Transcranial Magnetic Stimulation (TMS) is delivered by a coil on the surface of the head, which generates a brief but powerful magnetic pulse that induce a temporary current in a small area on the surface of the brain. This current can interfere with processing of the brain with high temporal and fair spatial precision. Our facility includes a stereotactic guidance system for the TMS coil that enables us to visualize the precise site of stimulation in the brain.
The laboratory houses two single pulse, monophasic stimulators (Magstim 200 Mono Pulse (http://goo.gl/CgGdT)). The stimulators are triggered either manually or by the control computer via digital I/O. Users have a choice between two 70-mm double coils and two 90-mm circular coils, capable of a maximum magnetic field of 2.2T and 2.0T, respectively. Each stimulator outputs TTL triggers to a Response Time Box for accurate time stamps.
Coil positioning is performed with image-guided neuro-navigation via a Rogue Research Brainsight 2 system (http://goo.gl/hbR9s ) . The Brainsight 2 software runs on a dedicated Apple iMac computer. The coils are tracked with a Northern Digital Polaris Hybrid Position Sensor (http://goo.gl/9iSox ) that communicates with the Brainsight 2 system. Subjects are seated in a specialized Rogue Research Gen 3 TMS chair surrounded by an aluminum frame that supports coil and head positioning (http://goo.gl/y4Mk3 ) . The chair provides a chin rest and forehead rest, and allows independent positioning of two coils. The chair may be rotated and reclined back for alternate subject positioning, depending on the needs of the experiment. The Brainsight 2 system also allows for the recording of motor-evoked potentials with a 2-channel built-in EMG device.
Stimulus control and display is performed with an Apple Mac Pro set up with both Windows 7 and OS X and a flat CRT monitor. A Response Time Box (http://goo.gl/7XkVG ) provides accurate time stamping of a photodiode and TTL pulses from each TMS stimulator.
The laboratory also houses a 120Hz infrared eye tracker (SMI RED ( http://goo.gl/v2tyv )
) underneath the stimulus display monitor. The eye tracker is controlled by a Dell laptop and communicates with the stimulus control Mac Pro via Ethernet communication. The TMS lab has a license for the SMI Experiment Suite 360 software. This Windows software suite includes BeGaze for eye data analysis, and Experiment Center for stimulus display.