We have taken our closest look at the activity of a tiny brain region thought to be involved in the human circadian clock.
at Leiden University in the Netherlands and her colleagues have been studying the suprachiasmatic nucleus, which sits in the hypothalamus and is thought to play a role in regulating our sleep cycles. However, because this structure is less than 2 millimetres wide it is difficult to image using an MRI 鈥� and that means it is challenging to record its activity.
鈥淒ue to the low spatial resolution of [most] MRI machines, it is not possible to determine if the [neuronal] signals are coming from the suprachiasmatic nucleus or from another nearby nucleus,鈥� says Meijer.
Advertisement
Her team got around this problem using an MRI machine with a particularly powerful 7-tesla magnetic field. This offers sufficiently high resolution to image this tiny part of the brain.
There are only about 90 7-tesla MRI scanners in the world. Meijer鈥檚 team used one of them to study suprachiasmatic nuclei in the brains of 12 men. She says these nuclei are the smallest brain structures to have been imaged in living people.
However, to then study a suprachiasmatic nucleus鈥檚 activity pattern, Meijer鈥檚 team needed to be able to shine lights of various frequencies into the eyes of the individual inside the MRI scanner and monitor how the nucleus responded. This was a challenge because standard LED lights would be affected by the unusually powerful magnetic field and radio pulses inside a 7-telsa MRI scanner.
The researchers custom-built an LED with voltage suppressors and shielding so it could to function under such conditions.
Although all of the measurements were taken at around 10pm, the study points to a future in which we can record the neuronal activity levels of the circadian clock throughout the day directly rather than having to rely on indirect measures like a person鈥檚 melatonin levels, says Meijer.
鈥淚 think that the method they鈥檙e using has a lot of potential,鈥� says . But she says the researchers used such bright pulses of light to elicit a response from the nucleus that it is unclear if this particular study tells us anything new about circadian clocks.
Reference: bioRxiv,
