A single word that means "mental reaction speed"?

I'm searching for a single-word descriptor that means "mental quickness", "mental reaction speed" or very similar with little additional connotation (unlike alacrity or wits).

EDIT: The word has to be able to stand on its own like an icon; I can't rely on context for meaning. It is an attribute for a table-top role playing game. The character will have a score or rating to represent how mentally quick they are that they will need to call up readily during a game. The word doesn't need to imply that their reactions are correct or accurate, only fast.

EDIT 2: The game is set in the mid-near future and is Post-Cyberpunk in nature. Any words that reflect that setting are especially helpful.

Impulse

Alternatives: Synapse, Neuron, Reflex

Since it's a one word name for a score in a table-top game, I don't think the definition has to mean exactly what the score represents, it just has to be memorable with the player and loosely correlated to the actual definition.

Acuity

sharpness or keenness of thought, vision or hearing: intellectual acuity; visual acuity

ODO; Wiktionary