Jitendra Sharma

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A key emergent property of the primary visual cortex (V1) is the orientation selectivity of its neurons. The extent to which adult visual cortical neurons can exhibit changes in orientation selectivity is unknown. Here we use single-unit recording and intrinsic signal imaging in V1 of adult cats to demonstrate systematic repulsive shifts in orientation(More)
BACKGROUND Cognition and magnetic resonance imaging correlations are well established in patients with multiple sclerosis (MS), but it is unclear whether lesion burden or atrophy accounts for most of the predictive variance. These indices have been directly compared in only a few studies. No such study included measurement of the third ventricle, which was(More)
A striking aspect of natural scenes is that image features such as line orientation are strongly correlated at neighboring spatial locations but not at distant locations. Thus, during the viewing of a scene, eye movements are often accompanied by a change in the orientation structure of the image. How does this behavior influence the discrimination of local(More)
Responses to subjective contours in visual cortical areas V1 and V2 in adult cats were investigated by optical imaging of intrinsic signals and single-unit recording. Both V1 and V2 contain maps of the orientation of subjective gratings that have their basis in specific kinds of neuronal responses to subjective orientations. A greater proportion of neurons(More)
Modules of neurons sharing a common property are a basic organizational feature of mammalian sensory cortex. Primary visual cortex (V1) is characterized by orientation modules--groups of cells that share a preferred stimulus orientation--which are organized into a highly ordered orientation map. Here we show that in ferrets in which retinal projections are(More)
Although cholinergic innervation of the cortex by the nucleus basalis (NB) is known to modulate cortical neuronal responses and instruct cortical plasticity, little is known about the underlying cellular mechanisms. Using cell-attached recordings in vivo, we demonstrate that electrical stimulation of the NB, paired with visual stimulation, can induce(More)
We used SPM99 to obtain normalized whole brain volumes of gray matter, white matter, and total parenchyma in patients with multiple sclerosis (MS) (n = 41) and age-/sex-matched normal controls (n = 18). As SPM99's automated gray/white matter volumes were significantly influenced by tissue compartment misclassification due to the effect of MS-related brain(More)
Brain atrophy is a proposed MRI marker of irreversible pathologic damage in multiple sclerosis (MS). The brain parenchymal fraction (BPF) is the ratio of brain parenchymal volume to the total volume within the surface contour. We developed a semiautomated measure of BPF using commercially available edge-finding and thresholding software (30-min analysis(More)
BACKGROUND AND PURPOSE Injury to deep gray matter structures in multiple sclerosis (MS) has been suggested by recent neuro-imaging and neuropathology studies. Diffusion-weighted magnetic resonance imaging (MRI) can assess tissue damage with greater sensitivity than conventional MRI. The authors' objective was to assess thalamic gray matter damage by(More)
OBJECTIVE To determine the incidence, risk factors, outcome, and pathogens of central venous catheter-related bloodstream infections (CVC-BSIs). DESIGN Prospective study. SETTING Escorts Heart Institute and Research Centre, New Delhi, India. PARTICIPANTS One thousand three hundred fourteen consecutive patients undergoing cardiac operations who were(More)