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Biomedical subjects

J Kaiser

Publications and source records attributed to J Kaiser.

At least 19 recordsLinked to original sources
PubMed2000

Simultaneous bilateral mismatch response to right- but not leftward sound lateralization.

Magnetoencephalography (MEG) was used to compare mismatch responses between hemispheres to changes in sound-source direction. Sixteen adults listened passively to two types of complex non-language sounds presented in separate blocks with midline standards and right- and left-lateralized deviants. Mismatch dipole amplitudes were larger contra- than ipsilaterally to the deviants. Both hemispheres processed right deviants simultaneously, whereas to left deviants, the left dipole peaked 20 ms later than the right dipole. A second experiment using the same standards but midline spectral deviants showed no interhemispheric differences. Here mismatch latencies were about 60 ms longer than in the location mismatch experiment. This suggested both fast, contralaterally dominant location mismatch responses and facilitated detection of auditory spatial deviance in the right hemifield.

Acoustic Stimulation↗
PubMed2000

Ecosystem assessment. New survey to collect global news you can use.

Researchers are hoping that the Millennium Ecosystem Assessment, a new 4-year, $20 million project that will get under way early next year, will synthesize what's known about the world's ecosystems and help policy-makers deal with those that are under siege. The assessment will turn loose ecologists and social scientists to gather and analyze data on the state of the world's ecosystems, assess nature's ability to provide essential "services" such as food and clean water, and project environmental trends such as deforestation, loss of species, and pollution. But some say that the assessment could end up a victim of its own lofty goals--to evaluate ecosystem health, supply data to implement treaties, and sell the message that ecosystems have economic value.

Conservation of Natural Resources↗
PubMed2000

Right-hemisphere dominance for the processing of sound-source lateralization.

Cortical processing of change in direction of a perceived sound source was investigated in 12 human subjects using whole-head magnetoencephalography. The German word "da" was presented either with or without 0.7 msec interaural time delays to create the impression of right- or left-lateralized or midline sources, respectively. Midline stimuli served as standards, and lateralized stimuli served as deviants in a mismatch paradigm. Two symmetrically linked dipoles fitted to the mismatch fields showed stronger moments in the hemisphere contralateral to the side of the deviant. The right dipole displayed equal latencies to both left and right deviants, whereas left dipole latencies were longer for ipsilateral than contralateral deviants. Frequency analysis between 20-70 Hz and statistical probability mapping revealed increased induced gamma-band activity at 53+/-2.5 Hz to both types of deviants. Right deviants elicited spectral amplitude enhancements in this frequency range, peaking at latencies of 160 and 240 msec. These effects were localized bilaterally over the angular gyri and posterior temporal regions. Coherence analysis suggested the existence of two separate interhemispheric networks. For left-lateralized deviants, both spectral amplitude enhancements at 110 and 220 msec and coherence increases were restricted to the right hemisphere. In conclusion, both mismatch dipole latencies at the supratemporal plane and gamma-band activity in posterior parietotemporal areas suggested a right hemisphere engagement in the processing of bidirectional sound-source shifts. In contrast, left-hemisphere regions responded predominantly to contralateral events. These findings may help to elucidate phenomena such as unilateral auditory neglect.

Acoustic Stimulation↗
PubMed2000

Ecology. Rift over biodiversity divides ecologists.

A long-simmering debate among ecologists over the importance of biodiversity to the health of ecosystems has erupted into a full-blown war. Opposing camps are dueling over the quality of key experiments, and some are flinging barbs at meetings and in journals. The dispute pits an outspoken group of ecologists against some of the leading lights in the field.

Ecology↗
PubMed2000

Air pollution. Panel backs EPA and 'six cities' study.

The Environmental Protection Agency (EPA) has won a major victory in the fierce battle over its tough new standard for particulate air pollution. Dealing a sharp blow to critics from industry, a nonpartisan research group has reevaluated key data that EPA relied upon to set that standard and has come out firmly behind the agency.

Air Pollution↗
PubMed2000

Toxicology. Mercury report backs strict rules.

The debate, finally, seemed to be settled. After an 18-month review, a panel of the National Academy of Sciences last week weighed in on the health risks of mercury, endorsing strict safety levels proposed by the Environmental Protection Agency in 1995. But already some scientists are contesting the panel's conclusions, and federal agencies are grappling with how to reconcile competing regulations.

Animals↗
PubMed2000

Air pollution. Evidence mounts that tiny particles can kill.

Four years ago, the U.S. Environmental Protection Agency (EPA) ignited a fire storm when it declared that tens of thousands of people were dying each year from breathing tiny particles of dust and soot--and issued tough new regulations to crack down on these pollutants. Industry groups and many scientists assailed the decision, arguing that the data underlying the new particulate matter standard were inconclusive at best, and industry took their case to court. Now, a long-awaited study, by a group widely perceived to be politically neutral, comes in solidly behind the earlier EPA decision and strongly implicates particles in excess deaths.

Air Pollutants↗
PubMed2000

Statistical probability mapping reveals high-frequency magnetoencephalographic activity in supplementary motor area during self-paced finger movements.

Investigations of both haemodynamic and electroencephalographic measures of brain activity have demonstrated supplementary motor area (SMA) involvement in self-paced finger movements. In contrast, analysis of magnetoencephalographic (MEG) signals in the time domain has usually failed to detect SMA activity in healthy individuals. We investigated oscillatory MEG activity in 12 normal adults during (a) a self-paced, complex sequence of finger movements and (b) a simple finger opposition task paced externally by tactile stimuli presented to the contralateral thumb. Statistical probability mapping revealed enhanced non-phase-locked spectral amplitudes in the 22-28 Hz range over bilateral frontal cortex during self-paced as compared to externally cued finger movements. This activity may reflect recruitment of cell assemblies in SMA during self-paced, complex movements.

Adult↗