34
M. Mukunda Rao
More than 85 years ago in 1927, Hans Berger (1873–1941), a German doctor and
scientist has succeeded in recording Electro-Encephalo-Gram (EEG)—the pattern
of minute changes in the electrical potential of the scalp of a human subject (his
own son!). He then hoped that it might be possible to establish a definite relationship between these potentials and the performance of the brain. Subsequent studies
showed that the EEG reflects only general functional states of the brain, such as
different states of wakefulness and sleep or metabolic disturbances, which, however,
only emphasizes the importance of EEG as a Non-Invasive Diagnostic Tool in gathering wealth of neurological information on brain-related disorders like: epilepsy,
early detection and localization of brain tumours, coma assessment in intensive care
units (ICU) and in the definition/assessment of sleep stages/disorders. [1]. In recent
decades, the advent of computers and signal processing techniques has enhanced the
capabilities of the present-day EEG machines which have emerged as a relatively
low-cost non-invasive diagnostic tool for neurological disorders. Consequently, they
are still in use worldwide both for diagnostics as well as for research.
In recent decades, medical technology has made breath-taking advances. Optical
sensors are increasingly being used for non-invasive diagnostics in biomedical applications. However, there is far very scanty information in the literature about their
possible application for investigating brain-related events. This could possibly due to
the fact that brain is optically opaque due to the surrounding skull and hair. However
at the temples, the tissue is relatively soft and by positioning the optical sensors at this
point, one can monitor the transcutaneous blood volumetric changes which are related
to the brain activity. Among the biomedical optical sensors, photoplethysmography
(PPG) has a unique position. They operate in the near infrared region (around 940 nm)
where the skin is relatively transparent and thereby could register the blood volume
changes in the near skin microcirculatory blood vessels [2]. Using the PPG realtime detection of brain events have been reported and the left & right brain activities
could be monitored thus opening the possibility of studying the brain asymmetry [3].
From the real-time data it is possible to obtain the frequency related information by
using the Fast Fourier Transform (FFT) techniques. Thus, it is possible to extract the
breathing-related information from the PPG signals. Further studies in this direction
have led to the understanding of the influence of breathing on brain using these PPG
sensors in conjunction with breathing sensors [4]. This has opened the gates for the
scientific studies of classical Indian breathing techniques called Pranayama. These
studies have revealed that deep breathing techniques like Pranayama caused what
might enhance the coupling and operation between the heart and the lungs which
might lead to an optimization of exchange of gases which is vital significance. In the
process, the emergence of the low-frequency rhythms in the range of 0.12–0.15 Hz
has been observed which are known to be linked to the relaxation of the human
body [5].
M. Mukunda Rao
More than 85 years ago in 1927, Hans Berger (1873–1941), a German doctor and
scientist has succeeded in recording Electro-Encephalo-Gram (EEG)—the pattern
of minute changes in the electrical potential of the scalp of a human subject (his
own son!). He then hoped that it might be possible to establish a definite relationship between these potentials and the performance of the brain. Subsequent studies
showed that the EEG reflects only general functional states of the brain, such as
different states of wakefulness and sleep or metabolic disturbances, which, however,
only emphasizes the importance of EEG as a Non-Invasive Diagnostic Tool in gathering wealth of neurological information on brain-related disorders like: epilepsy,
early detection and localization of brain tumours, coma assessment in intensive care
units (ICU) and in the definition/assessment of sleep stages/disorders. [1]. In recent
decades, the advent of computers and signal processing techniques has enhanced the
capabilities of the present-day EEG machines which have emerged as a relatively
low-cost non-invasive diagnostic tool for neurological disorders. Consequently, they
are still in use worldwide both for diagnostics as well as for research.
In recent decades, medical technology has made breath-taking advances. Optical
sensors are increasingly being used for non-invasive diagnostics in biomedical applications. However, there is far very scanty information in the literature about their
possible application for investigating brain-related events. This could possibly due to
the fact that brain is optically opaque due to the surrounding skull and hair. However
at the temples, the tissue is relatively soft and by positioning the optical sensors at this
point, one can monitor the transcutaneous blood volumetric changes which are related
to the brain activity. Among the biomedical optical sensors, photoplethysmography
(PPG) has a unique position. They operate in the near infrared region (around 940 nm)
where the skin is relatively transparent and thereby could register the blood volume
changes in the near skin microcirculatory blood vessels [2]. Using the PPG realtime detection of brain events have been reported and the left & right brain activities
could be monitored thus opening the possibility of studying the brain asymmetry [3].
From the real-time data it is possible to obtain the frequency related information by
using the Fast Fourier Transform (FFT) techniques. Thus, it is possible to extract the
breathing-related information from the PPG signals. Further studies in this direction
have led to the understanding of the influence of breathing on brain using these PPG
sensors in conjunction with breathing sensors [4]. This has opened the gates for the
scientific studies of classical Indian breathing techniques called Pranayama. These
studies have revealed that deep breathing techniques like Pranayama caused what
might enhance the coupling and operation between the heart and the lungs which
might lead to an optimization of exchange of gases which is vital significance. In the
process, the emergence of the low-frequency rhythms in the range of 0.12–0.15 Hz
has been observed which are known to be linked to the relaxation of the human
body [5].