Models for entrainment of neural rhythms

Abstract

Psychological results suggest that motor and perceptual behavior are organized by neural rhythms with periods from seconds to tenths of a second. It appears that their entrainment to external speech and music or to internal motor coordination rhythm is essential for effective performance. It is proposed that theta-alpha sensory-motor cycles (5–15 Hz) form the basis of these rhythms. They generate and entrain rhythmic motor output or temporal perceptual expectancies. It is hypothesized that cortical EEG and event-related potentials (ERPs) reflect thalamic biasing currents. The cortical evoked potential is a 5–15 Hz signal whose peaks and troughs correlate with stages of cortical information processing in sensory-motor tasks. Cortical rhythms are found in visual, auditory, and somatosensory areas as well as the hippocampus and reticular system that entrain to periodic inputs. If the arrival of an auditory stimulus is regular, it has been shown that 5–12 Hz auditory activity becomes phase locked in advance of the target stimulus to the expected arrival time. Our model of rhythmic expectation accounts for this since the theta-alpha rhythmic cycles constitute a fast clock that adjusts phase and frequency to match stimulus arrival, and longer period cycles are derived from this base clock.