Sherman and Guillery (2002) proposed that thalamic sensory nuclei might function as first- or higher-order relays. According to their hypothesis, first order relays (such as rat’s ventral postero-medial nucleus, VPM) transmit sensory information from the periphery to the cortex, while the function of higherorder relays (such as rat’s medial posterior nucleus, PoM) is to transmit information between cortical areas via cortico-thalamo-cortical connections. In our experiments on awake Wistar rats we recorded extracellular field potentials from VPM, PoM and barrel cortex, while mechanically stimulating the rats’ vibrissae and manipulating their level of arousal by additional aversive stimuli, i.e. loud sounds, or electric shocks applied on the skin of the ear. We assessed functional connection strengths between the three structures during stimuli processing using cross-trial correlation (Sobolewski et al. 2010). Our results from quiescent rats corroborate Sherman and Guillery’s proposition. At low arousal level (no aversive stimuli) the sensory signal was primarily relayed from VPM to the barrel cortex and from there to PoM. However at high arousal level this network scheme was short-circuited and the barrel cortex also received input directly from PoM. We show that sensory pathways,form a dynamic system, which is capable of reconfiguring the sensory signal’s route to cortical areas in step with the animal’s behavioral context. This research was supported by the Polish National Science Centre grant N N401 533040.
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