Biomedical subjects

Antonio Ferretti

Publications and source records attributed to Antonio Ferretti.

9 recordsLinked to original sources

PubMed2007

Cortical brain responses during passive nonpainful median nerve stimulation at low frequencies (0.5-4 Hz): an fMRI study.

Previous findings have shown that the human somatosensory cortical systems that are activated by passive nonpainful electrical stimulation include the contralateral primary somatosensory area (SI), bilateral secondary somatosensory area (SII), and bilateral insula. The present study tested the hypothesis that these areas have different sensitivities to stimulation frequency in the condition of passive stimulation. Functional MRI (fMRI) was recorded in 24 normal volunteers during nonpainful electrical median nerve stimulations at 0.5, 1, 2, and 4 Hz repetition rates in separate recording blocks in pseudorandom order. Results of the blood oxygen level-dependent (BOLD) effect showed that the contralateral SI, the bilateral SII, and the bilateral insula were active during these stimulations. As a major finding, only the contralateral SI increased its activation with the increase of the stimulus frequency at the mentioned range. The fact that nonpainful median-nerve electrical stimuli at 4 Hz induces a larger BOLD response is of interest both for basic research and clinical applications in subjects unable to perform cognitive tasks in the fMRI scanner.

Adult↗

PubMed2005

Dynamics of male sexual arousal: distinct components of brain activation revealed by fMRI.

The peripheral mechanisms of male sexual arousal are well known. Recently, neuroimaging techniques, such as PET or fMRI, allowed the investigation of the subjacent cerebral mechanisms. In ten healthy subjects, we have simultaneously recorded fMRI images of brain activation elicited by viewing erotic scenes, and the time course of penile tumescence by means of a custom-built MRI-compatible pneumatic cuff. We have compared activation elicited by video clips with a long duration, that led to sexual arousal and penile erection, and activation elicited by briefly presented still images, that did induce sexual arousal without erection. This comparison and the use of the time course of penile tumescence in video clips allowed to perform a time resolved data analysis and to correlate different patterns of brain activation with different phases of sexual response. The activation maps highlighted a complex neural circuit involved in sexual arousal. Of this circuit, only a few areas (anterior cingulate, insula, amygdala, hypothalamus, and secondary somatosensory cortices) were specifically correlated with penile erection. Finally, these areas showed distinct dynamic relationships with the time course of sexual response. These differences might correspond to different roles in the development and appraisal of the sexual response. These findings shed light on the psychophysiology of male sexuality and open new perspectives for the diagnosis, therapy, and possible rehabilitation of sexual dysfunction.

Adult↗

PubMed2005

Human cortical responses during one-bit delayed-response tasks: an fMRI study.

Neuroimaging study of cognition across aging requires simple tasks ensuring: (i) high rate of correct performances in neurophysiological settings; and (ii) significant modulation of cortical activity. As a preliminary step, the present functional magnetic resonance imaging (fMRI) study tested the hypothesis that very simple delayed-response tasks fit these requirements in normal young adults. The short-term memory (STM) variant included a sequence of cue stimulus (two vertical bars), delay period (blank screen for only 5s), go stimulus, and motor response compatible with the taller vertical bar. Noteworthy, the retention (only one bit) could be based on visuo-spatial, phonological, and somatomotor coding. In the control variant (no STM, NSTM), the cue stimulus was present during the delay period. Results showed high rate of correct performances in both tasks (about 95%). Compared to the NSTM task (delay period), the STM task enhanced cortical responses in bilateral dorsolateral prefrontal (Brodmann area 8-9 (BA 8-9)), lateral premotor (BA 6L), medial premotor (BA 6M), inferior parietal (BA 40), and superior parietal (BA 7) areas. In the STM task, cortical responses were stronger in right than left BA 8-9 and BA 6L. These results indicate that, in normal young adults, a simple STM variant of delayed-response tasks (one bit to be retained) is correctly performed and enhances bilateral fronto-parietal responses. Therefore, it may be used for future cognitive neuroimaging studies on aging.

Adult↗

PubMed2005

Neural systems underlying observation of humanly impossible movements: an FMRI study.

Previous studies have indicated that largely overlapping parts of a complex, mainly fronto-parietal, neural network are activated during both observation and execution of an action. If these two processes are inextricably linked, increases of neural activity contingent upon action observation should be found only for movements that can actually be performed. Using functional magnetic resonance imaging, we investigated whether observation of possible and biomechanically impossible movements of fingers activated the same neural systems. Thirteen healthy subjects were scanned during observation of video-clips showing abduction/adduction movements of the right index or the little finger, which were defined as biomechanically possible or impossible according to the range of their angular displacement at the metacarpo-phalangeal joint. The mere observation of possible and impossible hand movements induced a selective activation of left precentral and left inferior frontal regions, thus indicating that motor-related areas map body actions even when they violate the constraints of human anatomy. An increase of the blood oxygen level-dependent signal selectively linked to observation of impossible hand movements was found in sensorimotor parietal regions. Our results suggest that while premotor areas code human actions regardless of whether they are biologically possible or impossible, sensorimotor parietal regions may be important for coding the plausibility of actions.

Adult↗

PubMed2004

Functional topography of the secondary somatosensory cortex for nonpainful and painful stimulation of median and tibial nerve: an fMRI study.

Functional magnetic resonance imaging (fMRI) was used to study the cortical activity of the bilateral secondary somatosensory cortex (SII) during nonpainful (motor threshold) and painful electrical stimulation of median and tibial nerves. fMRI recordings were performed in eight normal young adults. The aim was at evaluating the working hypothesis of a spatial segregation of nonpainful and painful populations not only in the "hand" representation 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 nonpainful and painful stimuli: an fMRI study. NeuroImage 20, 1625-1638.] but also in its "foot" representation. Results showed that, in both "hand" and "foot" representations of bilateral SII, the activity elicited by the painful stimulation was localized more posteriorly with respect to that elicited by the nonpainful stimulation. A fine spatial analysis of the SII responses revealed a clear somatotopic organization in the bilateral SII subregion especially reactive to the nonpainful stimuli (i.e., segregation of the hand and foot representations). In contrast, it was not possible to disentangle the "hand" and "foot" representations of SII for painful stimuli. These results extended to the SII "foot" representation previous evidence of a spatial segregation in the SII "hand" representation of subregions for the painful and nonpainful stimuli. Furthermore, they suggest that noxious information is not somatotopically represented in human bilateral SII, at least as inferred from fMRI data at 1.5 T.

Adult↗

PubMed2003

Functional topography of the secondary somatosensory cortex for nonpainful and painful stimuli: an fMRI study.

The regional activity of the contralateral primary (SI) and the bilateral secondary (SII) somatosensory areas during median nerve stimulations at five intensity levels (ranging from nonpainful motor threshold to moderate pain) was studied by means of functional magnetic resonance imaging (fMRI). The aim was to characterize the functional topography of SII compared to SI as a function of the stimulus intensity. Results showed that the galvanic stimulation of the median nerve activated the contralateral SI at all stimulus intensities. When considered as a single region, SII was more strongly activated in the contralateral than in the ipsilateral hemisphere. When a finer spatial analysis of the SII responses was performed, the activity for the painful stimulation was localized more posteriorly compared to that for the nonpainful stimulation. This is the first report on such a SII segregation for transient galvanic stimulations. The activity (relative signal intensity) of this posterior area increased with the increase of the stimulus intensity. These results suggest a spatial segregation of the neural populations that process signals conveyed by dorsal column-medial lemniscus (nonpainful signals) and neospinothalamic (painful signals) pathways. Further fMRI experiments should evaluate the functional properties of these two SII subregions during tasks involving sensorimotor integration, learning, and memory demands.

Adult↗

PubMedDate not supplied

Are circular external fixators weakened by the use of hemispheric washers?

OBJECTIVES: To compare the axial mechanical stability of 3 circular external fixators systems with and without hemispheric washers. STUDY DESIGN: Experimental study. METHODS: The axial stiffness and load necessary to produce 0.5 and 1 mm of displacement of 10 circular external fixator constructs from 3 manufacturers were tested on a materials testing machine. The constructs tested included the Small Bone fixator (SBF; Hofmann S.a.S., Monza, Italy), the IMEX ring fixator (IMEX Inc., Longview, TX), and the Multiplanar C-Fix (MCF; PanVet Distribuzione, Seriate, Italy). Five configurations were tested for each construct: (1) conventional nut fixation, (2) hemispheric washer fixation with connecting rods offset by 0, (3) 1, and (4) 2 holes, and (5) with a ring placed at maximum angulation. RESULTS: The loads resisted at 0.5 and 1 mm of displacement did not differ when frame configurations were compared (P =.25733 and.33769, respectively). The linear stiffness of the following configurations were decreasingly stiff: standard constructs, hemispheric washers with connecting rods perpendicular to rings, hemispheric washers with connecting rods offset by 1 hole, hemispheric washers with connecting rods offset by 2 holes, and ring offset in relation to bone model. The SBF constructs tested were 34% and 41% more rigid than the IMEX and MCF constructs tested despite the larger diameter of the connecting rods for the IMEX frames (6 mm) compared with the SBF frames (5 mm). The IMEX constructs tested were 6% more rigid than the MCF constructs tested. CONCLUSIONS: Adding hemispheric washers and angling connecting rods in relation to rings did not influence the loads resisted at 0.5 and 1 mm displacement but decreased construct stiffness. CLINICAL RELEVANCE: The use of hemispheric washers had minor effects on the biomechanical performance of fixator frames tested in this study when used to angle a ring in relation to connecting rods for circular external fixators.

Animals↗

PubMedDate not supplied

Radiotherapy in the treatment of stage III-IV hypopharyngeal carcinoma.

BACKGROUND: The aim of this study was to evaluate the role of radiation therapy alone, employing standard fractionation, in stage III-IV hypopharyngeal carcinoma. MATERIALS AND METHODS: Fourteen (38.9%) stage III and 22 (61.1%) stage IV patients with hypopharyngeal carcinoma were submitted, with curative intent, to exclusive radiotherapy to the primary tumor and regional draining lymph nodes, level II, III, IV, V and VI. Total dose ranged from 68 to 72 Gy. RESULTS: The 5-year overall survival (OS) and disease-specific survival (DSS) rates were 15.6% and 28.1%, respectively. Five-year OS in stage III and IV patients was, respectively, 33% and 5% (p=0.028) and DSS was, respectively, 50% and 16% (p=0.029). Five-year OS and DSS rate in N0 versus N+ patients were respectively 37.5% and 75% versus 8.3% and 12.5% (p=0.07 and p=0.05). CONCLUSION: Overall survival at 5 years for III-IV hypopharyngeal tumor treated with radiotherapy alone is poor. It is possible that the addition of the best radiation fractionation to the best concurrent chemotherapy may improve the results, with acceptable toxicity.

Aged↗

PubMedDate not supplied

High-grade gliomas: results in patients treated with adjuvant radiotherapy alone and with adjuvant radio-chemotherapy.

BACKGROUND: Despite advances in the surgical, radiotherapeutic and chemotherapeutic fields, the outcome for patients with high-grade gliomas remains poor. Our experience of patients treated with and without chemotherapy is reported. MATERIALS AND METHODS: From April 1999 to July 2003, 30 patients with high-grade gliomas were treated: 13 received adjuvant radiotherapy (RT) alone whereas 17 received temozolomide 75 mg/m2/d during the irradiation time and 200 mg/m2 daily per 5 consecutive days, every 28 days for three to six cycles, starting 4 weeks after the end of radiotherapy. RESULTS: The median follow-up was 12.5 months. The median overall survival (OS) was 15 months. In patients treated with RT plus chemotherapy, no statistical difference was observed between those who had undergone partial surgical resection and those with total resection (p=0.5128). In patients with glioblastoma multiforme (GBM) treated with combined radiochemotherapy, the median OS was 18 months, while it was 7 months (p=0.0204) in those treated without chemotherapy. Multivariate analysis (Cox model) evidenced statistical differences for performance status (p =0.002) and for the type of adjuvant therapy (p=0.006). CONCLUSION: Radio-chemotherapy plus adjuvant temozolomide seemed to offer the best results in patients not submitted to debulking surgery. The performance status remained the most important prognostic factor. Tolerance to the combined regimen was very good.

Adult↗