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Keywords:

  • complex motion;
  • cortico-thalamo-cortical loops;
  • extrageniculate thalamus;
  • higher-order processing;
  • spatio-temporal integration

Abstract

Our laboratory previously showed that thalamic neurons in an extrageniculate nucleus, the lateral posterior-pulvinar complex (LP-pulvinar) could perform higher-order neuronal operations that had until then only been attributed to higher-level cortical areas. To further assess the role of the thalamus in the analysis of complex percepts, we have investigated whether neurons in the LP-pulvinar complex can signal the direction of motion of random-dot kinematograms wherein the individual elements of the pattern do not provide coherent motion cues. Our results indicate that a subset of LP-pulvinar cells can integrate the displacement of individual elements into a global motion percept and that their large receptive fields permit the integration of motion for elements separated by large spatial intervals. We also found that almost all of the global motion-sensitive neurons were not systematically pattern-motion-selective when tested with plaid patterns. The results indicate that LP-pulvinar cells can perform the higher-level spatio-temporal integration required to detect the global displacement of objects in a complex visual scene, further supporting the notion that extrageniculate thalamic cells are involved in higher-order motion processing. Furthermore, these results provide some evidence that there may be specialized mechanisms for processing different types of complex motion within the LP-pulvinar complex.