Kiuk Gwak

Freeing the visual channel by exploiting vibrotactile BCI feedback

Controlling a brain-actuated device requires the participant to look at and to split his attention between the interaction of the device with its environment and the status information of the Brain-Computer Interface (BCI). Such parallel visual tasks are partly contradictory, with the goal of achieving a good and natural device control. Is there a possibility to free the visual channel from one of these tasks? To address this, a stimulation system based on 6 coin-motors is developed, which provides a spatially continuous tactile illusion as BCI feedback, so that the visual channel can be devoted to the device. Several experiments are conducted in this work, to optimize the tactile illusion patterns and to investigate the influence on the electroencephalogram (EEG). Finally, 6 healthy BCI participants compare visual with tactile feedback in online BCI recordings. The developed stimulator can be used without interfering with the EEG. All subjects are able to perceive this type of tactile feedback well, and no statistical degradation in the online BCI performance could be identified between visual and tactile feedback.

Quantification and Reduction of Visual Load during BCI Operation

Operating a brain-actuated vehicle in real-world environments requires much of our visual attention. However, a typical brain-computer interface (BCI) sends the feedback information about the current status of the users brain also via the visual channel. As a result, users have to split their visual attention into two: one for the surroundings and the other for the visual BCI feedback. Therefore, we recently developed a tactile stimulation system that successfully replaced the conventional visual feedback. Here we employ the multiple object tracking experiments to quantify the visual load added by the visual feedback. The result show that the additional visual load is almost eliminated, and the true negative rate of the BCI operation (intentional non-control) is improved when the visual feedback is replaced by the tactile feedback.

P-181: A Charge-Share-Based Relative Read-Out Circuit for Capacitance Sensing

A new charge share based relative read-out circuit is proposed. The proposed relative scheme reduces number of integrators by half and alleviates requirements of following blocks, which can make the system more power-efficient. Charge share scheme increases read-out circuits sensitivity by cancelling parasitic capacitance effects of I/O pad.

Feel the BCI vibe – vibrotactile BCI feedback

Controlling a device via a brain-computer interface (BCI) requires the participant to look and to split the attention between the device and the BCI feedback, which is partly contradictory. Therefore, a stimulation system based on 6 coin-motors is developed, which provides a tactile illusion as BCI feedback. Several experiments are conducted to optimize the illusion parameters and to check the influence on the EEG. Furthermore, 6 healthy BCI subjects compared visual with tactile feedback in online MI recordings, and no performance degradation was found.

Improved Charge Pump with Reduced Reverse Current

A highly efficient charge pump that minimizes the reverse charge sharing current (in short, reverse current) is proposed. The charge pump employs auxiliary capacitors and diode-connected MOSFET along with an early clock to drive the charge transfer switches; this new method provides better isolation between stages. As a result, the amount of reverse current is reduced greatly and the clock driver can be designed with reduced transition slope. As a proof of the concept, a 1.1V-to-9.8 V charge pump was designed in a 0.35 μm 18 V CMOS technology. The proposed architecture shows 1.6 V ~ 3.5 V higher output voltage compared with the previously reported architecture.

A 2.048 Mb/s full-duplex free-space optical transceiver IC for a real-time in vivo neurofeedback mouse experiment under social interaction

We report the first free-space optical transceiver IC for social psychological neurofeedback experiments with multiple mice. The proposed IC, which includes a neural stimulator and neural recorder, is embedded in the head-mounted module of a mouse and communicates with an optical base station by using a mandatory 615 nm visible behavior tracking LED to save power. The proposed IC fabricated in a 0.18 μm BCDMOS process consumes 90 μW for optical TX while achieving a 2.048 Mb/s transmission rate.

Platform for analyzing multi-tasking capabilities during BCI operation

Operating brain-actuated devices requires split attention between the interaction of the device with its environment and the Brain-Computer Interface (BCI) feedback. Recently we demonstrated that BCI feedback could be provided via tactile stimulation and no difference between tactile and visual BCI feedback could be found. In this work we want to present a platform for analyzing these multi-tasking capabilities during BCI operation. Thereby, the subjects will have to perform a visual engaging and complex task in a game like setup while interacting with the BCI in a coordinated multi-tasking manner.

A novel tactile stimulation system for BCI feedback

When BCI based devices are operated, users are often desired to interact with environment. However, conventional visual BCI feedback disturbs continuous and smooth interactions. Therefore, a new tactile stimulation system suitable for delivering BCI feedback to user is developed. The system employs tactile illusion of movement to produce a continuous movement within six coin motors. Two protocols that convert the BCI feedback into spatiotemporal patterns of the stimulator are tested online. The results show that there are no identified artifacts in the EEG signal and no degradation of classification accuracy.

A novel stimulation method based on a neuromorphic mechanoreceptor model for haptic illusion

Vibrotactile stimulation system that generates haptic illusion by employing a RA mechanoreceptor model is developed. The developed stimulator consists of an array of 6 by 4 tiny ultrasonic linear motors [1,2] with nominal pitch of 2.9mm. Distal pad of human finger with RA mechanoreceptors is modeled using Bensmaias RA model [3]. In addition, stimulation characteristics of the motor are calibrated and modeled by measuring a trajectory using laser displacement sensor. Optimization algorithm with subgradient method derives the corresponding spatio-temporal stimulation patterns for 24 motors to provide a specified haptic illusion such as edge.