The human brain may be constantly analysing stimuli, orchestrating thousands of unique biological processes to maintain order throughout the body. The brain aims to educate when to satisfy hunger, when it is time to rest and when it is time to start a new day.
Travelling between time zones may effectively stun this carefully balanced routine, leaving a traveller in a temporary state of fatigue. The effects of jet lag, medically known as desynchronosis, may take more than a day to fully subside. This makes it a debilitating condition for individuals who excessively travel, as they may spend little more than a day at a time in one time zone.
There are different types of jet lag, resulting from travelling to different time zones ahead or behind the original point of departure. Passengers travelling to eastern countries delay their circadian rhythm, which takes longer to recover from than advancing it through western travel. Currently, the most effective treatment for jet lag may be the use of oral melatonin. Melatonin is a naturally occurring hormone responsible for sleep-wake patterns. However, this treatment may only be effective for eastern travel, this leaves space for a more effective jet lag treatment.
A team of Japanese scientists led by Yoshiaki Yamaguchi claims to have one such possible solution. Whilst the brain remains a relatively unexplored area of the body, several attempts have been made to understand the stimuli that maintain and modify our circadian rhythm. The brain, a complex and dynamic organ and as such it may be challenging to pinpoint methods of processing abstract concepts, such as the perception of time.
Thus the investigation had to begin with the most obvious manner of time perception and then refined accordingly. The dominant factor influencing the process of time perception is light intensity; light, a quick and efficient means to determine night from day. This focuses the search in an ocular direction, as it is the eyes that function as the primary conduit for light information to reach the brain. Yet in the late ‘90s a paper published in science displayed promising evidence that light shone upon the back of the knees might effectively control a person’s circadian rhythm. With the advent of more accurate methods of tracking melatonin levels, this concept, though novel, ceased to be taken seriously.
The human eye contains rod and cone cells for the purpose of sight, yet there are photosensitive cells known as photosensitive Retinal Ganglion Cells (pRGC). These act as a gauge for light intensity, absorbing quite specifically within the light blue area of the spectrum. These cells trigger pupil contraction and dilation even within blind mammals; but these cells are most active in travellers affected by jet lag, as they help maintain sleeping patterns.
Unlike the rod and cone cells that connect to the visual cortex, pRGC connects to an area of the brain known as the suprachiasmatic nucleus (SCN). Although the SCN is only the size of a grain of rice, it may control many biological processes throughout the day and night, and is considered the superior body clock. As such, it is the focal point for circadian biologists and the area of interest when developing a drug to alleviate jet lag.
In a study carried out by Yoshiaki Yamaguchi and team, they found through the inhibition of the neurotransmitter vasopressin, the SCN and other parts of the brain were unable to communicate. This created a resistance to jet lag, allowing for a much quicker recovery time from advances and delays in the circadian rhythm. Whilst this phenomenon has only been observed in mice, it has potential in the development of a drug treatment for travellers with jet lag. Furthermore, it might lead to discoveries that might result in far greater understanding of this area of the brain. For future holiday makers it might seem a very real decision may have to be made, to decide how extra holiday time shall be spent with the absence of jet lag.
What might there be to gain for frequent time-zone hoppers, if a drug is able to be made to quell jet lag?