Biomedical subjects

G Filligoi

Publications and source records attributed to G Filligoi.

3 recordsLinked to original sources

PubMed2001

Detection of fetal auditory evoked responses by means of magnetoencephalography.

MagnetoEncephaloGraphy (MEG) is proposed as a non-invasive technique to detect the physiological activity of fetal brain, due to its ability to record brain activity without direct contact with the head and the transparency of magnetic signals in passing through extracerebral fetal layers and the mother's abdomen. Healthy women with uncomplicated pregnancies and fetuses in breech presentation were examined; gestational ages at time of study ranged between 36 and 40 weeks. In order to evaluate fetal well-being, ultrasound and cardiotocographic data were assessed a few days before and after MEG recording sessions. The participating women were placed in a semi-reclining position in a magnetically shielded room; here the presentation of the fetus and precise region of the mother's abdomen corresponding to the fetal head were determined by ultrasound investigation in order to place the MEG detecting system as near as possible to the fetal brain. MEG recordings were performed by means of a 28-channel neuromagnetic system. Every MEG recording session was performed during the acoustic stimulation of fetuses, in order to detect the cerebral events evoked by peripheral stimuli. The auditory stimuli were delivered from a plastic tube placed on mother's abdomen, near the fetal head, and consisted of a 300 ms 103 dB pure tone at 500 and 1000 Hz, presented at a 0.4 c/s repetition rate. In six cases following accurate digital subtraction of maternal and fetal electrocardiographic (EKG) signals we remained with a stimulus-related response peaking at about 250 ms; this was considered to originate from the fetal brain. In favour of this in three cases a clear dipolar distribution was evident at the peak of brain response centered on the fetal head and consistent with a brain generator. Despite several technical problems requiring solution before a possible routine clinical application, MEG has been found to be suitable for the non-invasive exploration of the fetal brain.

Acoustic Stimulation↗

PubMed1979

[Multielectronic computerized EMG: technical notes on the recording and parallel off-line elaboration].

A Multielectrodic EMG analysis program is developing. The purpose is to get as short as possible the main EMG parameters (amplitude, duration, frequency) of most motor units, and to reach an estimation of the anatomical extent of single units. According to the muscle extent a variable number of electrodes are inserted crosswise the fibers. EMG signals are simultaneously recorded on a multichannel AMPEX FR1300 and then off-line processed by a 21MX HP minicomputer connected with a 5Mbytes disc drive. Some technical problems had to be solved:channel amplification adjustment to avoid any difference among preamplifiers calibration and filtering, severe hum filtering of main power that is specially strong in nultielectrodic recording systems, the need of sampling at the same Nyquist time the signals of different channels. The computer is instructed to identify the "sinchronous" units i.e. the motor units recorded from more than one channel. These motor units are detected, counted and deleted from all the channels, except the one where they show the maximum amplitude. The percentage of these sinchronous units depends upon the interelectrodic distance and their anatomical area, thus it can support an evaluation of motor unit anatomical spread.

Computers↗

PubMedDate not supplied

Detection of hidden rhythms in surface EMG signals with a non-linear time-series tool.

The analysis of the surface electromyographic (sEMG) signal is particularly attractive because it provides relatively easy access to those physiological processes that allow the muscle to generate force and movement. In this paper, one of the possible applications of recurrence plot strategy to the analysis of sEMG is described. Recurrence Quantification Analysis (RQA) is an efficient time-series analysis tool pertaining to the class of non-linear dynamics time-domain processing. We analysed sEMG recorded on the biceps brachii during isometric contraction both at constant (CF) and non constant force (NCF). For comparison purposes, experimental data were analysed over epochs of 1 s so that the hypothesis of sEMG stationarity could be accepted. The analysis concerned one of the most widely used frequency parameters (namely the median frequency, MDF) and one parameter (i.e., the percent determinism %DET) extracted using the non-linear technique. Our main results are: (i) the gross average evaluated for all subjects on %DET data shows a comparable variation with respect to MDF throughout the course of CF experiments; (ii) %DET seems able to detect motor unit (MU) synchronisation; (iii) during non constant force experiments, %DET is more effective than MDF in detecting sEMG changes determined by brisk transients of force output.

Electromyography↗