2021 Publication overview with Artinis Near-Infrared Spectroscopy (NIRS) devices
We are proud to share that multiple papers with use of our devices were published in 2021, despite a continued COVID-19 crisis. In total, more than 110 papers in both neuro- and sport science areas were submitted. As near-infrared spectroscopy (NIRS) can be applied in multiple areas to measure brain and / or muscle oxygenation, we divide our publications in different categories. This blogpost gives an overview of papers published in 2021 using Artinis NIRS or fNIRS devices for different application fields / categories, including:
multimodality, and
Additionally, publications per category are highlighted.
Cortical brain research
In 2021, no less than 32 interesting papers were published that investigated cortical activity using Artinis NIRS devices. Our equipment has been used to study cortical hemodynamic activity in a variety of application areas and in a wide range of experimental paradigms.
To illustrate, Li et al. Developed a new motor imagery brain-computer interface (BCI) paradigm based on NIRS signals measured with the Brite, aiming to improve the accuracy of motor imagery classification. NIRS signals were measured with the Brite placed over the hand motor region (i.e., primary motor cortex, premotor cortex and sensorimotor cortex). It was shown that the paradigm is effective to reach high classification accuracy of 89%.
Alternatively, the Brite has been used to study the relationship between prefrontal cortical activation and gait biomechanics by Belluscio et al. They observed increased prefrontal cortex activation and decreased motor performance during the performance of a dual-task consisting of curvilinear walking and a cognitive task. The findings of this study suggested that the neural correlates of executive function and gait control tend to be modified in response to the cognitive resources imposed by the motor task.
Sport Science
The field of Sports & Exercise Science encompasses everything from Exercise Physiology, Biomechanics, to Nutrition and Psychology, with the aim to improve sport performance or general fitness. With NIRS, local muscle oxygenation can be determined non-invasively, which is of growing interest in Sports Science studies. Especially the PortaMon, the gold-standard portable NIRS device for muscle research, has frequently been used by researchers to investigate muscle oxygen parameters. In addition, the OxyMon, PortaLite, and OctaMon or combinations of devices, are being more commonly used in Sports Science studies.
In 2021, 15 studies that were published in the field of Sports & Exercise Science used the PortaMon. These studies were done in a variety of sports. For example, Gajdošík et al. studied the effect of climbing speed on pulmonary oxygen uptake and muscle oxygen saturation (TSI) in the finger flexors by placing the PortaMon on the forearm. Woorons et al. studied the effect of repeated running bouts on muscle oxygenation, with the PortaMon on the vastus lateralis muscle to determine changes in deoxy-hemoglobin and total hemoglobin.
Additionally, 9 studies were published last year using our stationary NIRS system, the OxyMon, which can measure both on muscle and brain. Soo et al. used the OxyMon during cycling to determine the effects of graded hypoxia on exercise performance and neuromuscular function of the knee extensors.
Clinical and Rehabilitation
Using NIRS and fNIRS to measure brain and muscle oxygenation is of great interest in clinical and rehabilitation studies as shown by 29 published papers in 2021. It has been widely used to gain insights into different diseases and health conditions, or to evaluate effectiveness of therapy and treatment solutions.
The PortaLite was used in 11 studies for measuring both brain activity / oxygenation, as well as muscle oxygenation. In a longitudinal study of McDowell et al. the effect of physical activity on cerebral health of elderly subjects with anxiety disorder was investigated using the PortaLite to measure prefrontal brain oxygenation.
In a study of Boutou et al. the effects of oxygen (O2) therapy on muscle hemodynamics and cerebral oxygenation in patients suffering from pulmonary hypertension during exercise were investigated. Therefore, oxygenation was measured simultaneously in the brain with the OxyMon and quadriceps muscle with the PortaMon.
Hypoxia research
Hypoxia is the reduction of normal cellular oxygen levels, which arises when the demands of oxygen exceeds the amount that can be supplied. Over the years, hypoxia became an interest of various fields of research, leading to clinical applications in domains as varied as sleep apnea, COVID-19, high altitude training, exercise science, or even deep diving research.
With the help of NIRS, and more specifically, Artinis NIRS devices, the research in this field increased exponentially, with more than 20 articles published in 2021 compared to 6 in 2020. Both our stationary device (the OxyMon) and our wireless devices (PortaMon, PortaLite, etc.) showed promising results to investigate brain and muscle oxygenation alike.
Rupp et al., for example, successfully ascertained that a certain type of breathing, known as Positive Expiratory Pressure (PEP), could significantly increase cerebral, arterial and muscular oxygenation while trekking at very high altitude. This in turn helped reduce Acute Mountain Sickness symptoms.
Another notable example is the work of Rokkedal-Lausch et al.. Their results showed that optimized beetroot juice supplementation failed to improve oxygen uptake kinetics and exercise efficiency in athletes during moderate exercise. A valuable bit of training knowledge, which nuances the known positive effect beetroot juice has on untrained and moderately trained individuals or exercise at higher intensities.
Multimodality
fNIRS as an optical imaging technique can be combined with other techniques to bring complementary information due to its relatively high spatial resolution. Therefore, with new advances in hardware technology and data analysis, multi-modal measurement has become a promising tool to provide further insights into brain. In 2021, a couple of publications used our fNIRS devices along with EEG, examples as follows:
A study performed by Orcioli-Silva et al. investigated the effect of dopaminergic medication on brain activity of individuals with Parkinson disease (PD). This research group used concurrent EEG and fNIRS and found out that medication increases the PFC activation required for obstacle avoidance during walking and sensorimotor integration is walking. These findings were in line with behavioral measures obtained from gait analysis.
In another study by Rezaee et al., simultaneous EEG-fNIRS was used to verify effects of ctDCS in stroke survivors. GLM data analysis was deployed and showed the association of ctDCS measures with observed changes in EEG and fNIRS. Also, weak participants’ performance in the virtual-reality based training was predicted from GLM results.
Hyperscanning
Many real-life scenarios contain inter-personal interactions, so it’s interesting to investigate whether brain activations of two participants engaged in a task are coordinated/correlated or not.
In a recent publication of Panico et al., fNIRS was used to examine effect of work load on PFC activity of subjects during a working memory (WM) task. In addition, the correlation between examinee and examiner brain activations was investigated. This study showed PFC activity was modulated with workload and was increased when task demands around the spatial WM span. Additionally, it decreased while subject is overloaded or underloaded. Interestingly, findings in the examiners paralleled the ones in the examinees, as examiners' brain activity increased and decreased in a similar way as the examinees' one.