Biomedical subjects

E Yellin

Publications and source records attributed to E Yellin.

14 recordsLinked to original sources

PubMed2003

Properties and features of asymmetric partial devil's staircases deduced from piecewise linear maps.

A piecewise linear map with one discontinuity is used to link together iterated map properties with the shape of the ensuing staircases. In the main part of the paper, a three-segment map is treated, with a horizontal middle segment next to the discontinuity and the development of partial and asymmetric staircases is demonstrated. In particular, a possible hierarchy of partiality, connected with the ratio of the length of the horizontal segment to the discontinuity jump, is obtained. The map is used for constructing staircases that imitate various experimental and numerical staircases that appear in the literature for excitable systems.

Journal Article↗

PubMed2000

Auditory cortex accesses phonological categories: an MEG mismatch study.

The studies presented here use an adapted oddball paradigm to show evidence that representations of discrete phonological categories are available to the human auditory cortex. Brain activity was recorded using a 37-channel biomagnetometer while eight subjects listened passively to synthetic speech sounds. In the phonological condition, which contrasted stimuli from an acoustic /dae/-/tae/ continuum, a magnetic mismatch field (MMF) was elicited in a sequence of stimuli in which phonological categories occurred in a many-to-one ratio, but no acoustic many-to-one ratio was present. In order to isolate the contribution of phonological categories to the MMF responses, the acoustic parameter of voice onset time, which distinguished standard and deviant stimuli, was also varied within the standard and deviant categories. No MMF was elicited in the acoustic condition, in which the acoustic distribution of stimuli was identical to the first experiment, but the many-to-one distribution of phonological categories was removed. The design of these studies makes it possible to demonstrate the all-or-nothing property of phonological category membership. This approach contrasts with a number of previous studies of phonetic perception using the mismatch paradigm, which have demonstrated the graded property of enhanced acoustic discrimination at or near phonetic category boundaries.

Acoustic Stimulation↗

PubMed1997

Processing of vowels in supratemporal auditory cortex.

The auditory evoked neuromagnetic fields elicited by synthesized vowels of two different fundamental frequencies F0 were recorded in six subjects over the left and right temporal cortices using a 37-channel biomagnetometer. Single equivalent current dipole modeling of the fields elicited by all vowel types localized activity to a well-circumscribed area in supratemporal auditory cortex in both hemispheres. There were hemisphere asymmetries in the amplitude and latency of the M100 response. We also observed changes in M100 latency related to vowel type, but not to F0. There was no clear effect of vowel type or F0 on dipole localization for the M100, but a possible vowel type by latency interaction. These M100 data provide further evidence that vowels are processed independently of their pitch.

Adult↗

PubMed1996

Task-induced asymmetry of the auditory evoked M100 neuromagnetic field elicited by speech sounds.

The auditory evoked neuromagnetic fields elicited by synthesized speech sounds (consonant-vowel syllables) were recorded in six subjects over the left and right temporal cortices using a 37-channel SQUID-based magnetometer. The latencies and amplitudes of the peaks of the M100 evoked responses were bilaterally symmetric for passively presented stimuli. In contrast, when subjects were asked to discriminate among the same syllabic stimuli, the amplitude of the M100 increased in the left and decreased in the right temporal cortices. Single equivalent current dipole modeling of the activity elicited by all stimulus-types localized to a well-circumscribed area in supratemporal auditory cortex. The results suggest that attentional modulation affects the two supratemporal cortices in a differential manner. Task-conditioned attention to speech sounds is reflected in lateralized supratemporal cortical responses possibly concordant with hemispheric language dominance.

Acoustic Stimulation↗

PubMed1976

Hemodynamic correlates of the normal aortic valve echogram. A study of sound, flow, and motion.

The aortic valve echogram was recorded in open chest dogs simultaneously with aortic flow, acceleration of flow, aortic and left ventricular pressures, and intracardiac phonocardiograms. Comparison of echographic with hemodynamic data showed the following: The aortic valve started its opening with the onset of flow, at the same point that left ventricular pressure exceeded aortic pressure. Complete valve opening preceded peak aortic flow by an average of 43 msec and the cusps started to move toward closure while flow was still accelerating. Final closure of the valve was achieved at the time of zero flow and preceded the aortic second sound by 4-10 msec. The echographically determined "valve orifice area" correlated well with aortic stroke volume (r = 0.94). The intensity of the aortic first sound was related to peak acceleration of aortic flow. The intensity of the second sound was not related to the amplitude of cusp motion but correlated well with the aortic pressure at the time of closure and with peak flow deceleration.

Animals↗

PubMed1975

Dynamic stiffness profiles in the left ventricle.

Diastolic pressure-volume (P-V) curves were calculated on a beat-to-beat basis in the open-chest, pentobarbital-anesthetized dog, using the technique of direct transmitral flow measurement previously described. P-V curves were constructed and the slope (dP/dV) was plotted vs. pressure and time. dP/dV was used as an index of stiffness in each heart and its instantaneous changes with time were followed throughout the diastolic period. The end-diastolic P-V relation based on points from successive cycles during volume loading was found to be exponential. In contrast, the instantaneous P-V relation during any one diastolic period was not exponential. That is, the dynamic dP/dV vs. pressure plot was nonlinear. In the normal heart, stiffness was characterized in early diastole by a negative dP/dV as the ventricle continued to relax, and then frequently decreased prior to a second stiffness rise with atrial augmentation. These findings can be explained by a model containing an element whose deformation is rate dependent, i.e., a parallel viscous element. Stiffness profiles in mitral stenosis where dynamic effects are minimized substantiate this conclusion.

Animals↗

PubMed1975

A study of the dynamic relations between the mitral valve echogram and phasic mitral flow.

Echocardiographically recorded mitral valve motion was compared with phasic transmitral flow in 17 open chest dogs. The normal mitral valve opening started with the onset of mitral flow and reached its full excursion while flow was still accelerating. Complete valve opening occurred .044 sec (plus or minus .002 sem) before peak flow, during which time an average of 17.6 percent of total mitral filling volume had passed through the valve. In contrast to the opening movement, the closing motion of the anterior mitral valve cusp lagged behind the deceleration of mitral flow. The E-F phase of the mitral valve echogram started while mitral flow was still increasing and resulted from a combined posterior motion of the cusp and the ring. The E-F slope of the normal valve was found to decrease with reduced cardiac output. The amplitude of the anterior cusp excursion did not reflect the amount of mitral flow. Prolonged P-R interval may induce a mid-diastolic reversal of mitral flow which, in turn, may be accompanied by partial or complete valve closure, occurring before the onset of ventricular contraction. Such premature closure of the mitral valve may be accompanied by a certain amount of regurgitant flow.

Animals↗

PubMed1975