Gian Luca Romani

Selective localization of alpha brain activity with neuromagnetic measurements

A method of localizing brain activity by a new combination of magnetic and electrical recording, relative covariance, is described. The successful application of this method to alpha EEG is reported. Spontaneous human brain activity was recorded simultaneously with fixed scalp electrodes and a movable magnetometer. The analysis was restricted to the alpha rhythm, which was selected by a narrow bandpass filter centered at the observed alpha frequency. For each magnetometer location, the ratio of the covariance of the magnetic and electric signals to the electric variance was calculated, producing a map reflecting the magnetic field pattern. Clear maxima of opposite polarity over the left and right parietotemporal areas indicate bilateral current source areas near the midline, in the vicinity of the calcarine fissure, at a depth of 4-6 cm from the scalp. This relative covariance method may prove generally useful in localizing bioelectrical sources such as spontaneous brain rhythms.

Biomagnetic measurements of spontaneous brain activity in epileptic patients

In the last few years there has been an increasing interest in the magnetic activity due to bioelectrical currents flowing in the brain. In this paper preliminary results are reported concerning spontaneous magnetic brain activity in 36 patients affected by different kinds of brain disease; in most of these cases the symptoms were induced by localized pathology (atrophies, scars, tumors). Measurements were carried out with the simultaneous recording of the EEG. At present one of the most interesting features of magnetic detection seems to be its high localizing ability in cases of cortical foci, and sometimes its ability to show activities not evident in the EEG. These features seem to be very encouraging for the search for technical improvements, with the aim of making the magnetic technique a candidate for current diagnostic purposes.

SQUID instrumentation and the relative covariance method for magnetic 3D localization of pathological cerebral sources

SummaryMagnetic fields generated by bioelectric currents responsible for epileptic activity in the human brain have been measured by means of a movable magnetometer based on SQUID technology. Simultaneously detected magnetic and electric signals were studied by computing the covariance and dividing this quantity by the electric variance. The relative covariance so obtained was proved, to reliably reflect the distribution of magnetic field and, by means of an appropriate model, permitted 3D localization of the investigated epileptic source.

Altered Brain Long-Range Functional Interactions Underlying the Link Between Aberrant Self-experience and Self-other Relationship in First-Episode Schizophrenia

Self-experience anomalies are elementary features of schizophrenic pathology. Such deficits can have a profound impact on self-other relationship, but how they are related through aberrant brain function remains poorly understood. In this functional magnetic resonance imaging (fMRI) study, we provide new evidence for a cortical link between aberrant self-experience and social cognition in first-episode schizophrenia (FES). As identified in previous studies, ventral premotor cortex (vPMC) and posterior insula (pIC) are candidate brain regions underlying disturbances in both self-experience and self-other relationship due to their processing of predominantly externally guided (vPMC; goal-oriented behavior) and internally guided (pIC; interoception) stimuli. Results from functional interaction analysis in a sample of 24 FES patients and 22 healthy controls show aberrant functional interactions (background/intrinsic connectivity) of right vPMC and bilateral pIC with posterior cingulate cortex (PCC), a midline region that has been shown central in mediating self-experience. More specifically, our results show increased functional coupling between vPMC and PCC, which positively correlated with basic symptoms (subjective self-experience disturbances). pIC showed reduced functional coupling with PCC and postcentral gyrus and increased functional interactions with anterior insula. Taken together, our results suggest an imbalance in the processing between internally and externally guided information and its abnormal integration with self-referential processing as mediated by PCC. Due to our correlation findings, we suggest this imbalance to be closely related to basic symptoms in FES and thus anomalous self-experience. The findings further disentangle the cortical basis of how self-experience anomalies may pervade the social domain.

Use of a superconducting instrumentation for biomagnetic measurements performed in a hospital

A superconducting instrumentation has been set up to perform biomagnetic measurements for screening analysis in one of Rome hospitals. The magnetic detector is a 2nd derivative gradiometer, which can be balanced against both spatially uniform fields and field gradients. The overall noise level is sim 4 times 10^{-14} T.Hz-½ in the frequency range 0.5 ÷ 3000Hz. Main efforts are devoted to the recording of magnetocardio-graphic maps of normal and abnormal subjects while a detailed analysis of some segments of the heart cycle is carried on in subjects previously investigated by means of other techniques. Magnetomyograms of normal and abnormal subjects are detected and studied in the frequency domain. Magnetoencephalographic power spectra of various subjects have been mapped as well. Most remarkable results so far collected are presented. Some of the measurements have been performed in the hospital and some in the laboratory, always without the aid of any shielding.

The positioning problem in biomagnetic measurements: A solution for arrays of superconducting sensors

We propose a system to measure automatically the location of the subjects head in the reference frame identified by an array of superconducting biomagnetic sensors (the same procedure may be employed for Cardiac studies with little or no modification). The system consists of small reference coils (magnetic dipoles) to be properly positioned on the subjects head. The coils are driven by a known current signal. The generated magnetic fields are measured by the superconducting array and decoded by a suitable algorhythm which calculates the relative position of the coils with respect to the array itself. In this paper we present a schematic of the system. The results of a computer simulation, carried out for different types of superconducting detection coils are also illustrated.

Magnetic study of the spontaneous brain activity of normal subjects

SummaryAn investigation of the spontaneous brain activity from normal subjects has been carried out by means of the neuromagnetic method. Two different systems were used for magnetic measurements. Both used 2nd-order gradiometers specifically designed for brain studies: 2.9 cm diameter, 5 cm baseline. A r.f. SQUID and a d.c. SQUID were coupled to the gradiometers. The measured noise levels aren% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrVeFv0de9GqpGe9Ff% ea0dXdd91qFHe9FjuP0-is0dXdbba9pGe9xq-Jbba9suk9fr-xfr-x% frpeWZqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaiaaisdacaaIWa% acbaGaa8Nzaiaa-rfacaGGVaWaaOaaaeaacaWFibGaa8NEaaWcbeaa% aaa!3CDA!nn

Magnetic measurements and modelling for the investigation of the human-heart conduction system

40fT/sqrt {Hz}