ESA Astronaut Thomas Pesquet is aboard the ISS - and he's well on his way to executing some of the important ESA experiments. Today, as I write this, Thomas is completing his first on-board session of the GRASP payload. We have a time-limit on when he can perform this session in order for the science to be valid - GRASP Session #1 must be performed between flight-day 7 and Flight day 15.
We always couple the sessions of the GRASP experiment with the GRIP experiment - since they share some of the same hardware. Thomas performed the first session of GRIP last week.
So, what are GRIP and GRASP about? Well, quite simply, they are neurological experiments designed to understand how the brain interprets and processes signals to form the sense of our body - our proprioception.
Proprioception is the continuous feedback loop between sensory receptors in the peripheral nervous system (PNS) throughout the body and the central nervous system (CNS). This important bodily neuromuscular sense allows us to instantly integrate our sense of joint and body position, our awareness of motion (kinaesthesia), our sense of force, and our sense of change of velocity. Normal proprioception allows us to move freely without giving these movements a second thought. The human brain rapidly gains the capability for proprioception in the first years of life. Abnormal proprioception can be debilitating - causing symptoms that can interfere with even the simplest activities.
A number of medical conditions can impair proprioception. This includes the 10 Million people suffering from Parkinson’s Disease, 2.8 Million people suffering from Multiple Sclerosis, the 230,000 people suffering from ALS, and the 208,000 people suffering from Huntingon’s disease. Other medical conditions affecting proprioception include those with traumatic brain injury (TBI). The World Health Organization estimates that TBI is a leading cause of death and disability worldwide – with an estimated 69 Million TBIs each year. Autism, diabetes, stroke, arthritis, and herniated disk can also affect proprioception.
The GRIP and GRASP experiments help us to better understand how the brain detects and integrates signals from the PNS. The microgravity environment of the ISS provides a unique opportunity for this study. With the gravitational force absent, researchers gain insight into the integration of other PNS signals into the CNS. In other words, they’re researching how the brain learns new processes and how the brain and body can adapt to control movement in a new environment. Importantly, by studying how a healthy brain adapts to the loss of an important PNS signal, scientists can better understand and treat diseases that impair proprioception.
The GRIP experiment studies how the brain uses PNS signals to calculate, anticipate, and apply the correct amount of force needed to lift or lower an object. This experiment uses an instrument called a manipulandum, a sophisticated technology that measures pressure, acceleration, rotation, torque, and moisture. The astronaut’s motions with the manipulandum are also tracked by special cameras. (interesting note: this same manipulandum technology is used in the field of rehabilitation robotics for persons with cognitive impairment or physical disabilities).
The GRASP experiment studies how the brain encodes spatial information for eye-hand coordination. How do we orient ourselves and know where to “reach” when grasping for an object? Gravity plays a special role in this type of orientation and coordination since it gives us directional information through our vestibular system – and helps us coordinate the information coming in from other sensory channels (e.g. muscle receptors, visual receptors, cutaneous receptors and joint receptors). In microgravity, the vestibular receptors from the inner ear (otolithic cues) are repressed. Only in this environment can we learn how the brain uses specific reference frames to encode the position and orientation of objects that we want to manipulate.
Results to date for these experiment already look very interesting as they already show effects in microgravity conditions, as well as the capability of Astronauts to adapt to the microgravity environment. The data are novel and provide important inputs to inform and update current neuroscientific models of multi-sensory integration.
