Biomedical subjects

Gunnar Neumann

Publications and source records attributed to Gunnar Neumann.

5 recordsLinked to original sources

PubMed2006

Age-related changes of vergence under natural viewing conditions.

Vergence eye movements were recorded with the scleral search-coil system in 32 healthy subjects (ages 19-73 years) to characterize the age-related effects on the dynamic parameters of vergence responses to step (transient components) and ramp or sinusoidal targets (sustained components) under natural viewing conditions. Transient vergence showed an age-related increase in latency and decreases in peak velocity and acceleration in the binocular stimulus condition but not in accommodative vergence. Sustained vergence showed no age-related effect in the binocular condition, but there was an age-related decrease in accommodative vergence steady-state velocity and an increase in latency. Age-related changes of the transient and sustained components were very similar to those reported for saccades and smooth pursuit; they thus might support a distinction between a sustained and transient vergence system. Furthermore, such age-related effects have to be taken into account when assessing eye movement disorders in neurodegenerative and cerebrovascular diseases.

Accommodation, Ocular↗

PubMed2005

Palsy of "fast" and "slow" vergence by pontine lesions.

The role of pontine nuclei in vergence eye movements to "step" targets ("fast" vergence) is unknown. Eye movements were recorded in two patients with unilateral pontine infarctions and in 11 healthy controls. In addition to the deficit of "slow" vergence, "fast" vergence was particularly impaired. However, conjugate saccades did not differ from controls, but smooth pursuit eye movements did. The authors conclude that "fast" vergence palsy is not only caused by midbrain but also upper pontine lesions.

Aged↗

PubMed2004

Vergence deficits in pontine lesions.

Eye movements were recorded with the search coil system in two patients to determine whether lesions of the pontine nuclei selectively impair vergence to ramp targets (slow vergence) or step targets (fast vergence). Whereas conjugate saccades were not different from healthy control subjects, conjugate smooth pursuit eye movements had a reduced gain in horizontal and vertical directions. Slow convergence and divergence were impaired, whereas fast vergence did not differ from that of control subjects. Pontine nuclei appear to be involved in the slow vergence control.

Convergence, Ocular↗

PubMed2002

Peptide-beta2-microglobulin-MHC fusion molecules bind antigen-specific T cells and can be used for multivalent MHC-Ig complexes.

Recombinant soluble MHC molecules are widely used for visualization, activation and inhibition of antigen-specific immune responses. Using a genetic approach, we have generated two novel peptide-beta2-microglobulin-MHC constructs. We have linked the MHC molecule with the peptide of interest, without limiting the recognition by the cognate TCR. This molecule can also be joined with the IgG heavy chain resulting in a dimeric MHC-Ig fusion protein. These molecules bind antigen-specific T cells with high specificity and sensitivity, therefore, providing a valuable tool for detection as well as enrichment of antigen-specific T cells.

Animals↗

PubMed2002

Blink effect on slow vergence.

Blinks are known to change the kinematic properties of fast eye movements, probably by changes in the brain stem circuits. To determine whether slow disconjugate (slow vergence) eye movements are affected by blinks under natural viewing conditions, we elicited airpuff-evoked trigeminal blinks randomly during ongoing steady slow vergence eye movements. Lid and binocular eye movements were recorded by the scleral search coil method. Slow vergence eye movements showed a peak of vergence velocity during the final part of the blink, which depends on the stimulus direction. We propose that the direction-specific blink effect on slow vergence may be caused by changes in brain stem premotor circuits.

Adult↗