S Della Penna

Publications of S Della Penna

• Neuromagnetic responses reveal the cortical timing of audiovisual synchrony.

  Authors: R Franciotti, A Brancucci, S Della Penna, M Onofrj, L Tommasi

  Neuroscience. 07/2011; 193:182-92.

  Multisensory processing involving visual and auditory inputs is modulated by their relative temporal offsets. In order to assess whether multisensory integration alters the activation timing ofMultisensory processing involving visual and auditory inputs is modulated by their relative temporal offsets. In order to assess whether multisensory integration alters the activation timing of primary visual and auditory cortices as a function of the temporal offsets between auditory and visual stimuli, a task was designed in which subjects had to judge the perceptual simultaneity of the onset of visual stimuli and brief acoustic tones. These were presented repeatedly with three different inter-stimulus intervals that were chosen to meet three perceptual conditions: (1) physical synchrony perceived as synchrony by subjects (SYNC); (2) physical asynchrony perceived as asynchrony (ASYNC); (3) physical asynchrony perceived ambiguously (AMB, i.e. 50% perceived as synchrony, 50% as asynchrony). Magnetoencephalographic activity was recorded during crossmodal sessions and unimodal control sessions. The activation of primary visual and auditory cortices peaked at a longer latency for the crossmodal conditions as compared to the unimodal conditions. Moreover, the latency in the auditory cortex was longer in the SYNC than in the ASYNC condition, whereas in the visual cortex the latency in the AMB condition was longer than in the ASYNC condition. These findings suggest that multisensory processing affects temporal dynamics already in primary cortices, that such activity can differ regionally and can be sensitive to the temporal offsets of multisensory inputs. In addition, in the AMB condition the conscious awareness of asynchrony might be associated to a later activation of the primary auditory cortex.

• A frontoparietal network for spatial attention reorienting in the auditory domain: a human fMRI/MEG study of functional and temporal dynamics.

  Authors: M Brunetti, S Della Penna, A Ferretti, C Del Gratta, F. Cianflone, P Belardinelli, M Caulo, V Pizzella, M Olivetti Belardinelli, G L Romani

  Cerebral cortex (New York, N.Y. : 1991). 06/2008; 18(5):1139-47.

  Several studies have identified a supramodal network critical to the reorienting of attention toward stimuli at novel locations and which involves the right temporoparietal junction and the inferiorSeveral studies have identified a supramodal network critical to the reorienting of attention toward stimuli at novel locations and which involves the right temporoparietal junction and the inferior frontal areas. The present functional magnetic resonance imaging (fMRI)\magnetoencephalography (MEG) study investigates: 1) the cerebral circuit underlying attentional reorienting to spatially varying sound locations; 2) the circuit related to the regular change of sound location in the same hemifield, the change of sound location across hemifields, or sounds presented randomly at different locations on the azimuth plane; 3) functional temporal dynamics of the observed cortical areas exploiting the complementary characteristics of the fMRI and MEG paradigms. fMRI results suggest 3 distinct roles: the supratemporal plane appears modulated by variations of sound location; the inferior parietal lobule is modulated by the cross-meridian effect; and the inferior frontal cortex is engaged by the inhibition of a motor response. MEG data help to elucidate the temporal dynamics of this network by providing high-resolution time series with which to measure latency of neural activation manipulated by the reorienting of attention.

• Power map during painful and nonpainful stimulation using beamformer technique

  Authors: R Franciotti, L Ciancetta, S Della Penna, P Belardinelli, V Pizzella, G L Romani

  Noninvasive Functional Source Imaging of the Brain and Heart and the International Conference on Functional Biomedical Imaging, 2007. NFSI-ICFBI 2007. Joint Meeting of the 6th International Symposium on; 11/2007

  Pain can influence brain processing on many levels, not only in terms of proper pain processing but also in terms of consciousness such as attention, information selection, anticipation . FunctionalPain can influence brain processing on many levels, not only in terms of proper pain processing but also in terms of consciousness such as attention, information selection, anticipation . Functional neuroimaging attempts to distinguish brain responses related to the expectation of pain from those associated with the experience of pain. The aim of the present study is to investigate brain regions involved in the emotional aspect of pain perception using beamforming technique in the alpha range.

• Conditioning transcutaneous electrical nerve stimulation induces delayed gating effects on cortical response: a magnetoencephalographic study.

  Authors: K Torquati, R Franciotti, S Della Penna, C Babiloni, P M Rossini, G L Romani, V Pizzella

  NeuroImage. 06/2007; 35(4):1578-85.

  The present study was undertaken to investigate after-effects of 7 Hz non-painful prolonged stimulation of the median nerve on somatosensory-evoked fields (SEFs). The working hypothesis thatThe present study was undertaken to investigate after-effects of 7 Hz non-painful prolonged stimulation of the median nerve on somatosensory-evoked fields (SEFs). The working hypothesis that conditioning peripheral stimulations might produce delayed interfering ("gating") effects on the response of somatosensory cortex to test stimuli was evaluated. In the control condition, electrical thumb stimulation induced SEFs in ten subjects. In the experimental protocol, a conditioning median nerve stimulation at wrist preceded 6 electrical thumb stimulations. Equivalent current dipoles fitting SEFs modeled responses of contralateral primary area (SI) and bilateral secondary somatosensory areas (SII) following control and experimental conditions. Compared to the control condition, conditioning stimulation induced no amplitude modulation of SI response at the initial stimulus-related peak (20 ms). In contrast, later response from SI (35 ms) and response from SII were significantly weakened in amplitude. Gradual but fast recovery towards control amplitude levels was observed for the response from SI-P35, while a slightly slower cycle was featured from SII. These findings point to a delayed "gating" effect on the synchronization of somatosensory cortex after peripheral conditioning stimulations. This effect was found to be more lasting in SII area, as a possible reflection of its integrative role in sensory processing.

• Low- and high-frequency evoked responses following pattern reversal stimuli: a MEG study supported by fMRI constraint.

  Authors: B Perfetti, R Franciotti, S Della Penna, A Ferretti, M Caulo, G L Romani, M Onofrj

  NeuroImage. 05/2007; 35(3):1152-67.

  We investigated the neural generators of N1 and P1 components of visual magnetic responses through the concomitant study of low (1-15 Hz)- and high (15-30 Hz)-frequency brain activities phase-lockedWe investigated the neural generators of N1 and P1 components of visual magnetic responses through the concomitant study of low (1-15 Hz)- and high (15-30 Hz)-frequency brain activities phase-locked to stimulus and elicited by pattern reversal visual stimuli. Whole helmet magnetic recordings and dipole modeling technique with support of functional magnetic resonance imaging (fMRI) were used to characterize locations and orientations of N1 and P1 sources as a function of four stimulated visual field quadrants. A comparison between low- and high-frequency activities revealed fundamental differences among orientations of the quadrants dipoles thus suggesting partly distinct neural populations underlying low- and high-frequency responses to transient contrast visual stimuli. Moreover, for both low- and high-frequency bands the specific study of locations and orientations of N1 and P1 sources indicated V1/V2 cortex as the neural substrate generating the two components. In summary, we provided strong support for a cortical genesis of human oscillatory mass activity following transient contrast stimuli with specific neural districts active in the low- and high-frequency bands. The converging results obtained from the concomitant investigation of probably different brain activities provided new evidences for a striate genesis of N1 and P1 components of the broadband visual-evoked responses following pattern reversal.

• A cartesian time--frequency approach to reveal brain interaction dynamics.

  Authors: L Marzetti, S Della Penna, G Nolte, R Franciotti, G Stefanics, G L Romani

  Brain topography. 02/2007; 19(3):147-54.

  The study of large-scale interactions from magnetoencephalographic data based on the magnitude of the complex coherence computed at channel level is a widely used method to track the coupling betweenThe study of large-scale interactions from magnetoencephalographic data based on the magnitude of the complex coherence computed at channel level is a widely used method to track the coupling between neural signals. Traditionally, a measure based on the magnitude of the complex coherence estimated by Fourier analysis, has been used under the assumption that the neural signals are stationary. Here, we split the complex coherence in its real and imaginary parts and focus on the latter with the advantage that the imaginary part is insensitive to spurious connectivity resulting from volume conducted "self interaction". Furthermore, interacting sources alone contribute to a non-vanishing imaginary part of the complex coherence whereas the contribute of non-interacting sources is also mapped from the magnitude of the complex coherence. Since it has been extensively shown that non-stationary stochastic processes contribute to the generation of neural signals, it is fundamental to be able to define interaction measures that are able to follow the temporal variations in the coupling between neural signals. To this purpose time-frequency domain techniques to estimate the magnitude of the complex coherence have been developed in the past decades. Similarly, we extend the analysis of the imaginary part of complex coherence to the time-frequency domain, by using the short-time Fourier transform to analyze the complex coherence as a function of time. In this way, it is possible to get an indication about the dynamic of the underlying source interaction pattern by looking at channel level interactions without the bias introduced by artifactual self-interaction by volume conduction or by the contribute of non-interacting sources. Furthermore, the corresponding imaginary part of the cross-spectrogram can be used to estimate interactions on a source level by localizing pools of sources interacting at a given frequency and by characterizing their dynamics. The method has been applied to magnetoencephalographic data from a cross-modal visual auditory stimulation and provided evidence for the involvement of temporal and occipital areas in the integrated information processing for simultaneous audio-visual stimulation. Furthermore, the source interaction pattern shows a variation in time that reflects a dynamical synchronization of the involved brain sources in the frequency bands of interest.

• Cortical rhythms reactivity in AD, LBD and normal subjects: a quantitative MEG study.

  Authors: R Franciotti, D Iacono, S Della Penna, V Pizzella, K Torquati, M Onofrj, G L Romani

  Neurobiology of aging. 09/2006; 27(8):1100-9.

  The present study evaluated the reactivity of cortical rhythms in 15 Alzheimer's disease (AD) patients, 7 Lewy body dementia (LBD) patients and 9 control subjects using a 165 SQUID whole-head MEGThe present study evaluated the reactivity of cortical rhythms in 15 Alzheimer's disease (AD) patients, 7 Lewy body dementia (LBD) patients and 9 control subjects using a 165 SQUID whole-head MEG system. The absolute power values of the rhythms recorded over different areas over the brain (frontal, parietal, temporal, occipital) were analysed in the 3-47Hz frequency range. The cortical reactivity of the alpha (9-14Hz) and pre-alpha rhythms (7-9Hz) during open and closed eyes conditions differentiated the control group from the patient groups and moderate AD from severe AD and LBD groups, respectively. The cortical reactivity of the slow-band (3-7Hz) obtained by comparing a simple mental task and the rest discriminated the severe AD group from the other groups. In addition, spectral coherence analysis in the alpha band showed that the loss of coherence in AD and LBD patients mainly involved long connections. These results suggest that investigations on rhythms reactivity and spectral coherence might help on the study of the dementias with different etiology.

• Human brain activation during passive listening to sounds from different locations: an fMRI and MEG study.

  Authors: M Brunetti, P Belardinelli, M Caulo, C Del Gratta, S Della Penna, A Ferretti, G Lucci, A. Moretti, V Pizzella, A Tartaro, K Torquati, M Olivetti Belardinelli, G L Romani

  Human brain mapping. 01/2006; 26(4):251-61.

  Recent animal and human studies indicate the existence of a neural pathway for sound localization, which is similar to the "where" pathway of the visual system and distinct from the soundRecent animal and human studies indicate the existence of a neural pathway for sound localization, which is similar to the "where" pathway of the visual system and distinct from the sound identification pathway. This study sought to highlight this pathway using a passive listening protocol. We employed fMRI to study cortical areas, activated during the processing of sounds coming from different locations, and MEG to disclose the temporal dynamics of these areas. In addition, the hypothesis of different activation levels in the right and in the left hemispheres, due to hemispheric specialization of the human brain, was investigated. The fMRI results indicate that the processing of sound, coming from different locations, activates a complex neuronal circuit, similar to the sound localization system described in monkeys known as the auditory "where" pathway. This system includes Heschl's gyrus, the superior temporal gyrus, the supramarginal gyrus, and the inferior and middle frontal lobe. The MEG analysis allowed assessment of the timing of this circuit: the activation of Heschl's gyrus was observed 139 ms after the auditory stimulus, the peak latency of the source located in the superior temporal gyrus was at 156 ms, and the inferior parietal lobule and the supramarginal gyrus peaked at 162 ms. Both hemispheres were found to be involved in the processing of sounds coming from different locations, but a stronger activation was observed in the right hemisphere.

• Nociceptive and non-nociceptive sub-regions in the human secondary somatosensory cortex: an MEG study using fMRI constraints.

  Authors: K Torquati, V Pizzella, C Babiloni, C Del Gratta, S Della Penna, A Ferretti, R Franciotti, P M Rossini, G L Romani

  NeuroImage. 06/2005; 26(1):48-56.

  Previous evidence from functional magnetic resonance imaging (fMRI) has shown that a painful galvanic stimulation mainly activates a posterior sub-region in the secondary somatosensory cortex (SII),Previous evidence from functional magnetic resonance imaging (fMRI) has shown that a painful galvanic stimulation mainly activates a posterior sub-region in the secondary somatosensory cortex (SII), whereas a non-painful sensory stimulation mainly activates an anterior sub-region of SII [Ferretti, A., Babiloni, C., Del Gratta, C., Caulo, M., Tartaro, A., Bonomo, L., Rossini, P.M., Romani, G.L., 2003. Functional topography of the secondary somatosensory cortex for non-painful and painful stimuli: an fMRI study. Neuroimage 20 (3), 1625-1638.]. The present study, combining fMRI with magnetoencephalographic (MEG) findings, assessed the working hypothesis that the activity of such a posterior SII sub-region is characterized by an amplitude and temporal evolution in line with the bilateral functional organization of nociceptive systems. Somatosensory evoked magnetic fields (SEFs) recordings after alvanic median nerve stimulation were obtained from the same sample of subjects previously examined with fMRI [Ferretti, A., Babiloni, C., Del Gratta, C., Caulo, M., Tartaro, A., Bonomo, L., Rossini, P.M., Romani, G.L., 2003. Functional topography of the secondary somatosensory cortex for non-painful and painful stimuli: an fMRI study. Neuroimage 20 (3), 1625-1638.]. Constraints for dipole source localizations obtained from MEG recordings were applied according to fMRI activations, namely, at the posterior and the anterior SII sub-regions. It was shown that, after painful stimulation, the two posterior SII sub-regions of the contralateral and ipsilateral hemispheres were characterized by dipole sources with similar amplitudes and latencies. In contrast, the activity of anterior SII sub-regions showed statistically significant differences in amplitude and latency during both non-painful and painful stimulation conditions. In the contralateral hemisphere, the source activity was greater in amplitude and shorter in latency with respect to the ipsilateral. Finally, painful stimuli evoked a response from the posterior sub-regions peaking significantly earlier than from the anterior sub-regions. These results suggested that both ipsi and contra posterior SII sub-regions process painful stimuli in parallel, while the anterior SII sub-regions might play an integrative role in the processing of somatosensory stimuli.

• Temporal dynamics of alpha and beta rhythms in human SI and SII after galvanic median nerve stimulation. A MEG study.

  Authors: S Della Penna, K Torquati, V Pizzella, C Babiloni, R Franciotti, P M Rossini, G L Romani

  NeuroImage. 09/2004; 22(4):1438-46.

  In this MEG study, we investigated cortical alpha/sigma and beta ERD/ERS induced by median nerve stimulation to extend previous evidence on different resonant and oscillatory behavior of SI and SIIIn this MEG study, we investigated cortical alpha/sigma and beta ERD/ERS induced by median nerve stimulation to extend previous evidence on different resonant and oscillatory behavior of SI and SII (NeuroImage 13 [2001] 662). Here, we tested whether simple somatosensory stimulation could induce a distinctive sequence of alpha/sigma and beta ERD/ERS over SII compared to SI. We found that for both alpha/sigma (around 10 Hz) and beta (around 20 Hz) rhythms, the latencies of ERD and ERS were larger in bilateral SII than in contralateral SI. In addition, the peak amplitude of alpha/sigma and beta ERS was smaller in bilateral SII than in contralateral SI. These results indicate a delayed and prolonged activation of SII responses, reflecting a protracted information elaboration possibly related to SII higher order role in the processing of somatosensory information. This temporal dynamics of alpha/sigma and beta rhythms may be related to a sequential activation scheme of SI and SII during the somatosensory information processes. Future studies should evaluate in SII the possible different functional significance of alpha/sigma with respect to beta rhythms during somatosensory processing.

• "Gating" effects of simultaneous peripheral electrical stimulations on human secondary somatosensory cortex: a whole-head MEG study.

  Authors: K Torquati, V Pizzella, S Della Penna, R Franciotti, C Babiloni, G L Romani, P M Rossini

  NeuroImage. 12/2003; 20(3):1704-13.

  The secondary somatosensory cortex (SII) is strongly involved in the processing of somatosensory tactile and nociceptive sensations. We investigated the effect on SII responses of simultaneousThe secondary somatosensory cortex (SII) is strongly involved in the processing of somatosensory tactile and nociceptive sensations. We investigated the effect on SII responses of simultaneous painful and nonpainful electrical stimulations delivered to the thumb and little finger. According to the "bimodal" (i.e., nociceptive, tactile) organization of SII, it was expected that simultaneous painful and nonpainful stimulations would lead to modality interference with a marked reduction ("gating") of somatosensory evoked fields (SEFs) generated in SII. Eight different stimulus conditions were studied. Two conditions were simultaneous "unimodal" (thumb and little finger nonpainful; thumb and little finger painful) and two conditions were simultaneous "bimodal" (thumb nonpainful and little finger painful; thumb painful and little finger nonpainful). As a reference, four conditions included stimulations at single sites (thumb nonpainful, little finger nonpainful, thumb painful, little finger painful). The gating phenomenon was defined as the percentage of difference between the intensities of SII activation after simultaneous compared to the sum of the separate stimulations. Results showed that simultaneous stimulations induced gating effects on SEFs generated by SII. No significant gating differences were observed after the two unimodal stimulations, suggesting a negligible effect of global energy on gating. Instead, the gating effects on bilateral SII activity were stronger after simultaneous bimodal when compared to unimodal stimulations. Our findings hint that there could be a greater level of integration/convergence of painful and nonpainful stimuli in SII with respect to SI. Future studies should explore if it could have an important role in exploring pain relief.

• An AC magnetizing field biosusceptometer using a SQUID based sensor with additional compensation module

  Authors: S. Della Penna, C. Del Gratta, F. Cianflone, S.N. Erne, C. Granata, A. Pentiricci, V. Pizzella, M. Russo, G.L. Romani

  Applied Superconductivity, IEEE Transactions on. 07/2003;

  We present a new SQUID based susceptometer for liver iron concentration (LIC) assessment. The instrument is operated with an inhomogeneous AC magnetizing field. The susceptometer is based on 7We present a new SQUID based susceptometer for liver iron concentration (LIC) assessment. The instrument is operated with an inhomogeneous AC magnetizing field. The susceptometer is based on 7 channels, each consisting of a sensing unit and of an additional unit for the compensation of the applied field residual and its variation. Each unit is a second order gradiometer and is coupled to a dc SQUID with a parallel washer configuration. The compensation module output is digitally processed and coupled to the sensing gradiometer by means of an additional feedback path. The estimation of LIC is based on a numerical model of the subject's torso obtained from the segmentation of ultrasound images.

• Topographic organization of the human primary and secondary somatosensory cortices: comparison of fMRI and MEG findings.

  Authors: C Del Gratta, S Della Penna, A Ferretti, R Franciotti, V Pizzella, A Tartaro, K Torquati, L Bonomo, G L Romani, P M Rossini

  NeuroImage. 12/2002; 17(3):1373-83.

  We studied MEG and fMRI responses to electric median and tibial nerve stimulation in five healthy volunteers. The aim was to compare the results with those of a previous study using only fMRI on theWe studied MEG and fMRI responses to electric median and tibial nerve stimulation in five healthy volunteers. The aim was to compare the results with those of a previous study using only fMRI on the primary and secondary somatosensory cortices in which the somatotopic organization of SII was observed with fMRI. In the present work we focus on the comparison between fMRI activation and MEG equivalent current dipole (ECD) localizations in the SII area. The somatotopic organization of SII was confirmed by MEG, with the upper limb areas located more anteriorly and more inferiorly than the lower limb areas. In addition a substantial consistency of the ECD locations with the areas of fMRI activation was observed, with an average mismatch of about 1 cm. MEG ECDs and fMRI activation areas showed comparable differences in SI.

• NOTE: Sampling and reconstruction schemes for biomagnetic sensor arrays

  Authors: A. Naddeo, S. Della Penna, C. Nappi, E. Vardaci, V. Pizzella

  Physics in Medicine and Biology. 09/2002; 47:239-+.

• A study of the human primary and secondary somatosensory cortices with FMRI and MEG

  Authors: C Del Gratta, S Della Penna, A Ferretti, R Franciotti, V Pizzella, K Torquati, A Tartaro, L Bonomo, G L Romani, P M Rossini

  [Engineering in Medicine and Biology, 2002. 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society] EMBS/BMES Conference, 2002. Proceedings of the Second Joint; 02/2002

  We studied MEG and fMRI responses to electric median and tibial nerve stimulation in five healthy volunteers. The aim was to compare the fMRI activation and MEG equivalent current dipole (ECD)We studied MEG and fMRI responses to electric median and tibial nerve stimulation in five healthy volunteers. The aim was to compare the fMRI activation and MEG equivalent current dipole (ECD) localisations in the primary (SI) and secondary (SII) somatosensory cortices. EPI functional images were acquired with a SIEMENS 1.5 T scanner according to a block paradigm. MEG data were acquired with a 165-channel whole head neuromagnetometer. Matching of MEG and fMRI subject reference frames was performed with current carrying coils whose signal was recorded in MEG and whose position was identified in structural MRI with oil capsules. Stimuli were rectangular pulses with duration 200 to 400 microseconds and frequency 0.3 Hz for MEG and 1.9 Hz for fMRI. A higher stimulus rate in fMRI was used to increase regional cerebral blood flow. The stimulus intensity was settled at a level producing a painless, clearly visible thumb opposition or foot flexion. A somatotopic organization of SII was seen both with MEG and fMRI, with the upper limb areas located more anteriorly and more inferiorly than the lower limb areas. ECD locations and fMRI activation were substantially consistent, with an average mismatch of about 1 cm. Similar differences were observed in SI.

• Topographic Organization of the Human Secondary Somatosensory Cortex:

  Authors: C Del Gratta, S Della Penna, A Ferretti, R Franciotti, V Pizzella, K Torquati, A Tartaro, L Bonomo, G L Romani, P M Rossini

  12/2001;

  Introduction Functional Magnetic Resonance Imaging (fMRI) allows to localize an event-related increase of metabolism due to neuronal firing in active brain regions as reflected by blood flow andIntroduction Functional Magnetic Resonance Imaging (fMRI) allows to localize an event-related increase of metabolism due to neuronal firing in active brain regions as reflected by blood flow and oxygen consumption, during perception and processing of a sensory impulse from a given body district [1]. Magnetoencephalography (MEG), on the other hand, by localizing in 3D the sources of the associated magnetic field, directly investigates event-related cerebral activity with millisecond time resolution [2]. In contrast, fMRI has a temporal resolution in the order of 1 s, being limited by hemodynamics. There is an increasing interest in the scientific community for the combination and comparison of brain mapping techniques with complementary properties [3]. The Secondary Somatosensory Area (SII) is a center that receives sensory inputs from both sides of the body and is located near the primary auditory cortex [4]. In humans, activation of SII area has been observed during median and tibia

• A 165-Channel Neuromagnetometer for Multimodal Brain Imaging

  Authors: V Pizzella, S Della Penna, S. N. Ern, C. Granata, A Pasquarelli, K Torquati, R. Rossi, M. Russo

  12/2001;

  this paper we report about a 165-channel neuromagnetic system developed in an frame of an international multidisciplinary cooperation between the Advanced Biomedical Technologies (ITAB) of thethis paper we report about a 165-channel neuromagnetic system developed in an frame of an international multidisciplinary cooperation between the Advanced Biomedical Technologies (ITAB) of the University of Chieti (Italy), the Central Institute for Biomedical Engineering (ZIBMT) of the University of Ulm (Germany), the Istituto di Cibernetica of the National Research Council of Italy, and the Italian company Advanced Biomedical Technologies (ATB) [1]. This system, shown in figure 1, is installed at ITAB, and it is used in combination with a fMRI SIEMENS VISION 1.5 T system for multimodal brain imaging

• TOPICAL REVIEW: SQUID systems for biomagnetic imaging

  Authors: V. Pizzella, S. Della Penna, C. DelGratta, G. Luca Romani

  Superconductor Science Technology. 07/2001; 14:79-+.

• Topographic organization of the human primary and secondary somatosensory areas: an fMRI study.

  Authors: C Del Gratta, S Della Penna, A Tartaro, A Ferretti, K Torquati, L Bonomo, G L Romani, P M Rossini

  Neuroreport. 07/2000; 11(9):2035-43.

  The topographical organization of SI and SII somatosensory areas was investigated using fMRI at 1.5 T and electrical sensory stimulation. Electrical stimuli were delivered unilaterally to the medianThe topographical organization of SI and SII somatosensory areas was investigated using fMRI at 1.5 T and electrical sensory stimulation. Electrical stimuli were delivered unilaterally to the median nerve at the wrist and to the tibial nerve at the medial malleolus, during a block paradigm study. In all subjects, activation was observed, contralaterally to the stimulated side, in the post-central gyrus, in the posterior parietal cortex, in the mesial pre-frontal region and, bilaterally, in the supratemporal region at the level of the Sylvian fissure. The latter region, corresponding presumably to SII, showed a rough but clearcut topographical organization, with the median nerve areas located more posteriorly. In addition, weaker activations were observed in some subjects in the ipsilateral mesial prefrontal region and in the ipsilateral posterior parietal cortex. Information contained in the present study represent an interesting database for future investigations on the effects of sensorimotor learning in normal individuals on plastic reorganization following a lesion of the primary sensorimotor centers, i.e. in stroke patients, on the topography and balance between upper and lower limb representations in primary and secondary somatosensory cortices.

• The use of an inhomogeneous applied field improves the spatial sensitivity profile of an in vivo SQUID susceptometer.

  Authors: S Della Penna, C Del Gratta, S Di Luzio, V Pizzella, K Torquati, G L Romani

  Physics in medicine and biology. 04/1999; 44(3):N21-9.

  We present a SQUID susceptometer with a non-homogeneous magnetizing field which is null at the sensing coil and increases towards the patient position with a constant gradient plus a cubic term atWe present a SQUID susceptometer with a non-homogeneous magnetizing field which is null at the sensing coil and increases towards the patient position with a constant gradient plus a cubic term at large distances. Compared with the magnetizing fields of similar instruments described in the literature, our gradient field enhances the signal due to internal organs with respect to the signal due to superficial tissue. Preliminary measurements have been performed on phantoms of known magnetic susceptibility. The advantage of using a non-homogeneous field compared with a uniform field has been investigated in the case of a double-layer phantom.