This research investigated aspects of the morphosyntactic language development of 115 3-, 4-, and 5-year-old monolingual Spanish-speaking preschool children who resided in Cali, Colombia. Two general language measures were collected from the children: a standardized receptive vocabulary measure (Test de Vocabulario en Imágenes, TVIP), and a parental report of speech and language problems. In addition, morphosyntactic measures of language development were obtained using both a story retelling and an elicitation task. Developmental language measures such as number of T-units (NU-TU), mean length of T-units (MLTU), subordination index (SUB-I), and grammatical errors per T-unit (GRE-TU) were derived from the narratives. Percentages of correct use of direct and indirect object pronouns, reflexive pronouns, definite articles, indefinite articles, plurals and adjectives were obtained from an elicitation task that was specifically designed for this study. Counts of use of these grammatical structures were also calculated from the narratives. There were no statistically significant differences between the three age groups on standard scores for the TVIP or scores for the parent questionnaires, indicating that the three age groups were comparable. For the developmental language measures there was an increasing developmental pattern for NU-TU, MLTU and SUB-I, but no changes were found for GRE-TU. Statistically significant changes for the productive use of the grammatical structures of interest to this study were almost always seen between 3 and 4 years of age. Adult use of these grammatical structures was always statistically significantly more correct than child productions. This investigation provides novel normative data for NU-TU, MLTU, SUB-I and GRE-TU for preschool children. This investigation also offers original data on the productive use of object pronouns, articles, adjectives and plurals across the preschool years. The language battery used in this investigation proved to be sensitive to developmental changes between 3 and 4-5 year olds and has the potential to be used as an eventual diagnostic tool for the identification of children with language disorders. Speech-language pathologists who work with Spanish-speaking children will be able to use this normative information to conduct more objective language assessments.

Rapid compensatory reach-to-grasp reactions are prevalent and functionally important responses to instability. The need to react very rapidly (to prevent falling) imposes temporal constraints on acquisition and processing of the visuospatial information (VSI) needed to guide the reaching movement. Previous results suggested that the CNS may deal with these constraints by using VSI stored in memory proactively, prior to perturbation-onset; however, the extent to which online visual control is necessary or sufficient to guide these reactions has not been established. Furthermore, the influence of memory-decay and concurrent cognitive-task on the performance of these reactions has not been examined. This Thesis employed a novel paradigm wherein the participant is stationary and a motor-driven handhold is positioned unpredictably in front of the participant for each trial. Reach-to-grasp reactions were evoked in healthy young and older adults by sudden unpredictable antero-posterior platform translation (barriers deterred stepping reactions). Liquid-crystal goggles were used to occlude vision either before (recall-delay time=0s/2s/5s/10s) or after perturbation-onset to force reliance on either stored- or online-VSI, respectively. Participants performed a spatial- or non-spatial-memory task during the delay-time in a subset of trials. When forced to rely on stored-VSI, all participants showed reduction in reach accuracy; however, a tendency to undershoot the handhold was exacerbated in the older adults. Forced-reliance on online-VSI led to similar delays in all participants; however, the older adults were more likely to reach with the “wrong” arm or raise both arms. Comparison with normal-VSI trials suggests that both sources of VSI are utilized when grasping the movable handhold for support, with stored-VSI predominating during initiation/transport and online-VSI contributing primarily to final target acquisition/prehension. In terms of recall-delay, both age groups showed comparable reduction in medio-lateral endpoint accuracy when delay-time was longest. Moreover, both cognitive tasks had similar (slowing) effects in both age-groups, suggesting these effects were related to generic attentional demands. However, the older-adults also showed a dual-task interference effect (poorer cognitive-task performance) that was specific to the spatial-memory-task. Further research is needed to establish whether interventions aimed to improve visual/cognitive processing speed, visuospatial memory, and/or attention capacity can reduce risk of falling among senior populations.

Rapid compensatory reach-to-grasp reactions are prevalent and functionally important responses to instability. The need to react very rapidly (to prevent falling) imposes temporal constraints on acquisition and processing of the visuospatial information (VSI) needed to guide the reaching movement. Previous results suggested that the CNS may deal with these constraints by using VSI stored in memory proactively, prior to perturbation-onset; however, the extent to which online visual control is necessary or sufficient to guide these reactions has not been established. Furthermore, the influence of memory-decay and concurrent cognitive-task on the performance of these reactions has not been examined. This Thesis employed a novel paradigm wherein the participant is stationary and a motor-driven handhold is positioned unpredictably in front of the participant for each trial. Reach-to-grasp reactions were evoked in healthy young and older adults by sudden unpredictable antero-posterior platform translation (barriers deterred stepping reactions). Liquid-crystal goggles were used to occlude vision either before (recall-delay time=0s/2s/5s/10s) or after perturbation-onset to force reliance on either stored- or online-VSI, respectively. Participants performed a spatial- or non-spatial-memory task during the delay-time in a subset of trials. When forced to rely on stored-VSI, all participants showed reduction in reach accuracy; however, a tendency to undershoot the handhold was exacerbated in the older adults. Forced-reliance on online-VSI led to similar delays in all participants; however, the older adults were more likely to reach with the “wrong” arm or raise both arms. Comparison with normal-VSI trials suggests that both sources of VSI are utilized when grasping the movable handhold for support, with stored-VSI predominating during initiation/transport and online-VSI contributing primarily to final target acquisition/prehension. In terms of recall-delay, both age groups showed comparable reduction in medio-lateral endpoint accuracy when delay-time was longest. Moreover, both cognitive tasks had similar (slowing) effects in both age-groups, suggesting these effects were related to generic attentional demands. However, the older-adults also showed a dual-task interference effect (poorer cognitive-task performance) that was specific to the spatial-memory-task. Further research is needed to establish whether interventions aimed to improve visual/cognitive processing speed, visuospatial memory, and/or attention capacity can reduce risk of falling among senior populations.

Individuals with stroke suffer from impaired balance that increases their risk of falling. Controlling reactive balance is essential to maintaining stability. The objective of the first study was to identify the role of pre-perturbation stance asymmetry on limb preference for reactive stepping in healthy young adults. This study demonstrated that steps taken with a pre-loaded limb are short, directed laterally and have a rapid swing time. The objective of the second study was to investigate the challenges of reactive stepping among individuals with stroke. This study demonstrated that participants primarily execute reactive stepping with their non-paretic limb, although those steps are highlighted by delays in timing and increased incidence of multiple stepping compared to healthy controls, even though all participants had very good clinical balance scores. Outcomes from this thesis present the need for improved clinical assessment of reactive balance control to help reduce the incidence of falling following stroke.

This thesis examined post-stroke gait asymmetry: a prevalent issue and one that has a number of associated negative consequences (e.g. challenged balance control, gait inefficiencies, increased risk of musculoskeletal injury to the non-paretic limb and decreased overall activity levels). This thesis is comprised of three studies that focused on 1) how gait symmetry should be measured, 2) how gait asymmetry may change in the long term post-stroke and 3) whether gait asymmetry is responsive to a rehabilitation intervention. A comparison of the most common expressions of spatiotemporal gait symmetry revealed that the simple symmetry ratio calculation was most appropriate on the basis of ease of interpretation and clinical usefulness. Swing time, stance time and step length were found to be the most useful gait parameters to assess for symmetry. Although related, swing time, stance time and step length ratios exhibit variation in the discrimination of post-stroke individuals, in their inter-relationships and in their relationship velocity. When when used together, swing time, stance time and step length asymmetry ratios may provide a complementary picture of the gait pattern and the quality of gait control. It was also demonstrated that swing time and stance time asymmetry were worse in later stages post-stroke when assessed cross-sectionally. In contrast, gait velocity did not exhibit this pattern. These results indicate that the control of gait (symmetry) may decline over time post-stroke, independent from the capacity for gait which remains constant (velocity). This dissociation in characteristics supports the concept that these two variables (symmetry and velocity) may represent separate features of post-stroke gait. Finally, individuals with sub-acute stroke are capable of altering the temporal symmetry of their gait in response to visual biofeedback. Individuals with sub-acute stroke differ in terms of the strategy they employ in response to biofeedback and the observed improvements in gait symmetry were not always achieved in the desired manner: increased use of the paretic lower extremity. This thesis presents new information regarding the asymmetrical nature of post-stroke gait. Future work may extend these findings to develop a comprehensive approach to gait measurement as well as gait interventions that encourage increased paretic limb use instead of compensatory behaviour.

Individuals with stroke suffer from impaired balance that increases their risk of falling. Controlling reactive balance is essential to maintaining stability. The objective of the first study was to identify the role of pre-perturbation stance asymmetry on limb preference for reactive stepping in healthy young adults. This study demonstrated that steps taken with a pre-loaded limb are short, directed laterally and have a rapid swing time. The objective of the second study was to investigate the challenges of reactive stepping among individuals with stroke. This study demonstrated that participants primarily execute reactive stepping with their non-paretic limb, although those steps are highlighted by delays in timing and increased incidence of multiple stepping compared to healthy controls, even though all participants had very good clinical balance scores. Outcomes from this thesis present the need for improved clinical assessment of reactive balance control to help reduce the incidence of falling following stroke.

This study examines the factors that influence how patients, families, and clinicians make decisions about risk-taking and safety in brain injury rehabilitation. Despite the importance of these decisions, particularly during transitions in care, there is scant literature to help guide these care partners in ethical and clinical decision-making related to risk-taking and safety. This study suggests that there are tensions between rehabilitation and patient safety efforts. Risk-taking lies at the core of brain injury rehabilitation; however, decisions about risk-taking are also influenced by conflicting values, system pressures, and patient abilities. A relational approach to autonomy that addresses patients’ decisional and functional abilities within their social contexts is more nuanced than a liberal individualist approach to autonomy, and provides a better framework for understanding decision-making. Relational autonomy may help clinicians make decisions that better balance risk-taking and safety, decisions that are committed to the principles of respecting autonomy and advancing safety.

This study examines the factors that influence how patients, families, and clinicians make decisions about risk-taking and safety in brain injury rehabilitation. Despite the importance of these decisions, particularly during transitions in care, there is scant literature to help guide these care partners in ethical and clinical decision-making related to risk-taking and safety. This study suggests that there are tensions between rehabilitation and patient safety efforts. Risk-taking lies at the core of brain injury rehabilitation; however, decisions about risk-taking are also influenced by conflicting values, system pressures, and patient abilities. A relational approach to autonomy that addresses patients’ decisional and functional abilities within their social contexts is more nuanced than a liberal individualist approach to autonomy, and provides a better framework for understanding decision-making. Relational autonomy may help clinicians make decisions that better balance risk-taking and safety, decisions that are committed to the principles of respecting autonomy and advancing safety.

There are limited tools available for clinicians to affordably and objectively assess balance control to prescribe treatments and measure progress post-stroke. The objectives of this thesis were to: 1) develop a toolkit to quantitatively measure dynamic balance control and determine the repeatability of outcomes within and between-sessions in healthy adults; and 2) determine the repeatability of the tasks and the association between outcomes of an advanced clinical model of care in a post-stroke population. In study 1 a wireless balance assessment toolkit was developed using a grid of four Nintendo Wii Balance boards and custom software and repeatability of the outcomes were established in healthy adults. Study 2 revealed the measures to be repeatable in a sub-acute stroke population while further evidence is required to validate the toolkit, as it did not associate with outcomes from an advanced clinical model of care.

There are limited tools available for clinicians to affordably and objectively assess balance control to prescribe treatments and measure progress post-stroke. The objectives of this thesis were to: 1) develop a toolkit to quantitatively measure dynamic balance control and determine the repeatability of outcomes within and between-sessions in healthy adults; and 2) determine the repeatability of the tasks and the association between outcomes of an advanced clinical model of care in a post-stroke population. In study 1 a wireless balance assessment toolkit was developed using a grid of four Nintendo Wii Balance boards and custom software and repeatability of the outcomes were established in healthy adults. Study 2 revealed the measures to be repeatable in a sub-acute stroke population while further evidence is required to validate the toolkit, as it did not associate with outcomes from an advanced clinical model of care.