Data from: Encoding of speech modes and loudness in ventral precentral gyrus

The ability to vary the mode and loudness of speech is an important part
of the expressive range of human vocal communication. However, the
encoding of these behaviors in the ventral precentral gyrus (vPCG) has not
been studied at the resolution of neuronal firing rates. We investigated
this in two participants who had intracortical microelectrode arrays
implanted in their vPCG as part of a speech neuroprosthesis clinical
trial. Neuronal firing rates modulated strongly in vPCG as a function of
attempted mimed, whispered, normal, or loud speech. At the neural ensemble
level, mode/loudness and phonemic content were encoded in distinct neural
subspaces. Attempted mode/loudness could be decoded from vPCG with 94 %
and 89 % accuracy for the two participants, and corresponding neural
preparatory activity at 640 ms and 270 ms before speech onset enabled 80 %
decoding accuracy, respectively. We then developed a closed-loop loudness
decoder that achieved 94 % online accuracy in modulating a brain-to-text
speech neuroprosthesis output based on attempted loudness. These findings
demonstrate the feasibility of decoding mode and loudness from vPCG,
paving the way for speech neuroprostheses capable of synthesizing more
expressive speech.