Randy Summers

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The functional equivalence of overt movements and dynamic imagery is of fundamental importance in neuroscience. Here, we investigated the participation of the neocortical motor areas in a classic task of dynamic imagery, Shepard and Metzler's mental rotation task, by time-resolved single-trial functional Magnetic Resonance Imaging (fMRI). The subjects(More)
Exploratory data-driven methods such as Fuzzy clustering analysis (FCA) and Principal component analysis (PCA) may be considered as hypothesis-generating procedures that are complementary to the hypothesis-led statistical inferential methods in functional magnetic resonance imaging (fMRI). Here, a comparison between FCA and PCA is presented in a systematic(More)
We examined whether cerebral activation due to secondary hyperalgesia resulting from intrajoint capsaicin injection could be detected using functional magnetic resonance imaging (fMRI) in alpha-chloralose anesthetized rats. We also examined whether we could detect analgesic changes in the central nervous system response to pain as a result of physiotherapy(More)
OBJECTIVE We sought to identify central loci that activate in response to visceral stimuli (stool and pain). We had a particular interest in observing the anterior cingulate gyrus and frontal cortex in normals and in patients with intestinal disease, including inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). METHODS Subjects underwent(More)
In fMRI both model-led and exploratory data-driven methods are used to identify groups of voxels according to their correlation either with an external reference or with some similarity measure. Here we present a technique to assess intragroup homogeneity using Kendall's coefficient of concordance W once groups have been identified. We show that the(More)
To evaluate the effect of hypothermic circulatory arrest on brain metabolism, we used 31P-magnetic resonance spectroscopy to monitor brain metabolites in pigs during 2 hours of ischemia and 1 hour of reperfusion. Twenty-eight pigs were divided into five groups. Anesthesia (n = 5) and hypothermic cardiopulmonary bypass groups (n = 5) served as controls. In(More)
Groups of time-courses created from fMRI data by the frequently used correlation analysis are often highly heterogeneous. This heterogeneity is due to the limited selectivity of correlation when trying to match brain time-courses to an externally imposed activation paradigm. Thus, this process unnecessarily generates many type I errors (false positives).(More)
The present study used functional magnetic resonance imaging (fMRI) to compare the neural activation patterns of children diagnosed with autistic disorder (AD), attention deficit hyperactivity disorder (ADHD), and typically developing controls (TCs) in response to a task involving evaluation of facial expressions. Substantially greater functional activity(More)
In a systematic study of hybrid MR time-series with simulated "activation" (contrast-to-noise range 1-10) we investigated the power and compared the ability of the "novelty indices" (NI) kurtosis, negentropy, and 1-lag autocorrelation, to discriminate between potentially interesting ("structured") and uninteresting ("noisy") time-courses (TCs). NIs may be(More)
OBJECTIVE Retrograde cerebral perfusion (RCP) provides better brain protection than hypothermic circulatory arrest (HCA) alone. The mechanism by which RCP improves brain protection during circulatory arrest remains unknown. The purpose of the study in pigs was to determine if RCP improves brain protection mainly as a result of its ability to maintain(More)