Ray Guillery
All thalamic inputs that are relayed to cortex come in axons that also send a branch to motor structures. Thus, cortex receives information from sensory receptors about the body and the world and about subcortical activity from first order thalamic relays (see Sherman abstract) and about cortical processing of those inputs from higher order relays. In addition cortex also receives from all of these inputs copies of instructions for upcoming actions (efference copies) that are on their way to execution in the motor branches. That is, essentially all the information that cortex receives from thalamus, i.e. most of the information that cortex receives, concerns sensorimotor contingencies (O'Regan and No, 2001, Behav. Brain Sci, 24,939-973), not purely sensory information. 'Sensory' here refers to past, 'motor' to future events. Wolpert & Miall, (1996, Neural Netw., 9:1265-1279) discuss how efference copies generate "forward models" about upcoming actions. Thalamus, as a gate controlling information transfer to cortex, controls generation of ubiquitous cortical forward models. Vukadinovic (2012, EJN, 34,1031-9) relates the thalamic gate to control of forward models, arguing that a closed gate prevents actions from being recognized as generated by the organism, i.e. the self, and suggesting that this links functional and structural abnormalities of the thalamus to some symptoms of schizophrenia; Rolfs et al. (2011, Nature Neuroscience 14: 252-256) demonstrate the role of forward models in attention. The ubiquity of efference copies in thalamocortical circuits suggests that key problems of the self and of attention depend on readily identifiable thalamocortical pathways.
