Effect of selective attention on the latency of human frequency-following potentials.

While effects of attention on late and middle latency components of the evoked potential have been demonstrated, similar effects on brain stem evoked potentials--in particular on the human frequency-following potential (FFP)--are controversial. The FFP is a response to tone bursts in the frequency range of human language (optimum approximately 350 Hz). It has a latency of approximately 6.3 ms and is probably generated at a site peripheral to the inferior colliculus. We present data showing that the latency of the FFP can be shortened significantly (45 microseconds) if the subject is required to attend to the evoking auditory tone burst, while the amplitude of the FFP remains unaffected. This indicates an attention-controlled influence on signal processing in the earliest parts of the auditory pathway.