Feedback modality

The feedback modality is the sensory channel through which the decoder's output is returned to the user so they can close the control loop: most commonly vision (a cursor or rendered limb), but also audition, vibrotactile or electrotactile stimulation on the skin, natural somatosensation from a moving prosthesis, or intracortical microstimulation delivered directly to somatosensory cortex. The choice is not cosmetic — it sets the latency, bandwidth, and reliability of the feedback path, and therefore bounds the control performance achievable regardless of decoder quality.

Vision dominates because it is easy to instrument and information-rich, but it is comparatively slow, monopolizes attention and gaze, and competes with the visual demands of the task itself. Somatosensory channels, including biomimetic microstimulation, can be faster and can free vision for other purposes, at the cost of being harder to deliver and interpret. Combining modalities, or moving feedback from an artificial visual proxy toward naturalistic somatosensation, is a central goal of bidirectional BCI, since restoring a fast, intrinsic feedback channel is what makes fluent, eyes-free control plausible.