fNIRS-based BCIs: Can we catch up?

Famous physicist Stephen Hawking, sadly departed in 2018, was also affected by ALS. Picture taken from  http://www.nbcnews.com/id/45886738/ns/health-aging/t/stephen-hawking-how-has-he-survived-so-long/#.XZtMCSgzaUk

Famous physicist Stephen Hawking, sadly departed in 2018, was also affected by ALS. Picture taken from http://www.nbcnews.com/id/45886738/ns/health-aging/t/stephen-hawking-how-has-he-survived-so-long/#.XZtMCSgzaUk

Brain-Computer Interfaces (BCIs) are strategies used to establish communication between the brain and hardware without the need for any effectors of the body (e.g.: muscles used for movement). Such interfaces can allow communication with and restoration of motor function of, people with disorders such as Amyotrophic Lateral Sclerosis (ALS), spinal cord injury or Locked-in Syndrome (LIS). As well as to allow better control of prosthetic limbs in patients with such prosthetics.  While the prevalence of ALS may not be particularly high (there is a homogeneous rate across Europe of about 2,2 cases per 100.000 people [1]), the socioeconomic costs associated with it are significant because of its devastatingly debilitating symptoms. With Europe’s aging population the incidents of ALS have been predicted to increase by approximately 69% by 2040 [2], spelling an unprecedented demand for the development of these technologies.

Of the existing non-invasive modalities for imaging the human brain, EEG, MEG, fMRI and fNIRS have all been used in BCI research. Due to its relatively low cost, portability, safety and resilience to electrical noise, the latter has been gaining more and more users ever since its suitability for the purpose was proven [3]. To acquire a readout from the subject’s brain there have been various techniques recruited. Some of the most popular are: (a) Performing mental arithmetic while monitoring the PFC, and, (b) Using motor imagery while monitoring the activity of the motor cortex. These actions can be associated with one answer in a binary paradigm (e.g.: ‘yes’) while relaxation can signify the other (e.g.: ‘no’). A still from a participant undergoing one such experiment is shown below.

An obvious limitation of fNIRS as a tool for BCIs is its poor temporal resolution. Questions which are amenable to a binary answer are not usually very illuminating regarding one’s internal state, meaning that the paradigm needs to move fast if it is to facilitate meaningful communication. Similarly, if a speller is to be used to allow patients to construct sentences, alternative choices will be numerous and long waiting times needed for the haemodynamic response to develop may end up making the process daunting.

Figure was taken from the publication Borgheai et al., 2019. It shows the experimental design used for the selection of one letter in the speller created by the group. By using the matrix design the group severely cut down on the required time to choose one character.

Figure was taken from the publication Borgheai et al., 2019. It shows the experimental design used for the selection of one letter in the speller created by the group. By using the matrix design the group severely cut down on the required time to choose one character.

In recent attempts to cut down on waiting times, Borgheai et al., 2019 [4], came up with an innovative design which makes use of a visual matrix of letters (see Figure below). Participants were asked to do some mental arithmetic task for 6 seconds when the line or column containing their letter of choice was illuminated. Even though the interval between letter choices was set to six seconds in order to increase the accuracy of the classification, authors reported a good accuracy (approximately 75%) using data from only the first two seconds of stimulation.

This study used a BCI system based solely on fNIRS. However, in many recent publications of the field where a hybrid BCI system (combined EEG and fNIRS) was used, there has been an enhanced classification accuracy reported [5]. This is perhaps not so surprising since EEG is a fundamentally different modality with strengths which complement those of fNIRS. In the future, combining these innovations may well provide a cutting edge for communication and rehabilitation strategies aimed at patients who suffer from conditions which impair the motor system.

 

References

1.         Logroscino, G. et al. Incidence of amyotrophic lateral sclerosis in Europe. Journal of Neurology, Neurosurgery and Psychiatry 81, 385–390 (2010).

2.         Arthur, K. C. et al. Projected increase in amyotrophic lateral sclerosis from 2015 to 2040. Nature Communications 7, (2016).

3.         Coyle, S., Ward, T., Markham, C. & McDarby, G. On the suitability of near-infrared (NIR) systems for next-generation brain-computer interfaces. in Physiological Measurement 25, 815–822 (2004).

4.         Borgheai, S. B., Abtahi, M., Mankodiya, K., McLinden, J. & Shahriari, Y. Towards a Single Trial fNIRS-based Brain-Computer Interface for Communication. in International IEEE/EMBS Conference on Neural Engineering, NER 2019-March, 1030–1033 (IEEE Computer Society, 2019).

5.         Fazli, S. et al. Enhanced performance by a hybrid NIRS-EEG brain computer interface. NeuroImage 59, 519–529 (2012).

*Thumbnail picture was taken from https://aboveintelligent.com/brain-computer-interfaces-why-why-now-d02445090509

New Hyperscanning Study on Mother-Child pairs points to maternal stress as undermining factor of brain-to-brain synchrony

Hyperscanning using fNIRS is a technique that is set to revolutionize social neuroscience in humans. The full mobility of new acquisition devices (like NIRSport1 since 2012 and NIRSport2 2018) allows for experiments which are much more ecologically relevant than those conducted in the past, while recording data from multiple participants at the same time facilitates the portrayal of more delicate, and more accurate, neurophysiological phenomena.

 One such study which was recently conducted used mother and child dyads as its participants and measured the brain-to-brain synchrony of these pairs. Specifically, the study asked what the effect of parenting stress (coming from the mother) was, on the ability of the two to entrain to the same brain rhythm [1]. The experiment was conducted on 31 mothers with an average age of 35, and their children, which were a mixture of girls and boys, had an average age of 3.5 years.

The mothers were asked to fill in some questionnaires which allowed the experimenters to get an estimate of the perceived parenting stress that a mother had around parenting. fNIRS was then recorded from the prefrontal cortex of both the mother and the child while the two watched a series of short cartoon movie excerpts.

The group showed a statistically significant correlation between the parenting stress index score of the mother and the brain-to-brain synchrony of mother and child, as that was estimated using a cluster of channels which covered areas including the Inferior frontal Gyrus (IFG), the frontal eye field (FEF) and the dorsolateral PFC. While the findings of the study are not unprecedented, the authors were the first to trace the effects of this stress to specific neurological areas.

Since brain-to-brain synchrony of mother and child is closely tied to the emotional development of the child, this study underlines the importance of good mental health of the parenting mother. The implications of this are profound when we consider that in a lot of developed countries many mothers are forced to return to work, part-time or full-time, within a year of the birth of their baby, in order to support the family.

On the other hand, women who take longer maternity breaks (e.g.: more than 2 years) may have a hard time getting back into employment and climbing the career ladder. This not only increases stress in the life of these mothers but also contributes to the gender pay gap. To talk numbers, in Germany of 2015 only 25% of women with a child of two years of age had returned to full-time or near full-time employment [2]. This figure is up from 15% in 2006 and this is thought to be at least partly due to benefits like the ‘parental allowance’ which is widely accepted to have had a big positive impact on family planning [2]. It is clear however that more needs be done in order to give fathers more paternity leave or encourage them to take it. Equalizing the amount of time that the two parents spend working, as well as the time spent with their child, is bound to reduce stress for all family members.

References

1)      Azhari, A., Leck, W. Q., Gabrieli, G., Bizzego, A., Rigo, P., Setoh, P., … Esposito, G. (2019). Parenting Stress Undermines Mother-Child Brain-to-Brain Synchrony: A Hyperscanning Study. Scientific Reports, 9(1). https://doi.org/10.1038/s41598-019-47810-4

2)      Federal Ministry of Germany for Family Affairs, Senior Citizens, Women and Youth. n.d. "Family Report 2017: Benefits, Effects, Trends." Chapter 4: Equal Sharing of Responsibility for Work and Family Life: Wishful Thinking and Reality. https://www.bmfsfj.de/blob/123200/c5eed9e4f3242f9cfe95ee76ffd90fa6/familienreport-2017-englisch-data.pdf