Electroencephalography and Clinical Neurophysiology, 1985
A new technique for the clustering of EEG wave forms is proposed. This method, termed dynamic tim... more A new technique for the clustering of EEG wave forms is proposed. This method, termed dynamic time-warping (DTW) based clustering, involves the determination of a distance measure by allowing a certain degree of flexibility in the time axes of the two waves to be compared. Sharp waves and spikes, taken from actual EEG data, were subjected to the DTW-clustering approach. The results were compared with an approach based on features extracted from the wave forms and one based on computing the peak-aligned difference between wave forms. It was found that the DTW approach resulted in more homogeneous clusters than the other two approaches. These results, although preliminary, clearly indicate the feasibility of applying this new method for wave form clustering.
Images of the Twenty-First Century. Proceedings of the Annual International Engineering in Medicine and Biology Society
Two knowledge-based approaches for the detection of K-complexes in human sleep EEGs (electroencep... more Two knowledge-based approaches for the detection of K-complexes in human sleep EEGs (electroencephalograms) are compared. In the first approach the waveforms to be recognized are represented in the form of frames that capture the morphological and spatiotemporal characteristics of each object. This system has been equipped with an interface that guides inexperienced users with the definition of the frames and provides output to a signal analysis expert. It allows full flexibility to the user, including the definition of objects to be detected and features to be determined. The second approach is a stand-alone system for the (real-time) analysis of polysomnographic recordings. Data acquisition and preprocessing takes place in real time. In the preprocessing stage, the signal is divided into short, consecutive intervals, and a set of predefined features is extracted from each interval. The features describe so-called pattern candidates relevant to sleep classification. A multilevel approach is followed to weed out the false alarms. The user can modify certain of the thresholds used in the system and has some control over the reasoning strategy followed
International Journal of Bio-Medical Computing, 1993
Body movement related signals (i.e., activity due to postural changes and the ballistocardiac eff... more Body movement related signals (i.e., activity due to postural changes and the ballistocardiac effort) were recorded from six normal volunteers using the static-charge-sensitive bed (SCSB). Visual sleep staging was performed on the basis of simultaneously recorded EEG, EMG and EOG signals. A statistical classification technique was used to determine if reliable sleep staging could be performed using only the SCSB signal. A classification rate of between 52% and 75% was obtained for sleep staging in the five conventional sleep stages and the awake state. These rates improved from 78% to 89% for classification between awake, REM and non-REM sleep and from 86% to 98% for awake versus asleep classification.
1988., IEEE International Symposium on Circuits and Systems
The authors describe a coupled system for knowledge-based signal understanding. This system maint... more The authors describe a coupled system for knowledge-based signal understanding. This system maintains two separate, collaborating knowledge bases, one for the signal analysis knowledge and one for the domain specific knowledge. An object-oriented approach is followed to ease the knowledge representation for both fields of expertise. A vocabulary (or language) is provided to facilitate interaction between the two experts and
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2005
We investigated to what degree the detection rate of the P300 in single trial event-related poten... more We investigated to what degree the detection rate of the P300 in single trial event-related potentials is affected by short-term and long-term habituation effects, and we present an algorithm to eliminate eye-movement artifacts. Data from 26 subjects were collected using a visual oddball paradigm. P300 components were detected using a threshold algorithm operating on the delta band (0-4 Hz). Using data from four subjects, collected over a 7 to 12 week period, it was observed that the P300 amplitude tended to decrease within a session, and also between successive sessions. However, this decrease did not affect the detection rate. The eye-movement removal algorithm was tested on simulated and actual data, and resulted in a significant increase in detection rate.
2005 IEEE Engineering in Medicine and Biology 27th Annual Conference, 2005
The mid-latency auditory evoked response (MLAER) consists of the P50, N100 and P200 components. P... more The mid-latency auditory evoked response (MLAER) consists of the P50, N100 and P200 components. P50 is widely used to examine sensory gating. There is growing evidence that phase-reorganization of the oscillatory components comprising EEG activity, and especially in the 4-8 Hz (theta) band, is responsible for MLAER generation. Consequently, all or part of the MLAER may be an epiphenomenon, indicating intervals of increased phase reorganization. In this study, we investigated the nature of P50. AEPs were obtained from 14 normal subjects using a double stimulus paradigm, and each artifact-free trial was decomposed into its constituent oscillatory components. Single trials were classified into 16 groups on the basis of the presence of N100/P200-like activity and the phase at stimulus onset in the 4-8 Hz band. It was found that P50 consists of low-frequency (theta) and high frequency (gamma) activity. The appearance of P50-related theta activity was closely related to the presence of N100. The P50-related theta activity appeared only when the theta activity goes through a positive zero crossing at the moment of stimulus presentation. Thus it appears that the theta component of the P50 should be considered as an epiphenomenon.
International Journal of Bio-Medical Computing, 1978
This paper presents a method of segmenting the EEG based on the well-known power spectrum analysi... more This paper presents a method of segmenting the EEG based on the well-known power spectrum analysis. This procedure is applied to the EEG recordings of two normal subjects in order to determine the temporal EEG variability. These results are compared with a more classical approach.
Abstract A new approach to obtain evoked potential (EP) estimates is described. EPs are minute vo... more Abstract A new approach to obtain evoked potential (EP) estimates is described. EPs are minute voltage fluctuations in the electrical activity of the brain in response to an external stimulus. EPs are often buried in the spontaneous brain activity and special techniques are required to improve the signal-to-noise ratio. The method presented here uses a dynamic time-warping (DTW) algorithm to maximize the crosscorrelation between a template and the recorded block. The algorithm was evaluated using simulated data consisting of triangular shapes superimposed on white noise and a rhythm resembling alpha activity (8–12 Hz). It was found that warping increased the crosscorrelation between the template and single trial, however, the template occasionally converged to the background noise especially for low signal-to-noise ratios. For SNRs larger than 2, the time-warping approach obtained better latency estimates than the conventional averaging method. Amplitude estimates were consistently inferior for DTW.
Laterality: Asymmetries of Body, Brain and Cognition, 2012
The Halwes Fused Dichotic Words Test was used to divide a sample of university students into a gr... more The Halwes Fused Dichotic Words Test was used to divide a sample of university students into a group having a statistically significant right ear advantage (REA) and a group having either a significant left ear advantage or a non-significant ear asymmetry (NREA). Of these participants, 30 (14 REA, 16 NREA) had electrical potentials measured from temporal, central, and frontal sites as series of brief tones were presented monaurally. No behavioural response was required. Group differences were found in the latency but not the amplitude of the averaged event-related responses. The REA group showed faster conduction to the right hemisphere than to the left hemisphere. In both groups the amplitude of left hemisphere responses was greater for right ear stimulation than for left ear stimulation. The results for amplitude indicate that the crossed auditory pathway is a superior conductor of information to the left hemisphere but not to the right hemisphere. Group differences, however, are related only to the speed with which information reaches the right hemisphere.
The Journal of the Acoustical Society of America, 1989
An operational acoustic signature inspection system for railroad wheels is described. The purpose... more An operational acoustic signature inspection system for railroad wheels is described. The purpose is to inspect the wheels on a train as it goes past an inspection site and analyze the data in real time. The wheels on the train are sensed by magnetic wheel sensors that alert an electromechanical hammer installed on the inside of each rail. The hammers strike the wheels on each axle, and the sound is picked up by a microphone installed in front of each hammer and transmitted to a minicomputer at the remote location via dedicated telephone lines. Studies were performed on data obtained from a test consist, specially assembled for this work, and from revenue service trains. Various features were computed in both time and frequency domains, including the spectral cross correlation, the percentage of common peaks, and a measure based on resonance frequencies, and were analyzed using a pattern recognition package. It was concluded that the use of the package resulted in significant improvement in detection of d...
The Journal of the Acoustical Society of America, 1993
Reinforced concrete beams in practical use always contain cracks. This paper reports a study of t... more Reinforced concrete beams in practical use always contain cracks. This paper reports a study of the changes in decay rates of resonance frequencies when cracks occur in a vibrating concrete beam. The experiments were performed using model reinforced concrete beams with general end conditions as well as ideal pinned–pinned end conditions. The power spectrum and its time variation were studied. The short time Fourier transform (STFT) technique was used. Theoretical studies were made to establish the effects of damping on the vibration of the beam. A complication exists in that the reinforced concrete beam is in effect a composite material. The results will be compared with the data obtained from a steel beam of homogeneous material [J. Robin, Acoust. Soc. Am. 92, 2441 (A) (1992)]. The changed behavior of decay rates of resonance frequencies could be a feature in the vibration monitoring of reinforced concrete structures such as highway bridges. [Work supported by NSF Grant No. MSS‐9024224.]
The Journal of the Acoustical Society of America, 1995
An artificial neural network (ANN) approach was used to characterize vibration data for nondestru... more An artificial neural network (ANN) approach was used to characterize vibration data for nondestructive evaluation purposes. Acoustic signatures were obtained from clamped–clamped metal beams of rectangular cross section. The beams were either intact, or had one (small) slot in them. The digitized data were used to train the ANN to predict future samples of the measured time series given past and present samples. The trained ANNs were used in two ways. In the first method, an ANN was trained with vibration data from intact beams. Once the ANN could adequately predict the training signal, vibration signals obtained from beams with slots were presented. Significant differences between prediction errors for the intact beam and beams with slots as shallow as 0.1 in. were found. Furthermore, the resulting prediction errors gradually increased as the slots in the beams grow deeper, suggesting that this method is useful to estimate defect size. In the second method, the connection weights of the ANNs trained on v...
It was explored if the speed with which an individual learns to deal with new environments and ch... more It was explored if the speed with which an individual learns to deal with new environments and challenges can be predicted on the basis of his/her brain's response to irrelevant (repeating) and novel auditory stimuli. In this study, 26 subjects threw 30 light-weight balls at a target with and without vision-distorting goggles. The horizontal displacement from a bull's-eye target was measured and the rate and degree of adaptation were computed. The adaptation parameters were correlated with evoked and event-related potential (EP/ERP) measures of the subject's ability to suppress irrelevant information and respond to novel stimuli. Only a weak (or a trend to) correlation was found between the behavioral adaptation and some of the EP/ERP measures. The correlations were limited to EP parameters in the 100 to 200 ms post-stimulus range reflecting the ability to suppress irrelevant information. Thus we conclude that the speed with which an individual adapts to a new environment is at best weakly correlated with brain activity associated with stimulus memory and classification.
Electroencephalography and Clinical Neurophysiology, 1985
A new technique for the clustering of EEG wave forms is proposed. This method, termed dynamic tim... more A new technique for the clustering of EEG wave forms is proposed. This method, termed dynamic time-warping (DTW) based clustering, involves the determination of a distance measure by allowing a certain degree of flexibility in the time axes of the two waves to be compared. Sharp waves and spikes, taken from actual EEG data, were subjected to the DTW-clustering approach. The results were compared with an approach based on features extracted from the wave forms and one based on computing the peak-aligned difference between wave forms. It was found that the DTW approach resulted in more homogeneous clusters than the other two approaches. These results, although preliminary, clearly indicate the feasibility of applying this new method for wave form clustering.
Images of the Twenty-First Century. Proceedings of the Annual International Engineering in Medicine and Biology Society
Two knowledge-based approaches for the detection of K-complexes in human sleep EEGs (electroencep... more Two knowledge-based approaches for the detection of K-complexes in human sleep EEGs (electroencephalograms) are compared. In the first approach the waveforms to be recognized are represented in the form of frames that capture the morphological and spatiotemporal characteristics of each object. This system has been equipped with an interface that guides inexperienced users with the definition of the frames and provides output to a signal analysis expert. It allows full flexibility to the user, including the definition of objects to be detected and features to be determined. The second approach is a stand-alone system for the (real-time) analysis of polysomnographic recordings. Data acquisition and preprocessing takes place in real time. In the preprocessing stage, the signal is divided into short, consecutive intervals, and a set of predefined features is extracted from each interval. The features describe so-called pattern candidates relevant to sleep classification. A multilevel approach is followed to weed out the false alarms. The user can modify certain of the thresholds used in the system and has some control over the reasoning strategy followed
International Journal of Bio-Medical Computing, 1993
Body movement related signals (i.e., activity due to postural changes and the ballistocardiac eff... more Body movement related signals (i.e., activity due to postural changes and the ballistocardiac effort) were recorded from six normal volunteers using the static-charge-sensitive bed (SCSB). Visual sleep staging was performed on the basis of simultaneously recorded EEG, EMG and EOG signals. A statistical classification technique was used to determine if reliable sleep staging could be performed using only the SCSB signal. A classification rate of between 52% and 75% was obtained for sleep staging in the five conventional sleep stages and the awake state. These rates improved from 78% to 89% for classification between awake, REM and non-REM sleep and from 86% to 98% for awake versus asleep classification.
1988., IEEE International Symposium on Circuits and Systems
The authors describe a coupled system for knowledge-based signal understanding. This system maint... more The authors describe a coupled system for knowledge-based signal understanding. This system maintains two separate, collaborating knowledge bases, one for the signal analysis knowledge and one for the domain specific knowledge. An object-oriented approach is followed to ease the knowledge representation for both fields of expertise. A vocabulary (or language) is provided to facilitate interaction between the two experts and
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2005
We investigated to what degree the detection rate of the P300 in single trial event-related poten... more We investigated to what degree the detection rate of the P300 in single trial event-related potentials is affected by short-term and long-term habituation effects, and we present an algorithm to eliminate eye-movement artifacts. Data from 26 subjects were collected using a visual oddball paradigm. P300 components were detected using a threshold algorithm operating on the delta band (0-4 Hz). Using data from four subjects, collected over a 7 to 12 week period, it was observed that the P300 amplitude tended to decrease within a session, and also between successive sessions. However, this decrease did not affect the detection rate. The eye-movement removal algorithm was tested on simulated and actual data, and resulted in a significant increase in detection rate.
2005 IEEE Engineering in Medicine and Biology 27th Annual Conference, 2005
The mid-latency auditory evoked response (MLAER) consists of the P50, N100 and P200 components. P... more The mid-latency auditory evoked response (MLAER) consists of the P50, N100 and P200 components. P50 is widely used to examine sensory gating. There is growing evidence that phase-reorganization of the oscillatory components comprising EEG activity, and especially in the 4-8 Hz (theta) band, is responsible for MLAER generation. Consequently, all or part of the MLAER may be an epiphenomenon, indicating intervals of increased phase reorganization. In this study, we investigated the nature of P50. AEPs were obtained from 14 normal subjects using a double stimulus paradigm, and each artifact-free trial was decomposed into its constituent oscillatory components. Single trials were classified into 16 groups on the basis of the presence of N100/P200-like activity and the phase at stimulus onset in the 4-8 Hz band. It was found that P50 consists of low-frequency (theta) and high frequency (gamma) activity. The appearance of P50-related theta activity was closely related to the presence of N100. The P50-related theta activity appeared only when the theta activity goes through a positive zero crossing at the moment of stimulus presentation. Thus it appears that the theta component of the P50 should be considered as an epiphenomenon.
International Journal of Bio-Medical Computing, 1978
This paper presents a method of segmenting the EEG based on the well-known power spectrum analysi... more This paper presents a method of segmenting the EEG based on the well-known power spectrum analysis. This procedure is applied to the EEG recordings of two normal subjects in order to determine the temporal EEG variability. These results are compared with a more classical approach.
Abstract A new approach to obtain evoked potential (EP) estimates is described. EPs are minute vo... more Abstract A new approach to obtain evoked potential (EP) estimates is described. EPs are minute voltage fluctuations in the electrical activity of the brain in response to an external stimulus. EPs are often buried in the spontaneous brain activity and special techniques are required to improve the signal-to-noise ratio. The method presented here uses a dynamic time-warping (DTW) algorithm to maximize the crosscorrelation between a template and the recorded block. The algorithm was evaluated using simulated data consisting of triangular shapes superimposed on white noise and a rhythm resembling alpha activity (8–12 Hz). It was found that warping increased the crosscorrelation between the template and single trial, however, the template occasionally converged to the background noise especially for low signal-to-noise ratios. For SNRs larger than 2, the time-warping approach obtained better latency estimates than the conventional averaging method. Amplitude estimates were consistently inferior for DTW.
Laterality: Asymmetries of Body, Brain and Cognition, 2012
The Halwes Fused Dichotic Words Test was used to divide a sample of university students into a gr... more The Halwes Fused Dichotic Words Test was used to divide a sample of university students into a group having a statistically significant right ear advantage (REA) and a group having either a significant left ear advantage or a non-significant ear asymmetry (NREA). Of these participants, 30 (14 REA, 16 NREA) had electrical potentials measured from temporal, central, and frontal sites as series of brief tones were presented monaurally. No behavioural response was required. Group differences were found in the latency but not the amplitude of the averaged event-related responses. The REA group showed faster conduction to the right hemisphere than to the left hemisphere. In both groups the amplitude of left hemisphere responses was greater for right ear stimulation than for left ear stimulation. The results for amplitude indicate that the crossed auditory pathway is a superior conductor of information to the left hemisphere but not to the right hemisphere. Group differences, however, are related only to the speed with which information reaches the right hemisphere.
The Journal of the Acoustical Society of America, 1989
An operational acoustic signature inspection system for railroad wheels is described. The purpose... more An operational acoustic signature inspection system for railroad wheels is described. The purpose is to inspect the wheels on a train as it goes past an inspection site and analyze the data in real time. The wheels on the train are sensed by magnetic wheel sensors that alert an electromechanical hammer installed on the inside of each rail. The hammers strike the wheels on each axle, and the sound is picked up by a microphone installed in front of each hammer and transmitted to a minicomputer at the remote location via dedicated telephone lines. Studies were performed on data obtained from a test consist, specially assembled for this work, and from revenue service trains. Various features were computed in both time and frequency domains, including the spectral cross correlation, the percentage of common peaks, and a measure based on resonance frequencies, and were analyzed using a pattern recognition package. It was concluded that the use of the package resulted in significant improvement in detection of d...
The Journal of the Acoustical Society of America, 1993
Reinforced concrete beams in practical use always contain cracks. This paper reports a study of t... more Reinforced concrete beams in practical use always contain cracks. This paper reports a study of the changes in decay rates of resonance frequencies when cracks occur in a vibrating concrete beam. The experiments were performed using model reinforced concrete beams with general end conditions as well as ideal pinned–pinned end conditions. The power spectrum and its time variation were studied. The short time Fourier transform (STFT) technique was used. Theoretical studies were made to establish the effects of damping on the vibration of the beam. A complication exists in that the reinforced concrete beam is in effect a composite material. The results will be compared with the data obtained from a steel beam of homogeneous material [J. Robin, Acoust. Soc. Am. 92, 2441 (A) (1992)]. The changed behavior of decay rates of resonance frequencies could be a feature in the vibration monitoring of reinforced concrete structures such as highway bridges. [Work supported by NSF Grant No. MSS‐9024224.]
The Journal of the Acoustical Society of America, 1995
An artificial neural network (ANN) approach was used to characterize vibration data for nondestru... more An artificial neural network (ANN) approach was used to characterize vibration data for nondestructive evaluation purposes. Acoustic signatures were obtained from clamped–clamped metal beams of rectangular cross section. The beams were either intact, or had one (small) slot in them. The digitized data were used to train the ANN to predict future samples of the measured time series given past and present samples. The trained ANNs were used in two ways. In the first method, an ANN was trained with vibration data from intact beams. Once the ANN could adequately predict the training signal, vibration signals obtained from beams with slots were presented. Significant differences between prediction errors for the intact beam and beams with slots as shallow as 0.1 in. were found. Furthermore, the resulting prediction errors gradually increased as the slots in the beams grow deeper, suggesting that this method is useful to estimate defect size. In the second method, the connection weights of the ANNs trained on v...
It was explored if the speed with which an individual learns to deal with new environments and ch... more It was explored if the speed with which an individual learns to deal with new environments and challenges can be predicted on the basis of his/her brain's response to irrelevant (repeating) and novel auditory stimuli. In this study, 26 subjects threw 30 light-weight balls at a target with and without vision-distorting goggles. The horizontal displacement from a bull's-eye target was measured and the rate and degree of adaptation were computed. The adaptation parameters were correlated with evoked and event-related potential (EP/ERP) measures of the subject's ability to suppress irrelevant information and respond to novel stimuli. Only a weak (or a trend to) correlation was found between the behavioral adaptation and some of the EP/ERP measures. The correlations were limited to EP parameters in the 100 to 200 ms post-stimulus range reflecting the ability to suppress irrelevant information. Thus we conclude that the speed with which an individual adapts to a new environment is at best weakly correlated with brain activity associated with stimulus memory and classification.
Uploads
Papers