Brain-computer communication based on the dynamics of brain oscillations.

This chapter presents a review of brain-computer communication based on motor imagery and the dynamics of brain oscillations. The concept of motor imagery as experimental strategy and the two different modes of operation a brain-computer interface can have are explained. An EEG based brain switch that can control a FES-induced hand grasp of a tetraplegic and an approach towards an ECoG based brain switch are presented.

Spatiotemporal patterns of beta desynchronization and gamma synchronization in corticographic data during self-paced movement.

OBJECTIVE: To study the spatiotemporal pattern of event-related desynchronization (ERD) and event-related synchronization (ERS) in electrocorticographic (ECoG) data with closely spaced electrodes. METHODS: Four patients with epilepsy performed self-paced hand movements. The ERD/ERS was quantified and displayed in the form of time-frequency maps. RESULTS: In all subjects, a significant beta ERD with embedded gamma ERS was found. CONCLUSIONS: Self-paced movement is accompanied not only by a relatively widespread mu and beta ERD, but also by a more focused gamma ERS in the 60-90 Hz frequency band.

Frequency component selection for an ECoG-based brain-computer interface.

The aim of the present study was to investigate the most significant frequency components in electrocorticogram (ECoG) recordings in order to operate a brain computer interface (BCI). For this purpose the time-frequency ERD/ERS map and the distinction sensitive learning vector quantization (DSLVQ) are applied to ECoG from three subjects, recorded during a self-paced finger movement. The results show that the ERD/ERS pattern found in ECoG generally matches the ERD/ERS pattern found in EEG recordings, but has an increased prevalence of frequency components in the beta range.

Evaluation of an occupational health and safety management system performance measurement tool-II: scoring methods and field study sites.

With the proliferation of occupational health and safety management systems (OHSMSs) in the 1990s, an assessment instrument was developed at the University of Michigan to measure a wide range of OHSMSs. Due to the range of systems it was designed to measure, the instrument is referred to as a universal assessment instrument (UAI). This article is part of a series of UAI-related articles and presents methods used in the UAI's initial field evaluation efforts. The UAI's measurement scale, case study methods, data management methods, and test site selection criteria are presented. Three test sites were selected from a pool of 15 that responded to a study solicitation. The case study methods, measurement scales, and data management system were found to be effective in performing the initial validation efforts. It is concluded that the qualitative methods used were effective in collecting the necessary information to further understand the complex nature of management system measurement. Companion articles address the actual evaluation assessment.

Evaluation of an occupational health and safety management system performance measurement tool-III: measurement of initiation elements.

With the proliferation of occupational health and safety management systems (OHSMS) in the 1990s, an assessment instrument was developed at the University of Michigan to measure a wide range of OHSMSs. Due to the range of systems it was designed to measure, the instrument is referred to as a universal assessment instrument (UAI). Initial evaluation of the instrument's first four sections is reported here. This study shows that the UAI's initiation measurement criteria and measurement scales could make distinctions between the OHS management systems at three test sites. This was particularly evident in the case in an organization in which a standards-based OHSMS was not implemented. In this case the UAI's two measurement scales could distinguish between areas that were being developed (development scale) and areas that were in conformance with the measurement criteria (conformance scale). The score totals were consistent with the qualitative assessment using case study methods during field pilot testing; with the exception of Section 2.0, Employee Participation, in which scoring at one test site was not consistent with case study findings. It is suggested that the variables/measures presented in the UAI's OHSMS initiation organizing category may contain performance measures that may serve as key leading indicators of overall OHS performance.

Visualization of significant ERD/ERS patterns in multichannel EEG and ECoG data.

OBJECTIVES: Analysis of event-related desynchronization (ERD) and event-related synchronization (ERS) often requires the investigation of diverse frequency bands. Such analysis can be difficult, especially when using multichannel data. Therefore, an effective method for the visualization of event-related changes in oscillatory brain activity is required. METHODS: A bootstrap-based method is presented which gives time-frequency maps showing only significant changes of ERD or ERS in predetermined frequency bands. RESULTS: Examples from an electroencephalographic study and an electrocorticographic study are shown. The results demonstrate how easily reactive channels and their spatio-temporal and frequency-specific characteristics can be identified by means of this method. CONCLUSIONS: The proposed method is a simple but effective way to visualize significant ERD/ERS patterns.

Community exposure assessment and intervention effectiveness at Trinity American Corporation, Glenola, North Carolina.

This case study was a critical investigation of the analytical methodology and exposure assessment components of an intervention that led to the closure of a polyurethane foaming plant in Glenola, N.C., where plant neighbors reported a wide range of adverse health effects. Resident complaints and reports of nuisance odors and health effects persisted for many years, coming to a head in late 1995 and early 1996. Central to state and federal agency activities was the determination of the concentrations of air contaminants including toluene diisocyanate (TDI) at the plant fence line to establish an empirical foundation for resident complaints. Well over 2000 air concentration measurements were collected in the 18-month period prior to intervention and plant closure in September 1997. Results showed that flawed methodology, including poor quality assurance and improper interpretation of the data, may have led to improper conclusions and the inappropriate closing of this facility. Agency data did not show that ambient air concentrations of TDI at the plant fence line exceeded any required or recommended concentration limit. Furthermore, the identity and concentration of other air contaminants were not thoroughly investigated. Key lessons learned are that such interventions must be based on well-designed and executed exposure assessments. Resultant risk determinations must be based on sound science and methods.

Electrical stimulation for pressure sore prevention and wound healing.

This paper reviews applications of therapeutic electrical stimulation (ES) specific to wound healing and pressure sore prevention. The application of ES for wound healing has been found to increase the rate of healing by more than 50%. Furthermore, the total number of wounds healed is also increased. However, optimal delivery techniques for ES therapy have not been established to date. A study of stimulation current effects on wound healing in a pig model has shown that direct current (DC) stimulation is most effective in wound area reduction and alternating current (AC) stimulation for wound volume reduction at current densities of 127 microA/cm2 and 1,125 microA/cm2, respectively. Preliminary studies have been carried out at two research centers to assess the role of ES in pressure sore prevention. Surface stimulation studies have shown that ES can produce positive short-term changes in tissue health variables such as regional blood flow and pressure distribution. The use of an implanted stimulation system consisting of intramuscular electrodes with percutaneous leads has been found to produce additional long-term changes. Specifically, gluteal muscle thickness increased by 50% with regular long-term ES application concurrent with a 20% decrease in regional interface pressures and increased tissue oxygen levels. These findings indicate that an implantable ES system may have great potential for pressure sore prevention, particularly for individuals who lack sensation or who are physically unable to perform regular independent pressure relief.

A direct brain interface based on event-related potentials.

Cross-correlation between a trigger-averaged event-related potential (ERP) template and continuous electrocorticogram was used to detect movement-related ERP's. The accuracy of ERP detection for the five best subjects (of 17 studied), had hit percentages >90% and false positive percentages <10%. These cases were considered appropriate for operation of a direct brain interface.

Tomographic reconstruction of tracer gas concentration profiles in a room with the use of a single OP-FTIR and two iterative algorithms: ART and PWLS.

Computed tomographic (CT) reconstructions of air contaminant concentration fields were conducted in a room-sized chamber employing a single open-path Fourier transform infrared (OP-FTIR) instrument and a combination of 52 flat mirrors and 4 retroreflectors. A total of 56 beam path data were repeatedly collected for around 1 hr while maintaining a stable concentration gradient. The plane of the room was divided into 195 pixels (13 x 15) for reconstruction. The algebraic reconstruction technique (ART) failed to reconstruct the original concentration gradient patterns for most cases. These poor results were caused by the "highly underdetermined condition" in which the number of unknown values (156 pixels) exceeds that of known data (56 path integral concentrations) in the experimental setting. A new CT algorithm, called the penalized weighted least-squares (PWLS), was applied to remedy this condition. The peak locations were correctly positioned in the PWLS-CT reconstructions. A notable feature of the PWLS-CT reconstructions was a significant reduction of highly irregular noise peaks found in the ART-CT reconstructions. However, the peak heights were slightly reduced in the PWLS-CT reconstructions due to the nature of the PWLS algorithm. PWLS could converge on the original concentration gradient even when a fairly high error was embedded into some experimentally measured path integral concentrations. It was also found in the simulation tests that the PWLS algorithm was very robust with respect to random errors in the path integral concentrations. This beam geometry and the use of a single OP-FTIR scanning system, in combination with the PWLS algorithm, is a system applicable to both environmental and industrial settings.

National Occupational Health Service policies and programs for workers in small-scale industries in China.

Over the 14 years since economic reform began, and the restructuring of the economy to encourage international trade, a large number of township enterprises have been developed and put into operation in the Peoples Republic of China. From 1978 to 1991, the number of enterprises has increased 11.5 times; the number of employees has increased 2.4 times; the fixed assets have increased 13.7 times; and the value of the total output has increased 22.5 times. In this article, a report is given on a sample survey in 30 counties in 1990, which showed that 82.69% of rural industrial enterprises had at least one type of occupational hazard in their work environments. Workers engaged in at least one type of hazardous working environment accounted for 33.91% of the blue-collar workers. Physical examinations were performed for seven types of occupational diseases: silicosis, coal worker's pneumoconiosis, asbestosis, chronic lead poisoning, benzene analogs poisoning, chronic chromium poisoning, and noise-induced hearing loss. The total detectable rate of the seven types of occupational diseases was 4.4% among those workers. In addition, 11% had illnesses suspected of being (though not proven to be) caused by occupational exposures. Most township enterprises do not provide basic occupational health services. The coverage of five routine occupational health service activities provided for township enterprises were very limited, from 1.4 to 36%.

The NavChair Assistive Wheelchair Navigation System.

The NavChair Assistive Wheelchair Navigation System [19] is being developed to reduce the cognitive and physical requirements of operating a power wheelchair for people with wide ranging impairments that limit their access to powered mobility. The NavChair is based on a commercial wheelchair system with the addition of a DOS-based computer system, ultrasonic sensors, and an interface module interposed between the joystick and power module of the wheelchair. The obstacle avoidance routines used by the NavChair in conjunction with the ultrasonic sensors are modifications of methods originally used in mobile robotics research. The NavChair currently employs three operating modes: general obstacle avoidance, door passage, and automatic wall following. Results from performance testing of these three operating modes demonstrate their functionality. In additional to advancing the technology of smart wheelchairs, the NavChair has application to the development and testing of "shared control" systems where a human and machine share control of a system and the machine can automatically adapt to human behaviors.

Automatic adaptation in the NavChair Assistive Wheelchair Navigation System.

The NavChair Assistive Wheelchair Navigation System [7] is an adaptive shared control system being developed to provide mobility to those individuals who would otherwise find it difficult or impossible to use a power wheelchair due to cognitive, perceptual, or motor impairments. The NavChair provides task-specific navigation assistance to the wheelchair operator in the form of several distinct operating modes, each of which distributes control differently between the wheelchair and the operator. This paper describes the NavChair's mechanism for automatically selecting the most appropriate operating mode based on a combination of the wheelchair's immediate situation and its global location. Results from two experimental evaluations of the adaptation method are presented.

Identification of electrocorticogram patterns as the basis for a direct brain interface.

This study reports on the first step in the development of a direct brain interface based on the identification of event-related potentials (ERPs) from an electrocorticogram obtained from the surface of the cortex. Ten epilepsy surgery patients, undergoing monitoring with subdural electrode strips and grid arrays, participated in this study. Electrocorticograms were continuously recorded while subjects performed multiple repetitions for each of several motor actions. ERP templates were identified from action-triggered electrocorticogram averages using an amplitude criterion. At least one ERP template was identified for all 10 subjects and in 56% of all electrode-recording sets resulting from a subject performing an action. These results were obtained with electrodes placed solely for clinical purposes and not for research needs. Eighty-two percent of the identified ERPs began before the trigger, indicating the presence of premovement ERP components. The regions yielding the highest probability of valid ERP identification were the sensorimotor cortex (precentral and postcentral gyri) and anterior frontal lobe, although a number were recorded from other areas as well. The recording locations for multiple ERPs arising from the performance of a specific action were usually found on close-by electrodes. ERPs associated with different actions were occasionally identified from the same recording site but often had noticeably different characteristics. The results of this study support the use of ERPs recorded from the cortical surface as a basis for a direct brain interface.

Detection of event-related potentials for development of a direct brain interface.

The study presented here is part of an ongoing effort to develop a direct brain interface based on detection of event-related potentials (ERPs). In a study presented in a companion article, averaged ERP templates were identified from electrocorticograms recorded during repetition of voluntary motor actions. Here the authors report on the detection of individual motor ERPs within the electrocorticogram using cross-correlation. An averaged ERP template was created from the first half of each electrocorticogram and then cross-correlated with the continuous electrocorticogram from the second half. Points where the cross-correlation value exceeded an experimentally determined detection threshold were considered to be detection points. A detection point was considered to be a valid "hit" if it occurred between 1 second before and 0.25 second after the recorded time of a voluntary action. The difference between the hit and false-positive percentages (HF-difference) was used as a metric of detection accuracy. HF-differences greater than 90 were found for 5 of 15 subjects, HF-differences greater than 75 were found for 8 of 15 subjects, and HF-differences greater than 50 were found for 12 of 15 subjects. The three other subjects with HF-differences less than 50 had electrode locations not well suited for recording movement-related ERPs. Recordings from sensorimotor and supplementary motor areas produced the highest yield of channels with HF-difference greater than 50; however, a number of channels with good performance were found in other areas as well. The results demonstrate the likely prospect of using ERP detection as the basis of a single-switch direct brain interface and that furthermore, there is a good possibility of obtaining multiple control channels using this approach.

Progress in characterization of pre-implantation factor in embryo cultures and in vivo.

PROBLEM: Pre-implantation factor (PIF), a small, embryo-derived peptide is detected in the maternal serum prior to implantation and is associated with successful pregnancy outcome. However, its identity is not known. METHOD OF STUDY: PIF was isolated from mouse embryo conditioned media and from pregnant porcine sera, using high-performance liquid chromatography (HPLC) followed by mass spectrometry. RESULTS: Conditioned culture media was separated by gel filtration chromatography followed by reversed phase chromatography. At each step, PIF activity was determined by the lymphocyte/platelet binding autorosette assay (LPBA). Mass spectrometry yielded a single peak with a mass of 1300 Da. The peptide is, however, present in very low concentrations (fM), which has so far precluded complete identification. Pregnant porcine sera that exhibit potent PIF activity were deproteinated by acetone and further fractionated by reversed phase HPLC. Active fractions contain peptides of molecular masses 523 and 551 Da. CONCLUSION: PIF, likely to be peptides, represents a novel substance related to pregnancy initiation and maintenance.

Field validation of passive monitors for the determination of employee exposures to methylene chloride in pharmaceutical production facilities.

A series of field evaluations was performed to estimate the overall uncertainty of three manufacturers' passive monitors (Assay Technology Model 541 and 546, 3M Model 3520, and SKC Model 575-001) to determine methylene chloride (MeCl2) concentrations. Area samples were exposed in a pharmaceutical production facility at five MeCl2 air concentrations for both permissible exposure limit (PEL) and short-term exposure limit (STEL) periods. A specially designed evaluation chamber was used to concurrently expose six of each type of passive monitor while concurrently collecting six active samples from locations surrounding the dosimeter array. The active samples were used to estimate the actual concentration during the evaluation period. The precision, bias, and overall uncertainty were estimated for each monitor type at concentrations bracketing the Occupational Safety and Health Administration proposed exposure limits. The actual MeCl2 concentrations for the PEL sampling periods ranged from 0.9 to 63 ppm. The pooled overall uncertainty results for all the passive monitors evaluated under PEL sampling conditions met the NIOSH accuracy recommendations. Pooled overall uncertainty for PEL evaluations for the monitors were: Assay Technology Model 546 +/- 17%; 3M +/- 13%; and SKC +/- 17%. Actual MeCl2 concentrations for the STEL sampling periods ranged from 14 to 357 ppm. Pooled overall uncertainty results for Assay Technology and 3M monitors evaluated under STEL sampling conditions met the NIOSH accuracy recommendations; however, the SKC passive monitor was slightly greater than the NIOSH recommendation. Pooled overall uncertainty for STEL evaluations for the monitors were: Assay Technology Model 541 +/- 18%; 3M +/- 16%; and SKC +/- 27%.

Analysis of third-party certification approaches using an occupational health and safety conformity-assessment model.

The occupational health and safety conformity-assessment model presented in this article was developed (1) to analyze 22 public and private programs to determine the extent to which these programs use third parties in conformity-assessment determinations, and (2) to establish a framework to guide future policy developments related to the use of third parties in occupational health and safety conformity-assessment activities. The units of analysis for this study included select Occupational Safety and Health Administration programs and standards, International Organization for Standardization-based standards and guidelines, and standards and guidelines developed by nongovernmental bodies. The model is based on a 15-cell matrix that categorizes first-, second-, and third-party activities in terms of assessment, accreditation, and accreditation-recognition activities. The third-party component of the model has three categories: industrial hygiene/safety testing and sampling; product, equipment, and laboratory certification; and, occupational health and safety management system registration/certification. Using the model, 16 of the 22 programs were found to have a third-party component in their conformity-assessment structure. The analysis revealed that (1) the model provides a useful means to describe and analyze various third-party approaches, (2) the model needs modification to capture aspects of traditional governmental conformity-assessment/enforcement activities, and (3) several existing third-party conformity-assessment systems offer robust models that can guide future third-party policy formulation and implementation activities.

Comparison of AIHA ISO 9001-based occupational health and safety management system guidance document with a manufacturer's occupational health and safety assessment instrument.

Numerous manufacturing and service organizations have integrated or are considering integration of their respective occupational health and safety management and audit systems into the International Organization for Standardization-based (ISO) audit-driven Quality Management Systems (ISO 9000) or Environmental Management Systems (ISO 14000) models. Companies considering one of these options will likely need to identify and evaluate several key factors before embarking on such efforts. The purpose of this article is to identify and address the key factors through a case study approach. Qualitative and quantitative comparisons of the key features of the American Industrial Hygiene Association ISO-9001 harmonized Occupational Health and Safety Management System with The Goodyear Tire & Rubber Co. management and audit system were conducted. The comparisons showed that the two management systems and their respective audit protocols, although structured differently, were not substantially statistically dissimilar in content. The authors recommend that future studies continue to evaluate the advantages and disadvantages of various audit protocols. Ideally, these studies would identify those audit outcome measures that can be reliably correlated with health and safety performance.

Activity-based cost management. Part II: Applied to a respiratory protection program.

To demonstrate the relevance of activity-based cost management (ABCM) for the occupational and environmental health community, the investigators used data generated by an ABCM model of a respiratory protection program (RPP) to develop options for solving a business problem. The RPP manager in this hypothetical but realistic business scenario is faced with a 25% budget cut and a 10% increase in demand for RPP services. The manager's dilemma is to maintain the integrity of the RPP while absorbing a significant budget cut. Various cost savings options are developed, and the assumptions under which these options operate are presented. It is emphasized that the RPP manager's primary responsibility is to assure worker health and safety by first understanding the technical issues, merits, and implications of any cost-cutting option that may be considered. It is argued that only then should the manager consider the financial merits of the possible solutions to this business problem. In this way worker health and safety, and environmental protection goals, can continue to be achieved in an economic climate of cost cutting and downsizing.