Abascal, F. J., Mejuto, J., Quintans, M., and Ramos-Cartelle, A. 2010. Horizontal and vertical mo... more Abascal, F. J., Mejuto, J., Quintans, M., and Ramos-Cartelle, A. 2010. Horizontal and vertical movements of swordfish in the Southeast Pacific. – ICES Journal of Marine Science, 67: 466–474. In all, 21 swordfish (Xiphias gladius) were tagged with pop-up archival satellite tags in the Southeast Pacific. Despite problems of premature release, the information obtained provided insight into the horizontal and vertical behaviour of the species in the area. A consistent migratory pattern was observed, fish moving northwest by autumn and presumably returning south by early spring. Swordfish typically forage in deep water during the day and stay in the mixed layer at night, although this behaviour is occasionally modified. The maximum depth recorded was 1136 m, and dives deeper than 900 m were found in five of the six tags analysed. There was a significant positive relationship between average depth by night and visible moon fraction.
ABSTRACT Management measures for South African line-caught fish include output controls such as c... more ABSTRACT Management measures for South African line-caught fish include output controls such as closed seasons, bag and size limits and no-take moratoria. The main condition for these measures to be effective is that undesirable catches can be successfully released. However, most of the line-caught fish species are susceptible to barotrauma, a condition caused in physoclists by the rapid reduction of hydrostatic pressure during the ascent to the surface during capture. We investigated the effects of barotrauma on five commercially important species: roman Chrysoblephus laticeps, silver kob Argyrosomus inodorus, hottentot Pachymetopon blochii, santer Cheimerius nufar and carpenter Argyrozona argyrozona. A classification of the external signs of barotrauma was developed and internal and external signs of barotrauma were examined in relation to fishing depth and fish size, and compared between species. Immediate post-release mortality was investigated during a catch-and-release experiment. Medium-term survival of C. laticeps (~1 d) was examined by returning fish to depth in cages and subsequent monitoring on SCUBA. Our results indicate that most of the fish experience barotrauma even when caught at relatively shallow depths. External signs include extension of the inflated, everted stomach through the mouth, distended eyes, protrusion of the hind-gut and other organs through the cloaca, and gas bubbles in the dermal tissue between the fin rays. The absence of any obvious external signs of barotrauma can be misleading as dissections of such fish revealed ruptures of the swimbladder and other internal injuries consistent with barotrauma. Our results indicate that there might be significant post-release mortality, a factor that needs to be taken into account during stock assessment predictions and during the implementation of catch restrictions.
The aim of this paper is to develop a new algorithm to enhance the performance of EEG-based brain... more The aim of this paper is to develop a new algorithm to enhance the performance of EEG-based brain-computer interface (BCI). We improved our time-frequency approach of classification of motor imagery (MI) tasks for BCI applications. The approach consists of Laplacian filtering, band-pass filtering and classification by correlation of time-frequency-spatial patterns. Through off-line analysis of data collected during a "cursor control" experiment, we evaluated the capability of our new method to reveal major features of the EEG control for enhancement of MI classification accuracy. The pilot results in a human subject are promising, with an accuracy rate of 96.1%.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2011
Electroencephalogram (EEG) is an important component of the pre-surgical evaluation in the treatm... more Electroencephalogram (EEG) is an important component of the pre-surgical evaluation in the treatment of medically intractable epilepsy. However, clinical EEG uses 19 to 32 electrodes that significantly limits its localization ability. Recent development of dense-array recording techniques has suggested that increased spatial sampling rate improves the accuracy of source localization. In the current study, we proposed a 76-channel EEG system for the long-term monitoring of epilepsy patients, and proposed a dynamic seizure imaging (DSI) technique to image the ictal rhythmic activity that may evolve through time, space and frequency. We tested the system in a cohort of 8 patients and our results show that the DSI estimated the seizure activity in good correlation with intracranial recordings, successful surgery outcomes and other clinical evidence. The proposed dense-array recording and DSI imaging approach enable a non-invasive but quantitative imaging of continuous seizure activity. ...
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2009
In the present study, we utilize methods from graph theory to analyze epileptogenic network prope... more In the present study, we utilize methods from graph theory to analyze epileptogenic network properties during periods of ictal activity. Using these methods, we analyzed the DTF-based causal information flow in nine seizures recorded from two patients undergoing presurgical monitoring for the treatment of medically intractable epilepsy. From the results, we observed a high degree of correlation between the regions with a high amount of information outflow (termed the outdegree) and the cortical areas identified clinically as the generators of the ictal activity. We furthermore observe a frequency-dependent correlation between the co-localization of these "activated regions" and the clinical foci. These findings suggest that application of network analysis tools to ictal activity could provide clinically useful information concerning these epileptogenic networks.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2007
This paper proposes the application of the directed transfer function (DTF) to a set of time-vary... more This paper proposes the application of the directed transfer function (DTF) to a set of time-varying coefficients obtained through the use of a multivariate adaptive autoregressive (MVAAR) model. We define this time-varying measure of causality as the adaptive directed transfer function (ADTF) and compare its ability to discern changes in the causal interaction pattern as compared with the conventional DTF. To accomplish this task, two multivariate models with predefined interaction patterns were created in which the causal interaction between the nodes was altered during the course of the time series. In both models, the ADTF has the capability to discern the dynamic changes in the primary source of the information outflow. The results obtained by using the ADTF were subsequently compared to those calculated through use of the conventional DTF method and the present simulation result suggests that use of the ADTF could provide useful information regarding dynamic causality.
Advances in neuroelectric recordings and computational tools allow investigation of interactive b... more Advances in neuroelectric recordings and computational tools allow investigation of interactive brain activity and connectivity in a group of subjects engaged in social interactions.
Abascal, F. J., Mejuto, J., Quintans, M., and Ramos-Cartelle, A. 2010. Horizontal and vertical mo... more Abascal, F. J., Mejuto, J., Quintans, M., and Ramos-Cartelle, A. 2010. Horizontal and vertical movements of swordfish in the Southeast Pacific. – ICES Journal of Marine Science, 67: 466–474. In all, 21 swordfish (Xiphias gladius) were tagged with pop-up archival satellite tags in the Southeast Pacific. Despite problems of premature release, the information obtained provided insight into the horizontal and vertical behaviour of the species in the area. A consistent migratory pattern was observed, fish moving northwest by autumn and presumably returning south by early spring. Swordfish typically forage in deep water during the day and stay in the mixed layer at night, although this behaviour is occasionally modified. The maximum depth recorded was 1136 m, and dives deeper than 900 m were found in five of the six tags analysed. There was a significant positive relationship between average depth by night and visible moon fraction.
ABSTRACT Management measures for South African line-caught fish include output controls such as c... more ABSTRACT Management measures for South African line-caught fish include output controls such as closed seasons, bag and size limits and no-take moratoria. The main condition for these measures to be effective is that undesirable catches can be successfully released. However, most of the line-caught fish species are susceptible to barotrauma, a condition caused in physoclists by the rapid reduction of hydrostatic pressure during the ascent to the surface during capture. We investigated the effects of barotrauma on five commercially important species: roman Chrysoblephus laticeps, silver kob Argyrosomus inodorus, hottentot Pachymetopon blochii, santer Cheimerius nufar and carpenter Argyrozona argyrozona. A classification of the external signs of barotrauma was developed and internal and external signs of barotrauma were examined in relation to fishing depth and fish size, and compared between species. Immediate post-release mortality was investigated during a catch-and-release experiment. Medium-term survival of C. laticeps (~1 d) was examined by returning fish to depth in cages and subsequent monitoring on SCUBA. Our results indicate that most of the fish experience barotrauma even when caught at relatively shallow depths. External signs include extension of the inflated, everted stomach through the mouth, distended eyes, protrusion of the hind-gut and other organs through the cloaca, and gas bubbles in the dermal tissue between the fin rays. The absence of any obvious external signs of barotrauma can be misleading as dissections of such fish revealed ruptures of the swimbladder and other internal injuries consistent with barotrauma. Our results indicate that there might be significant post-release mortality, a factor that needs to be taken into account during stock assessment predictions and during the implementation of catch restrictions.
The aim of this paper is to develop a new algorithm to enhance the performance of EEG-based brain... more The aim of this paper is to develop a new algorithm to enhance the performance of EEG-based brain-computer interface (BCI). We improved our time-frequency approach of classification of motor imagery (MI) tasks for BCI applications. The approach consists of Laplacian filtering, band-pass filtering and classification by correlation of time-frequency-spatial patterns. Through off-line analysis of data collected during a "cursor control" experiment, we evaluated the capability of our new method to reveal major features of the EEG control for enhancement of MI classification accuracy. The pilot results in a human subject are promising, with an accuracy rate of 96.1%.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2011
Electroencephalogram (EEG) is an important component of the pre-surgical evaluation in the treatm... more Electroencephalogram (EEG) is an important component of the pre-surgical evaluation in the treatment of medically intractable epilepsy. However, clinical EEG uses 19 to 32 electrodes that significantly limits its localization ability. Recent development of dense-array recording techniques has suggested that increased spatial sampling rate improves the accuracy of source localization. In the current study, we proposed a 76-channel EEG system for the long-term monitoring of epilepsy patients, and proposed a dynamic seizure imaging (DSI) technique to image the ictal rhythmic activity that may evolve through time, space and frequency. We tested the system in a cohort of 8 patients and our results show that the DSI estimated the seizure activity in good correlation with intracranial recordings, successful surgery outcomes and other clinical evidence. The proposed dense-array recording and DSI imaging approach enable a non-invasive but quantitative imaging of continuous seizure activity. ...
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2009
In the present study, we utilize methods from graph theory to analyze epileptogenic network prope... more In the present study, we utilize methods from graph theory to analyze epileptogenic network properties during periods of ictal activity. Using these methods, we analyzed the DTF-based causal information flow in nine seizures recorded from two patients undergoing presurgical monitoring for the treatment of medically intractable epilepsy. From the results, we observed a high degree of correlation between the regions with a high amount of information outflow (termed the outdegree) and the cortical areas identified clinically as the generators of the ictal activity. We furthermore observe a frequency-dependent correlation between the co-localization of these "activated regions" and the clinical foci. These findings suggest that application of network analysis tools to ictal activity could provide clinically useful information concerning these epileptogenic networks.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2007
This paper proposes the application of the directed transfer function (DTF) to a set of time-vary... more This paper proposes the application of the directed transfer function (DTF) to a set of time-varying coefficients obtained through the use of a multivariate adaptive autoregressive (MVAAR) model. We define this time-varying measure of causality as the adaptive directed transfer function (ADTF) and compare its ability to discern changes in the causal interaction pattern as compared with the conventional DTF. To accomplish this task, two multivariate models with predefined interaction patterns were created in which the causal interaction between the nodes was altered during the course of the time series. In both models, the ADTF has the capability to discern the dynamic changes in the primary source of the information outflow. The results obtained by using the ADTF were subsequently compared to those calculated through use of the conventional DTF method and the present simulation result suggests that use of the ADTF could provide useful information regarding dynamic causality.
Advances in neuroelectric recordings and computational tools allow investigation of interactive b... more Advances in neuroelectric recordings and computational tools allow investigation of interactive brain activity and connectivity in a group of subjects engaged in social interactions.
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