Browsing by Author "Slone, Edward"

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    Artifact reduction in long-term monitoring of cerebral hemodynamics using near-infrared spectroscopy
    (Society of Photo-optical Instrumentation Engineers, 2015-05-26) Vinette, Sarah; Dunn, Jeff; Slone, Edward; Federico, Paolo
    Near-infrared spectroscopy (NIRS) is a noninvasive neuroimaging technique used to assess cerebral hemodynamics. Its portability, ease of use, and relatively low operational cost lend itself well to the long-term monitoring of hemodynamic changes, such as those in epilepsy, where events are unpredictable. Long-term monitoring is associated with challenges including alterations in behaviors and motion that can result in artifacts. Five patients with epilepsy were assessed for interictal hemodynamic changes and alterations in behavior or motion. Based on this work, visual inspection was used to identify NIRS artifacts during a period of interest, specifically prior to seizures, in four patients. A motion artifact reduction algorithm (MARA, also known as the spline interpolation method) was tested on these data. Alterations in the NIRS measurements often occurred simultaneously with changes in motion and behavior. Occasionally, sharp shift artifacts were observed in the data. When artifacts appeared as sustained baseline shifts in the data, MARA reduced the standard deviation of the data and the appearance improved. We discussed motion and artifacts as challenges associated with longterm monitoring of cerebral hemodynamics in patients with epilepsy and our group’s approach to circumvent these challenges and improve the quality of the data collected.
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    The Cognitive, Behavioural, and Neural Effects of Environmental Complexity During Navigation
    (2016) Slone, Edward; Iaria, Giuseppe; Pexman, Penny; Levy, Richard
    A variety of factors combine to determine the outcome of a navigational scenario. Age, sex, and strategy preference, for example, have quantitative and qualitative influences on how an individual is able to find their way in the environment. However, the structure of the environment itself also plays a critical role. Some environments are easier to understand and navigate than others, but it is not always clear why this is the case. The complexity of the environment appears to be an important determinant of navigational success, bur it is notoriously difficult to define and systematically assess its behavioural consequences. In a series of studies, I provide evidence showing that the complexity of the environment not only affects behaviour and cognition, but also activity in several brain regions that are important for navigation. Chapter 2 describes a behavioural study in which participants performed a navigation task in one simple and one complex virtual environment. Navigation in the complex environment was slower and more error prone, and maps drawn of the complex environment were less accurate, suggesting that complexity makes it difficult to form an accurate cognitive map. Chapter 3 describes an experiment in which participants performed the same task while their brain activity was being assessed using functional magnetic resonance imaging. Navigation in the simple environment was associated with increased brain activity in a number of regions, including the precuneus, retrosplenial cortex, hippocampus, and dorsolateral prefrontal cortex. Chapter 4 describes a series of functional connectivity analyses that characterized how the different regions of the brain identified in Chapter 3 altered their dynamic functional properties measured during the task and at rest. Together, these studies suggest that complexity exerts a powerful influence over cognition, behaviour, and brain activity during navigation.
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    The pre-ictal state in focal epilepsy
    (2011) Slone, Edward; Federico, Paolo; Dunn, Jeffrey F.