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F Grandori

Publications and source records attributed to F Grandori.

At least 55 records · Page 3Linked to original sources
PubMed1988

A method of digital filtering to enhance the peaks of evoked potentials: application to auditory brainstem responses.

The aim of this paper is to propose a method of data processing for the analysis of evoked potentials, in particular for auditory brainstem responses. The present method has been developed to simplify and speed up the interpretation of the recordings by means of an enhancement of the response peaks. Even for experienced observers, identification of the response waves and subsequent latency measurements may sometimes constitute a difficult task, due to the presence of residual noise or to interference between the temporal waveforms of adjacent peaks and troughs. The method is implemented with a digital non-causal (zero-phase shift) filter, based on the convolution with a finite impulse response, to make the computation time compatible with the use of low-cost microcomputers. The performance is shown to be very good in several examples.

Evoked Potentials, Auditory↗
PubMed1988

Topographic brain mapping of middle latency auditory evoked potentials in normal subjects.

Topographic brain mapping of auditory middle latency evoked responses (MLR) were obtained from 20 subjects (10 males and 10 females), all right-handed and with normal pure tone audiograms. Clicks with alternative polarity, with a rate of 7.7/sec. were delivered at an intensity of 75 dB HL monoaurally to both ears. Responses from 21 channels were amplified and band-pass filtered (3-150). All the surface maps were analyzed with a Bio-Logic Brain Atlas III system. MLR maps obtained show a quite small intrasubjective variability at the latencies of the principal components Na and Pa. The grand averages of MLR maps at the corresponding latencies in males and females were compared each other. All the entire temporal window has been segmented into some subepochs, showing similar spatial characteristics of the maps, like location of maxima and minima and, overall, shape.

Adult↗
PubMed1987

Audiologic diagnosis of central versus eighth nerve and cochlear auditory impairment.

122 subjects divided into four groups according to the site of lesion (cochlea, eighth nerve, brainstem and temporal lobe) were subjected to an audiometric test battery, including pure-tone sensitivity measures, recruitment testing, tone decay, Békésy audiometry, speech audiometry, stapedius reflex measures and auditory brainstem response (ABR) audiometry. The results were contrasted among the four groups by calculating several measures of test performance, including sensitivity, specificity, efficiency, A' (test performance) and plots on the receiver operating characteristic (ROC) space of pure positives versus false alarms. In the differential diagnosis between eighth nerve and cochlear site, the various measures did not rank the tests in the same order: (a) for efficiency: ABR, Békésy audiometry; (b) for A' (similarly to the analysis into the ROC space): ABR, recruitment, Békésy, stapedius reflex, speech audiometry, tone decay. In distinguishing an eighth nerve from a brainstem site, it is important to consider amount of hearing loss, presence of tinnitus, abnormal tone decay and Békésy audiometry patterns. ABR adds significant diagnostic efficiency only when waves II, III and V are detectable: a prolonged I-II interpeak interval (IPI) and a normal III-V IPI are characteristic of the eighth nerve site. ABR gives good diagnostic support in the intrinsic brainstem lesions by suggesting changes in the generator sites of the component waves. The audiometric diagnosis of temporal lobe lesions involving the auditory cortex still relies upon speech audiometry: tests specifically designed for this purpose by Bocca and Calearo and by Jerger - i.e. the 'sensitized sentences' and the identification of synthetic sentences under ipsi- or contralateral competing message - are commendable for their sensitivity and efficiency in distinguishing brainstem from temporal lobe sites. In brainstem sites, the most affected ear is ipsilateral to the lesion for ABR, but contralateral for speech audiometry.

Adolescent↗
PubMed1986

Field analysis of auditory evoked brainstem potentials.

Surface distribution maps of auditory evoked brainstem potentials (AEBPs) are presented for time instants corresponding to the waves of major interest (I, III and V) in humans. Maps are shown to be fully consistent with the results of two approaches that have been recently proposed for the analysis of AEBPs, namely dipole localization methods and three-channel Lissajous trajectories, thus confirming the technical feasibility of methods for extracting information on the sources of AEBPs from surface data.

Adult↗
PubMed1986

Pitch discrimination for complex sounds in normal and hearing impaired ears.

On the grounds of previous researches on periodicity and virtual pitch, the present paper describes the results of some experiments on pitch extraction in normal ears and in subjects with sensorineural hearing loss of cochlear origin, with harmonic and inharmonic stimuli. The latter stimuli are constituted by complex tones with constant ratios between the frequency of adjacent components; for this reason the term geometric spectrum is used. These stimuli can be considered as an alternative to harmonic stimuli, since inharmonic components play an important role in sound analysis and therefore in the perception of sound. Comparison between the data obtained in experimental measurements from normal and hearing impaired subjects (also in relation to the estimates predicted by a mathematical model for pitch), revealed that pitch extracted by hearing impaired subjects tends to be shifted towards the high frequencies.

Hearing Loss, Sensorineural↗
PubMed1986

Long term stability, influence of the head position and modelling considerations for evoked otoacoustic emissions.

This paper presents the results of two experiments on evoked otoacoustic emissions (EOAEs). The first experiment was conceived to study in the same subjects the temporal stability of the response waveforms, over a period of about four years. A second experiment studied the influence of the relative position between the head and the body on the responses. The generation of EOAEs is then discussed on the base of a first approximation model of the cochlea.

Acoustic Stimulation↗
PubMed1985

Nonlinear phenomena in click- and tone-burst-evoked otoacoustic emissions from human ears.

Otoacoustic emissions have been recorded from normally hearing subjects in response to clicks and 1-kHz tone bursts. Input-output relationships for response magnitudes and wave delays are presented. For the response magnitudes, two main effects are seen: (i) nonlinearities are maximal at moderate to high intensity levels (saturation), while deviations from linearity are minimal at the lowest levels (around the psychoacoustic threshold); (ii) the nonlinear behaviour is different at different time intervals (after stimulation): deviations from linearity are maximal for the latest parts of the response. Level- and time-dependent phenomena are also observed in the delay of identifiable response waves.

Acoustic Stimulation↗
PubMed1984

Theoretical and experimental analysis of a central optimal processor for pitch of multicomponent inharmonic tones.

This paper describes some experiments on the pitch produced by multicomponent tones. Stimuli used were the sum of a pure tone at frequency f = 1 kHz and of the first six successive subharmonics at frequencies psi i = f/i (i = 2, 3, 4, 5, 6, 7) or, in separate experiments, the sum of six (i = 2, 3, 4, 5, 6, 7), five (i = 3, 4, 5, 6, 7) or four (i = 4, 5, 6, 7) subharmonics, respectively. Pitch data produced by these stimuli have been compared with the predictions of the optimum processor theory developed by Goldstein and coworkers (Goldstein, J.L. (1973): J. Acoust. Soc. Am. 54, 1496-1516; Goldstein, J.L. et al. (1978): J. Acoust. Soc. Am. 63, 486-497; Gerson, A. and Goldstein, J.L. (1978): J. Acoust. Soc. Am. 63, 498-510). Model predictions are shown to deviate significantly from the experimental results. By assuming the existence of an additional transformation to be included into the original mathematical model, without any other modification, predictions are in complete agreement with pitch data.

Acoustic Stimulation↗
PubMed1984

Some aspects of the auditory nerve responses evoked by tone bursts.

Short latency (10 ms post-stimulus-time) auditory evoked potentials are a useful tool for assessing the hearing integrity at different frequency bands, especially if frequency-specific stimuli, like tone bursts, are used. However, a proper interpretation of the evoked potentials should rely upon the understanding of the single auditory nerve units activity patterns and their relations with the gross potentials, under the same stimulating conditions. In this paper, the basic properties of the burst evoked PST histograms of single units are explained with the aid of a model for the cochlear events. The relationships between single units activity and the gross potentials are then analysed on this ground, in particular for what concerns the Action Potential input-output latency curve, the off-response rising at the burst offset and the growth of N2.

Acoustic Stimulation↗
PubMed1982

A mathematical model of the Pacinian corpuscle.

This article describes a mathematical model of the Pacinian corpuscle based on the analysis of the available experimental data and on previous theoretical research. The model includes the main anatomofunctional constituents of the corpuscle: the capsula and the mechano-to-neural transduction; its structure accounts for the formation of the receptor potential and of the spikes on the nerve terminal. Comparison of the theoretical predictions with the experimental results, in response to different types of stimuli provides a substantial validation of the model and an explanation for the basic aspects of the transduction, in particular for: a) the receptor potential time course for isolated stimuli; b) the frequency response, in terms of receptor potential; c) the frequency threshold curve for the spikes; d) the firing rate, I.S.I. and P.S.T. histograms and the synchronization coefficient, in response to sustained sinusoidal inputs. Possible lines for future experimental research are suggested from the model predictions.

Electrophysiology↗
PubMed1981

Some effects of the stimulus repetition rate on N1 and N2 in transtympanic and surface recordings.

The early auditory evoked electrical activity has been recorded in man at the promontory (transtympanic approach) and on the scalp vertex-mastoid derivation), in response to clicks delivered at different rates. Latency and amplitude of the first two peaks (N1 and N2), as a function of the repetition rate, have been measured and compared. The differences between the latencies of transtympanic and surface N1 are very small, at any rate, with a maximum value of 0.08 msec. In the transtympanic recording, the latency difference between N2 and N1 is constant throughout the whole range of rate values, from 3 to 100 clicks per second. In the surface responses, on the contrary, the latency difference between N2 and N1 tends to increase as the rate is increased. The amplitude of the transtympanic N2 is consistently reduced at click rates above 20-50 per second (more markedly than the amplitude of N1), while the amplitude of the surface N2 is much more insensitive to the rate increase. Some implications of these results are discussed with respect to the origin of N2 in the two recording conditions.

Action Potentials↗
PubMed1978

A model for the auditory evoked brainstem responses.

The present research was undertaken to approach the formation of the Brainstem Evoked Response (BSER) by means of modelling techniques similar to those previously successfully adopted to interpret the generation of the Auditory Nerve Action Potential. The definition of a model intended to reproduce the compound electrical response of a given ensemble of neural units, firing after stimulation, is taken as the basic constituent for the formulation of the complete model. The activity of the primary auditory neurons is assumed to be the input to the BSER model; then, a simplified structure for the connections among the neural complexes contributing to the BSER is proposed to account for monaurally evoked, homolaterally recorded responses. Computer simulations of the model show a satisfactory degree of approximation between the experimental data taken as reference and the final output, in spite of the rather small number of parameters and the simplicity of the structure used. Even though this work has to be considered as preliminary in character, at least in certain respects, some applicative implications of the present approach can be outlined.

Brain Stem↗