Pondering the silence of reason

“As a man who, rejoicing in his gains,
suddenly seeing his gain turn into loss,
will grieve as he compares his then and now,

so she made me do, that relentless beast;
coming toward me, slowly, step by step,
she forced me back to where the sun is mute.

While I was rushing down to that low place,
my eyes made out a figure coming toward me
of one grown faint, perhaps from too much silence.”
-Dante (The Divine Comedy: Inferno, Canto 1)

I was rereading part of Inferno the other day and was stunned to find that someone had been sneaking around in my room and putting new phrases into my Dante book! I’ve probably read that canto close to fifteen times now, and I never thought of what Dante meant by the line “grown faint, perhaps from too much silence”; when did he put that there?!?! Anyway, it got me thinking of how Dante uses Virgil (the figure he sees coming toward him) as a symbol of human reason that guides him through hell. What does Dante mean by describing human reason as “growing faint, perhaps from too much silence”? Does this mean that reason grows faint not from exhaustion, but by neglect? Does this mean that “reason” is to be exercised in order to grow or even be maintained, and that when silenced, slowly degenerates?
Does anyone have any thoughts?