Physiological signal processing

Abstract not available

A simple, low-cost demonstration of wavelength division multiplexing

Optics and photonics can be used to motivate students in physics courses at the high school, college, or university level. Many fundamental ideas and concepts can be taught by exploring wavelength division multiplexing as used in optical fiber communication systems. We describe a safe, simple, low-cost experimental apparatus that can be used to demonstrate the key concepts of wavelength division multiplexing. The apparatus can form the basis of several hands-on, active-learning activitie

Robust chaos in a model of the electroencephalogram: implications for brain dynamics

Various techniques designed to extract nonlinear characteristics from experimental time series have provided no clear evidence as to whether the electroencephalogram (EEG) is chaotic. Compounding the lack of firm experimental evidence is the paucity of physiologically plausible theories of EEG that are capable of supporting nonlinear and chaotic dynamics. Here we provide evidence for the existence of chaotic dynamics in a neurophysiologically plausible continuum theory of electrocortical activity and show that the set of parameter values supporting chaos within parameter space has positive measure and exhibits fat fractal scaling

Is collecting anonymous but code-identified intervention assessment data worth the effort? Reflections on a recent study in electronics

Often the effectiveness of an educational intervention for a large lecture group is assessed by testing the cohort before and after the intervention and measuring any improvement in the aggregated data from pre- to post-testing. A limitation of this method is that not all students may attend the pre-test, post-test or the lectures where the intervention is administered, diluting the significance of the results. An alternative approach is for students to use a unique but anonymous research code that allows researchers to 'tag' each individual student and hence identify those students who participate in all intervention activities and tests ('complete responders'). This paper argues that tagged data can increase the statistical significance of an intervention hypothesis when compared to untagged data even when the statistical sample is small. In a recent study that tested the efficacy of interactive lecture demonstrations (ILDs) in improving students' conceptual understanding for an advanced topic in electronics (AC resonance), the 'complete responders' formed a relatively small subgroup (N=21) of the full group (N=86) that participated in all or only some of the activities or tests ('all responders'). The learning gains for the 'complete responders' were more significant than those of 'all responders'. The reasons for the increased significance are discussed in this paper

P3 latency jitter assessed using 2 techniques I : simulated data and surface recordings in normal subjects

Latency variability measurement using cross-correlational techniques has the drawback of alignment to background noise not related to ERP activity. We compared latency jitter estimation in simulated and real P3 recordings using Woody's algorithm and a non-cross-correlational technique, the maximum likelihood technique (MLT). Simulated ERPs (with introduced latency jitter) were generated using either a 1/2 cycle 2 Hz sine wave or an averaged P3 ERP with 1 of 3 added noise types in 5 signal to noise ratios (SNRs): (i) white noise; (ii) a 10 Hz sine wave; (iii) a 7.5 Hz sine wave. Jitter measurement accuracy was assessed using mean square error (MSE) for 1 iteration of the Woody method and each of 4 iterations of the MLT. Lowest MSEs occurred for higher SNRs and 1 iteration of the MLT. The MLT; and Woody method were applied to P3 ERPs of 13 subjects with SNRs greater than 0.4. P3 latency jitter was significantly lower for the MLT. Latency jitter (both methods) did not differ between homologous electrodes and was highest in posterior electrodes. In the latency corrected ERP data of subjects with persistent alpha activity periodic components occurred in the Woody corrected average (not seen:in the conventional or the MLT corrected averages). Our data indicate that the MLT is the more accurate method for determining latency jitter

Real-time recording of neuropsychophysiological parameters during 50 Hz magnetic field exposure

In order to assess the possible effects of occupational levels of 50 Hz magnetic fields (MF) on human performance it is preferable to monitor performance during rather than subsequent to MF exposure. We previously reported studies of heart rate and cognitive behaviour where the issue of contamination was not a serious one. Our present study involves electrophysiological measures, which have a greater capacity to identify the effects and assist in localising them. The contamination of EEG signal by the MF exposure is clearly a problem in this type of study. Previous investigators have not reported these types of measurement concurrent with MF exposure due to the contamination difficulty; but this paper reports means of accomplishing this. Overall a combination of 12 methods for reducing pickup were employed. These were: 1) Distancing recording instruments from the MF source; 2) Shielding the devices and wiring; 3) Appropriate choice of cables; 4) Grounding the instrumentation; 5) Orientation of conduits; 6) Isolation of electrical mains power supplies; 7) Balancing the input impedances; 8) Applying a driven shield technique; 9) Improved electronics design incorporating pre-amplification and circuit impedance level control; 10) Analogue filtering; 11) Signal Averaging; and 12) Post acquisition digital filtering using frequency and time domain techniques

Real-time recording of neuropsychophysiological parameters during ELF MF exposure

Abstract not available

A continuum theory of electrocortical activity

A set of non-linear continuum field equations are presented which describe the macroscopic dynamics of neural activity in cortex. Numerical solutions of the coupled non-linear system of partial differential equations show properties analogous to cortical evoked potentials, oscillations at the frequency of the mammalian alpha rhythm and non-stationary epileptic spikes

A continuum theory of electro-cortical activity,”Neurocomputing,

Abstract A set of non-linear continuum field equations are presented which describe the macroscopic dynamics of neural activity in cortex. Numerical solutions of the coupled non-linear system of partial differential equations show properties analogous to cortical evoked potentials, oscillations at the frequency of the mammalian alpha rhythm and non-stationary epileptic spikes