Virginia R. de Sa

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Cortically projecting basal forebrain neurons play a critical role in learning and attention, and their degeneration accompanies age-related impairments in cognition. Despite the impressive anatomical and cell-type complexity of this system, currently available data suggest that basal forebrain neurons lack complexity in their response fields, with activity(More)
Neuroimaging studies provide evidence of cortical involvement immediately before and during gait and during gait-related behaviors such as stepping in place or motor imagery of gait. Here we attempt to perform single-trial classification of gait intent from another movement plan (point intent) or from standing in place. Subjects walked naturally from a(More)
Common spatial patterns (CSPs) are a way of spatially filtering EEG signals to increase the discriminability between the filtered variance/power between the two classes. The proposed canonical correlation approach to CSP (CCACSP) utilizes temporal information in the time series, in addition to exploiting the covariance structure of the different classes, to(More)
Observers judged whether a periodically moving visual display (point-light walker) had the same temporal frequency as a series of auditory beeps that in some cases coincided with the apparent footsteps of the walker. Performance in this multisensory judgment was consistently better for upright point-light walkers than for inverted point-light walkers or(More)
One of the advantages of supervised learning is that the nal error metric is available during training. For classiiers, the algorithm can directly reduce the number of misclassiications on the training set. Unfortunately, when modeling human learning or constructing classiiers for autonomous robots, supervisory labels are often not available or too(More)
In supervised learning there is usually a clear distinction between inputs and outputs | inputs are what you measure, outputs are what you predict from those measurements. The distinction between inputs and outputs is not this simple. Previously, we demonstrated that on synthetic problems some input features are more useful when used as extra outputs than(More)
Is brightness represented in a point-for-point neural map that is filled in from the response of small, contrast-sensitive edge detector cells? We tested for the presence of this filled-in map by adapting to illusory flicker caused by a dynamic brightness-induction stimulus. Thereafter flicker sensitivity was reduced when our test region was the same size(More)
The computational recognition of precise splice junctions is a challenge faced in the analysis of newly sequenced genomes. This is challenging due to the fact that the distribution of sequence patterns in these regions is not always distinct. Our objective is to understand the sequence signatures at the splice junctions, not simply to create an artificial(More)
Freezing of gait (FOG) is an elusive phenomenon that debilitates a large number of Parkinson's disease (PD) patients regardless of stage of disease, medication status, or deep brain stimulation implantation. Sensory feedback cues, especially visual feedback cues, have been shown to alleviate FOG episodes or even prevent episodes from occurring. Here, we(More)
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