FIGURE 1.

Prestimulus beta-frequency coherence and (conditional spectral) Granger causality maps derived from the sensorimotor cortices of two monkeys (A,B). A self-generated hand press (–1250 to –500 msec) cued the monkey that a visual stimulus (0 msec onset; 100 msec duration) was soon to appear on a visual display screen. The stimulus was subsequently perceptually discriminated as part of a visual pattern discrimination task (water reward given on response trials 500 msec after stimulus onset) (Bressler et al., 1993). In each case, the pattern of synchronization (coherence) and Granger causality of beta-band oscillations from primary and secondary somatosensory and motor cortices consistent with execution of the hand press cue: somatosensory input is fed to the primary somatosensory cortex and motor output is transmitted from the primary motor cortex to the motor spinal cord to the hand muscles to execute the hand press. Sulci: Cs – Central; As – Anterior; Ls – Lunate; STs – Superior Temporal; IPs – IntraParietal (Figure modified from Brovelli et al., 2004).