Preliminary novel research findings indicate that a subset of individuals with moderate to severe traumatic brain injury show bilateral hippocampal atrophy progressing beyond the acute stage post-injury. The present study proposes a novel, integrated model of neuroprotection against subacute hippocampal atrophy (i.e., atrophy occurring beyond the initial 3 months post-injury) via environmental enrichment, drawing on theoretical models and research findings from the fields of environmental enrichment, brain and cognitive reserve, and neuroplastic models of functional recovery from brain injury. Objectives: (a) to examine the relationship between environmental enrichment factors and subacute hippocampal atrophy and (b) to examine the relationship between subacute hippocampal atrophy and return to productivity. Design: Retrospective observational within-subjects. Participants: Patients (N=21) with moderate to severe TBI. Measures: Primary predictors: Self-report ratings of environmental enrichment factors (i.e., hours of cognitive, physical, and social activities, meditation/prayer, and therapy). Primary outcome: hippocampal volume change between 5 months and 24+ months post-injury based on initial and follow-up MRI scans; Brain Injury Community Rehabilitation Outcome Scales-39 (BICRO-39). Results: Generalized environmental enrichment (i.e., an aggregate of cognitive, physical, and social activity) was significantly negatively correlated with subacute bilateral hippocampal atrophy (p<.05). Cognitive activity was the environmental enrichment element that accounted for the greatest degree of variance (32%) in subacute bilateral hippocampal atrophy (p<.01). Frequency of meditation/prayer was significantly negatively correlated with right hippocampal subacute atrophy (<.05) after controlling for socioeconomic status and generalized environmental enrichment. Level of education and pre-injury occupational attainment did not correlate with subacute hippocampal atrophy. Conclusion: Findings suggest that a fixed degree of neural reserve at the time of brain injury may not confer neuroprotection against structural pathology in the manner suggested by the present study’s proposed model of neuroprotection via environmental enrichment. Instead, findings suggest that in order for environmental enrichment to positively modulate susceptibility to subacute hippocampal atrophy post-TBI, environmental enrichment exposure must occur during the subacute phase post-injury rather than prior to injury.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OTU.1807/29930 |
| Date | 31 August 2011 |
| Creators | Miller, Lesley |
| Contributors | Chen, Charles, Green, Robin |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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