DSpace Repository :: Browsing by Author "Kaski, Diego"

Browsing by Author "Kaski, Diego"

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Head shaking does not alter vestibulo ocular reflex gain in vestibular migraine
(2022) Patel, Priyani; Castro, Patricia; Kooh, Nehzat; Arshad, Qadeer; Gargallo, Lucia; Carmona, Sergio; Kaski, Diego
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.
Priming overconfidence in belief systems reveals negative return on postural control mechanisms
(2022) Castro, Patricia; Papoutselou, Efstratia; Mahmoud, Sami; Hussain, Shahvaiz; Fuentealba Bassaletti, Constanza; Kaski, Diego; Bronstein, Adolfo; Arshad, Qadeer
Background: Modulation of postural control strategies and heightened perceptual ratings of instability when exposed to postural threats, illustrates the association between anxiety and postural control. Research question: Here we test whether modulating prior expectations can engender postural-related anxiety which, in turn, may impair postural control and dissociate the well-established relationship between sway and subjective instability. Methods: We modulated expectations of the difficulty posed by an upcoming postural task via priming. In the visual priming condition, participants watched a video of an actor performing the task with either a stable or unstable performance, before themselves proceeding with the postural task. In the verbal priming paradigm, participants were given erroneous verbal information regarding the amplitude of the forthcoming platform movement, or no prior information. Results: Following the visual priming, the normal relationship between trunk sway and subjective instability was preserved only in those individuals that viewed the stable but not the unstable actor. In the verbal priming experiment we observed an increase in subjective instability and anxiety during task performance in individuals who were erroneously primed that sled amplitude would increase, when in fact it did not. Significance: Our findings show that people's subjective experiences of instability and anxiety during a balancing task are powerfully modulated by priming. The contextual provision of erroneous cognitive priors dissociates the normally 'hard wired' relationship between objective measures and subjective ratings of sway. Our findings have potential clinical significance for the development of enhanced cognitive retraining in patients with balance disorders, e.g. via modifying expectations.
Saccadic Direction Errors are Associated with Impulsive Compulsive Behaviours in Parkinson's Disease Patients
(IOS Press, 2019) Barbosa, Pedro; Kaski, Diego; Castro, Patricia; Andrew, Andrew; Warner, Thomas; Djamshidian, Atbin
Fifteen individuals with Parkinson's disease (PD) and impulsive compulsive behaviours (PD+ICB) were compared to 15 PD patients without ICBs (PD-ICB) and 15 healthy controls (HC) on a pro-saccades and an anti-saccades task to assess if ICBs are associated with distinct saccadic abnormalities. PD+ICB made shorter saccades than HC and more direction errors in the anti-saccades task than PD-ICB and HC, suggesting that patients with ICBs have greater difficulty in suppressing automatic saccades towards a given target. Saccadic assessment has the potential to evolve into a marker to guide therapeutic decisions in patients at risk of developing ICBs.
Subjective stability perception is related to postural anxiety in older subjects
(Elsevier B.V., 2019-02) Castro, Patricia; Kaski, Diego; Schieppati, Marco; Furman, Michael; Arshad, Qadeer; Bronstein, Adolfo
Background: Under static conditions, the objective and subjective measures of postural stability correlate well. However, age-related changes in postural control and task-related anxiety may modify the relationship between these subjective and objective measures. Ultimately, patients' symptoms represent subjective reports, thus understanding this relationship has clinical implications. Aims: This study investigates the relationship between subjective-objective measures of postural stability in dynamic conditions and whether this relationship is influenced by age or task-related anxiety. Methods: 50 healthy participants (aged 18-83 years) stood on a platform oscillating at variable amplitudes, with-without a fall-preventing harness to modulate task-related anxiety. Trunk sway path, hip velocity and foot lifts (objective measures) and subjective scores of instability and task-related anxiety were recorded. Results: The subjective perception of stability accurately matched objective body sway, following a logarithmic function profile (r2 = 0.72, p < 0.001). This function did not change significantly with age, harness or task presentation order. A strong relationship was observed between subjective measures of stability and task-related anxiety for all subjects (r = 0.81, p < 0.001). Task repetition reduced anxiety in the young, uncoupling anxiety changes from subjective instability, but not in the elderly who retained higher anxiety levels in line with subjective unsteadiness. Discussion: Subjects accurately rate their own instability during dynamic postural challenges, irrespective of age and actual fall risk. However, anxiety may selectively modulate the perception of instability in older subjects. The perception of stability relies upon the integration of sensory afferents but also recruits emotional-cognitive processes, particularly in older individuals. The use of a safety harness has no influence on subjective or objective postural stability.
Towards an explanation for 'unexplained' dizziness in older people
(2024) Castro, Patricia; Ibitoye, Richard; Ellmers, Toby; Kaski, Diego; Arshad, Qadeer; Bronstein, Adolfo M.
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.
Vestibular loss disrupts visual reactivity in the alpha EEG rhythm
(2023) Ibitoye, Richard; Castro, Patricia; Ellmers, Toby; Kaski, Diego; Bronstein, Adolfo
The alpha rhythm is a dominant electroencephalographic oscillation relevant to sensory-motor and cognitive function. Alpha oscillations are reactive, being for example enhanced by eye closure, and suppressed following eye opening. The determinants of inter-individual variability in reactivity in the alpha rhythm (e.g. changes with amplitude following eye closure) are not fully understood despite the physiological and clinical applicability of this phenomenon, as indicated by the fact that ageing and neurodegeneration reduce reactivity. Strong interactions between visual and vestibular systems raise the theoretical possibility that the vestibular system plays a role in alpha reactivity. To test this hypothesis, we applied electroencephalography in sitting and standing postures in 15 participants with reduced vestibular function (bilateral vestibulopathy, median age = 70 years, interquartile range = 51-77 years) and 15 age-matched controls. We found participants with reduced vestibular function showed less enhancement of alpha electroencephalography power on eye closure in frontoparietal areas, compared to controls. In participants with reduced vestibular function, video head impulse test gain - as a measure of residual vestibulo-ocular reflex function - correlated with reactivity in alpha power across most of the head. Greater reliance on visual input for spatial orientation ('visual dependence', measured with the rod-and-disc test) correlated with less alpha enhancement on eye closure only in participants with reduced vestibular function, and this was partially moderated by video head impulse test gain. Our results demonstrate for the first time that vestibular function influences alpha reactivity. The results are partly explained by the lack of ascending peripheral vestibular input but also by central reorganisation of processing relevant to visuo-vestibular judgements.

Browsing by Author "Kaski, Diego"

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