Browsing by Author "Yang, Lixia"

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    Neuroanatomical Changes Associated with Working Memory Training in Healthy Adults
    (2018-06-26) Savage, Linette; Goghari, Vina M.; Campbell, Tavis S.; Bodner, Glen E.; Lebel, Catherine A.; MacMaster, Frank P.; Yang, Lixia
    The potential for working memory training to enhance cognitive and intellectual abilities is alluring across scientific disciplines and the general public. However, the field has been fraught with inconsistency and controversy. Heterogeneous methodological implementations have led to a divided and contrasting body of literature, which has collectively limited scientific transparency and advancement in the field. However, neuroimaging has the potential to clarify what, if any, benefit working memory training has on the adult human brain. A recent series of studies used functional neuroimaging to investigate neural activations associated with working memory training. This dissertation uses structural imaging to address another theoretical area: the neuroanatomical correlates of working memory training. Forty-eight healthy community dwelling adults, aged 18 - 40 years, completed a series of cognitive tasks and underwent magnetic resonance imaging (MRI) before and after completing a 6-week trial of working memory training (experimental condition) or processing speed training (active control condition). Group by time repeated measures Analyses of Variance (rm-ANOVAs) were conducted on MRI data to identify changes in surface area, thickness, and volume in theoretically relevant gray matter regions of interest, as well as overall gray and white matter volumes, associated with working memory training. Similar analyses were conducted to investigate changes in cognitive task performance in this sample. Null results were present across all neuroanatomical metrics after correction for multiple comparisons, and findings from cognitive tasks were consistent with the subset of literature suggesting that working memory training does not meaningfully benefit cognitive performance. Albeit limited by low statistical power and the confines of available technology, findings of this study, in consort with recently published investigations, strongly support the idea that working memory training is not an effective method for enhancing cognitive performance or inducing neoplastic changes in brain structure. We suggest that future studies continue attempts to resolve heterogeneity and polarization in this field, or alternatively, concentrate resources on identifying and refining mechanisms of change in populations who may benefit from rehabilitative forms of cognitive training.
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    On the Malleability of Human Cognition: Working Memory Training and Transfer
    (2017) Clark, Cameron; Goghari, Vina; Campbell, Tavis; Longman, Richard Stewart; Goodyear, Bradley; Ramasubbu, Rajamannar; Yang, Lixia
    Training working memory (WM) to increase WM capacity and fluid intelligence (Gf) has received much experimental attention in recent years, though its efficacy remains highly controversial. The current study investigated the effect of a randomized six-week online WM intervention on cognitive abilities and patterns of neural activation in a community-recruited sample of healthy young adults, in relation to both a processing speed training active control condition, as well as a no-contact control condition. Results of this randomized trial are discussed in three parts: Chapter 2 examines group-level fMRI activation patterns for tasks of WM and Gf before the training intervention. Consistent with previous research, results indicate large areas of fronto-parietal activation in response to increasing task demands for our WM task, which largely subsume more circumscribed regions of activation for our Gf task. These results are discussed in terms of a task-general central network which may underlie performance of WM, Gf, and perhaps even goal-directed behaviour more generally. Chapter 3 investigates potential differences in a wide range of cognitive test scores before and after WM training, processing speed training, or no-contact. Results revealed support for the null hypothesis across all cognitive tests administered. Because these results are consistent with experimental trials of equal or greater methodological rigor, we suggest that future research re-focus on promising interventions known to increase memory performance in healthy young adults; and/or examine alternative populations in which WM training may be efficacious. Chapter 4 examines potential differences in pre- and post-training patterns of neural activation for WM and Gf tasks in our WM training, and processing speed training groups. Results indicated significant post-training reductions in activation for the WM trained group in relation to the processing speed group for the WM task, but not the Gf task. These results suggest that WM training does not affect patterns of neural activation for Gf tasks. We suggest that future research investigate neural correlates of WM training in populations for which WM itself is impaired; and/or WM training interventions in populations that have returned more promising results compared to those with healthy young adults.