Deficits in daytime performance due to sleep loss are experienced universally and associated with a significant social, financial, and human cost. Microsleeps, sleep attacks, and lapses in cognition increase with sleep loss as a function of state instability. Sleep deprivation studies repeatedly show a variable (negative) impact on mood, cognitive performance, and motor function due to an increasing sleep propensity and destabilization of the wake state. Specific neurocognitive domains including executive attention, working memory, and divergent higher cognitive functions are particularly vulnerable to sleep loss. In humans, functional metabolic and neurophysiological studies demonstrate that neural systems involved in executive function (i.e., prefrontal cortex) are more susceptible to sleep deprivation in some individuals than others. Recent chronic partial sleep deprivation experiments, which more closely replicate sleep loss in society, demonstrate that profound neurocognitive deficits accumulate over time in the face of subjective adaptation to the sensation of sleepiness. Sleep deprivation associated with disease-related sleep fragmentation (i.e., sleep apnea and restless legs syndrome) also results in neurocognitive performance decrements similar to those seen in sleep restriction studies. Performance deficits associated with sleep disorders are often viewed as a simple function of disease severity; however, recent experiments suggest that individual vulnerability to sleep loss may play a more critical role than previously thought.

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Neurocognitive Consequences of Sleep Deprivation

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

We review the current state-of-the-art of diffuse optical imaging, which is an emerging technique for functional imaging of biological tissue. It involves generating images using measurements of visible or near-infrared light scattered across large (greater than several centimetres) thicknesses of tissue. We discuss recent advances in experimental methods and instrumentation, and examine new theoretical techniques applied to modelling and image reconstruction. We review recent work on in vivo applications including imaging the breast and brain, and examine future challenges.

https://iopscience.iop.org/article/10.1088/0031-9155/50/4/R01/pdf

Recent advances in diffuse optical imaging.

Near-infrared spectroscopy (NIRS) is a noninvasive neuroimaging tool for studying evoked hemodynamic changes within the brain. By this technique, changes in the optical absorption of light are recorded over time and are used to estimate the functionally evoked changes in cerebral oxyhemoglobin and deoxyhemoglobin concentrations that result from local cerebral vascular and oxygen metabolic effects during brain activity. Over the past three decades this technology has continued to grow, and today NIRS studies have found many niche applications in the fields of psychology, physiology, and cerebral pathology. The growing popularity of this technique is in part associated with a lower cost and increased portability of NIRS equipment when compared with other imaging modalities, such as functional magnetic resonance imaging and positron emission tomography. With this increasing number of applications, new techniques for the processing, analysis, and interpretation of NIRS data are continually being developed. We review some of the time-series and functional analysis techniques that are currently used in NIRS studies, we describe the practical implementation of various signal processing techniques for removing physiological, instrumental, and motion-artifact noise from optical data, and we discuss the unique aspects of NIRS analysis in comparison with other brain imaging modalities. These methods are described within the context of the MATLAB-based graphical user interface program, HomER, which we have developed and distributed to facilitate the processing of optical functional brain data.

/pdf/homer-a-review-of-time-series-analysis-methods-for-near-4ln9n7d315.pdf

HomER: a review of time-series analysis methods for near-infrared spectroscopy of the brain.

In the last decade the study of the human brain and muscle energetics underwent a radical change, thanks to the progressive introduction of noninvasive techniques, including near-infrared (NIR) spectroscopy (NIRS). This review summarizes the most recent literature about the principles, techniques, advantages, limitations, and applications of NIRS in exercise physiology and neuroscience. The main NIRS instrumentations and measurable parameters will be reported. NIR light (700-1000 m) penetrates superficial layers (skin, subcutaneous fat, skull, etc.) and is either absorbed by chromophores (oxy- and deoxyhemoglobin and myoglobin) or scattered within the tissue. NIRS is a noninvasive and relatively low-cost optical technique that is becoming a widely used instrument for measuring tissue O2 saturation, changes in hemoglobin volume and, indirectly, brain/muscle blood flow and muscle O2 consumption. Tissue O2 saturation represents a dynamic balance between O2 supply and O2 consumption in the small vessels such as the capillary, arteriolar, and venular bed. The possibility of measuring the cortical activation in response to different stimuli, and the changes in the cortical cytochrome oxidase redox state upon O2 delivery changes, will also be mentioned.

/pdf/principles-techniques-and-limitations-of-near-infrared-1u2ea4e3xb.pdf

Principles, techniques, and limitations of near infrared spectroscopy.

https://www.nmr.mgh.harvard.edu/optics/PDF/Strangman_NeuroImage_17_719_2002.pdf

A quantitative comparison of simultaneous BOLD fMRI and NIRS recordings during functional brain activation.

We have performed a noninvasive bilateral optical imaging study of the hemodynamic evoked response to unilateral finger opposition task, finger tactile, and electrical median nerve stimulation in the human sensorimotor cortex. This optical study shows the hemoglobin-evoked response to voluntary and nonvoluntary stimuli. We performed measurements on 10 healthy volunteers using block paradigms for motor, sensory, and electrical stimulations of the right and left hands separately. We analyzed the spatial/temporal features and the amplitude of the optical signal induced by cerebral activation during these three paradigms. We consistently found an increase (decrease) in the cerebral concentration of oxy-hemoglobin (deoxy-hemoglobin) at the cortical side contralateral to the stimulated side. We observed an optical response to activation that was larger in size and amplitude during voluntary motor task compared to the other two stimulations. The ipsilateral response was consistently smaller than the contralateral response, and even reversed (i.e., a decrease in oxy-hemoglobin, and an increase in deoxy-hemoglobin) in the case of the electrical stimulation. We observed a systemic contribution to the optical signal from the increase in the heart rate increase during stimulation, and we made a first attempt to subtract it from the evoked hemoglobin signal. Our findings based on optical imaging are in agreement with results in the literature obtained with positron emission tomography and functional magnetic resonance imaging.

/pdf/hemodynamic-evoked-response-of-the-sensorimotor-cortex-154rrjek1g.pdf

Hemodynamic evoked response of the sensorimotor cortex measured noninvasively with near-infrared optical imaging

Several neuroimaging studies have demonstrated compensatory cerebral responses consequent to sleep deprivation (SD), but all have focused on simple tasks with limited behavioral response options. We assessed the cerebral effects associated with SD during the performance of a complex, open-ended, dual-joystick, 3D navigation task (simulated orbital docking) in a cross-over protocol, with counterbalanced orders of normal sleep (NS) and a single night of total SD (approximately 27 h). Behavioral performance on multiple measures was comparable in the two sleep conditions. Functional magnetic resonance imaging revealed multiple compensatory SD > NS cerebral responses, including the posterior superior temporal sulcus [Brodmann area (BA) 39/22/37], prefrontal cortex (BA 9), lateral temporal cortex (BA 22/21), and right substantia nigra. Right posterior cingulate cortex (BA 31) exhibited NS > SD activity. Our findings extend the compensatory cerebral response hypothesis to complex, open-ended tasks.

Functional brain imaging of a complex navigation task following one night of total sleep deprivation: a preliminary study.

In this paper we investigate the potential of near-infrared spectroscopy (NIRS) to monitor both the direct effects of neural activation (the so-called fast signal) and the consequent changes in local cerebral hemodynamics. To this end we mapped contra- and ipsi-lateral motor and sensorimotor cortex during hand tapping, hand tactile, and electrical median nerve stimulation.

Looking for the fast signal: Neuronal and hemodynamic evoked responses of the sensory-motor cortex

Study Objectives: To assess the cerebral effects associated with sleep deprivation in a simulation of a complex, real-world, high-risk task Design and Interventions: A two-week, repeated measures, cross-over experimental protocol, with counterbalanced orders of normal sleep (NS) and total sleep deprivation (TSD) Setting: Each subject underwent functional magnetic resonance imaging (fMRI) while performing a dual-joystick, 3D sensorimotor navigation task (simulated orbital docking) Scanning was performed twice per subject, once following a night of normal sleep (NS), and once following a single night of total sleep deprivation (TSD) Five runs (eight 24s docking trials each) were performed during each scanning session Participants: Six healthy, young, right-handed volunteers (2 women; mean age 20) participated Measurements and Results: Behavioral performance on multiple measures was comparable in the two sleep conditions Neuroimaging results within sleep conditions revealed similar locations of peak activity for NS and TSD, including left sensorimotor cortex, left precuneus (BA 7), and right visual areas (BA 18/19) However, cerebral activation following TSD was substantially larger and exhibited higher amplitude modulations from baseline When directly comparing NS and TSD, most regions exhibited TSD>NS activity, including multiple prefrontal cortical areas (BA 8/9,44/45,47), lateral parieto-occipital areas (BA 19/39, 40), superior temporal cortex (BA 22), and bilateral thalamus and amygdala Only left parietal cortex (BA 7) demonstrated NS>TSD activity Conclusions: The large network of cerebral differences between the two conditions, even with comparable behavioral performance, suggests the possibility of detecting TSD-induced stress via functional brain imaging techniques on complex tasks before stress-induced failures

John H. Thompson

Papers

A quantitative comparison of simultaneous BOLD fMRI and NIRS recordings during functional brain activation.

Hemodynamic evoked response of the sensorimotor cortex measured noninvasively with near-infrared optical imaging

Functional brain imaging of a complex navigation task following one night of total sleep deprivation: a preliminary study.

Looking for the fast signal: Neuronal and hemodynamic evoked responses of the sensory-motor cortex

Functional brain imaging of a complex navigation task following one night of total sleep deprivation