Short Latency Effects of Auditory Frequency Change on Human Motor Behavior

Auditory frequency change (FC) might be crucial to respond to. We hypothesized that FC affects human motor behavior within short latency, and that upwards <i>vs</i> downwards changes exert distinct effects. Behavioral correlates of asymmetries in FC processing are scarcely researched. Previous work of ours showed direction-biased FC effect in a tapping task. Here we probed the effect’s specificity to the frequency domain, and its latency. Twenty-three musicians synchronized finger-tapping to isochronous beeps, set in sequences presenting increments/decrements, in frequency/intensity (Loud, Soft, Up, Down). We recorded tap-timing, finger acceleration, and muscle activity. Diverging behavior patterns implied domain-specificity: Intensity conditions yielded responses correlated with change-direction – increments elicited earlier taps of aroused <i>action profile</i> and vice versa, whereas FC to <i>both</i> directions elicited <i>early action triggering</i>. Within Frequency, Up’s effect arose 160 ms post-change, Down’s effect significantly later. These results cannot be accounted for by mere surprise effect. Swift modulation of motor behavior elicited by task-irrelevant FC was shown, biased by FC direction. Latencies imply early cortical components involved in the bias. Early latency covert human motor responses evoked by FC may form a facet of everyday auditory perception, and of specialized domains as music.