When the human brain goes diving: using near-infrared spectroscopy to measure cerebral and systemic cardiovascular responses to deep, breath-hold diving in elite freedivers

Thus far, ecophysiology research has predominantly been conducted within controlled laboratory-based environments, owing to a mismatch between the recording technologies available for physiological monitoring in wild animals and the suite of behaviours and environments they need to withstand, without unduly affecting subjects. While it is possible to record some physiological variables for free-living animals using animal-attached logging devices, including inertial-measurement, heart-rate and temperature loggers, the field is still in its infancy. In this opinion piece, we review the most important future research directions for advancing the field of ‘physiologging’ in wild animals, including the technological development that we anticipate will be required, and the fiscal and ethical challenges that must be overcome. Non-invasive, multi-sensor miniature devices are ubiquitous in the world of human health and fitness monitoring, creating invaluable opportunities for animal and human physiologging to drive synergistic advances. We argue that by capitalizing on the research efforts and advancements made in the development of human wearables, it will be possible to design the non-invasive loggers needed by ecophysiologists to collect accurate physiological data from free-ranging animals ethically and with an absolute minimum of impact. In turn, findings have the capacity to foster transformative advances in human health monitoring. Thus, we invite biomedical engineers and researchers to collaborate with the animal-tagging community to drive forward the advancements necessary to realize the full potential of both fields. This article is part of the theme issue ‘Measuring physiology in free-living animals (Part II)’.

Section: Current State Of Physiologgingmentioning

confidence: 99%

Future trends in measuring physiology in free-living animals

Williams

Shipley

Rutz

et al. 2021

“…Measuring heart rate through haemoglobin concentration fluctuations also provides information on cardiac waveform, which can provide information such as proxies for changes in blood pressure and potentially proxies for changes in intracranial pressure dynamics [51]. Further, analysis of both [HbO] and [HbR] cardiac waveforms can be used to calculate percentage arterial blood oxygen saturation [52] as recently employed to estimate SpO 2 in deep freediving humans [53]. Changes in [HbO] and [HbR] also provide measures of relative blood volume and tissue-specific blood oxygenation [21].…”

Section: (E) Physiological Monitoringmentioning

confidence: 99%

“…Appropriate ruggedization/marinization while maintaining optical-integrity and appropriate attachment protocols is, therefore, required to allow fNIRS to be used on wild animals. Initial work on seals [21] and deep-diving humans [53], although restricted to single-channel systems, has shown that this is readily achievable even for extreme environmental conditions.…”

Section: (G) Development Considerations For An Animal-borne Functional Near-infrared Spectroscopy Loggermentioning

confidence: 99%

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

McKnight

Ruesch

Bennett

et al. 2021

Self Cite

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)’.

“…dairy cattle [45,46] and fishes [47,48]). For example, the portable and commercially available near infraRed spectroscopy data logging devices introduced in 2006 were originally designed for measuring muscle oximetry in sports athletes [49], but have now also been used to show anticipatory adjustments of blood flow prior to diving in seals [18,50,51]. A wide range of variables can be measured with current physiologging technologies, which includes heart rate [52][53][54][55][56], brain activity [57,58], tissue oxygenation [50,51], respiratory rhythms [59,60] and body temperature [61,62].…”

Section: Part Ii: the Present State-of-the-artmentioning

confidence: 99%

Introduction to the theme issue: Measuring physiology in free-living animals

Hawkes

Fahlman²,

Sato

2021

By describing where animals go, biologging technologies (i.e. animal attached logging of biological variables with small electronic devices) have been used to document the remarkable athletic feats of wild animals since the 1940s. The rapid development and miniaturization of physiologging (i.e. logging of physiological variables such as heart rate, blood oxygen content, lactate, breathing frequency and tidal volume on devices attached to animals) technologies in recent times (e.g. devices that weigh less than 2 g mass that can measure electrical biopotentials for days to weeks) has provided astonishing insights into the physiology of free-living animals to document how and why wild animals undertake these extreme feats. Now, physiologging, which was traditionally hindered by technological limitations, device size, ethics and logistics, is poised to benefit enormously from the on-going developments in biomedical and sports wearables technologies. Such technologies are already improving animal welfare and yield in agriculture and aquaculture, but may also reveal future pathways for therapeutic interventions in human health by shedding light on the physiological mechanisms with which free-living animals undertake some of the most extreme and impressive performances on earth. This article is part of the theme issue ‘Measuring physiology in free-living animals (Part I)’.