A key concept in the field of neuromotor control is that of defining the frames of reference used by the central nervous system (CNS) to interpret sensory information and to control movements. At the level of individual sensors and effectors, the coordinate systems employed are well defined. It is not in the coordinate system of an individual receptor, but rather, in examining the coordination of sensory and motor activity that the question of reference frames becomes interesting.
This experiment was testing the role of gravity in defining the reference frames used for 3D navigation and for representing the orientation of our own bodies and the orientation of visual stimuli. In a series of psychophysical tests it was compared how human subjects perform these types of task both on the ground and in the weightless conditions of orbital flight. Also evoked potentials were measured through surface electrodes applied to the scalp in order to measure the spatial and temporal components of information processing in the brain in the absence of gravity.
This experiment had two specific objectives concerning the functioning of the human nervous system for the perception of orientation and the performance of 3D navigation in space:
The human perceptual system represents and stores the orientation of visual stimuli in a reference frame that combines egocentric information about the orientation of the body axis with graviceptor information about the vertical axis. Visual stimuli that are aligned with the vertical and horizontal axes are treated preferentially in this multi-modal reference frame. In the absence of gravity, the human nervous system may substitute a cognitive reference frame defined by the stable mechanical base provided by an orbiting spacecraft. When operating in free-floating conditions, subjects will lose the haptic cues that indicate their orientation with respect to the local environment. In this situation, the CNS may use a purely egocentric reference frame aligned with the body, or the system may lose its stable reference frame and treat all orientations equally.
We hypothesize that in free floating the cognitive task will be changed by the absence of gravitational reference. In particular, we expect all readiness for movement - called "Bereitschaftspotential" (BP) - and late positive component (LPC) amplitudes and latencies to be higher than in normal gravitational environment. This would indicate that alternative spatial motor reference needs to be constructed in free-floating, implying additional cognitive processing at each stage of movement. If BP and LPC amplitudes and latencies are similar to normal gravitational condition, the same type of cognitive processing (independent of graviception) would appear conserved. Finally, gradual normalisation of BP and LPC during the task would indicate rapid adaptation of attentional process.
This experiment was designed to test each of the above hypotheses through a series of psychophysical tests performed in a simple virtual-reality environment.
Role of the gravitational component of the efference copy in the control of upper limb movements (CNES)
2nd Joint European Partial gravity Parabolic Flight campaign 2012
Role of the gravitational component of the efference copy in the control of upper limb movements (CNES)
1st Joint European Partial gravity Parabolic Flight campaign - 2011
Effects of Changing Gravity on Ocular-motor coordination
51st ESA Parabolic Flight Campaign 2009
Dexterous Manipulation in microgravity
48th ESA Parabolic Flight Campaign 2008
Cosmonaut subjects will perform a set of 2 psychophysical tasks with simultaneous recording of EEG activity. For each subject, the performance on these tasks will be compared for a set of pre-flight, in-flight and post-flight procedures to test for an effect of weightlessness on the visual perception of orientation and movement and on the ability to navigate in three dimensions. Back-up crew members will be asked to perform all pre-flight training and baseline data collection (BDC) tests and may be asked to work in parallel with the orbital crew during and after the flight to provide a matched control group for comparison.
The subject takes up the position and postural support depending on the gravitational conditions (ground or inflight) and on the instructions for a particular protocol:
Ground - Seated: The subject is seated upright comfortably in a chair, with the elbows resting on the adjustable-height elbow supports of the ground support stand. The ground support stand is adjusted to position the mask/tunnel/laptop at the level of the eyes for viewing. The height of the elbow pads is adjusted to allow the subject to comfortable grasp the grips on the laptop support.
In-flight - Restrained: The subject sits in front of the laptop, which is attached to a mechanical support. Waist and foot straps are used to hold the subject securely in a seated posture.
Inflight - Free-floating: The subject adopts a free-floating posture and should have no rigid contact with the station structure during the performance of the experiment in this mode. A second cosmonaut aids the subject to stabilize his or her posture at the beginning of this phase of the experiment.
In all cases, the subject places the face into the face mask and attaches an elastic band behind the head to help hold the head in place. By manipulating the buttons and trackball, the subject launches the experiment program on the laptop, identifies him or herself to the program and then performs a set of experimental trials consisting of the following:
FO1: Virtual Turns
The subject is situated in a visually presented 3D virtual tunnel. On the press of a button, the subject will appear to either move through a tunnel at constant speed, passing through a single bend between two linear segments or the subject may appear to undergo a rotation in place (no apparent translation). At the end of the trial, the subject indicates the extent of the turn (i.e. how many degrees) in one of two different fashions:
EEG is recorded during the above trials. EEG will also be recorded under four control conditions. In condition 1, the subject relaxes and does nothing, first with eyes closed, then while looking at a neutral screen. In condition 2, an alternating checkerboard is presented to the subject on the screen, with the colours switching between black and white every 3 seconds. In control condition 3 the subject follows the movement of a luminous spot as it makes a sinusoidal movement across the screen. In control condition 4 subjects blink their eyes in synchrony with an audible metronome. Control recordings are expected to last no more than 5 minutes.
The subject performs a total of 48 such trials for either stimulus type, for a total of 96 trials per session. Trials are broken into blocks of 12 trials each, with pauses programmed between blocks. At a nominal rate of 4-5 trials per minute (including pauses), one complete execution of this protocol (turning in-place or passage through the tunnels) is performed in 20-25 minutes.
FO2: Visual Orientation
A reference line of a fixed orientation is displayed on the video monitor. At the press of the button by the subject, the stimulus line is erased and a distracter screen (with lines in many orientations) is displayed momentarily. Finally a second response line is displayed at an orientation different from the first. Using the trackball, the subject must adjust the orientation of the second line to match that of the first. The subject performs 6 such trials for each of 7 different reference orientations, for a total of 42 trials. Trials are broken into 3 blocks of 14 trials each, with pauses programmed between each block. At a nominal rate of 4 trials per minute (including pauses), one complete execution of this protocol is performed in10-15 minutes.
(1) Weightlessness specifically affects visual evoked potential related to the presentation of a virtual 3D navigation tunnel: In NeuroCOG experiments subjects observed a simulated passive movement through a virtual tunnel. Each tunnel contained a bend. After subjects emerged from the end of the tunnel, they were asked to report the perceived turn angle by adjusting a visual indicator with a trackball. On Earth the estimation of pitch turns was greater for forward (nose-down) turns versus backward (nose-up) turns. This asymmetry does not exist to this extent in weightlessness.The research from this experiment is continuing within a follow‐on experiment (NEUROCOG 2) which is embedded within the ESA-sponsored NEUROSPAT experiment.
(2) Weightlessness increases the alpha rhythm gain during the transition between eyes-closed and eyes-opened states.
(3) Moving in virtual navigation induced midfrontal N200 event related potentials supported by a transient theta ringing altered in weightlessness.
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Execution of Neurocog experiment using visual tunnel
Neurocog mounting frame and tunnel
Preparing for floating protocol of Neurocog experiment flight day 5