Reduced global processing bias in people with a history of mild traumatic brain injury: Grass everywhere and not a field in sight
Mild traumatic brain injury (mTBI) is increasingly recognized as a disconnection syndrome, due to the prevalence of disrupted long-range connections. Long-range connections refer to neural pathways that span across brain regions, allowing communication and synchronization between different brain areas. Disruption of these connections is associated with the inability to efficiently integrate local information (i.e., multiple visual attributes) into the percept of a single global shape. The aim of this thesis was to investigate whether people with a history of mTBI exhibit a reduced ability to integrate local information into meaningful context. Chapter 2 investigated whether visual integration was impaired in people with a history of mTBI, using visual illusions. Susceptibility to visual illusions demonstrates effective integration of visual information to provide a global picture, with surrounding elements automatically integrated into the perception of local elements. Results from Chapter 2 revealed that people with a history of mTBI exhibited decreased susceptibility to visual illusions, suggesting diminished automatic integration of visual information in a global manner; rather, these individuals appeared to prioritize analysis of local details within a visual stimulus. To further investigate this assumption, we employed the Navon task in Chapter 3 to assess whether people with a history of mTBI demonstrated a tendency to prioritize the processing of local details over global information when presented with multiple objects. This task was chosen as it provides a reliable measure of the extent to which individuals engage in global or local processing. The results revealed that people with a recent history of mTBI (within 12 months) had a reduced bias towards processing global elements of a figure (i.e., attending to the overall configuration of the object), indicating a reduced automatic tendency to process visual information as a coherent global percept. In contrast, individuals who sustained their most recent mTBI more than one year earlier displayed the same global processing bias as control participants (i.e., they attended to the overall structure of the visual stimulus first). Following this observation, it was speculated that people with a history of mTBI may also apply a de-automatized processing style to their movements. It has been argued that individuals with a high propensity to consciously process their movements are more likely to display de-automaticity (inefficient or disrupted movement); therefore, in Chapter 4 we assessed the propensity of people with a history of mTBI to consciously monitor and control their movements, using the Movement Specific Reinvestment Scale (MSRS). The results showed that people with a history of mTBI had a higher propensity for MSRS than controls. In addition, we found that time since most recent mTBI was negatively associated with the conscious motor processing subscale of the MSRS. Chapter 5 builds upon the findings presented in Chapters 2 and 3, delving into the potential implications for real-world behaviours like visual anticipation. Specifically, this chapter investigated the impact of mTBI on individuals' ability to anticipate both deceptive and non-deceptive movements. The results demonstrate that people with a history of mTBI display significantly better anticipation of both deceptive and non-deceptive movements compared to control. Additionally, it was observed that people with a history of mTBI took longer to respond compared to controls. The findings of this thesis suggest that there is an increased tendency to deconstruct visual and movement information following mTBI, highlighting a need for further research to better understand the effects of mTBI on information processing and to develop effective diagnostic and treatment strategies.
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