CASTRO ABARCA, PATRICIA BERNARDITA
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CASTRO ABARCA, PATRICIA BERNARDITA
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pcastro@udd.cl
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57205147799

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Priming overconfidence in belief systems reveals negative return on postural control mechanisms

2022 , CASTRO ABARCA, PATRICIA BERNARDITA , Efstratia Papoutselou , Sami Mahmoud , Shahvaiz Hussain , Constanza Fuentealba Bassaletti , Diego Kaski , Adolfo Bronstein , Qadeer Arshad

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Head shaking does not alter vestibulo ocular reflex gain in vestibular migraine

2022 , Priyani Patel , CASTRO ABARCA, PATRICIA BERNARDITA , Nehzat Koohi , Qadeer Arshad , Lucia Gargallo , Sergio Carmona , Diego Kaski

Vestibular Migraine (VM) is the most common cause of non-positional episodic vestibular symptoms. Patients with VM commonly report increased motion sensitivity, suggesting that vestibular responses to head movement may identify changes specific to VM patients. Here we explore whether the vestibulo-ocular reflex (VOR) gain alters in response to a clinical “headshake” maneuver in patients with VM. Thirty patients with VM in the inter-ictal phase, 16 patients with Benign Positional Paroxysmal Vertigo (BPPV) and 15 healthy controls were recruited. Patients responded to the question “Do you feel sick reading in the passenger seat of a car?” and completed a validated motion sickness questionnaire as a measure of motion sensitivity. Lateral canal vHIT testing was performed before and after headshaking; the change in VOR gain was calculated as the primary outcome. Baseline VOR gain was within normal limits across all participants. There was no significant change in VOR gain after headshaking in any group (p = 0.264). Patients were 4.3 times more likely to be in the VM group than in the BPPV group if they reported nausea when reading in the passenger seat of a car. We postulate that a headshake stimulus may be insufficient to disrupt cortical interactions and induce a change in VOR gain. Alternatively, changes in VOR gain may only be apparent in the acute phase of VM. Reading in the passenger seat of a car was considered uncomfortable in all VM patients suggesting that this specific question may be useful for the diagnosis of VM.

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Multisensory contribution in visuospatial orientation: an interaction between neck and trunk proprioception

2021 , Jason McCarthy , CASTRO ABARCA, PATRICIA BERNARDITA , Rachael Cottier , Joseph Buttell , Qadeer Arshad , Amir Kheradmand , Diego Kaski

AbstractA coherent perception of spatial orientation is key in maintaining postural control. To achieve this the brain must access sensory inputs encoding both the body and the head position and integrate them with incoming visual information. Here we isolated the contribution of proprioception to verticality perception and further investigated whether changing the body position without moving the head can modulate visual dependence—the extent to which an individual relies on visual cues for spatial orientation. Spatial orientation was measured in ten healthy individuals [6 female; 25–47 years (SD 7.8 years)] using a virtual reality based subjective visual vertical (SVV) task. Individuals aligned an arrow to their perceived gravitational vertical, initially against a static black background (10 trials), and then in other conditions with clockwise and counterclockwise background rotations (each 10 trials). In all conditions, subjects were seated first in the upright position, then with trunk tilted 20° to the right, followed by 20° to the left while the head was always aligned vertically. The SVV error was modulated by the trunk position, and it was greater when the trunk was tilted to the left compared to right or upright trunk positions (p < 0.001). Likewise, background rotation had an effect on SVV errors as these were greater with counterclockwise visual rotation compared to static background and clockwise roll motion (p < 0.001). Our results show that the interaction between neck and trunk proprioception can modulate how visual inputs affect spatial orientation.

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Dissociated motor learning and de-adaptation in patients with functional gait disorders

2020 , Denise Lin , CASTRO ABARCA, PATRICIA BERNARDITA , Amy Edwards , Akila Sekar , Mark J Edwards , Jan Coebergh , Adolfo M Bronstein , Diego Kaski

Abstract Walking onto a stationary platform that had been previously experienced as moving generates a locomotor after-effect—the so-called ‘broken escalator’ phenomenon. The motor responses that occur during locomotor after-effects have been mapped theoretically using a hierarchal Bayesian model of brain function that takes into account current sensory information that is weighted according to prior contextually-relevant experiences; these in turn inform automatic motor responses. Here, we use the broken escalator phenomenon to explore motor learning in patients with functional gait disorders and probe whether abnormal postural mechanisms override ascending sensory information and conscious intention, leading to maladaptive and disabling gait abnormalities. Fourteen patients with functional gait disorders and 17 healthy control subjects walked onto a stationary sled (‘Before’ condition, five trials), then onto a moving sled (‘Moving’ condition, 10 trials) and then again onto the stationary sled (‘After’ condition, five trials). Subjects were warned of the change in conditions. Kinematic gait measures (trunk displacement, step timing, gait velocity), EMG responses, and subjective measures of state anxiety/instability were recorded per trial. Patients had slower gait velocities in the Before trials (P &lt; 0.05) but were able to increase this to accommodate the moving sled, with similar learning curves to control subjects (P = 0.87). Although trunk and gait velocity locomotor after-effects were present in both groups, there was a persistence of the locomotor after-effect only in patients (P &lt; 0.05). We observed an increase in gait velocity during After trials towards normal values in the patient group. Instability and state anxiety were greater in patients than controls (P &lt; 0.05) only during explicit phases (Before/After) of the task. Mean ‘final’ gait termination EMG activity (right gastrocnemius) was greater in the patient group than controls. Despite a dysfunctional locomotor system, patients show normal adaptive learning. The process of de-adaptation, however, is prolonged in patients indicating a tendency to perpetuate learned motor programmes. The trend to normalization of gait velocity following a period of implicit motor learning has implications for gait rehabilitation potential in patients with functional gait disorders and related disorders (e.g. fear of falling).

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Subjective stability perception is related to postural anxiety in older subjects

2019 , CASTRO ABARCA, PATRICIA BERNARDITA , Diego Kaski , Marco Schieppati , Michael Furman , Qadeer Arshad , Adolfo Bronstein

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Towards an explanation for ‘unexplained’ dizziness in older people

2024 , CASTRO ABARCA, PATRICIA BERNARDITA , Richard Ibitoye , Toby Ellmers , Diego Kaski , Qadeer Arshad , Adolfo M Bronstein

Abstract Background Subjective unsteadiness or dizziness, usually without increase in body sway, is common in older people. The absence of mechanistic understanding of such symptoms renders clinical management difficult. Here, we explore the mechanisms behind such idiopathic dizziness (ID), focusing on postural control abnormalities. Methods Thirty patients with ID and 30 age-matched controls stood on a moving platform. Platform oscillations were randomly delivered at different velocities (from 0 to 0.2 m/s). Markers of postural control, including objective sway (trunk sway path, recorded via a sensor attached to vertebrae C7), stepping responses, subjective instability and anxiety ratings were obtained. MRI scans were available for correlations with levels of cerebral small vessel disease in 28 patients and 24 controls. Results We observed a significant relationship between objective and subjective instability in all groups. The slope of this fit was significantly steeper for patients than controls, indicating greater perceived instability for the same body sway. Stepwise linear regression showed that the slopes of this objective–subjective instability relationship were best explained by concerns about falling (Falls Efficacy Scale-International), clinical physical functioning (Short Physical Performance Battery) and, to some degree, by neuroimaging markers of cerebral small vessel disease. In addition, patients had a reduced stepping threshold, suggesting an overly cautious postural response. Conclusion The distorted perception of instability and subtle impairments in balance control, including abnormal and overly cautious stepping responses, underlies the emergence of ID. It appears to relate to changes in postural performance, psychological functioning and disruption of postural brain networks associated with cerebral small vessel disease.

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Viewing Target Distance Influences the Vestibulo-Ocular Reflex Gain when Assessed Using the Video Head Impulse Test

2019 , CASTRO ABARCA, PATRICIA BERNARDITA , Sara Sena Esteves , Florencia Lerchundi , David Buckwell , Michael A. Gresty , Adolfo M. Bronstein , Qadeer Arshad

Gaze stabilization during head movements is provided by the vestibulo-ocular reflex (VOR). Clinical assessment of this reflex is performed using the video Head Impulse Test (vHIT). To date, the influence of different fixation distances on VOR gain using the vHIT has not been explored. We assessed the effect of target proximity on the horizontal VOR using the vHIT. Firstly, we assessed the VOR gain in 18 healthy subjects with 5 viewing target distances (150, 40, 30, 20, and 10 cm). The gain increased significantly as the viewing target distance decreased. A second experiment on 10 subjects was performed in darkness whilst the subjects were imagining targets at different distances. There were significant inverse relationships between gain and distance for both the real and the imaginary targets. There was a statistically significant difference between light and dark gains for the 20- and 40-cm distances, but not for the 150-cm distance. Theoretical VOR gains for different target distances were calculated and compared with those found in light and darkness. The increase in gain observed for near targets was lower than predicted by geometrical calculations, implying a physiological ceiling effect on the VOR. The VOR gain in the dark, as assessed with the vHIT, demonstrates an enhancement associated with a reduced target distance.

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Evaluación de un programa piloto para trabajar habilidades narrativas en niños con hipoacusia usuarios de ayudas auditivas

2020 , PAMELA MAGDALENA TOMICIC GUELL , GLORIA FERNANDA GARCIA DEL SOLAR , MATUTE WILLEMSEM, MARIA ISABEL , Javiera Drapela , Fabiola Marín , CASTRO ABARCA, PATRICIA BERNARDITA

El Discurso Narrativo (DN) es una unidad lingüística compleja utilizada en ciertos contextos y que refleja la organización del pensamiento. La evidencia científica muestra que la población sorda, usuaria de ayudas auditivas, presenta dificultades en los diferentes niveles del lenguaje, tanto expresivos como comprensivos, incluida la habilidad para narrar. Además, existe evidencia de que la intervención terapéutica ayudaría a mejorar su rendimiento. Sin embargo, los datos disponibles sobre las características y abordaje del DN en esta población son escasos. El objetivo del estudio es evaluar un programa piloto para trabajar habilidades narrativas en niños chilenos usuarios de ayudas auditivas. Se estudiaron 22 niños con un promedio de edad de 6,5 años, adaptados con audífonos y/o implante coclear. Se aplicó a este grupo de niños una evaluación inicial del DN utilizando el instrumento Evaluación del Discurso Narrativo (EDNA), obteniéndose la Etapa y Desempeño narrativo de cada niño. Luego, se creó y aplicó individualmente un programa de estimulación del discurso narrativo de 12 sesiones una vez por semana. Finalmente, se repitió la evaluación al final del programa. Se encontraron diferencias significativas entre los resultados obtenidos previo y posterior a la implementación del programa de estimulación. En relación con la Etapa del DN, antes de la intervención el 45,5% de los niños no estructuraba, lo cual se redujo a un 9.1% en la evaluación final. En cuanto al Desempeño, previo a la intervención el 72,7% de los niños presentaba un “déficit narrativo”, lo cual se redujo a un 18,2% posterior a la aplicación del programa.

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Saccadic Direction Errors are Associated with Impulsive Compulsive Behaviours in Parkinson’s Disease Patients

2019 , Pedro Barbosa , Diego Kaski , CASTRO ABARCA, PATRICIA BERNARDITA , Andrew J. Lees , Thomas T. Warner , Atbin Djamshidian

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Body sway during postural perturbations is mediated by the degree of vestibulo-cortical dominance

2019 , CASTRO ABARCA, PATRICIA BERNARDITA , Diego Kaski , Hussein Al-Fazly , Deniz Ak , Liam Oktay , Adolfo Bronstein , Qadeer Arshad

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