1,721,084 research outputs found
Education for biomedical engineering professionals - crossing boundaries between disciplines II
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Assessing cardiovascular control by modelling methods for clinical and physiological research
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Improving the assessment of dynamic cerebral autoregulation from spontaneously varying signals
No full textEEG and cerebral blood flow in newborns during quiet sleep
No full textCerebral blood flow (CBF) alterations in the newborns (NB) can lead to brain damage by adecrease in the supply of oxygen and glucose. Aiming at contributing to an understanding of themechanisms involved, the association between the EEG (right front-temporal derivation) and Dopplervelocimetry of the middle cerebral artery from term NB has been investigated. These signals weresimultaneously collected from 20 NB and then epochs during quiet sleep (Tracé Alternant, TA, andHigh Voltage Slow, HVS) were selected. EEG power in theta band (Pthet, 4-8 Hz), was estimated eachsecond. For CBF, obtained from velocimetry, the average velocity (V) was extracted for each heartcycle. To investigate the association in the time (cross correlation function - CCF) and frequencydomains (magnitude square coherence - MSC) signal processing techniques were developed that candeal with interruptions in the data (missing samples). During TA, the CCF between Pthet and V resulted in a maximum value around -5 s (Pthet leading V) in 85% of the NBs with p? 0.05(significance was tested by Monte Carlo simulations). The maximum of the MSC occurred around 0.10Hz in 92 % of the NB (p? 0.05). These findings indicate association between the neuronal activity and CBF during TA. The high coherence could be interpreted as TA
Individual frequency profile of photic driving in children and adolescents
No full textIn 15 normal subjects, individual "profiles" of the driving reaction to intermittent photic stimulation were calculated in 15 leads, by combining EEG amplitude spectra at 11 fixed frequencies (3-24 Hz), and their higher harmonics. This was compared to the resting EEG spectrum by Pearson's correlation (R). Driving was found in 70-100% of cases in the occipital and in 30-80% in central areas, when using as criterion peak amplitudes 20%
larger than those of the neighbours, with strongest responses in the alpha band, and a secondary maximum in the theta range. In the resting EEG, no theta maxima were observed. Theta maxima in profile negatively correlated with Rs between profile and resting EEG spectra. Profiles in the second and third harmonics were highly correlated with that in fundamental, when considering the corresponding frequencies of evoked EEG activity. The frequencies of the peaks in the three profiles were close to the individual's alpha rhythm, and peak amplitudes were comparable. The profile amplitudes,
and their Rs calculated against occipital profiles, decreased towards the fi'ontal
region, where the maxima in theta and alpha bands were similar. There was high interhemisphric correlation between profiles
Validating a volterra model of the fast extensor tibia motor neuron in the locusts hind leg reflex control loop using physiological input signals
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