Transcranial direct current stimulation

Transcranial direct current stimulation delivers constant low current to the brain area of interest via electrodes on the scalp. StarStim (Neuroelectrics, Barcelona, Spain) is a wireless hybrid EEG/tDCS 8-channel neurostimulator that includes a comfortable neoprene headcap with 39 positions based on the 10-10 system where the electrodes can be easily inserted.

CAVE system

A 4-wall 3D CAVE system (Barco N.V., Kortrijk, Belgium) allows user immersion in stereoscopic scenarios with a 7.1 sound system or with Bluetooth headphones. The system uses 4 projectors F35 AS3D WUXGA (ProjectionDesign, Fredrikstad, Norway) and incorporates head and hands tracking through 4 infrared tracking cameras ARTTRACK2 (Advanced Realtime Tracking GmbH, Weilheim in Oberbayern, Germany)  and navigation through Flystick3 (Advanced Realtime Tracking GmbH, Weilheim in Oberbayern, Germany).

Videowall system

A setup that consists of two video projectors Mirage HD3 projector (Christie Digital Systems USA Inc, Cypress, CA, USA) provides a stereoscopic 6 x 2 meter display that also allows head and hands tracking through other 4 infrared tracking cameras ARTTRACK2 and navigation through Flystick3.

Walking room-size virtual reality system

An optical-based system that consists of a head mounted display, a Bluetooth headset and a videocamera allows navigation in virtual and mixed reality environments by walking in an area of 4 x 6 meter.

Head mounted displays

Different head mounted displays are available for augmented, mixed, and virtual reality applications. Available devices for virtual reality applications include the Oculus Rift DK1, the Oculus Rift DK2 (Oculus VR, Irvine, CA, USA), and the Samsung Gear VR (Samsung, Suwon, South Korea). Optical see-through devices available for augmented reality applications are the Meta1 (Meta Company, Portola Valley, CA), which incorporates a 3D time-of-flight depth camera with 320×240 pixel resolution, the Moverio BT-200 (Epson, Suwa, Japan), the Google Glass (Google, Menlo Park, CA, USA), and the Vuzix M200 (Vuzix, Rochester, NY, USA).

Scent emitting system

The Scent Palette (HeadHunter200 Inc., Northlake, IL, USA) can emit a selected scent and produce a sequence of different smells controlled by a computer. The stimulation can also be provided additionally to other sensory stimulation in virtual reality settings.

TV screens and projectors

Different additional TV and projectors with different features are available to customize the required setup for each experiment.

Electroencephalography

Electroencephalography records the electrical activity of the brain through electrodes that are fixed to the scalp. Different solutions can be used depending on the experimental conditions. The TMSi Refa (Twente Medical Systems International B.V., Oldenzaal, Netherlands) is a 32-channel ambulatory and stationary system for physiological research that allows to retrieve data from water based sensors. For mobile applications, the StarStim allows to retrieve data from 8 channels wirelessly in hybrid configurations of transcraneal direct current stimulation, and the B-Alert X10 (Advanced Brain Monitoring, Inc., Carlsbad, CA, USA) provides 9 channels of combined mid-line and lateral EEG sites plus an additional channel of electrocardiography, electromyography, or electroculography. In addition, four EPOC headsets (Emotiv Systems, Kwun Tong, Hong Kong).

Eye tracking

Eye tracking technology estimates where individuals direct their eyes along time. These data can provide information about attention, information processing, presence, focus, drowsiness, consciousness, or other mental states. Eye tracking information can be retrieved using different devices. The Tobii TX300 (Tobii Technology AB, Danderyd, Sweden) collects gaze data at 300 Hz yet allows large head movements, thus enabling the study of saccades, correction saccades, fixations, pupil size changes, and blinks. Other portable solutions are also available for different setups, as the low-cost Tobii EyeX (Tobii Technology AB, Danderyd, Sweden) and the Eye Tribe (Copenhagen, Sweden) or the high performance SMI Eye Tracking Glasses 2 (SensoMotoric Instruments GmbH, Teltow, Germany). This device not only allows to record a person’s natural gaze behaviour in real-time in a broad range of daily life applications but also in our CAVE system, for which the Arrington Scene Camera Eye Tracking (Arrington Research Inc, Scottsdale, AZ, USA).

Electromyography

The TMSi Refa can provide surface electromyography data, a non-invasive technique that estimates the electrical activity of a muscle placing electrodes on (not into) the skin overlying it.

Galvanic skin response

Galvanic skin response or skin conductance represents the changes in the electrical properties of the skin, which can illustrate the autonomic nerve responses as a parameter of the sweat gland function. This physiological measure can be estimated using the TMSi Refa , which uses two electrodes that are attached to a finger, the Q-sensor (Affectiva, Waltham, MA, USA), a wireless Bluetooth bracelet, or the E4 wristband (Empatica, Milan, Italy).

Electrocardiography

The electro-physiological measurement of the heart muscle signal or electrocardiography can be obtained using the TMSi Refa. Besides the heart rate variability, the system also allows to extract the size and position of the chambers and the presence and place of any damage to the heart. Measures of the blood volume pulse, from which heart rate, heart rate variability, and other cardiovascular features may be derived can be estimated using the photoplethysmography sensor of the E4 wristband.

Skin temperature

The skin temperature can be measured via a thermic sensor using the TMSi Refa or via infrared thermopile using the E4 wristband.

Oxygen saturation

The fraction of oxygen-saturated hemoglobin relative to total hemoglobin in the blood can be provided by the TMSi Refa.

Motion tracking

Human movements can be detected by many different devices. The IGS150 (Synertial, Brighton, United Kingdom) is a motion capture solution that estimates de orientation of 15 inertial sensors made up of 9 axes of accelerometers, magnetometers and gyroscopes combined together. Two IGS-Cobra gloves with 7 sensors are also available for hand tracking capture. Conventional tracking systems detect the position of markers, as the optical solution using OptiTrack V100:R2 cameras (NaturalPoint, Corvallis, OR, USA), or sensors, as the electromagnetic G4 (Polhemus, Colchester, VT, USA), which are usually attached to specific body parts to determine their position in a 3D environment. Recent advances in computer vision have made human pose recognition from depth images reality. Even though it cannot be considered as a tracking system in the literal sense, the skeleton tracking provides the 3D position of many body joints from depth information estimated by depth sensors, such as the Kinect and Kinect v2 (Microsoft, Redmond, WA, USA), the Intel RealSense F200 (Creative Technology Ltd, Singapore), and the Structure Sensor (Occipital Inc, Boulder, CO, USA).

Other devices for natural interaction are also available. The Leap Motion (Leap Motion Inc, San Francisco, CA, USA) allows user to interact with finger and hand movements. The Razer Hydra (Razer, Irvine, CA, USA) estimates arm movements by using a weak magnetic field to detect the absolute position and orientation of the controllers with high precision. In contrast to these devices, the Myo armband (Thalmic Labs, Kitchener, ON, Canada) allows users to interact with gestures by detecting the surface electrical activity of the wrist muscles.

Capture

Full 360º video recordings can be obtained combining 14 GoPro Hero 3 (360Heros, Olean, NY, USA). Natural audio can be captured using the binaural audio microphone 3Dio Free Space (J.Tesori Co, Tokyo, Japan) and the Zoom H4n handy recorder (Zoom Corporation, Tokyo, Japan).

Robotics

The LokomatPro V6 (Hocoma AG, Volketswil, Switzerland) supports weight shift and balance activation and offers a gait pattern with constant virtual reality-based feedback. The ArmeoSpring (Hocoma AG, Volketswil, Switzerland) supports weight shift for upper limb rehabilitation. Exercises are self-initiated and self-directed, and encourage patients to achieve a higher number of repetitions. Both systems aim to improve patient outcomes by increasing therapy volume and intensity, providing task-specific training, and increasing patient engagement. In addition, they provide assessment tools to examine the patient’s clinical progress.

Virtual reality systems

Many different systems are available for the rehabilitation of different skills. Customized exercises using the Wii Balance Board (Nintendo, Kyoto, Japan) and the Kinect are available to train cephalic and trunk control while sitting, weight transferences using the ankle and hip strategies in standing position, and stepping exercises. Users interact through movements or weight transferences. There are 8 systems distributed in our neurorehabilitation network.

Large format multitouch displays provide visual stimulation during interaction through finger touches.  The visual feedback is provided by a conventional 42” LCD screen oriented in a horizontal plane (parallel to the ground). The interactive capability is provided by a multitouch frame fixed over and along the screen frame, which allows up to 32 simultaneous touches. Four tabletop systems provide attention, memory, and self-awareness tools for group interventions for patients attending rehabilitation in our network.

Assessment

The NedSVE/IBV (Instituto de Biomecánica de Valencia, Valencia, Spain) is a laboratory grade posturography system for the analysis, re-education, and monitoring of balance disorders with easy-to-interpret graphical outputs. It has been designed for the functional assessment and rehabilitation of balance disorders through comparison with normal ranges. The application combines static posturography tests with dynamic tests based on gait analysis, stability limits, and monitoring the centres of pressure for moving targets. Customized low-cost systems based on the Wii Balance Board and the Kinect are also available for objective posturography and gait analysis, respectively.