This is your brain on microgravity

Some of the neuroplastic changes from space travel persist a surprisingly long time.

---

It’s well known that spending time in space does funny things to your bones and muscles, which tend to take a load off when they no longer have to contend with gravity.  

But what does it do to your brain? 

Previous work using fMRI has looked at some of the more macroscopic changes, such as redistribution of cerebrospinal fluid, enlarged ventricles and grey matter changes – the kind of thing caused by having more fluids sloshing around upstairs instead of draining downwards.  

How the brain copes with an environment where nothing physically behaves as it should is still a relatively unexplored frontier.  

A new study in Nature has sought to map changes in connectivity among brain regions and try to interpret what they mean functionally for tomorrow’s galactic jetset. The first part is relatively easy, the interpreting bit not so much.  

A team led out of the University of Liège fMRIed the brains of 15 cosmonauts in a resting state before, immediately after and eight months after a stint in the International Space Station.  

They found reduced connectivity between some regions and the rest of the brain, and increased connectivity in others; some changes had reverted to baseline after eight months, but some persisted. An earthbound control group showed no such changes.  

The persistent changes were decreased connectivity in the left precuneus, posterior cingulate cortex and the thalamus, and increased connectivity in the right angular gyrus. Connectivity increased in the bilateral insular cortex but then returned to normal.  

So what on earth – or off it – does that mean?  

The right angular gyrus helps with spatial processing and assessing whether you’re vertical – that’s a straightforward one. But it also contributes to “action-outcome monitoring, sensory mismatch detection and sense of agency”, which hints at how the brain has to adapt when spoons no longer fall out of your hand and you can play a game of Pong with a ball of water.  

The role of the posterior cingulate cortex “remains quite elusive”, the authors write, but is part of the default mode network – which is thought to be involved in “enabling long-term memory, divergent thinking patterns, and dealing with changes between world models and task sets”. The changes seen in space may “contribute to mediating adaptation triggered by unfamiliar sensory input in microgravity, based on their roles in choosing task sets, world models, and detecting environmental changes”. 

The regions of the thalamus that showed decreased connectivity are involved in working memory, spatial processing, attention, and decision making. 

The insular cortex is linked to cognition (language, memory), perception and interoception, or perception of signals from inside the body.  

It is also part of the salience network, which assesses stimuli and generates appropriate responses, such as attention shifts, motor responses or autonomic responses. The authors suspect the temporary reduction in connectivity between it and the rest of the brain is a coping mechanism that suppresses autonomic responses to the weirdness of space – such as space sickness, which commonly affects space travellers for the first few days in space and back on Earth, but then abates.  

Further research is needed to establish the neuroplastic effects of faster-than-light travel and teleportation.  

If you encounter a space oddity, let penny@medicalrepublic.com.au know.