A review on continuous wave functional near-infrared spectroscopy and imaging instrumentation and methodology.

Illuminating the developing brain: The past, present and future of functional near infrared spectroscopy

Braincomputer interfaces (BCIs) allow their users to communicate or control external devices using brain signals rather than the brain's normal output pathways of peripheral nerves and muscles. Motivated by the hope of restoring independence to severely disabled individuals and by interest in further extending human control of external systems, researchers from many fields are engaged in this challenging new work. BCI research and development has grown explosively over the past two decades. Efforts have begun recently to provide laboratory-validated BCI systems to severely disabled individuals for real-world applications. In this paper, we discuss the current status and future prospects of BCI technology and its clinical applications. We will define BCI, review the BCI-relevant signals from the human brain, and describe the functional components of BCIs. We will also review current clinical applications of BCI technology and identify potential users and potential applications. Lastly, we will discuss current limitations of BCI technology, impediments to its widespread clinical use, and expectations for the future.

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Clinical Applications of Brain-Computer Interfaces: Current State and Future Prospects

Brain-machine interfaces (BMIs) combine methods, approaches, and concepts derived from neurophysiology, computer science, and engineering in an effort to establish real-time bidirectional links bet...

Brain-Machine Interfaces: From Basic Science to Neuroprostheses and Neurorehabilitation

The combination of reducing birth rate and increasing life expectancy continues to drive the demographic shift toward an aging population. This, in turn, places an ever-increasing burden on healthcare due to the increasing prevalence of patients with chronic illnesses and the reducing income-generating population base needed to sustain them. The need to urgently address this healthcare “time bomb” has accelerated the growth in ubiquitous, pervasive, distributed healthcare technologies. The current move from hospital-centric healthcare toward in-home health assessment is aimed at alleviating the burden on healthcare professionals, the health care system and caregivers. This shift will also further increase the comfort for the patient. Advances in signal acquisition, data storage and communication provide for the collection of reliable and useful in-home physiological data. Artifacts, arising from environmental, experimental and physiological factors, degrade signal quality and render the affected part of the signal useless. The magnitude and frequency of these artifacts significantly increases when data collection is moved from the clinic into the home. Signal processing advances have brought about significant improvement in artifact removal over the past few years. This paper reviews the physiological signals most likely to be recorded in the home, documenting the artifacts which occur most frequently and which have the largest degrading effect. A detailed analysis of current artifact removal techniques will then be presented. An evaluation of the advantages and disadvantages of each of the proposed artifact detection and removal techniques, with particular application to the personal healthcare domain, is provided.

/pdf/artifact-removal-in-physiological-signals-practices-and-2y8osovn8v.pdf

Artifact Removal in Physiological Signals—Practices and Possibilities

This article brings together the various elements that constitute the signal processing challenges presented by a hemodynamics-driven functional near-infrared spectroscopy (fNIRS) based brain-computer interface (BCI). We discuss the use of optically derived measures of cortical hemodynamics as control signals for next generation BCIs. To this end we present a suitable introduction to the underlying measurement principle, we describe appropriate instrumentation and highlight how and where performance improvements can be made to current and future embodiments of such devices. Key design elements of a simple fNIRS-BCI system are highlighted while in the process identifying signal processing problems requiring improved solutions and suggesting methods by which this might be accomplished.

/pdf/hemodynamics-for-brain-computer-interfaces-xi7a09ri43.pdf

Hemodynamics for Brain-Computer Interfaces

A continuous wave near-infrared spectroscopy (NIRS) instrument for brain-computer interface (BCI) applications is presented. In the literature, experiments have been carried out on subjects with such motor degenerative diseases as amyotrophic lateral sclerosis, which have demonstrated the suitability of NIRS to access intentional functional activity, which could be used in a BCI as a communication aid. Specifically, a real-time, multiple channel NIRS tool is needed to realise access to even a few different mental states, for reasonable baud rates. The 12-channel instrument described here has a spatial resolution of 30mm, employing a flexible software demodulation scheme. Temporal resolution of ∼100ms is maintained since typical topographic imaging is not needed, since we are only interested in exploiting the vascular response for BCI control. A simple experiment demonstrates the ability of the system to report on haemodynamics during single trial mental arithmetic tasks. Multiple trial averaging is not required.

/pdf/a-12-channel-real-time-near-infrared-spectroscopy-instrument-2fpdklzg4u.pdf

A 12-Channel, real-time near-infrared spectroscopy instrument for brain-computer interface applications

This paper describes a concept for the extension of constraint-induced movement therapy (CIMT) through the use of feedback of primary motor cortex activity. CIMT requires residual movement to act as a source of feedback to the patient, thus preventing its application to those with no perceptible movement. It is proposed in this paper that it is possible to provide feedback of the motor cortex effort to the patient by measurement with near infrared spectroscopy (NIRS). Significant changes in such effort may be used to drive rehabilitative robotic actuators, for example. This may provide a possible avenue for extending CIMT to patients hitherto excluded as a result of severity of condition. In support of such a paradigm, this paper details the current status of CIMT and related attempts to extend rehabilitation therapy through the application of technology. An introduction to the relevant haemodynamics is given including a description of the basic technology behind a suitable NIRS system. An illustration of the proposed therapy is described using a simple NIRS system driving a robotic arm during simple upper-limb unilateral isometric contraction exercises with healthy subjects.

https://downloads.hindawi.com/journals/cin/2007/051363.pdf

A concept for extending the applicability of constraint-induced movement therapy through motor cortex activity feedback using a neural prosthesis

This article brings together the various elements that constitute the signal processing challenges presented by a hemodynamics-driven functional near-infrared spectroscopy
(fNIRS) based brain-computer interface (BCI). We discuss the use of optically derived measures of cortical hemodynamics as control signals for next generation
BCIs. To this end we present a suitable introduction to the underlying measurement principle, we describe appropriate instrumentation and highlight how and where performance
improvements can be made to current and future embodiments of such devices. Key design elements of a simple fNIRS-BCI system are highlighted while in the process identifying signal processing problems requiring improved solutions and suggesting methods by which this might be accomplished.

Hemodynamics for brain-computer interfaces: optical correlates of control signals

This paper describes a safety assessment study of near-infrared sources used in an optical brain-computer interface (BCI). The measurement elements of an optical BCI consist of sets of optical sources and detectors. Our current system utilises sources which comprise of dual wavelength light emitting diodes (LED) at 760 nm and 880 nm. An optical analysis demonstrated that NIR radiation is a negligible source of heating in this case. LED heat conduction however is a major source of heating, and LEDs, though much safer than laser diodes, have been known to cause burns if improperly used. We describe a procedure by which we measure the heat conduction effect of LEDs. We show that the LED systems used in our current generation BCI produce safe levels of thermal energy and are within published safety levels.

/pdf/optical-safety-assessment-of-a-near-infrared-brain-computer-4o7skuce4j.pdf

C. Soraghan

Papers

Hemodynamics for Brain-Computer Interfaces

A 12-Channel, real-time near-infrared spectroscopy instrument for brain-computer interface applications

A concept for extending the applicability of constraint-induced movement therapy through motor cortex activity feedback using a neural prosthesis

Hemodynamics for brain-computer interfaces: optical correlates of control signals

Optical safety assessment of a near-infrared brain-computer interface