Figure 4—figure supplement 1. | High performance communication by people with paralysis using an intracortical brain-computer interface

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High performance communication by people with paralysis using an intracortical brain-computer interface

Figure 4—figure supplement 1.

Affiliation details

Stanford University, United States; Emory University and Georgia Institute of Technology, United States; Emory University, United States; Massachusetts General Hospital, United States; Brown University, United States; Rehabilitation R&D Service, Department of VA Medical Center, United States; Case Western Reserve University, United States; Louis Stokes VA Medical Center, United States; Harvard Medical School, United States
Figure 4—figure supplement 1.
Download figureOpen in new tabFigure 4—figure supplement 1. Participant T6’s movements are greatly reduced when movements are actively suppressed.

In the previous analysis (Figure 4), we demonstrated that T6’s performance was largely unchanged even when she actively suppressed her movements. Here we quantified the degree to which movements were suppressed during those sessions. We first analyzed the participant’s movements during decoder calibration (panels a and b) and then closed-loop BCI control (panel c). For decoder calibration, we compared freely moving sessions and sessions in which movements were suppressed (see Materials and methods: Quantifying movement suppression). Decoders were calibrated using a center-out-and-back task, with the cursor’s position tied to the measured finger position (freely moving sessions) or with the cursor’s position following pre-programmed movements (i.e., ‘open-loop’ calibration) and finger movements were imagined (movement suppressed sessions). For each condition (i.e., freely moving vs. suppressed movement), we measured finger position as a function of time (relative to the starting position for each trial), and averaged these positions across all trials for a given target direction (the position of each pair of traces denotes the target’s position relative to the center target). (a) During movement-based decoder calibration (freely moving sessions), thumb movements (red) controlled the vertical axis, while index finger movements (blue) controlled the horizontal axis. Horizontal scale bars represent 200 ms, and the vertical scale bar represents 100 units on the glove sensor scale (arbitrary units). (b) During open-loop decoder calibration (movement suppressed sessions), in which T6 was asked to simply imagine finger movements but avoid moving to the best of her abilities, finger movements were largely suppressed but minute movement was still detectable. Scale bars match the previous panel. Overall, during decoder calibration, movements were greatly reduced (p<0.01, paired Student’s t test), and the median suppression ratio was a factor of 7.2 (index finger) and 12.6 (thumb). (c) We also quantified the amount of movement during closed-loop BCI control (grid task) in sessions in which movements were suppressed. Because individual trials were highly variable (targets appeared in random locations during the grid task), we grouped trials by the target direction (i.e., the angle between the previous target and the prompted target for the current trial). The position of each pair of traces in the circle denotes the target direction. To ensure that any minute movements were captured in the analysis, the absolute value (rather than the signed value) of the finger position was taken prior to averaging across trials. Scale bars match the previous panel. As shown, movement during closed-loop BCI control was comparable to or less than movement during decoder calibration (panel b), which itself was a factor of 7.2–12.6 times less than movement during movement-based decoder calibration (panel a).

DOI: http://dx.doi.org/10.7554/eLife.18554.028