This procedure applies a combined EEG and near infrared spectroscopy recording technique to determine to what extent decreased neurocognitive performance in weightlessness is due to the primary effects of hemodynamic and electro cortical changes or to secondary stress related effects. This is accomplished by monitoring changes in electro cortical activity of participants during a parabolic flight, including phases of microgravity, microgravity, and normal gravity. Hemodynamic changes within the frontal brain can be monitored in parallel using near infrared spectroscopy or nerves.
The changes in brain cortical activity can then be localized using electromagnetic tomography. The final step is to correlate the electro cortical and hemodynamic changes. Ultimately, results show that the hemodynamic changes due to changed gravity conditions are associated with changes in electro cortical function.
The main advantage of this technique over existing methods like MRI or PET, is that electrophotography combined with electro tomography and near infrared spectroscopy is feasible during extreme environments like parabolic flights or space flights with HyperV weightlessness limited loads and limited space, and it allows to measure and correlate changes in neural electrical activity and hemodynamic kill changes within the brain. This method helps answering key questions in the field of neurophysiology and space research, such as changed gravity conditions leading to hemodynamic and electric cortical changes. It helps answering where exactly in the brain these changes happen and what the consequences of these changes are.
Once we have identified the underlying neurophysiological processes, once we have identified what happens to brain cortical function and to hemodynamic while we are in space, while we are in weightlessness, we are able to develop specific countermeasures to improve life quality, mission success, and mission safety. So this method can provide insights into brain working mechanisms, or it could also be applied to other systems like neurological impairments of neurological patients, or the fundamental idea of how our brain works. We first had the idea for this research when we heard about neurocognitive decrements from astronauts living in space.
The visual demonstration of this method is critical because it is difficult to learn the analyzing steps because there are many ways to treat and analyze the data One to two hours prior to the flight. The participants are taken to a room at the airport to prepare for the experiments. First, their head circumference is measured and their scalp is cleaned so that the EEG cap with the integrated nurse optos and receiver can be placed on the participant's head.
The next step is to mark the positions for the FP one and FP two electrodes. First, the distance between the nasn and inion is measured next at a distance, one 10th of the way between the Sian and the inion. Starting from the Sian, two marks are made to the left and right of the midline at a distance that is one 20th of the head circumference.
The cap contains the electrodes that will be attached to the scalp and ensures the correct position of the sensors. An EEG cap is chosen that is appropriate for the participant's head size. Next, the cap is pulled over.
The participant's head and its position is checked. The CZ electrode should be on the vertex and the FP one and FP two, and the O one and O2 electrodes should be horizontal and on the marks, a chin strap is fastened to assure that the cap remains in a symmetric and proper position. Next, the heart rate electrode is placed to do this one EEG electrode can be used and the sensor is placed on the participant's chest.
Now the impedance of the electrodes is minimized and the signal conduction is checked. Each electrode contains LEDs, which will be read when the impedance measurement is started. The hair is moved away from the tip of the electrode with a blunt tipped needle, and gel is injected between the tip of the electrode and the surface of the skin, starting with the reference and ground electrodes.
As the gel is injected, the color of the LEDs will change as the impedance decreases, such that the initial red color will first become yellow and then green. As the target impedance value is achieved at 25 kilo ohms, the act of electrodes will provide good signal to noise ratio at or below this target value. This procedure is repeated for all of the cap electrodes.
Once the electrode cap is prepped for both participants, the participants are given instructions on the details of parabolic flight and the experimental time schedule that will be followed. A schematic overview of parabola zero through 30 and the tasks to be performed is presented to the participants. Also, the verbal announcements detailing when and how to start and stop the tests are reviewed.
Finally, the participants are brought to the airplane for onboard flight preparation. Once on board, the participants are seated next to each other in the experimental setup, and the seat belts are fastened loosely. The EEG cables are connected to the electrode control box and the electrode control box is connected to the amplifier.
Next, the nerves OIDs and receiver are fixed into the OID holder in the EEG cap. At this point, the EEG NERS module is started. This controls the connectivity and the quality of the signal.
Then the nerves and EEG software is started and a workspace to record. The data is opened. Then the file name, the recording frequency, and the montage are entered.
If any signals are suboptimal. The impedance values for EEG or the DAQ values for nerves are readjusted or more gel is injected as needed. At this point, the recording of the EEG and nerve signal is started and the resting state prem measurements are collected.
The participants do not have any tasks at this point, but should remain still relax and keep their eyes closed. Recording is stopped after three minutes. After the rest period, the participants will perform a baseline test of the cognitive task chalkboard challenge.
Finally, all devices are turned off and the EEG electrode control box as well as the nurse's optos and receiver are disconnected. All equipment, including the camera and the iPhones are stored in a compartment for takeoff preparation for the in, in-flight experiments is started. Once the aircraft has reached a cruising altitude, the first step is to mount the video camera to the handrail, then to start the video recording.
Next, the participants are placed in their seats and the seat belts are fastened loosely. Participants should remain seated at least for parabola zero through 25. The iPhones are attached to the upper leg of the participants with Velcro.
Now, the EEG electrode control box is connected and the nerves optos and receiver are fixed into the opto holder in the cap. The EEG and nerves module is started and the quality of the EEG nerve signal is verified by checking the EEG impedance and the NS DAQ values. Rest recording is performed for three minutes.
The first parabola, which is designated parabola zero, will be used to allow the participants to accommodate to the procedure and to the change to gravity conditions. Then during parabola one through 10, only resting state EEG nurse is recorded while the participants sit quietly in their seats with their eyes closed. Next, the participants are prepared for the cognitive tasks that will be performed during two blocks of five parabola.
The recording is controlled by the operator who gives instructions to the participants and also saves the results of the cognitive tests and times. In this cognitive processing task, the participant identifies which side of an equation is larger than the other speed and accuracy of the participant's. Response is recorded by the program, and a final high score is given, dependent on accuracy, speed, and the highest level that the participant reached during parabola 11 through 15.
Participant one will perform this task in zero G and participant in one G.Then during parabola 16 through 20, participant one will perform this task in one G and participant two in zero G occasionally. Rest measurements are recorded during the parabolic sequence as well as before the first and after the last parabola. The last 10 parabola can be used in case any previous measurements or experiments need to be repeated.
Once back on the ground, the participants and operator are allowed to leave the plane temporarily before getting back into the experimental setup and preparing everything for the post measurements. At this time, the resting state EEG nurse measurements are repeated. Once all recording is completed and the cap is removed from the participant, the experiment is finished using low resolution brain electromagnetic tomography or Loretta.
It is possible to determine individual changes in frontal brain cortical activity. For participant one, the change occurring 2000 milliseconds after the beginning of microgravity was localized to Broadman area nine, which belongs to the dorsal lateral prefrontal cortex. This region plays an important role in the integration of sensory and mnemonic information in the course of motor planning organization and regulation.
For participant two, these changes could be localized to Broadman area nine and also to Broadman area six, the pre-motor cortex, which is known for its role in sensory regulation in the course of body stabilization. This next trace shows near infrared spectroscopy in the frontal brain region. The black curve indicates the G level.
The yellow background indicates normal gravity. The blue background indicates hyper gravity and the pink background indicates microgravity as expected. There is a decrease of oxygenated blood as shown by the red trace in the microgravity phase, followed by an increase of oxygenated blood in the microgravity phase.
Similar results are seen in this figure from another participant. Interestingly, the amount of deoxygenated blood as shown by the blue trace, showed no consistent behavior for the first HyperV phase or the weightlessness phase, but in both subjects showed a decrease in the second HyperV phase. This figure shows the cognitive task for two subjects for three measurement points during training, which was measured before the flight in zero Gs, which was measured during the flight, and at one G also measured during the flight.
The scores differ between the subjects indicating that previously reported neurocognitive decrements during parabolic flights are most likely due to individual stress reactions. After having watched this video, you should have a good understanding of how to apply the combined e, e, g and knees technique, as well as how to monitor electro cortical activity and hemodynamic changes in parallel. While attempting this procedure, it is important to check the quality of the signal and to monitor the behavior of the subjects.
These techniques might pave the way for researchers who are interested in brain cortical function and to explore the effects of microgravity on brain cortical function, and once we have identified these mechanisms, this might help patients, astronauts as well as normal people.
