g.Estim PRO: Specs & Features

fully programmable constant-current electrical stimulator for invasive use in human patients

brain-mapping in clinical and research environments

g.Estim PRO is a constant current, biphasic electrical stimulator intended for stimulation of neural tissue. g.Estim PRO has an applied part of type BF with connectors for bipolar stimulation electrodes (anode and cathode). The device is controlled by a computer via USB connection. It also has digital outputs for synchronization with other devices. A hand-switch allows you to perform stimulation manually. Alternatively, a foot-switch can be used to explicitly enable/disable stimulation.

g.Estim PRO includes an impedance check and measures the actually applied stimulation current and voltage for verification purposes. With its 80V compliance voltage, it is perfectly suited for use with standard as well as high-impedance electrodes and is able to produce the required stimulation current. The device is CE certified (Europe) and FDA-cleared (USA) for use in human patients for investigations like electrical cortical stimulation (ECS) mapping.

The g.Estim PRO is intended for functional brain mapping via electrical stimulation prior to cortical resections in the vicinity of essential cortex. The device must be used by medically trained and qualified personnel within a medical environment.

For closed-loop experiments, a g.USBamp or g.HIamp is used with g.HIsys to record EEG/ECoG data, perform real-time analysis and to control the g.Estim PRO for cortical stimulation (for research purposes only).

Product Highlights

  • Delivers bi-phasic constant current pulses
  • Stand-alone device that can be controlled in real-time from a computer system
  • Can send triggers to other devices for synchronization
  • Includes electrode impedance check and stimulation current monitoring
  • CE-certified and FDA-cleared medical device for use in human patients

Product details

The rear side of g.Estim PRO offers a switch to power the device on and off, a USB socket for the connection to the computer, one socket for digital input and two sockets for digital outputs. At the front side of the battery housing, the label shows how to insert the batteries.
The hand switch is an accessory of the g.Estim PRO. Users connect the hand switch to the hand/foot switch input of the g.Estim PRO. The hand switch allows them to start stimulation by pressing the blue STIMULATE button after the device has been set active via the software and the 'active' LED is on. During stimulation, the hand switch allows users to abort stimulation by pressing the grey ABORT button.
The foot switch is another accessory of the g.Estim PRO and can be connected to the hand/foot switch input of the g.Estim PRO. When the foot switch is used and pressed, the stimulator accepts a cue to start stimulation from the software or from devices connected to the digital input ports (in Advanced Mode). When the foot switch is released, stimulation is aborted.
The g.Estim PRO Simulink interface allows to control the stimulator in real-time in Advanced Mode. This allows to realize close-loop experiments with g.USBamp or g.HIamp. The model needs g.HIsys Highspeed Online Processing for SIMULINK.
There are three different session modes which can be accessed from the startup window: Basic, Handheld and Advanced modes. The Advanced Mode is only visible with a dongle connected for research applications.

The Advanced Mode (only for research applications) is suitable for advanced mapping procedures. This mode provides an extended configuration interface with additional settings. 

  • The Pulse settings group contains controls for defining the shape of the stimulation pulses. If the desired stimulus shall consist of more than one pulse, a train can be set.
  • Therefore, the Train settings group contains controls for defining the layout of more than one pulse into a stimulation train. 
  • The Sequence settings group contains controls for defining the layout of more than one train into a stimulation sequence. This group is only available in the Advanced mode. 
  • The Session group provides an overview about the chosen operation mode, the Doctor, the Operator and the Session identifier.
  • The Electrode Type and Surface group provides information about the chosen Electrode. The specified Electrode type and Surface area are shown. A click to the electrode type leads to the Electrode specification dialog (described above) and allows for changing the electrode type/surface area.
  • The Status/Control area contains all the elements for controlling the stimulation.
  • At the right side of the area, the stimulation control buttons are located. By clicking the Activate button, the device changes to the ACTIVE state and is ready for stimulation. After a click to Activate, no settings can be changed. For changing settings, the stimulator has to be brought to the STOP state by clicking the Stop button.

The following parameters are available:

  • Stimulation phase amplitude: 0.05 mA – 15 mA, Resolution 10 µA, Accuracy ± 10 % or 50 µA, whichever greater
  • Pulse form: biphasic and monophasic
  • Pulse onset interval: 2 ms – 10000 ms
  • Pulse rate (per s): 0.1 – 500 pulses per second with a resolution of 0.1 pulses per second, Accuracy ± 10%
  • Inter-phase duration: 0 – 1.0 ms in 10 µs increments, ± 10 % or ± 20 µs whichever greater
  • Train duration: 1 – 30000 pulses

The Basic Mode is suitable for standard ECS mapping procedures using standard cortical electrode grids. This mode provides a basic configuration interface with the most important settings. The following parameters are available:

  • Stimulation phase amplitude: 0.2 – 15 mA, Resolution 10 µA, Accuracy ± 10 % or 50 µA, whichever greater
  • Phase shape: rectangular
  • Pulse form: only biphasic
  • Train duration: 1 pulse – 20 seconds
  • Pulse onset interval: 10 ms – 500 ms
  • Pulse rate (per s): 2 – 100 pulses per second with a resolution of 0.1 pulses per second, Accuracy ± 10%
  • Phase duration: 0.1 – 1.0 ms in 10 µs increments, ± 10 % or ± 20 µs whichever greater
  • Inter-phase duration: always 0 ms

The Handheld Mode is suitable for intraoperative situations where the surgeon wants to stimulate multiple locations of the cortex with a hand-held probe. This mode provides a configuration interface with the most important settings. In this mode, the stimulator constantly measures the resistance between the electrodes. The following parameters are available:

  • Stimulation phase amplitude: 0.2 – 15 mA, Resolution 10 µA, Accuracy ± 10 % or 50 µA, whichever greater
  • Phase shape: rectangular
  • Pulse form: only biphasic
  • Train duration: 1 pulse – 20 seconds
  • Pulse onset interval: 10 ms – 500 ms
  • Pulse rate (per s): 2 – 100 pulses per second with a resolution of 0.1 pulses per second, Accuracy ± 10%
  • Phase duration: 0.1 – 1.0 ms in 10 µs increments, ± 10 % or ± 20 µs whichever greater
  • Inter-phase duration: always 0 ms

Application Fields of g.Estim PRO

Facephenes and Rainbows: Causal Evidence for Functional and Anatomical Specificity of Face and Color Processing in the Human Brain

The human brain handles several mental processes and cognitive tasks like the visual perception of the environment. Many studies investigated the role of individual brain regions during dedicated mental processes and tried to understand whether a specific brain region is exclusively engaged in such a process. In a recent study we partly answered that question by electrically stimulating the ventral temporal brain of a patient who underwent surgical treatment of epilepsy. Electrical stimulation of color- and face-selective sites, which were identified by means of visual evoked responses in the brain waves, affected only color and face percepts, respectively. The reported symptoms included illusory faces on top of objects and changed perception of faces during stimulation of face-selective regions, and the appearance of illusory rainbows near color-preferring sites. These findings support the theory that the brain at least partly consists of specialized regions that are exclusively and causally engaged in a dedicated mental process.

Watch the videos: Facephenes and Rainbows Part 1 | Facephenes and Rainbows Part 2

Read the publication: Schalk, G., Kapeller, C., Guger, C., Ogawa, H., Hiroshima, S., Lafer-Sousa, R., Saygin, Z.M., Kamada, K. and Kanwisher, N., 2017. Facephenes and rainbows: Causal evidence for functional and anatomical specificity of face and color processing in the human brain. Proceedings of the National Academy of Sciences , p.201713447.


Available configurations

Hardware and Accessories

product no.: 1150 read more g.Estim PRO bundle — intracranial electrical stimulator; AC stimulation, single & repetitive pulses; programmable, trigger able; required: Simulink Highspeed and g.tec biosignal amplifier.

See some related products

Software

read more High-Speed Online Processing under Simulink: Specs & Features — read biosignal data directly into SIMULINK; highly optimized hardware-interrupt controlled device driver; data processing with maximum system speed; signal analysis blocks

Hardware and Accessories

read more g.USBamp: Specs & Features — g.tec's high performance biosignal amplifier, acquisition and processing system
read more g.HIamp: Specs & Features — multi-channel biosignal amplifier

Related Media and Documents

Product Manuals/Handbooks

g.Estim

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g.ESTIM PRO cortical stimulator — 21/06/2017 — 257.98 kB

Product Brochures

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g.Estim PRO product card 2018 — 08/02/2018 — 536.16 kB