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Biomedical subjects

B Merker

Publications and source records attributed to B Merker.

7 recordsLinked to original sources
PubMed2001

Voice source characteristics in Mongolian "throat singing" studied with high-speed imaging technique, acoustic spectra, and inverse filtering.

Mongolian "throat singing" can be performed in different modes. In Mongolia, the bass-type is called Kargyraa. The voice source in bass-type throat singing was studied in one male singer. The subject alternated between modal voice and the throat singing mode. Vocal fold vibrations were observed with high-speed photography, using a computerized recording system. The spectral characteristics of the sound signal were analyzed. Kymographic image data were compared to the sound signal and flow inverse filtering data from the same singer were obtained on a separate occasion. It was found that the vocal folds vibrated at the same frequency throughout both modes of singing. During throat singing the ventricular folds vibrated with complete but short closures at half the frequency of the true vocal folds, covering every second vocal fold closure. Kymographic data confirmed the findings. The spectrum contained added subharmonics compared to modal voice. In the inverse filtered signal the amplitude of every second airflow pulse was considerably lowered. The ventricular folds appeared to modulate the sound by reducing the glottal flow of every other vocal fold vibratory cycle.

Culture↗
PubMed2000

Observations on the behavior of gibbons (Hylobates leucogenys, H. gabriellae, and H. lar) in the presence of mirrors.

Three captive gibbons (Hylobates leucogenys, H. gabriellae, and H. lar) were videotaped in the course of longitudinal exposure to mirrors introduced into their familiar cage or island housing situation. The gibbons, which differed in age, sex, species, and rearing condition, exhibited great individual differences in their behavioral reactions to mirrors, spanning from a minimal reaction dominated by social responses to a dramatic sequence of progressive behavioral change that featured a variety of contingency testing behaviors and included mirror-mediated, self-directed behavior. Additional information on the mirror competence of gibbons was provided by modified mark tests and a hidden object task. The results are discussed in relation to current criteria for self-recognition in primates and factors involved in individual and species differences in reactions to mirror exposure.

Animals↗
PubMed1985

Role of intralaminar thalamus in gaze mechanisms: evidence from electrical stimulation and fiber-sparing lesions in cat.

Information on eye movement related activity in the internal medullary lamina (IML) of the thalamus is consistent with an IML role in the control of eye movements, or with its serving to convey information to the forebrain on impending events in the oculomotor system. Interpretation is impeded by the fact that eye movements evoked by electrical stimulation of the IML might be triggered by antidromic activation of projections to the IML from brainstem preoculomotor centers. In order to address this issue, thresholds for the elicitation of eye movements and cortical recruiting responses (as a marker for IML integrity) were studied before and after destruction of IML neuronal populations by the fiber-sparing neurotoxin ibotenic acid. Experiments were performed in alert cats chronically implanted with a scleral search coil for the monitoring of eye movements and an electrode-cannula assembly that permitted threshold determinations and drug injections at the stimulating site without any movement of probes in the tissue. Drastic elevation of the threshold for cortical recruiting responses, but not for eye movements following ibotenic acid destruction of IML neurons uncomplicated by myelin damage at the site of stimulation suggests an antidromic route for eye movements elicited by IML stimulation.

Animals↗
PubMed1983

Comparison of EOG and search coil techniques in long-term measurements of eye position in alert monkey and cat.

In cat and monkey a comparison was made of simultaneous records of eye movements obtained by the electro-oculographic and the magnetic search coil techniques. The major drawback of the electro-oculographic method is the slow d.c. drift, still present despite careful preparation of the electrodes. The d.c. level varies considerably with lighting conditions over long periods of time. In addition, the EOG picks up blink artifacts in monkey and other movement artifacts which are described in detail. The objective of this study was to document and evaluate the relative importance of these technical problems. Because of its simplicity and convenience the EOG method still has some applications in neurophysiological experiments. Its use requires the possibility of making frequent calibrations of gain and d.c. level.

Animals↗
PubMed1983

Silver staining of cell bodies by means of physical development.

A method for silver impregnation of cell bodies is detailed. It is based on Gallyas' physical development procedure, and adds a silver stain for cell bodies to the list of histological elements stainable with high contrast by means of physical development. Its black pigment on a clear background aids visibility, localization of cytoarchitectonic boundaries, and photographic reproduction. It also stains regions of tissue damage, such as tracks from micropipettes or electrodes. A manipulation for enhancement of dendritic staining is also described.

Animals↗
PubMedDate not supplied

Development of the female great call in Hylobates gabriellae: A case study.

Although the structure of adult gibbon duet singing has been characterised in most species, little is known about the ontogeny of gibbon song. The present study describes the developmental trajectory of the female great call in a captive infant Hylobates gabriellae female, on the basis of periodic tape recordings made while she participated in the duetting of her parents. The major part of great call development is completed between 5 and 32 months of age, and a differential time course is apparent for different portions of the female great call, raising the question of the role of the protracted period of vocal development in this species.

Animals↗