Anticipatory behavior reveals itself in the perceptual domain and in the motor domain. Expectant attention and motor preparation are characterized by selection, aimed at an amelioration of the signal-to-noise ratio in the information to be processed. The functional similarity of anticipatory attention and motor preparation is re¯ected in the underlying anatomical substrate. The prefrontal cortex, involved in a number of dierent networks, organizes anticipatory behavior in a top-down way by

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... ating cortico-cortical loops and thalamo-cortical loops to sensory and motor areas. The sensory areas are set to receive the impinging stimulus presentation, the motor areas are set to implement and execute the different motor programs. Thalamic nuclei are also activated from the prefrontal cortex, especially the large association nuclei, the dorsomedial nucleus and the pulvinar. In dierent models of selective attention the reticular nucleus of the thalamus has a special role in the distribution of the inhibitory control upon the information processing in the"relay" nuclei. It is hypothesized that it has the same pivotal position in motor preparation. Although the anatomical relations do not allow a direct test of the proposed hypothesis, the available psychophysiological evidence does not contradict it. Ó 0001-6918/99/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 1 -6 9 1 8 ( 9 9 ) 0 0 0 0 6 -2