Motor control in old age: evidence of impaired low-level inhibition.

In the masked prime task, responses to supraliminal targets are influenced by previously presented subliminal primes. When targets follow primes immediately, positive compatibility effects are obtained such that performance is better when prime and target are compatible (mapped to the same response) than when they are incompatible (mapped to opposite responses). In young adults, this pattern reverses with longer interstimulus intervals (negative compatibility effect). These effects reflect an activation-followed-by-inhibition process: Primes trigger an initial activation of their corresponding motor response, which is subsequently inhibited. The present study demonstrates that healthy older adults (M = 76 years) show a substantial positive compatibility effect with a short prime-target interval, but they fail to produce reliable negative compatibility effects with longer intervals, indicating an age-related impairment in low-level motor control.