Biomedical subjects

Z Lagidze

Publications and source records attributed to Z Lagidze.

3 recordsLinked to original sources

PubMed1993

Auditory middle-latency response: intramodal and intermodal interactions.

Intramodal and intermodal interactions have been studied in generators of the auditory middle-latency response (MLR). The MLRs were recorded to the wide-band clicks. Similar clicks or electric shocks to the median nerve served as conditioning stimuli. A procedure was employed permitting to avoid distortions of test MLRs due to superimposition upon potentials to the conditioning stimuli. A rapid recovery of responsiveness in MLR generators was revealed in intramodal experiments. Poorly discernible test MLRs were identified at conditioning interval of 10 ms, while already at interval of 50 ms the MLR restoration was completed. No effects of shocks upon MLRs were evident in intermodal experiments. The starting knee was only altered in most test MLRs, outlining a narrow strip of intermodal interaction. The sources of the MLR are discussed and a subcortical rather than cortical, polylevel rather than monolevel, monomodal rather than polymodal nature of the MLR is proposed.

Acoustic Stimulation↗

PubMed1987

Masking level difference: an electrophysiological approach.

Auditory brainstem responses (ABRs), middle latency responses (MLRs), and slow cortical potentials (SCPs) were registered in normal-hearing adults to trains of low-frequency signals delivered binaurally on a background of a continuous masking noise. Two stimulus conditions, labelled as S0M0 and S pi M0 paradigms, respectively, were systematically compared. In the S0M0 paradigm, both the signals and the masker were in-phase at two ears. In the S pi M0 paradigm, the signals were out-of-phase at two ears, while the masker was in-phase. The psychoacoustic release from masking in S pi M0 vs. S0M0 paradigms was regularly accompanied by an increase in amplitudes and a shortening in peak latencies of the SCPs. In contrast, no differences were evidenced between the S0M0 and the S pi M0 paradigms with respect to the ABRs and the MLRs. Considering the generation loci of the studied electric responses, it is concluded that the binaural psychoacoustic phenomenon, referred to as the masking level difference, is operated primarily at the cortical level.

Adult↗

PubMedDate not supplied

Recovery function of the human brain stem auditory-evoked potential.

Amplitude reduction and peak latency prolongation were observed in the human brain stem auditory-evoked potential (BEP) with preceding (conditioning) stimulation. At a conditioning interval (CI) of 5 ms the alteration of BEP was greater than at a CI of 10 ms. At a CI of 10 ms the amplitudes of some BEP components (e.g. waves I and II) were more decreased than those of others (e.g. wave V), while the peak latency prolongation did not show any obvious component selectivity. At a CI of 5 ms, the extent of the amplitude decrement of individual BEP components differed less, while the increase in the peak latencies of the later components was greater than that of the earlier components. The alterations of the parameters of the test BEPs at both CIs are ascribed to the desynchronization of intrinsic neural events. The differential amplitude reduction at a CI of 10 ms is explained by the different durations of neural firings determining various effects of desynchronization upon the amplitudes of individual BEP components. The decrease in the extent of the component selectivity and the preferential increase in the peak latencies of the later BEP components observed at a CI of 5 ms are explained by the intensification of the mechanism of the relative refractory period.

Adult↗