemisphere lesions, such as hemineglect, may show improvement following prism adaptation shifting the visual field to the right. We therefore investigated the effect of prism adaptation on postural imbalance in left-hemiparetic patients. Three groups of five patients were either adapted to prisms deviating the visual field to the right or left or exposed to neutral prisms while performing reaching movements of the right arm. Postural imbalance was reduced only following prism adaptation to the right. Thus, brief adaptation (i.e., 3 min) to rightward-shifting prisms can dramatically improve postural imbalance. This result shows that the effect of exposure to prisms that horizontally shift the visual field to the right in a reaching task generalizes to the postural system, and it suggests an interaction between horizontal and vertical reference frames. This also supports the theory that predominant postural imbalance in patients with right-brain damage may be partly related to a distortion of an internal postural map.

Prism adaptation improves spatial dysgraphia following right brain damage.

Visuo-manual adaptation to prisms produces a long-lasting improvement of visuo-spatial neglect. Improvement is also observed in tasks that do not involve visuo-manual component and that can all be consider to rely on a rightward (ipsilesional) orienting bias. Here, we report positive effects of prism adaptation on spatial dysgraphia, in a neglect patient following right brain damage. A long-lasting improvement concerned the right-page preference reflecting the ipsilesional bias but also the sloping lines and the broken lines reflecting visuo-constructive disorders in handwriting. Moreover, a transient improvement was also evidenced for the graphic errors. These results reinforce the idea that the process of prism adaptation may activate brain functions related to multisensory integration and higher spatial representations and show a generalization at a functional level. Prism adaptation therefore appears as useful tool in the theoretical attempt to identify the underlying 'core' mechanisms of the neglect syndrome.

[Handicap and quality of life evaluation in amyotrophic lateral sclerosis]. / Evaluation du handicap et de la qualité de vie.

The impact of amyotrophic lateral sclerosis and consequent disability on everyday life can be assessed with generic or specific and/or functional quality of life scales. Generic scales SF36, SIP (Sickness Impact Profiles) and SIP/ALS 19, SEIQoL have been validated for the assessment of quality of life in SLA. A specific scale has also been worked out and validated in this disease, the ALSAQ-40 scale. The ALSFRS (ALS Functional Rating Scale) is a tool validated to evaluate the patient's functional capacities. However, the patient's quality of life felt does not depend only on the disease course but also the patient's previous psychological profile, the environmental, social conditions and spiritual aspirations. The absence of a cognitive deficit makes the patient particularly lucid about the progressive degradation of health status. Evaluation must be carried out with individually for each patient, taking into account the social and familial environments, to appreciate real living conditions, and the impact of this degenerative disease.

[Physical therapy in amyotrophic lateral sclerosis]. / Quelles sont les modalités de thérapie physique symptomatique dans la Sclérose Latérale Amyotrophique (techniques de désencombrement bronchique exclues)?

Amyotrophic lateral sclerosis is a neurodegenerative disease, without any curative treatment. Clinical expression is variable and related to loss of motor neurons in the cortex, brain stem and spinal cord. There is little scientific evidence demonstrating the usefulness of physical therapy in this disease. Only stretching exercises, proprioceptive neuromuscular facilitation techniques and functional mobility training seem to have a real benefit in terms of spasticity, quality-of-life and pain. The main objective of physical therapy appears to be the preservation of optimal quality-of-life throughout the course of this incurable degenerative disease.

[What are management practices for speech therapy in amyotrophic lateral sclerosis?]. / Quelles sont les modalités de la prise en charge orthophonique dans la Sclérose Latérale Amyotrophique?

Amyotrophic lateral sclerosis involves deterioration of speech and swallowing. The objectives of rehabilitation are to maintain a comprehensible speech, using exercises on airflow-phonic coordination and breath, lingual and labial movements. Rehabilitation exercises also focus on the different times of swallowing to improve management of the food bolus in the mouth, to learn facilitating techniques and to adopt postures favoring passage of the food bolus. No studies have addressed the question of the effectiveness of rehabilitation in amyotrophic lateral sclerosis, in term of quality of life, maintenance of comprehensible speech or reduction of respiratory risks. Rehabilitation programs are established on an individual basis according to the clinical presentation and course.

Visually guided reaching: bilateral posterior parietal lesions cause a switch from fast visuomotor to slow cognitive control.

The visually guided reaching of two patients with bilateral optic ataxia was explored in two experiments. In Experiment 1 simple delayed pointing was compared with immediate pointing. In the immediate pointing task both variable and constant errors increased with target eccentricity. In contrast to the performance of control subjects and contrary to their own beliefs, the patients both showed improved accuracy in the delay condition. This improvement was manifest as a reduction in both pointing variability and in the constant angular error towards the point of fixation. Both angular errors and their improvement with the delay were proportional to target eccentricity. Experiment 2 used a task in which the target was pre-viewed 5s prior to its re-exposure for pointing ('delayed real pointing'). On some trials a conflict was introduced between the present and previous visual information by changing the target's location during the delay. In contrast to control subjects, who ignored the pre-viewed location and aimed directly at the current target, both patients with optic ataxia initiated their movements towards the previously viewed target location. Evidently they relied on off-line information in preference to on-line visual information. In addition, the patients often failed to detect the changes in target location. One of the patients sometimes even guessed incorrectly that the target had changed its location, and her movement trajectory was then more affected by her false belief than by the target's actual location. These findings confirm that posterior parietal lesions severely disrupt direct visuomotor transformations, and suggest that the residual performance is mediated indirectly by expectations or beliefs about target position.

[Assessment of disability and quality of life in patients with cognitive disorders]. / Evaluation des incapacités et de la qualité de vie des patients présentant des troubles cognitifs.

OBJECTIVE: To identify disability, handicap and quality of life questionnaires available for patients with cognitive impairment. MATERIALS AND METHODS: We systematically reviewed the literature in Medline using the keywords assessment, evaluation, deficiency, disability, disadvantage, handicap, quality of life, scale, index, questionnaire, ICIDH-1, and ICIDH-2, combined with the cognitive deficits dysexecutive syndrome, memory deficits, attention deficits, neglect, apraxia, aphasia, agnosia and mood disorders. We focused on validated scales and distinguished scales dedicated to assess disability, handicap and quality of life. RESULTS: At the level of disability, global and specific scales are available. Specific scales exist for dysexecutive syndrome, memory deficits, attention deficits, unilateral neglect, aphasia and mood disorders. French adaptations of foreign language tests and original tests developed in French have been validated in these areas. No specific tool is available for isolated apraxia or agnosia. Generic scales and pathology-specific scales (for stroke, traumatic brain injury, and multiple sclerosis) are available for quality of life. For aphasia, specific tools are available for incapacity handicap and quality of life. CONCLUSION: Previous results show the impact of the ICIDH-1 framework on functional outcome assessment of cognitive impairments. This approach is often limited by the lack of theoretical background and by the difficulty to assess the involvement of environment and anosognosia.

Inverse relationship between sensation of effort and muscular force during recovery from pure motor hemiplegia: a single-case study.

A 39-year-old patient with a right pure motor hemiplegia, who complained of a striking sensation of effort when he performed a movement, was regularly examined during 4 months. The effort sensation and the force recovery have been measured during the execution of upper limb movements: shoulder antepulsion up to horizontal, supined elbow flexion up to horizontal and full hand digital grip. The subject was asked to realize a movement with the paretic arm and to concentrate on the felt effort; then he had to perform the same movement against a resistance with the healthy arm, until the perceived heaviness matched the effort sensation felt on the other side. Recovery of force and evolution of effort sensation did not follow linear trends over time. The curves displayed significant steps and plateaus, which were mainly observed for the proximal movements. The steps tended to be clustered within a few days, consistent with crucial periods in the restoration process. Within these, significant reduction of the effort sensation and increase of the force were together observed. These critical moments of the motor recovery could be analyzed as the result of an improvement of the neural traffic in the internal capsule and an activation of specific structures involved in the representation of the force and effort.

Prism adaptation improves representational neglect.

Previous work has shown that various symptoms of unilateral neglect, including the pathological shift of the subjective midline to the right, may be improved by a short adaptation period to a prismatic shift of the visual field to the right. We report here, in two neglect patients the improvement of imagery neglect after prism exposure. Despite a strong neglect observed for mental images, as well as for conventional tests, the mental evocation of left-sided information from an internal image of the map of France was fully recovered following prism adaptation to the right. This improvement could not be explained by the alteration of visuomotor responses induced by the prism adaptation. Therefore, prism adaptation may act not only on sensory-motor levels but also on a higher cognitive level of mental space representation and/or exploration.

Bilateral vestibular stimulation does not improve visual hemineglect.

This work compared the effect of unilateral (right and left) and bilateral vestibular stimulation in a right-brain-damaged patient with neglect. Neglect was improved following left caloric vestibular stimulation, and worsened following right vestibular stimulation. On the other hand, no modification of neglect was observed after bilateral vestibular stimulation. These results support the idea that caloric vestibular stimulation may improve neglect through a specific effect; bilateral stimulation making the putative activation bilateral and symmetrical does not affect the lateral bias of neglect.

Visuo-motor control of the ipsilateral hand: evidence from right brain-damaged patients.

We investigated the extent to which the right hemisphere is involved in the control of the ipsilateral hand by analysing the kinematics of right-hand prehension in right brain-damaged (RBD) patients. We required patients to grasp one of five possible objects, equally-sized and distributed over a 40 degrees wide workspace. With the purpose of investigating the right hemisphere contribution to the on-line visuo-motor control, we also assessed patients' ability to correct their movement "in-flight", in response to a sudden change of object position. Patients' performance was compared to that of aged-matched controls. A Younger group of healthy subjects, matching the population classically tested on double-step paradigms, was also evaluated to fully assess whether patients' kinematics could be partially due to normal ageing. As a further aim, the possible influence of hemispatial neglect was evaluated by comparing the performances of right brain-damaged patients with and without neglect. In normal subjects, the results confirmed and extended the notion of (a). positional tuning of grip formation, and (b). fast reactions following a change in object position. In addition, subtle effects of ageing on visuo-motor behaviour were shown by less efficient movement correction in the Elderly group. Patients executing reach-to-grasp actions into the left contralesional hemispace were selectively affected in both temporal and spatial aspects of movements. While their performances were relatively well preserved in the right hemispace, patients did not show positional tuning of grip formation, nor fast corrections of their movements when acting in the left hemispace. Interestingly, similar deficits were found irrespective of the presence of neglect. These results show that the right hemisphere contributes to the processing of visuo-motor information that is necessary for executing actions with the ipsilateral hand in the contralateral space.

Implicit processing of somaesthetic information: a dissociation between where and how?

We present the case of a patient with a lesion of the thalamus who was completely anaesthetized on his right side. He was unable to detect and describe a tactile stimulus applied to his affected right arm, but could direct his normal left hand toward the specific right hand site where the stimulus had been applied when so instructed ('blind touch'). Strikingly, this pointing ability disappeared when the patient had to indicate on a picture of an arm where the stimulus was applied, and when he had to name the stimulus location during his pointing. Similar results were also obtained for localizing the unfelt fingertip ('blind proprioception'). Neuropsychological case studies have demonstrated that brain lesions can produce reciprocal dissociations between object identification (what is the object) and object-oriented action (how to direct a movement to the object). Along these lines, it is suggested that our patient exhibited a dissociation between a 'where' system and a 'how' system for tactile and proprioceptive stimuli.

Multi-centre, double-blind trial of a novel antispastic agent, tizanidine, in spasticity associated with multiple sclerosis.

A multi-centre, double-blind study was carried out in 100 patients suffering from chronic spasticity due to multiple sclerosis to compare the effectiveness of tizanidine hydrochloride with that of baclofen. Patients were allocated at random to receive treatment initially with daily doses of either 6 mg tizanidine or 15 mg baclofen and the dose was increased during the first 2 weeks up to a maximum of 24 mg tizanidine or 60 mg baclofen per day. Patients were then treated with the optimum dose for 6 weeks. Efficacy and tolerability parameters were evaluated after 2 and 8 weeks. Tizanidine and baclofen improved the functional status of patients in 80% and 76% of cases, respectively, but there were no significant differences between the two drugs. The antispastic efficacy of tizanidine was greater after 8 weeks than after 2 weeks, whereas the efficacy of baclofen decreased slightly with time. Both drugs showed good overall tolerability in more than 60% of patients. Thus, tizanidine is a well tolerated and effective muscle relaxant, the antispastic efficacy of which is well maintained over time, and it promises to be particularly useful in the treatment of spasticity due to multiple sclerosis.

[Proliferation of the transverse tubular system during a tardive and familial myopathy]. / Prolifération du système tubulaire transversal au cours d'une myopathie tardive et familiale

The authors report a case of non-progressive, late-onset, recessive, sex-linked myopathy. Electron microscopy reveals a striking proliferation of the T system. This proliferation might be interpreted as indicating an abortive attempt of muscle to regenerate, which could explain the clinical course. Some basic ultrastructural aspects concerning the T system are reported. The signification of the findings of numerous "zebra bodies" is discussed.