Computerized Dynamic Posturography
Dr. Black contributed to the development of the Neurocom EquiTest system, one of the most widely used clinical assessment tools for balance disorders. This system consists of a movable, dual-forceplate support surface and a moveable visual surround, both under computer control. In addition to the commercial EquiTest system, the laboratory also has a hydraulic-driven research platform controlled through versatile software (e.g. ability to implement sway-referencing of the support and surround using different gains or to induce perturbations using programmed profiles, ability to provide different audio stimuli for head movement protocols). Small head-mounted orientation sensors (InterSense, InertiaCube) and a 3-D multi-marker position sensor (Northern Digital Inc OptoTrak) provide high resolution body segment kinematic data. Electro-myogram recording of postural muscles is also available.
Vestibulo-Ocular Reflex (VOR) and Optokinetic (OKN) Testing
The laboratory has developed one of the most comprehensive published horizontal VOR and OKN test batteries. A direct-drive high torque rotator (150 ft-lb, NeuroKinetics) is enclosed with full-field surround with optokinetic and laser target projection stimuli. In addition to conventional electro-oculography (EOG), eye movements can be measured with videography. An adjustable head restraint allows the subject to be positioned for horizontal or vertical canal testing about an earth-vertical axis, and a linear actuator at the base of the rotator allows for Off-Vertical Axis Rotation (OVAR) test capabilities.
Research subjects and clinical patients are screened through a standard battery of oculomotor test procedures including: spontaneous nystagmus, caloric (closed-loop irrigator system), positional and Dix-Hallpike testing, smooth pursuit, optokinetic, gaze holding and saccades. This laboratory is outfitted with a Visual Lab system (Interacoustics) and non-invasive videography.
Vestibular Autorotation Test (VAT)
In addition to the VOR testing during passive rotations, the laboratory employs active head rotation in horizontal and vertical planes at high frequencies (2-6 Hz) using the Vestibular Autorotation Test (VAT98-1, Western Systems Research).
Vestibular Evoked Myogenic Potentials (VEMP)
The VEMP is a new clinical test under validation testing for otolith (saccule) function. This test involves recording short-latency electromyograms (EMG) in neck (sternocleidomastoid) muscles evoked by high intensity acoustic clicks or tone bursts. A laptop-based stimulator (Sierra II, Cadwell Laboratories) is configured for measuring vestibular-evoked myogenic potentials, and a second EMG system provides the subject visual feedback to control the level of neck muscle contraction.
In addition to performing functional assessment of gait using subjective criteria, our laboratory employs a long (1.5 m) force plate (Balance Master, Neurocom) to quantify assessment of gait. An OptoTrak system (Northern Digital, Inc.) provides precise kinematic data for these experiments.
Variable Radius Centrifuge
A variable radius rotator (centrifuge) allows the subject to be oriented for yaw, pitch or roll rotation about an earth-vertical axis, translation along a 2m linear sled, or combined rotation and translation. The combination of rotation and translation allows linear acceleration stimuli at low frequencies (e.g., 0.01 Hz) that would require >900m of linear track to perform otherwise! Custom visual displays are available for tilt-translation adaptation studies. Eye movements are recorded with videography, and motion perception can be recorded with chair-fixed 'somatosensory' bars placed in front of the subject.
Pitch and Roll Tilt Chair (Static and Dynamic)
A hydraulic-driven tilt chair allows a subject to be oriented for pitch or roll rotation about an earth-horizontal axis. This system can be operated over a frequency range of 0-2 Hz, and provides tilts up to +/- 90 deg. The same chair design as utilized on the centrifuge allows comparison of eye movement and motion perception recordings evoked by tilt and centrifugation stimuli.
3-D Eye Movement Recording
In addition to conventional electro-oculography, the laboratory relies heavily on non-invasive near-infrared videography for eye movement recording using both commercial (SensoMotoric Instruments or Iscan) and custom systems developed by NASA. These systems track the pupil orientation (horizontal and vertical) and size, and utilize iris features to measure ocular torsion.
This laboratory includes a custom-built motorized two-axis tilt table on loan from the Navy to provide a standing subject pitch and roll rotation about an earth-horizontal axis, or off-vertical yaw rotation. The autonomic measurement equipment on loan from NASA include: an enhanced autonomic system with impedance cardiography (CNSystems Task-Force Monitor) a transcranial Doppler system (DWL, Germany), secondary blood pressure (Finapres, Datex-Ohmeda, ) and heart rate monitors (Ivy Biomedical), CO2 monitor (Datex-Ohmeda), and Respritrace (Ambulatory Monitoring Inc) for recording respiratory rate and volume.
Under the direction of Gin McCollum, Ph.D., the theoretical sensorimotor neurobiology group develops mathematics that reflects the organization of sensorimotor systems. Aside from collaborating with experimenters within the Neurotology Department, the theoretical neurobiology group collaborates with researchers on the neuronal and circuit levels of analysis, leading to multilevel investigations and understandings of sensorimotor systems. Current research interests include the conditional dynamics of sensorimotor coordination, the role of the vestibular nuclei in axial movements, and a group theoretic approach