Investigations on the influence of breathing on brain activity using optical sensors

In recent years investigation and understanding of the brain activity is receiving much attention. Such investigations are generally confined to few select premier research institutions where expensive and sophisticated facilities like EEG, PET. FMRI etc. are available. Of late optical sensors are receiving much attention for biomedical applications because they are relatively simple in construction, easy to use and comparatively inexpensive. Among the biomedical optical sensors, photoplethysmographic (PPG) measuring systems have a unique position. They function as transcutaneous registration of blood volume changes in the near skin blood vessels. By recording the signals from the PPG optical sensors positioned on the temples of a subject, one could monitor the blood supply to the left and right lobes of the brain in the cerebral cortex. The oxygen content in the arterary blood flow to the brain will naturally have an important role to play in the activity of the brain. It is suggested that by positioning sensitive temperature sensors in the nostrils of a subject, one could monitor his breathing activity. By recording the outputs from these temperature sensors for several hours, it has been noticed that the breathing activity Of a subject will change from one nostril to another periodically. Besides, it has also been observed that any sudden fluctuations in the breathing pattern is accompanied by changes in the blood flow to the brain as monitored by PPG optical sensors mounted on the temples of a subject. An attempt is made to understand such events.