Shining new light on mammalian diving physiology using wearable near-infrared spectroscopy

Investigation of marine mammal dive-by-dive blood distribution and oxygenation has been limited by a lack of non-invasive technology for use in freely diving animals. Here, we developed a non-invasive near-infrared spectroscopy (NIRS) device to measure relative changes in blood volume and haemoglobin oxygenation continuously in the blubber and brain of voluntarily diving harbour seals. Our results show that seals routinely exhibit preparatory peripheral vasoconstriction accompanied by increased cerebral blood volume approximately 15 s before submersion. These anticipatory adjustments confirm that blood redistribution in seals is under some degree of cognitive control that precedes the mammalian dive response. Seals also routinely increase cerebral oxygenation at a consistent time during each dive, despite a lack of access to ambient air. We suggest that this frequent and reproducible reoxygenation pattern, without access to ambient air, is underpinned by previously unrecognised changes in cerebral drainage. The ability to track blood volume and oxygenation in different tissues using NIRS will facilitate a more accurate understanding of physiological plasticity in diving animals in an increasingly disturbed and exploited environment

Diving behaviour and physiology of the Korean Haenyeo

There is a long history of breath-hold diving cultures in East Asia, with references in Japanese chronicles as early as the third century BC. Given evidence of genetic adaptations for phenotypes associated with enhanced diving capacity within such populations1, it is likely they hold the most prodigious human diving abilities — abilities that may be akin to semi-aquatic mammals, and even some marine mammals. Yet, a dearth of fine-scale information exists on the combined natural diving behaviour and physiological responses within these diving populations. One such extraordinary population is the all-female Haenyeo. Here, we assess the fine-scale diving behaviours and physiological responses of these women during natural harvest diving. Our results show that Haenyeo divers demonstrate the highest proportions of time underwater of any humans, also exceeding those of semi-aquatic mammals and being comparable with some marine mammals. Additionally, they do not exhibit an overt cardiovascular depression, or ‘dive response’, classically associated with consummate diving mammals.Peer reviewe

Heart Rate Extraction From Neonatal Near-Infrared Spectroscopy Signals

Near-infrared spectroscopy (NIRS) intensity signals provide useful additional physiological information, of which the most prominent one is the pulsatile fluctuation by heartbeats. This allows for the extraction of heart rate (HR), one of the primary clinical indicators of health in neonates. In this study, we propose a novel algorithm, NIRS HR (NHR), for extracting HR from NIRS signals acquired from neonates admitted to the neonatal intensive care unit (NICU). After parental consent, we synchronously recorded NIRS at 100 Hz and reference HR (RHR) at 1 Hz, from ten newborn infants (gestational age=38 \pm 5 weeks; 3092 ± 990 g). The NHR algorithm consists of two main parts. The first part includes four steps implemented once on the whole NIRS measurement: preprocessing; HR frequency bandwidth determination; interquartile range (IQR) computation; and segmentation. The second part includes three steps implemented on each signal segment: motion artifact detection, signal quality assessment, and HR computation. We compared the NHR algorithm with two existing algorithms. The results showed that the proposed NHR algorithm provides a significantly ( p < 0.05) higher correlation ( r = 99.5%) and lower Bland-Altman ratio (BAR = 3.6%) between the extracted and RHRs, compared to the existing algorithms. Extracting HR from NIRS in a clinical setting of critically ill neonates admitted to neonatal intensive care is feasible. With NIRS and HR combined in a single monitoring system, it is possible to have a perfectly time-synced integrated analysis of cerebral hemodynamics, as well as systemic hemodynamics and autonomic nervous system tone

Estimation of Respiratory Rate from Functional Near-Infrared Spectroscopy (fNIRS): A New Perspective on Respiratory Interference

Objective: Respiration is recognized as a systematic physiological interference in functional near-infrared spectroscopy (fNIRS). However, it remains unanswered as to whether it is possible to estimate the respiratory rate (RR) from such interference. Undoubtedly, RR estimation from fNIRS can provide complementary information that can be used alongside the cerebral activity analysis, e.g., sport studies. Thus, the objective of this paper is to propose a method for RR estimation from fNIRS. Our primary presumption is that changes in the baseline wander of oxygenated hemoglobin concentration (O2Hb) signal are related to RR. Methods: fNIRS and respiratory signals were concurrently collected from subjects during controlled breathing tasks at a constant rate from 0.1 Hz to 0.4 Hz. Firstly, the signal quality index algorithm is employed to select the best O2Hb signal, and then a band-pass filter with cut-off frequencies from 0.05 to 2 Hz is used to remove very low- and high-frequency artifacts. Secondly, troughs of the filtered O2Hb signal are localized for synthesizing the baseline wander (S1) using cubic spline interpolation. Finally, the fast Fourier transform of the S1 signal is computed, and its dominant frequency is considered as RR. In this paper, two different datasets were employed, where the first one was used for the parameter adjustment of the proposed method, and the second one was solely used for testing. Results: The low mean absolute error between the reference and estimated RRs for the first and second datasets (2.6 and 1.3 breaths per minute, respectively) indicates the feasibility of the proposed method for RR estimation from fNIRS. Significance: This paper provides a novel view on the respiration interference as a source of complementary information in fNIRS

Shining new light on sensory brain activation and physiological measurement in seals using wearable optical technology

Sensory ecology and physiology of free-ranging animals is challenging to study but underpins our understanding of decision-making in the wild. Existing non-invasive human biomedical technology offers tools that could be harnessed to address these challenges. Functional near-infrared spectroscopy (fNIRS), a wearable, non-invasive biomedical imaging technique measures oxy- and deoxyhaemoglobin concentration changes that can be used to detect localized neural activation in the brain. We tested the efficacy of fNIRS to detect cortical activation in grey seals (Halichoerus grypus) and identify regions of the cortex associated with different senses (vision, hearing and touch). The activation of specific cerebral areas in seals was detected by fNIRS in responses to light (vision), sound (hearing) and whisker stimulation (touch). Physiological parameters, including heart and breathing rate, were also extracted from the fNIRS signal, which allowed neural and physiological responses to be monitored simultaneously. This is, to our knowledge, the first time fNIRS has been used to detect cortical activation in a non-domesticated or laboratory animal. Because fNIRS is non-invasive and wearable, this study demonstrates its potential as a tool to quantitatively investigate sensory perception and brain function while simultaneously recording heart rate, tissue and arterial oxygen saturation of haemoglobin, perfusion changes and breathing rate in free-ranging animals.This article is part of the theme issue ‘Measuring physiology in free-living animals (Part I)’.</jats:p

Shining new light on mammalian diving physiology using wearable near-infrared spectroscopy

Investigation of marine mammal dive-by-dive blood distribution and oxygenation has been limited by a lack of non-invasive technology for use in freely diving animals. Here, we developed a non-invasive near-infrared spectroscopy (NIRS) device to measure relative changes in blood volume and haemoglobin oxygenation continuously in the blubber and brain of voluntarily diving harbour seals. Our results show that seals routinely exhibit preparatory peripheral vasoconstriction accompanied by increased cerebral blood volume approximately 15 s before submersion. These anticipatory adjustments confirm that blood redistribution in seals is under some degree of cognitive control that precedes the mammalian dive response. Seals also routinely increase cerebral oxygenation at a consistent time during each dive, despite a lack of access to ambient air. We suggest that this frequent and reproducible reoxygenation pattern, without access to ambient air, is underpinned by previously unrecognised changes in cerebral drainage. The ability to track blood volume and oxygenation in different tissues using NIRS will facilitate a more accurate understanding of physiological plasticity in diving animals in an increasingly disturbed and exploited environment

Figures 2 and 3

Ulf 7th March 2017; where R1 is the shortest emitter-receiver channel and R3 is the longes

Figure 6B Ulf

Figure 6B Ul

Metadata

Metadat

Shining new light on sensory brain activation and physiological measurement in seals using wearable optical technology

Folder containing fNIRS data files (.nirs) and a file containing analysis