The ALTEA/ALTEINO projects: studying functional effects of microgravity and cosmic radiation.

The ALTEA project investigates the risks of functional brain damage induced by particle radiation in space. A modular facility (the ALTEA facility) is being implemented and will be operated in the International Space Station (ISS) to record electrophysiological and behavioral descriptors of brain function and to monitor their time dynamics and correlation with particles and space environment. The focus of the program will be on abnormal visual perceptions (often reported as "light flashes" by astronauts) and the impact on retinal and brain visual structures of particle in microgravity conditions. The facility will be made available to the international scientific community for human neurophysiological, electrophysiological and psychophysics experiments, studies on particle fluxes, and dosimetry. A precursor of ALTEA (the 'Alteino' project) helps set the experimental baseline for the ALTEA experiments, while providing novel information on the radiation environment onboard the ISS and on the brain electrophysiology of the astronauts during orbital flights. Alteino was flown to the ISS on the Soyuz TM34 as part of mission Marco Polo. Controlled ground experiments using mice and accelerator beams complete the experimental strategy of ALTEA. We present here the status of progress of the ALTEA project and preliminary results of the Alteino study on brain dynamics, particle fluxes and abnormal visual perceptions.

Increasing the bandwidth of resonant gravitational antennas: the case of explorer.

Resonant gravitational wave detectors with an observation bandwidth of tens of hertz are a reality: the antenna Explorer, operated at CERN by the ROG Collaboration, has been upgraded with a new readout. In this new configuration, it exhibits an unprecedented useful bandwidth: in over 55 Hz about its center operating frequency of 919 Hz the spectral sensitivity is better than 10(-20) Hz(-1/2). We describe the detector and its sensitivity and discuss the foreseeable upgrades to even larger bandwidths.

The ALTEA facility on the International Space Station.

The ALTEA project studies the problems related to possible functional damage to the Central Nervous System (CNS) due to particle radiation in space environment. The project is a large international and multi-disciplinary collaboration. The ALTEA instrumentation is an helmet-shaped multi-sensor device that will measure concurrently the dynamics of the functional status of the visual system and the passage of each particle through the brain within a pre-determined energy window. ALTEA is scheduled to fly in the International Space Station in February 2003. One part of the multi-sensor device, one of the advanced silicon telescopes, will be launched in the ISS in early 2002 and serve as test for the final device and as discriminating dosimeter for the particle fluences within the ISS.

Cosmic rays observed by the resonant gravitational wave detector NAUTILUS

The passage of cosmic rays has been observed to excite mechanical vibrations in the resonant gravitational wave detector NAUTILUS operating at temperature of 100 mK. A very significant correlation (more than 10 standard deviations) is found.

Neuromagnetic somatosensory homunculus: a non-invasive approach in humans.

The somatosensory homunculus has been identified during stimulation of median (at wrist and elbow), femoral, tibial and pudendal nerves of the left hemibody via the neuromagnetic imaging technique. The somatic representations of different body districts have been localized in the somatosensory cortex, by means of an equivalent dipole localization algorhythm. Dipole locations agree with the well-known somatotopic organization obtained with invasive techniques. The proposed method is, therefore, an important investigating tool for studies on normal and diseased subjects.

Study of focal epilepsy by multichannel neuromagnetic measurements.

A systematic investigation of several cases of focal epilepsy has been performed in an unshielded environment using a 4-channel neuromagnetic sensor. The localizations provided by the magnetic measurements have been compared with clinical evidence and confirmed by X-ray findings, and in one case also by intracranial surgery. The results show the importance of simultaneous detection of magnetic fields at different sites of the scalp in order to get a dynamic view of the epileptic activity and to detect multifocal activity unsuspected on the basis of the EEG investigation.

Neuromagnetic evidence of synchronized spontaneous activity in the brain following repetitive sensory stimulation.

Neuromagnetic measurements in the visual and somatosensory modalities reveal that, following repetitive stimulation, the brain persists in emitting synchronized after-discharges in the form of oscillations with highly specific spectral composition. In the visual modality, this rhythmic activity is centered at the frequency of the resting alpha rhythm and it is most readily induced by stimulation of the same frequency. This suggests that the phenomenon is due to synchronization of the generators responsible for the natural rhythms by the steady-state stimulation and that these generators behave as resonant oscillators. The phenomenon could then be referred to as Synchronized Spontaneous Activity (SSA). The discovery of this phenomenon has important implications for modelling the dynamics of normal evoked and spontaneous cerebral activity as well as for the understanding of pathological conditions such as photically induced epilepsies.

Neuromagnetic characterization of the cortical response to median nerve stimulation in the steady state paradigm.

Magnetic methods for localizing evoked neural activity in the human brain have been used to search for evidence of a functional organization in primary somatosensory cortex. We have found that in response to median nerve stimulation the deduced source for the evoked component with a latency of 45 ms lies at a depth in the central sulcus that depends on stimulus repetition rate, whereas the sources of the 20 ms and 24 ms components lie at a fixed depth. Moreover we have identified this 45 ms component with the dominant sinusoidal feature characteristic of steady state response.

Novel data analysis for synchronised spontaneous neuromagnetic activity.

A novel approach to neuromagnetic data analysis is presented. This technique is aimed at studying synchronised spontaneous activity (SSA) and has been used to resolve two different signals from one single evoked response, providing evidence for two possibly distinct sources. The data presented are consistent with a model that permits the generators of spontaneous activity to be synchronised by sensory stimuli.

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.