Oxygen is essential for normal aerobic metabolism in mammals. Hypoxia is the presence of lower than normal oxygen content and pressure in the cell. Causes of hypoxia include hypoxemia (low blood oxygen content and pressure), impaired oxygen delivery, and impaired cellular oxygen uptake/utilization. Many compensatory mechanisms exist at the global, regional, and cellular levels to allow cells to...

It is well-known that directing attention to a location in space enhances the processing efficiency of stimuli presented at that location. Previous studies have shown that directing spatial attention manifests itself as an increase in spontaneous firing rate of neurons (the baseline signal) in extrastriate cortex at the retinotopic corresponding location. There has been considerable debate as t...

1. Responses of oxygen-sensitive units in the prosomal haemal nerve of Limulus polyphemus were examined while varying the oxygen content of sea water bathing the intercoxal cuticle. 2. When exposed to high oxygen levels these units units maintained a continuous background discharge of spikes. Unit activity was inhibited when oxygen content decreased. Upon reintroduction of oxygen tonic spike di...

The structure of LaSr2CuTiO6.5, a novel (ABO3)nAO n ) 2 Ruddlesden-Popper phase, has been solved by powder X-ray diffraction and electron microscopy. The diffraction patterns are consistent with I4/mmm symmetry, with tetragonal lattice parameters a ) 3.8816(1) Å and c ) 20.296(2) Å. The structure of LaSr2CuTiO6.5 is similar to Sr3Ti2O7, with copper and titanium disordered over the single B-cati...

Six anaesthetized, paralyzed, hypothermic (30° C) dogs were hyperventilated for 2 hours. During the final 30 minutes, die inspired mixture was altered from oxygen to air. The rates at which alveolar and arterial oxygen concentrations approached their new steady state values were represented by the half-times (t£) of 0.19 and 0.26 minutes, respectively. The turnover rate in venous blood oxygen c...

Radiative equilibrium and radiative (:onvective temperature profiles fiw the Earth's evolving atmosphere have been cah.ulated. If the atmosphere evolved from one rich in carbon dioxide, and deficient in oxygen, to its present composilion, the temperature structure showed considerable change. The models of 3 to 4 billi(m years ago display steadily decreasing temperatures with altitude, being 185...

Spatial selective attention is the mechanism that facilitates the selection of relevant information over irrelevant information in the visual field. The current study investigated whether foreknowledge of the presence or absence of distractors surrounding an impending target stimulus results in preparatory changes in visual cortex. We cued the location of the target and the presence or absence ...

We measured blood oxygen level dependent (BOLD) responses to the onset of dynamic noise stimulation in defined regions of the primary retinotopic projection (V1) in visual cortex. The response waveforms showed a remarkable diversity across stimulus types, violating the basic assumption of a unitary general linear model of a uniform BOLD response function convolved with each stimulus sequence. W...

The ability to continuously acquire simultaneous EEG and fMRI data during seizures presents a formidable challenge both clinically and technically. Published ictal fMRI reports have so far been unable to benefit from simultaneous electrographic recordings and remain largely assumptive. Unique findings from a Continuous EEG-correlated fMRI experiment are presented in which a focal subclinical se...

Changes in regional blood oxygen level dependent (BOLD) signals in response to brief visual stimuli can exhibit a variety of time-courses. To demonstrate the anatomical distribution of BOLD response shapes during a match to sample task, a formal analysis of their time-courses is presented. An event-related design was used to estimate regional BOLD responses evoked by a cue word, which instructe...