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Imaging of scattered and reflected light from the surface of neural structures can reveal the functional architecture within large populations of neurons. These techniques exploit, as one of the principal signal sources, reflectance changes produced by local variation in blood volume and oxygen saturation related to neural activity. We found that a major(More)
The rodent whisker sensory system is a commonly used model of cortical processing; however, anesthetics cause profound differences in the shape and timing of evoked responses. Evoked response studies, especially those that use spatial mapping techniques, such as fMRI or optical imaging, will thus show significantly different results depending on the(More)
Sleep is vital to cognitive performance, productivity, health and well-being. Earlier theories of sleep presumed that it occurred at the level of the whole organism and that it was governed by central control mechanisms. However, evidence now indicates that sleep might be regulated at a more local level in the brain: it seems to be a fundamental property of(More)
This study used high-resolution hemispheric mapping of somatosensory evoked potentials to determine the number and organization of secondary somatosensory areas (SII) in rat cortex. Two areas, referred to as SII and PV (parietoventral), revealed complete (SII) or nearly complete (PV) body maps. The vibrissa and somatic representation of SII was upright,(More)
Surface evoked potentials (SEPs) during auditory clicks and whisker twitches are usually larger during quiet sleep (QS) over waking and REM sleep. However, SEP amplitudes from single trials fluctuate periodically between high and low values regardless of sleep-wake cycle. To test the hypothesis that state-independent fluctuations represent local functional(More)
Collecting continuous video together with multichannel electrophysiological data and other experimental modalities requires high bandwidth and storage capacities, as well as accurate synchronization to detect correlations between different recorded events. Often, experiments are highly complex, with many variables requiring immediate analysis and feedback(More)
We imaged fast optical changes associated with evoked neural activation in the dorsal brainstem of anesthetized rats, using a novel imaging device. The imager consisted of a gradient-index (GRIN) lens, a microscope objective, and a miniature charged-coupled device (CCD) video camera. We placed the probe in contact with tissue above cardiorespiratory areas(More)
Substantial evidence suggests that brain regions that have been disproportionately used during waking will require a greater intensity and/or duration of subsequent sleep. For example, rats use their whiskers in the dark and their eyes during the light, and this is manifested as a greater magnitude of electroencephalogram (EEG) slow-wave activity in the(More)
We developed an optical probe for cross-polarized reflected light measurements and investigated optical signals associated with electrophysiological activation in isolated lobster nerves. The cross-polarized baseline light intensity (structural signal) and the amplitude of the transient response to stimulation (functional signal) measured in reflected mode(More)