The effect of a concurrent cognitive task on cortical potentials evoked by unpredictable balance perturbations

BACKGROUND: Although previous studies suggest that postural control requires attention and other cognitive resources, the central mechanisms responsible for this relationship remain unclear. To address this issue, we examined the effects of altered attention on cortical activity and postural responses following mechanical perturbations to upright stance. We hypothesized that cortical activity would be attenuated but not delayed when mechanical perturbations were applied during a concurrent performance of a cognitive task (i.e. when attention was directed away from the perturbation). We also hypothesized that these cortical changes would be accompanied by alterations in the postural response, as evidenced by increases in the magnitude of anteroposterior (AP) centre of pressure (COP) peak displacements and tibialis anterior (TA) muscle activity. Healthy young adults (n = 7) were instructed to continuously track (cognitive task) or not track (control task) a randomly moving visual target using a hand-held joystick. During each of these conditions, unpredictable translations of a moving floor evoked cortical and postural responses. Scalp-recorded cortical activity, COP, and TA electromyographic (EMG) measures were collected. RESULTS: Results revealed a significant decrease in the magnitude of early cortical activity (the N1 response, the first negative peak after perturbation onset) during the tracking task compared to the control condition. More pronounced AP COP peak displacements and EMG magnitudes were also observed for the tracking task and were possibly related to changes in the N1 response. CONCLUSION: Based on previous notions that the N1 response represents sensory processing of the balance disturbance, we suggest that the attenuation of the N1 response is an important central mechanism that may provide insight into the relationship between attention and postural control

The influence of sensory and attentional components of ongoing movement on the timing of compensatory upper limb balance reactions

grantor: University of TorontoThis thesis investigated the effects of ongoing movement on the timing of compensatory upper limb balance reactions (ULBRs) and the mechanisms underlying these effects. Subjects were instructed to maintain stability while performing tasks of active or passive lower limb movement, an attention-demanding task, or a control condition (no lower limb movement or attention-demanding task). Hypotheses, that a concurrent movement or attention-demanding task would produce delayed or slower ULBRs, were supported in these experiments. Active and passive lower limb movement had similar effects on ULBRs, suggesting that sensory discharge played a large role in these movement-conditioning effects. Attention-demanding tasks also influenced these responses, suggesting an attentional component in the control of ULBRs. Since these results strongly suggest that rhythmic lower limb movement can significantly delay and slow upper limb balance responses, this thesis has important implications for our understanding of how ongoing movement regulates balance control.M.Sc

Cerebral potentials evoked by balance perturbations

To investigate the role of the cerebral cortex in human compensatory postural control, electroencephalography was used to record perturbation-evoked cerebral potentials (PEPS). Previous studies have identified a large negative cerebral potential termed the N1 response (peak latency being 100-200 ms with respect to the perturbation onset), which was accompanied by a positive cerebral potential termed the P2 response (peak latency being 200-500 ms with respect to the perturbation onset). As these studies provided a limited understanding of the role of PEPS in compensatory postural control, the main thesis goals were: (1) to further explore N1 and its relation to sensory processing of the postural perturbation, and (2) to determine whether P2 represented sensorimotor events associated with the control of the postural response. N1 and P2 responses were examined in four interconnected studies which involved: (1) determining whether N1 represented sensory inputs related to the perturbation or sensorimotor events related to the control of evoked balance responses, (2) determining the influence of altered attention on N1 by comparing conditions that featured the presence and absence of a concurrent cognitive task, (3) examining the influence of stimulus predictability on N1, and (4) altering the later components of balance responses in order to establish influence over P2. Based on these studies, there were several important findings that have led to a better understanding of these potentials. Firstly, N1 appeared to represent sensory events related to the perturbation that were independent of ankle automatic postural reactions (APRs). Secondly, N1 appeared to be modulated by altered attention. Thirdly, as opposed to a simple reflection of sensory volume or perturbation intensity, N1 appeared to represent a 'mismatch event detector' that alerted the CNS to unpredictable changes in the perturbation. Lastly, P2 did not appear to represent sensorimotor events related to ankle APRs, suggesting that the control of ankle APRs could mainly reside within subcortical structures. Future work will determine whether the cerebral cortex uses sensory information about the perturbation in order to influence immediate or future postural reactions. Future studies will also examine whether P2 responses might reflect cognitive events associated with postural control.Ph.D

Using a Virtual Community of Practice to Support Stroke Best Practice Implementation: Mixed Methods Evaluation (Preprint)

BACKGROUND Successful best practice implementation is influenced by access to peer support and knowledge exchange. The Toronto Stroke Networks Virtual Community of Practice, a secure social media platform, is a knowledge translation tool supporting dissemination and adoption of stroke best practices for interprofessional stroke stakeholders. OBJECTIVE The aim of this study is to evaluate the use of a virtual community of practice (VCoP) in supporting regional stroke care best practice implementation in an urban context. METHODS A mixed methods approach was used. Qualitative data were collected through focus groups and interviews with stroke care provider members of the VCoP working in acute and rehabilitation settings. Thematic analysis was completed, and the Wenger Value Creation Model and developmental evaluation were used to reflect practice change. Quantitative data were collected and analyzed using website analytics on VCoP use. RESULTS A year after implementation, the VCoP had 379 members. Analysis of web analytics data and transcripts from focus groups and interviews conducted with 26 VCoP members indicated that the VCoP provided immediate value in supporting user networking, community activities, and interactions. Skill acquisition and changes in perspective acquired through discussion and project work on the VCoP were valued by members, with potential value for supporting practice change. Learning about new stroke best practices through the VCoP was a starting point for individuals and teams to contemplate change. CONCLUSIONS These findings suggest that the VCoP supports the early stages of practice change and stroke best practice implementation. Future research should examine how VCoPs can support higher levels of value creation for implementing stroke best practices. </sec

Using a Virtual Community of Practice to Support Stroke Best Practice Implementation: Mixed Methods Evaluation

BackgroundSuccessful best practice implementation is influenced by access to peer support and knowledge exchange. The Toronto Stroke Networks Virtual Community of Practice, a secure social media platform, is a knowledge translation tool supporting dissemination and adoption of stroke best practices for interprofessional stroke stakeholders. ObjectiveThe aim of this study is to evaluate the use of a virtual community of practice (VCoP) in supporting regional stroke care best practice implementation in an urban context. MethodsA mixed methods approach was used. Qualitative data were collected through focus groups and interviews with stroke care provider members of the VCoP working in acute and rehabilitation settings. Thematic analysis was completed, and the Wenger Value Creation Model and developmental evaluation were used to reflect practice change. Quantitative data were collected and analyzed using website analytics on VCoP use. ResultsA year after implementation, the VCoP had 379 members. Analysis of web analytics data and transcripts from focus groups and interviews conducted with 26 VCoP members indicated that the VCoP provided immediate value in supporting user networking, community activities, and interactions. Skill acquisition and changes in perspective acquired through discussion and project work on the VCoP were valued by members, with potential value for supporting practice change. Learning about new stroke best practices through the VCoP was a starting point for individuals and teams to contemplate change. ConclusionsThese findings suggest that the VCoP supports the early stages of practice change and stroke best practice implementation. Future research should examine how VCoPs can support higher levels of value creation for implementing stroke best practices

Abstract TP355: Supporting and Sustaining Systems Change Through the Development of Common Standards of Stroke Care

Background/Issues: The Stroke Flow initiative is a system-wide redesign of stroke services to enhance access to stroke best practices. Specifically, its focus is to ensure access to acute stroke units and timely and appropriate rehabilitation. To support this work, the Toronto Stroke Networks (TSNs) held forums with stroke nursing leaders (SNLs) within the Greater Toronto Area (GTA). Purpose: Through these forums, the purpose of this work was to develop evidenced-informed common standards of stroke care across the continuum and set priorities for implementation within the GTA. Methods: Six forums (from December 2011 to June 2012) were held for 43 SNLs from 16 acute and rehabilitation hospitals within the GTA. Using an appreciative inquiry approach, meetings focused on: 1) identifying common core elements (CCEs) for stroke care; 2) validating CCEs through consultation with interprofessional stroke teams; 3) forming consensus on CCEs; 4) identifying organizational priorities for implementation planning using thematic analysis; 5) integrating CCEs into existing processes of care; and 6) sustaining this work through the establishment of a stroke community of practice. Results: Through collaborative planning, CCEs were developed and reflect current and emerging best practices. Preliminary results from thematic analysis identified priorities related to: transitions of care, improved team communication processes, patient/family education, and integration of outcome measures across the care continuum. Conclusions: Common core elements of stroke care were collectively developed by the TSNs, stroke nursing leaders, and interprofessional teams to promote a standardization of stroke care that integrates best practices and identifies areas for improvement. Impact of this work has led to the development of CCE documents to support the integration and standardization of stroke care and the establishment of a stroke nursing community of practice. Final thematic analysis is currently underway to further identify priorities for implementation. </jats:p

Abstract T P119: Challenges Associated with Access to Stroke Rehabilitation for Patients with Cognitive Impairment in Toronto

Background: Cognitive Impairment (CI) affects up to 60% of stroke survivors and is associated with poorer recovery and decreased function. Toronto clinicians report limited access to inpatient rehabilitation for stroke patients with CI. Purpose: To inform system planning that aligns with best practice for stroke patients with CI, the Toronto Stroke Networks examined: 1) access to inpatient rehabilitation services for stroke patients with CI; 2) facility differences with respect to referral decisions; and 3) the frequency of documented standardized cognitive screening (SCS) in inpatient rehabilitation referrals. Methods: Data were abstracted from the E-Stroke Rehab Referral System for fiscal years 2012-2014. Initial high intensity rehabilitation (HIR) referrals for 5 rehabilitation facilities in Toronto were analyzed to examine: percentage of referrals accepted, declined, and declined due to CI, and percentage of referrals reporting SCS in referral documentation. These data were further stratified by facility. A survey of cognitive rehabilitation was completed across 6 rehabilitation facilities. Results: There are no cognitive rehabilitation services that cater specifically to stroke patients reported in Toronto. Of the total number of HIR referrals (n=5005), 68.3% of initial referrals were accepted and 18.2% declined. Of the declined referrals (n=910), 17.5% were declined due to CI with variability across the 5 rehabilitation facilities ranging from 0.6 to 46.5%. Further, when examining referrals that were pending a decision or declined due to CI (n=508), 78.5% (range 48-100%) of these referrals across, 10 referring acute care facilities, had no documented SCS. Conclusions: Stroke patients with CI do not have adequate or consistent access to stroke rehabilitation across sites within Toronto. Additionally, there is a lack of documented SCS in rehabilitation referrals, which could impact access to rehabilitation. This work will further inform educational initiatives that support increased access to inpatient rehabilitation for persons with stroke and CI. </jats:p