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Biomedical subjects

S Salinari

Publications and source records attributed to S Salinari.

At least 19 recordsLinked to original sources
PubMed2004

EEG deblurring techniques in a clinical context.

OBJECTIVES: EEG scalp potential distributions recorded in humans are affected by low spatial resolution and by the dependence on the electrical reference used. High resolution EEG technologies are available to drastically increase the spatial resolution of the raw EEG. Such technologies include the computation of surface Laplacian (SL) of the recorded potentials, as well as the use of realistic head models to estimate the cortical sources via linear inverse procedure (low resolution brain electromagnetic tomography, LORETA). However, these deblurring procedures are generally used in conjunction with EEG recordings with 64-128 scalp electrodes and with realistic head models obtained via sequential magnetic resonance images (MRIs) of the subjects. Such recording setup it is not often available in the clinical context, due to both the unavailability of these technologies and the scarce compliance of the patients with them. In this study we addressed the use of SL and LORETA deblurring techniques to analyze data from a standard 10-20 system (19 electrodes) in a group of Alzheimer disease (AD) patients. METHODS: EEG data related to unilateral finger movements were gathered from 10 patients affected by AD. SL and LORETA techniques were applied for source estimation of EEG data. The use of MRIs for the construction of head models was avoided by using the quasi-realistic head model of the Brain Imaging Neurology Institute of Montreal. RESULTS: A similar cortical activity estimated by the SL and LORETA techniques was observed during an identical time period of the acquired EEG data in the examined population. CONCLUSIONS: The results of the present study suggest that both SL and LORETA approaches can be usefully applied in the clinical context, by using quasi-realistic head modeling and a standard 10-20 system as electrode montage (19 electrodes). These results represent a reciprocal cross-validation of the two mathematically independent techniques in a clinical environment.

Aged↗
PubMed2003

Computerized processing of EEG-EOG-EMG artifacts for multi-centric studies in EEG oscillations and event-related potentials.

The aim of this study is to present a package including standard software for the electroencephalographic (EEG), electro-oculographic (EOG) and electromyographic (EMG) preliminary data analysis, which may be suitable to standardize the results of many EEG research centers studies (i.e. multi-centric studies) especially focused on event-related potentials. In particular, our software package includes (semi)automatic procedures for (i) EOG artifact detection and correction, (ii) EMG analysis, (iii) EEG artifact analysis, (iv) optimization of the ratio between artifact-free EEG channels and trials to be rejected. The performances of the software package on EOG-EEG-EMG data related to cognitive-motor tasks were evaluated with respect to the preliminary data analysis performed by two expert electroencephalographists (gold standard). Due to its extreme importance for multi-centric EEG studies, we compared the performances of two representative "regression" methods for the EOG correction in time and frequency domains. The aim was the selection of the most suitable method in the perspective of a multi-centric EEG study. The results showed an acceptable agreement of approximately 95% between the human and software behaviors, for the detection of vertical and horizontal EOG artifacts, the measurement of hand EMG responses for a cognitive-motor paradigm, the detection of involuntary mirror movements, and the detection of EEG artifacts. Furthermore, our results indicated a particular reliability of a 'regression' EOG correction method operating in time domain (i.e. ordinary least squares). These results suggest that such a software package could be used for multi-centric EEG studies.

Algorithms↗
PubMed2003

Introducing BF++: AC++ framework for cognitive bio-feedback systems design.

OBJECTIVE: This paper addressed the issue of building-up a framework for the realization of several cognitive bio-feedback (CBF) systems. It minimizes the programming effort and maximizes the efficiency and the cross-platform portability so that it can be used with many platforms (either software or hardware). METHODS: A generic CBF system was decomposed into six modules: acquisition, kernel, feedback rule, patient feedback, operator user interface and persistent storage. The way in which these modules interact was defined by immutable software interfaces in a way that allows to completely substitute a module without the need to modify the others. RESULTS: Three Brain Computer Interface engines were developed with less than 40 lines of C++ code each. They can also be used under virtually any platform that supports an ANSI C++ compiler. CONCLUSION: A framework for the implementation of a wide range of CBF systems was developed. Compared to the other approaches that are described in the literature, the proposed one is the most efficient, the most protable across different platforms, the most generic and the one that allows the realization of the cheapest final systems.

Cognition↗
PubMed2002

New bioimpedance model accurately predicts lower limb muscle volume: validation by magnetic resonance imaging.

Conventional bioimpedance analysis (BIA) methods now simplify the representation of lower limb geometry and electrical properties for body composition estimation. In the present study, a three-dimensional model of the lower limb was assembled by segmentation of magnetic resonance cross-sectional images (MRI) for adipose tissue, skeletal muscle, and bone. An electrical network was then associated with this model. BIA and MRI measurements were made in six lean subjects (3 men and 3 women, age 32.2 +/- 6.9 yr). Assuming 0.85 S/m for the longitudinal conductivity of the muscle, the model predicted in the examined subjects an impedance profile that conformed well to the BIA impedance profile; predicted and measured resistances were similar (261.3 +/- 7.7 vs. 249 +/- 9 Omega; P = not significant). The resistance profile provided, through a simpler model, muscle area estimates along the lower limb and total leg muscle volume (mean 4,534 cm(3) for men and 4,071 cm(3) for women) with a mean of the absolute value of relative error with respect to MRI of 6.2 +/- 3.9. The new approach suggests that BIA can reasonably estimate the distribution and volume of muscles in the lower extremities of lean subjects.

Adipose Tissue↗
PubMed2002

Classification of EEG mental patterns by using two scalp electrodes and Mahalanobis distance-based classifiers.

OBJECTIVES: In this paper, we explored the use of quadratic classifiers based on Mahalanobis distance to detect mental EEG patterns from a reduced set of scalp recording electrodes. METHODS: Electrodes are placed in scalp centro-parietal zones (C3, P3, C4 and P4 positions of the international 10-20 system). A Mahalanobis distance classifier based on the use of full covariance matrix was used. RESULTS: The quadratic classifier was able to detect EEG activity related to imagination of movement with an affordable accuracy (97% correct classification, on average) by using only C3 and C4 electrodes. CONCLUSIONS: Such a result is interesting for the use of Mahalanobis-based classifiers in the brain computer interface area.

Biomedical Engineering↗
PubMed2001

Recognition of imagined hand movements with low resolution surface Laplacian and linear classifiers.

EEG-based Brain Computer Interfaces (BCIs) require on-line detection of mental states from spontaneous EEG signals. In this framework, it was suggested that EEG patterns can be better detected with EEG data transformed with Surface Laplacian computation (SL) than with the unprocessed raw potentials. However, accurate SL estimates require the use of many EEG electrodes, when local estimation methods are used. Since BCI devices have to use a limited number of electrodes for practical reasons, we investigated the performances of spline methods for SL estimates using a limited number of electrodes (low resolution SL). Recognition of mental activity was attempted on both raw and SL-transformed EEG data from five healthy people performing two mental tasks, namely imagined right and left hand movements. Linear classifiers were used including Signal Space Projection (SSP) and Fisher's linear discriminant. Results showed an acceptable average correlation between the waveforms obtained with the low resolution SL and these obtained with the SL computed from 26 electrodes (full resolution SL). More importantly, satisfactorily recognition scores for mental EEG-patterns were obtained with the low-resolution surface Laplacian transformation of the recorded potentials when compared with those obtained by using full resolution SL (82%). These results demonstrated also the utility of linear classifiers for the detection of mental patterns in the BCI field.

Biomedical Engineering↗
PubMed2001

Unreliable use of standard muscle hydration value in obesity.

Intramuscular water content is assumed to be constant in humans independent of their anthropometric characteristics. To verify whether this assumption is correct, intramuscular water, proteins, glycogen, and both total and intramyocytic triglycerides were measured in 51 samples of rectus abdominis muscle obtained from 16 lean and 35 overweight and obese subjects (body mass index cutoff 24.9 kg/m2). Data (referred to as wet tissue) were analyzed by means of a composition model at the cellular level of the skeletal muscle (SM). The average SM water content was 76.3 +/- 3.3% in normal-weight individuals and 65.7 +/- 5.8% in obese subjects (P < 0.0001). Total triglycerides were 5.5 +/- 2.3% in controls and 19.0 +/- 7.0% in obese subjects (P < 0.0001). The intramyocytic triglyceride fraction was also increased in obese subjects. The composition model provides an explanation for the negative correlation between total triglycerides and intramuscular water, and some of the model parameters were determined from the experimental data. In conclusion, although the hydration of fat-free SM mass may be unchanged in obese subjects, the hydration of in toto muscle mass decreases as its lipid content increases.

Adult↗
PubMed2000

Disposition of dodecanedioic acid in humans.

The disposition of dodecanedioic acid (C12) was investigated in six overnight-fasting healthy male volunteers, who received a 165-min i. v. infusion of 42.45 mmol of C12 added to 150 microCi of [1-12-(14)C]C12. Blood samples were collected up to 360 min after the start of infusion, and concentration of serum labeled C12 was determined. Expired radioactivity (microCi/min) was measured up to 600 min and at 24 h. The 24-h C12 urinary excretion was around 5% of the administered amount. The percentage of C12 oxidized was 81.7 +/- 9.5% (mean +/- S.D.) of administered amount as estimated from the area under the curve of measured (14)CO(2) expiration rate. C12 kinetics was described by assuming a single compartment. A saturable rate of C12 tissue uptake (model A) and a linear rate of tissue uptake (model B) were considered. The kinetics of CO(2) produced by C12 oxidation was described by a fast pathway acting in parallel to a slow pathway modeled by first order kinetics. Parameters of model B were estimated for each subject, whereas model A was identified by fitting the pooled data of all subjects. On the basis of estimates obtained from model B, an average calorie delivery of 500 kcal/day was predicted in the plateau phase for the infusion rate of our experiments. When estimated from model A, the maximal rate of tissue uptake was 0.38 +/- 0.08 mmol/min, with a maximal calorie delivery of 750 kcal/day. These results appear promising for C12 utilization in parenteral nutrition, because C12 elimination with urine is low, whereas tissue uptake and oxidation are rather efficient.

Adult↗
PubMed1997

Kinetics of dodecanedioic acid and effect of its administration on glucose kinetics in rats.

Dodecanedioic acid (C12), a saturated aliphatic dicarboxylic acid with twelve C atoms, was given as an intraperitoneal bolus to male Wistar rats, with the aim of evaluating C12 suitability as an energy substrate for parenteral nutrition. The 24 h urinary excretion of C12 was 3.9% of the administered dose. C12 kinetics were investigated by a one-compartment model with saturable tissue uptake and reversible binding to plasma albumin. The analysis of plasma concentration and urinary excretion data from different animals yielded the population means of the kinetic parameters: renal clearance was 0.72 ml/min per kg body weight (BW) (much smaller than inulin clearance in the rat), and maximal tissue uptake was 17.8 mumol/min per kg BW corresponding to 123.7 J/min per kg BW. These results encourage the consideration of C12 as a possible substrate for parenteral nutrition. To investigate the effect of C12 administration on glucose kinetics, two other groups of rats, one treated with an intraperitoneal bolus of C12 and the other with saline, were subsequently given an intravenous injection of D[-U-14C]glucose in a tracer amount. Radioactivity data of both control and C12-treated rats were analysed by means of a two-compartment kinetic model which takes into account glucose recycling. The estimates of glucose pool size (2.3 mmol/kg BW) and total-body rate of disappearance (82.1 mumol/min per kg BW) in control rats agreed with published values. In C12-treated rats, the rate of disappearance appeared to be reduced to 36.7 mumol/min per kg BW and the extent of recycling appeared to be negligible.

Animal Nutritional Physiological Phenomena↗
PubMed1994

Statistical analysis of topographic maps of short-latency somatosensory evoked potentials in normal and parkinsonian subjects.

This work had the following objectives: i) to integrate temporal analysis (N30 peak) with power-spectrum topographic mapping of short-latency somatosensory evoked potentials (SEP's) recorded in parkinsonian and normal control subjects; and ii) to analyze with a new statistical approach the between-group topographical differences in both the time and frequency domains. The principal aim was to better determine the topography of the scalp frontal areas where the amplitude of the N30 wave was previously found to be significantly reduced in parkinsonians. The statistical procedure was based on the combined use of descriptive data analysis (DDA) and multivariate analysis. In the context of DDA, an improved version of significance probability mapping (SPM) was used by which it is possible to evaluate homo- and nonhomoscedastic data with parametric tests. The statistical evaluation of between-group differences was performed with the multivariate Hotelling's T2 test and the associated post hoc test. With this statistical procedure, it was possible to determine that the between-group statistical differences in both the temporal and power spectrum distributions were localized only in midline and contiguous contralateral frontal areas of the scalp.

Brain Mapping↗
PubMed1991

Pharmacokinetic analysis of azelaic acid disodium salt. A proposed substrate for total parenteral nutrition.

Azelaic acid was the first dicarboxylic acid proposed as an alternative energy substrate in total parenteral nutrition. In this study, the pharmacokinetics of azelaic acid were investigated in 12 healthy volunteers, 7 receiving a constant infusion (10g over 90 min) and 5 a bolus dose (1g). The 24h urinary excretion and plasma concentration in blood samples taken at regular intervals were assayed by gas-liquid chromatography. Experimental data were analysed by a 2-compartment nonlinear model that describes both tubular secretion and cellular uptake in Michaelis-Menten terms. A high value of urinary excretion (mean 76.9% of infused dose) and a mean clearance of 8.42 L/h were found, suggesting the presence of tubular secretion. Estimating the population mean of the pharmacokinetic model parameters gave a maximal cellular uptake of 0.657 g/h. The model predicts that 90% of the maximal uptake should be reached in the plateau phase of a constant infusion of 2.2 g/h. The presence of extensive and rapid losses through urinary excretion, and the low estimated value of the maximal cellular uptake, indicate that azelaic acid is not suitable as an energy substrate for total parenteral nutrition.

Adult↗
PubMed1990

Computerized mapping system of cerebral evoked potentials.

The introduction of computerized analysis systems in the study of bioelectrical signals is enhancing the understanding of the physiological mechanisms which underlie cerebral evoked potentials (EPs) in response to externally applied stimuli. In the present study, short latency (0-50-ms) and long latency (0-500-ms) somatosensory evoked potentials (SEPs) were recorded by 32 scalp electrodes from normal and pathological subjects during median nerve stimulation. An interpolation procedure for estimating data values between the neighboring electrodes allowed the mapping of cortical activity across the scalp. Time signals were also transformed by an FFT algorithm and frequency maps obtained following the same interpolation procedure. Temporal and frequency maps were graphically displayed using color and three-dimensional plots. The usefulness of computerized topographical analysis is discussed; the time and frequency computer maps obtained from the same subjects are compared and their relative advantages are evaluated.

Adult↗
PubMed1988

In vitro motility of non-pregnant rat uterine horns.

The in vitro spontaneous mechanical and electrical activity of the non-pregnant rat uterine horn was investigated. An isometric isovolumic preparation was used to obtain records of intraluminal pressure, axial force, extracellular electrical activity and horn morphology. Mean intraluminal pressure was 28.6 cmH2O and mean force 2.5 g. Burst electrical activity was initiated at the ovarian end in 70% of the cases. Detailed analysis of electrical and mechanical events during a single contraction showed a preparatory phase involving the longitudinal muscle layer, followed by a stronger contractile event involving both longitudinal and circular layers. Moreover, the mechanical activity was modulated at the frequency of a component (0.16-0.20 Hz) of the slow electrical activity of the horn. Burst electrical activity appeared at five equidistant electrodes along the horn with variable delays: the highest delays (mean values 7.4 s for burst activity initiated at the ovarian end and 6.5 s at the vaginal end) were observed in the middle part of the horn. The spontaneous contraction of the segment appeared to be due to the activation of separate regions of the horn (i.e. an ovarian and a cervical region), more than to a propagated excitatory action.

Action Potentials↗
PubMed1983

Peristaltic transport of a solid bolus.

An analysis of the peristaltic propulsion of a solid spherical bolus enclosed in a contractile membrane is presented. The model is based on in vitro preparations of intestinal segments, and utilizes a simplified representation of the mechanical properties of the muscular coats of the wall. The sequence of deformed configurations of the membrane and the displacement of the bolus are obtained by numerical solution of the model equations. The analysis presented in this paper could be useful for other studies in biomechanics (e.g. uterine contraction and motion of red blood cells in narrow capillaries).

Gastrointestinal Motility↗
PubMed1983

Some parameters of descending inhibition during colonic propulsion.

Isolated segments of rabbit distal colon were stimulated by distension of intraluminal balloons, with the aim of investigating the electrophysiological pattern of descending inhibition (DI) during the peristaltic reflex. Incidence, duration, and latency of DI were studied by varying the parameters of stimulation. A linear correlation was found between stimulus duration and DI duration for stimuli up to 10 s long. DI duration increased with the distance of the recording site from the stimulus up to 3 cm. A more complex relation was found between balloon volume and DI duration. Propagation velocity decreased with the distance from the stimulus. The relation between ascending excitation and DI was also studied: ascending excitation could always be suppressed by DI. DI was examined after addition of anticholinergics, ganglionic blocking agents, and tetrodotoxin to the organ bath. The results show that DI parameters are partially related to the stimulus characteristics and that propagation of DI is neurally mediated through nonadrenergic inhibitory nerves.

Animals↗
PubMed1979

An analysis of the peristaltic reflex.

A mathematical model describing the dynamics of the peristaltic reflex in an isolated intestinal segment is presented. The model is referred to a preparation that makes it possible to record the relevant mechanical and electrical variables during the course of the reflex. A simplified representation is used for the structure and the operation of the intrinsic nervous plexus, but the interaction between mechanical and elctrical events appears quite clearly and some features of the experimental data are well predicted.

Biomechanical Phenomena↗
PubMed1979

Peristalsis in distal colon of the rabbit: an analysis of mechanical events.

The mechanical behavior of isolated segments of rabbit distal colon was studied by experimental and theoretical techniques. The isometric isovolumic preparation was adopted to obtain records of endoluminal pressure, force, and wall morphology during 59 spontaneous and 53 electrostimulated peristaltic contractions. On strips of longitudinal and circular muscle, excised from the same segments, the tension-velocity and tension-length relationships were also measured. To describe mechanical events occurring during propulsion, a mathematical model was developed that incorporates the measured characteristics of the muscle. In response to given waveforms for the activation of the two muscular coats, the solution of model equations provides the time courses of pressure, force, and wall morphology. A number of parameters measured in the experimental contractions (e.g., pressure and force peaks, time lag between the stimulus and the peaks, velocity of progression of the peristaltic wave) were compared with model outputs, and a similar pattern of response was found. Therefore the model made it possible to relate segment and strip experimental data and to investigate the temporal and quantitative relationship between the contraction of longitudinal and circular layer.

Animals↗