1. Introduction
This review will look into the article, “Monitoring the Impact of Spaceflight on the Human Brain,” written by Micheal F Dinatolo and Luchino Y Cohen from Western University, Canada. It will provide an overview, citing the important and interesting features of this paper. The paper explains how long-term exposure to radiation, microgravity, and isolation will affect the brains of astronauts who will travel in deep space in the future. It gives examples of various brain monitoring technologies that could be beneficial in an in-flight environment while in deep space, as well as technologies that are not suitable for these environments. The technologies not suitable for spaceflight can be used in pre and post-flight studies. I decided to look into this topic due to my curiosity about the brain and deep space exploration, and how exactly space travel affects astronauts and their brain health. As more and more advancements are made in understanding our universe and as humans venture further away from Earth’s orbit, an understanding of how our brains are affected in deep space is vital.
2. The Effects of Spaceflight on the Brain
Changes in gray matter structure, CSF distribution, behavior and cognitive functioning have been observed with the astronauts on the ISS, and these changes may be more extreme in deep space.
How high radiation in deep space affects astronauts’ brains:
Radiation in deep space is higher than in low Earth orbit due to high linear energy transfer (LET) and no protection from Earth’s atmosphere
LET - amount of energy transferred by ion to material
Radiation is not good for health (damage to CNS, cognitive processing, cancer, death, impaired memory and learning, anxiety/mental health issues, degradation of synapses between neurons)
How microgravity in deep space affects astronauts’ brains:
Long space flights can increase the volume of the brain (which affects brain structure and pressures) due to the zero g, which affects vestibular system and vestibular processing
Pressure in the brain can lead to Spaceflight-Associated Neuro-Ocular Syndrome (SANS), which impairs cognitive processing and performance
How isolation in deep space affects astronauts’ brains:
The long-term isolation experienced in deep space travel can inhibit cognitive function and behavior, impact immune system response, and have psychological effects
Isolated, confined, and extreme (ICE) environments negatively affect sleep which causes adverse effects on mental health and concentration on tasks
Cites “Mars500” study: volunteers were put in a Mars mission simulation for 520 days, miniscule damages/differences in white matter were observed
Data is all from low earth orbit (LEO) since no other data has been gathered
Data is from pre and post-flight which have risk of exposing to factors that can skew results (an in-flight method should be used instead to gather more accurate data)
3. Monitoring Technologies Adaptable to Space flight
How EEGs can be a valuable tool for studying the brain in-flight:
Electroencephalogram (EEG)
Monitors electrical signals in the cerebral cortex
Measures activity between neuron synapses to create chart of brain and brain waves
Abnormalities in these brain waves indicate some kind of brain issue
EEGs have been used in space before by recording effects of isolation, sleep, and microgravity on the brain
EEGs have shown reduced slow-wave sleep cycle for astronauts in space, EEG activity anomalies due to less sensory motor input in microgravity, and a slower reaction time in zero g
These observations collected using the EEG may also be due to the high stress environment, and not necessarily just microgravity. A study where participants on Earth were put in head-down bed rest (simulating a microgravity environment) showed that due to more blood rushing into the head, the participants were more likely to feel anxiety and stress
It has also been shown that cortical processes are inhibited when blood flow to brain in zero g (the effects of this inhibition on performance still require more research)
EEGs are useful for the diagnosis of brain disorders and damages, such as tumors, in high radiation of deep space
How fNIRS can be a valuable tool for studying the brain in-flight:
Functional Near-Infrared Spectroscopy (fNIRS)
Looks at changes in concentration of hemoglobin using a “near infrared” absorption range to measure activity in the cerebral cortex.
fNIRS have not been used in space flight but have been used in parabolic flights
Used to identify attention states (could be helpful for studying how lack of sleep affects performance and decision making in real-time)
Cheaper, uses less power, portable
fNIRS help study sleep deprivation, attention and decision making while subjected to the ICE environments in space flight
Data can be combined with EEG for further conclusions
How ultrasounds can be a valuable tool for studying the brain in-flight:
Ultrasound
Uses sounds at high frequency waves to paint an image of inside the body
Can help with understanding the consequences of intracranial pressure and volume changes in astronauts’ faces when they go to space (ultrasounds can measure the intracranial pressure and volume)
Ultrasounds have been used in the ISS. They measured distributions of fluids in the body from bottom to top in space, measured the effects on the optic nerve due to increased intracranial pressure (SANS). More research could be done on the SANS topic.
4. Monitoring Tech Not Suitable for Spaceflight Environment
The functions of MRIs, the three different types of MRI machines, and why they cannot be used in-flight in deep space:
Magnetic Resonance Imaging (MRI)
Creates images of the body and the brain by measuring the concentrations of hydrogen atoms found in the water/fat in the body
5. Structural Magnetic Resonance Imaging (MRI)
Can identify CSF movements
Measures brain structure (volume and surface area)
Can only be used in pre and post-flight studies, or simulations (Suitable for measuring/recording the effects of deep spaceflight travel on the brain)
MRIs have been used to find changes in intracranial pressure, volume, and changes in size of cerebral cortex
Long term microgravity effects can cause an increase in CSF volume and flow as well as a larger brain size after flight and more white matter volume
Hydrocephalus symptoms may occur during flight (not permanent)
6. Functional Magnetic Resonance Imaging (fMRI)
Studies the functions of parts of the brain by measuring changes in blood flow (oxygenated blood flows towards activated areas of the brain)
Creates 3D models of the brain on computer
Used in pre and post flight or simulations
70 days of head-down bed rest revealed balance issues due to reduced neural capabilities in participants while performing mobility tasks (short-term effects of head down bed rest)
fMRI during resting states have shown various changes in neural connections between different sections of brain
7. Diffusion MRI (dMRI)
Studies water diffusion and white/gray matter and translates it into an image of brain (this process is called diffusion weighted imaging — DWI)
Differentiates white matter and gray matter
Measures the direction of diffusion, which determines how water passes through neurons and white matter tracts
Studies on spaceflight reported small changes in white matter tracts
Gray matter increased in the postcentral gyrus (which is in charge of proprioception) and the precuneus (which is responsible for perception of environments, memory, and others) while in microgravity
The “Mars500” study found that long-term isolation leads to lower “fractional anisotropy” in the corpus colosseum and right hemisphere of the brain (meaning disrupted connectivity of the neurons), which could result in lower prediction error when it comes to processing visuospatial info due to less stimulus in the confined environments
The functions of PET scans and why they are not suitable for an in-flight environment while in deep space:
Positron Emission Tomography (PET)
Measures cellular metabolism by using radioactive tracers
Gamma rays are produced to create an image of where the radioactive tracers are in the body
PET scans are useful for post-flight data to measure metabolism in the brain, physiological effects and activity, and blood flow
Can identify tumors due to radiation in deep space
The functions of CT scans and why they are not suitable for an in-flight environment while in deep space:
Computerized Tomography (CT)
Produces 3D image of body and brain using x-rays
Pre-flight use (too big and risk of radiation from x-rays)
A good tool to make sure that astronauts’ brains and bodies are healthy so they are ready to fly into deep space
8. Neurological Monitoring Technologies in Deep Space
The best technologies that should be used in the future for deep space travel:
It would be helpful to build MRI machines/CT/PET for deep space travel
The paper concludes that EEG and fNIRS are the best for examining the brain during spaceflight in deep space
fNIRS, and some of the negatives of using them in deep space long-term:
fNIRS help look at astronaut’s brains while in deep space (more portable versions have been invented, even though it is already relatively portable)
fNIRS may not work well long-term in the high radiation present in deep space
fNIRS and EEGs can be used together to study the astronaut brain, but more tests are required (more in-flight tests)
Why ultrasounds should not be the first choice over EEGs and fNIRS:
EEG/fNIRS should be prioritized over ultrasounds (they basically have the same functionality as ultrasounds, and more)
Ultrasound cannot show pictures of the brain (only intracranial pressure and fluids/blood flow)
EEGs and their various functions, and why they are the best for traveling in deep space:
EEGs are portable and have many functions
EEGs are good for measuring mental health, long-term exposure to microgravity, isolation/confinement, radiation, motor functions, and more
Monitoring tech has been created to give EEGs more versatility in its functions as a way to study effects of deep space on brain and its ability to act as a medical tool
EEGs can help scientists discover what they need to improve on when it comes to protection of brain health in deep space
Source:
Dinatolo, M.F.; Cohen, L.Y. Monitoring the Impact of Spaceflight on the Human Brain. Life 2022, 12, 1060. https://doi.org/10.3390/life12071060