Identifying Patients with Poststroke Mild Cognitive Impairment by Pattern Recognition of Working Memory Load-Related ERP

The early detection of subjects with probable cognitive deficits is crucial for effective appliance of treatment strategies. This paper explored a methodology used to discriminate between evoked related potential signals of stroke patients and their matched control subjects in a visual working memory paradigm. The proposed algorithm, which combined independent component analysis and orthogonal empirical mode decomposition, was applied to extract independent sources. Four types of target stimulus features including P300 peak latency, P300 peak amplitude, root mean square, and theta frequency band power were chosen. Evolutionary multiple kernel support vector machine (EMK-SVM) based on genetic programming was investigated to classify stroke patients and healthy controls. Based on 5-fold cross-validation runs, EMK-SVM provided better classification performance compared with other state-of-the-art algorithms. Comparing stroke patients with healthy controls using the proposed algorithm, we achieved the maximum classification accuracies of 91.76% and 82.23% for 0-back and 1-back tasks, respectively. Overall, the experimental results showed that the proposed method was effective. The approach in this study may eventually lead to a reliable tool for identifying suitable brain impairment candidates and assessing cognitive function

Using Electrophysiology to Investigate Changes in Brain Activation in Individuals with Chronic Stroke

Many individuals who have experienced a stroke also experience persistent decrements in several domains, such as sensorimotor, language, and cognition. While rehabilitation for these deficits is helpful even decades after a stroke, there is limited information available to determine the most effective pairing of treatment with individual deficits. Further, despite decades of neuroimaging research, our understanding of optimal recovery patterns following stroke is relatively poor. In order to improve outcomes for individuals living with chronic deficits due to stroke, neurophysiological biomarkers corresponding to recovery patterns and treatment response are needed. Electroencephalography (EEG) holds great potential for identifying biomarkers as it directly measures brain activation, and is non-invasive, reliable, replicable, and portable. Further, almost all individuals post-stroke are able to tolerate EEG recording. In addition, different methods of analyzing EEG data allow multiple information streams to be gleaned from a single dataset. In this study, 27 persons with chronic stroke (PWCS) and 27 neurologically healthy controls completed speech, language, cognitive, and sensorimotor behavioral assessments. Participants also completed two EEG sessions approximately one month apart which included recording of brain activity at rest and during language, cognitive, and motor tasks. Spectral EEG and event-related potential (ERP) analyses revealed significant differences between neurologically healthy controls and PWCS both at rest and during an auditory oddball task. Test-retest reliability measured across a one-month interval varied by group, task, and electrode montages or regions of interest from poor to excellent. The spectral EEG analysis showed changes previously reported during the acute and sub-acute phase of recovery persist into the chronic phase. ERP analysis demonstrated that individuals with a wide range of post-stroke deficits perform significantly differently during a cognitive task. However, no statistically significant differences were observed between healthy controls and this mixed group during language tasks. Finally, reliability findings indicate some tasks and measures may be appropriate for use in determining treatment response. These results provide support for the use of EEG as a biomarker in the chronic phase in a general stroke population. Future research should investigate the utility of EEG in specific subgroups of persons with chronic stroke

The Clinical Utility of a Short Form Version for the Rey Complex Figure Test (RCFT) in Identifying Visual Memory Impairments with Older Adults

The aim of this study was to examine if a short-form version of the Rey Complex Figure Test (RCFT-SF) was equivalent to the measure’s standard administration procedures as part of a neuropsychological battery for testing visual memory in an older adult population as well as the impact of anxiety on their performance. The RCFT-SF consisted of a similar administration procedure to the standard form (e.g., copy, immediate recall, delayed recall, and recognition trial) while reducing the period between the immediate and delayed recall portions of the measure to 10 minutes. Participants involved with this study were divided into two groups, the RCFT-SF group and a control group consisting of individuals that were already tested with the standard Rey Complex Figure Test (RCFT). Results from an independent samples t-test for the delayed recall trial indicated there was no significant difference between the two measures suggesting the shortened delay period on the RCFT-SF is equivalent to the delay period in the standard RCFT. Non-parametric testing indicated participants in the RFCT group had significantly higher scores than the RCFT-SF group on the copy trial, while there were no significant differences were identified between the two measures on the immediate and recognition trials. When examining the impact of both state and trait levels of anxiety on performance during the RCFT-SF, correlational analyses indicated there was no significant relationship found. Finally, a series of independent samples t-tests found that level of impairment did not impact performance on the scores for the delayed and recognition trials on the RCFT-SF. However, impaired individuals scored significantly lower than those in the unimpaired group on the immediate recall trial for the RCFT. While the limited sample size impacted the results in determining equivalency to the RCFT across all trials, these findings suggest the shortened delay period in the RCFT-SF produces equivalent scores to the standard administration procedure in terms of the delay period

Falling Head Over Heels: Investigating the higher-level cognitive and electrophysiological processes underlying gait control and falls in older adults and stroke survivors

Falls are a common problem for Ireland’s older adults and stroke survivors, which have severe consequences for the individual and high care costs for the state. Current clinical interventions that focus solely on musculoskeletal function are not evidenced to be consistently effective in the long term, or in those older adults without muscle and bone impairments (Cadore, Rodríguez-Mañas, Sinclair, & Izquierdo, 2013; Teasell, McRae, Foley, & Bhardwaj, 2002). The role of cognition in gait control and falls has become increasingly apparent, with higher-level executive functions exhibiting a clear relationship with falls and cognitive decline with ageing (Morris, Lord, Bunce, Burn, & Rochester, 2016). This research aims to address a gap in the literature by identifying the specific higher-level executive processes that play a role in gait control, and examining if these processes are impaired in older adults and stroke survivors with a high risk of falling. Behavioural and electrophysiological measures were used to examine walking gait in both single- and dual-task conditions, as well as cognitive performances and the associated event-related potentials in healthy young and older adult “fallers” and “non-fallers”, and also in a sample of stroke survivors. The results suggest that executive top-down processes (working memory in particular), play a role in gait control during dual-task walking generally, and that executive processes are relied upon more in older age. This work suggests that there may also be neural markers of “successful” ageing that differentiate fallers from non-fallers, and that there can be substantial recovery of both cognition and gait post-stroke. These findings support the resource capacity and compensatory theories of neurocognitive ageing, and suggest that executive neuropsychological tasks could be developed to offer alternative cognitive/neural fall screening assessments and rehabilitation programmes for stroke patients and the wider older adult population

Falling Head Over Heels: Investigating the higher-level cognitive and electrophysiological processes underlying gait control and falls in older adults and stroke survivors

Falls are a common problem for Ireland’s older adults and stroke survivors, which have severe consequences for the individual and high care costs for the state. Current clinical interventions that focus solely on musculoskeletal function are not evidenced to be consistently effective in the long term, or in those older adults without muscle and bone impairments (Cadore, Rodríguez-Mañas, Sinclair, & Izquierdo, 2013; Teasell, McRae, Foley, & Bhardwaj, 2002). The role of cognition in gait control and falls has become increasingly apparent, with higher-level executive functions exhibiting a clear relationship with falls and cognitive decline with ageing (Morris, Lord, Bunce, Burn, & Rochester, 2016). This research aims to address a gap in the literature by identifying the specific higher-level executive processes that play a role in gait control, and examining if these processes are impaired in older adults and stroke survivors with a high risk of falling. Behavioural and electrophysiological measures were used to examine walking gait in both single- and dual-task conditions, as well as cognitive performances and the associated event-related potentials in healthy young and older adult “fallers” and “non-fallers”, and also in a sample of stroke survivors. The results suggest that executive top-down processes (working memory in particular), play a role in gait control during dual-task walking generally, and that executive processes are relied upon more in older age. This work suggests that there may also be neural markers of “successful” ageing that differentiate fallers from non-fallers, and that there can be substantial recovery of both cognition and gait post-stroke. These findings support the resource capacity and compensatory theories of neurocognitive ageing, and suggest that executive neuropsychological tasks could be developed to offer alternative cognitive/neural fall screening assessments and rehabilitation programmes for stroke patients and the wider older adult population

Clinical Pathways in Stroke Rehabilitation

This open access book focuses on practical clinical problems that are frequently encountered in stroke rehabilitation. Consequences of diseases, e.g. impairments and activity limitations, are addressed in rehabilitation with the overall goal to reduce disability and promote participation. Based on the available best external evidence, clinical pathways are described for stroke rehabilitation bridging the gap between clinical evidence and clinical decision-making. The clinical pathways answer the questions which rehabilitation treatment options are beneficial to overcome specific impairment constellations and activity limitations and are well acceptable to stroke survivors, as well as when and in which settings to provide rehabilitation over the course of recovery post stroke. Each chapter starts with a description of the clinical problem encountered. This is followed by a systematic, but concise review of the evidence (RCTs, systematic reviews and meta-analyses) that is relevant for clinical decision-making, and comments on assessment, therapy (training, technology, medication), and the use of technical aids as appropriate. Based on these summaries, clinical algorithms / pathways are provided and the main clinical-decision situations are portrayed. The book is invaluable for all neurorehabilitation team members, clinicians, nurses, and therapists in neurology, physical medicine and rehabilitation, and related fields. It is a World Federation for NeuroRehabilitation (WFNR) educational initiative, bridging the gap between the rapidly expanding clinical research in stroke rehabilitation and clinical practice across societies and continents. It can be used for both clinical decision-making for individuals and as well as clinical background knowledge for stroke rehabilitation service development initiatives. ; Provides evidence-based clinical practice guidelines for stroke rehabilitation Discusses clinical problems and evidence, comments on assessment, therapy and technical aids Written by experienced experts with a background in clinical practic

Clinical Pathways in Stroke Rehabilitation

This open access book focuses on practical clinical problems that are frequently encountered in stroke rehabilitation. Consequences of diseases, e.g. impairments and activity limitations, are addressed in rehabilitation with the overall goal to reduce disability and promote participation. Based on the available best external evidence, clinical pathways are described for stroke rehabilitation bridging the gap between clinical evidence and clinical decision-making. The clinical pathways answer the questions which rehabilitation treatment options are beneficial to overcome specific impairment constellations and activity limitations and are well acceptable to stroke survivors, as well as when and in which settings to provide rehabilitation over the course of recovery post stroke. Each chapter starts with a description of the clinical problem encountered. This is followed by a systematic, but concise review of the evidence (RCTs, systematic reviews and meta-analyses) that is relevant for clinical decision-making, and comments on assessment, therapy (training, technology, medication), and the use of technical aids as appropriate. Based on these summaries, clinical algorithms / pathways are provided and the main clinical-decision situations are portrayed. The book is invaluable for all neurorehabilitation team members, clinicians, nurses, and therapists in neurology, physical medicine and rehabilitation, and related fields. It is a World Federation for NeuroRehabilitation (WFNR) educational initiative, bridging the gap between the rapidly expanding clinical research in stroke rehabilitation and clinical practice across societies and continents. It can be used for both clinical decision-making for individuals and as well as clinical background knowledge for stroke rehabilitation service development initiatives. ; Provides evidence-based clinical practice guidelines for stroke rehabilitation Discusses clinical problems and evidence, comments on assessment, therapy and technical aids Written by experienced experts with a background in clinical practic

The Nature of Working Memory in Aphasia

Thesis (PhD) - Indiana University, Speech and Hearing, 2007It is well known that many adults with aphasia demonstrate concomitant deficits in higher-level cognitive functions, including attention, executive function, and short-term and working memory. This has led to two premises: (a) the domain-specific hypothesis, in which aphasia is associated with additional cognitive deficits only to the extent that these are dependent upon language; and (b) the domain-general hypothesis, in which aphasia is associated with nonlinguistic cognitive impairments as a consequence of either overlapping anatomy or widespread cortical changes post-insult. The purpose of this research was to disentangle these competing hypotheses with regards to working memory (WM) in adults with aphasia. Like other categories of cognitive impairment in this patient group, past research has identified but failed to elucidate WM impairments in aphasic language processing. Toward this end, 15 adults with left-hemisphere damage and aphasia (LHD) and 12 non-brain-damaged controls (NBD) completed a parametric WM task with systematic variation of psycholinguistic complexity (high-frequency, low-frequency, or non-nameable stimuli) and WM load (0-, 1-, and 2-back). Data were analyzed with respect to the differential impact of these variables within and across subjects and groups. Whereas expected effects of word frequency were elicited in stimulus confrontation naming, LHD subjects were affected only minimally by frequency manipulations during the n-back task. Instead, these subjects demonstrated a significant performance decrement relative to controls with increasing WM load. Moreover, aphasia severity was moderately correlated with WM for non-nameable (i.e., more difficult) but not nameable stimuli. At the theoretical level, these results support a resource-based processing model in aphasia; at the neurobiological level, these findings are consistent with the proposition of widespread cortical connectivity changes irrespective of type or location of brain damage. A secondary purpose of this study was to investigate the reliability of LHD performance on the n-back task, given the known performance variability associated with aphasia and the general dearth of reliability data for higher-level tasks. Results demonstrated that the n-back task is a reliable WM indicator over time for this population