Thalamic encoding of complex sensory patterns and its possible role in cognition

Abstract

The function of the higher-order sensory thalamus remains unresolved. Here, POm nucleus was examined by in vivo extracellular recordings across a range of complex sensory patterns. We found that POm was highly sensitive to multiwhisker stimuli involving complex spatiotemporal interactions. The dynamical spatiotemporal structure of sensory patterns and the different complexity of their parts were accurately reflected in precise POm activity changes. Importantly, POm was also able to respond to ipsilateral stimulation and was implicated in the representation of bilateral tactile events by integrating simultaneous signals arising from both whisker pads. We found that POm nuclei are mutually connected through the cortex forming a functional POm-POm loop. We unravelled the nature and content of the messages travelling through this loop showing that they were structured patterns of sustained activity. These structured messages were transmitted preserving their integrated structure. The implication of different cortical areas was investigated revealing that S1 plays a protagonist role in this functional loop. Our results also demonstrated different laminar implication in the processing of sustained activity in this cortical area and its transmission between hemispheres. We propose a theoretical model in which these structured patterns of sustained activity generated by POm may play important roles in perceptual, motor and cognitive functions. From a functional perspective, this proposal, supported by the results described here, provides a novel theoretical framework to understand the implication of the thalamus in cognition. In addition, a profound difference was found between VPM and POm functioning. The hypothesis of Complementary Components is proposed here to explain it. HighlightsPOm is implicated in the representation of complex sensory patterns. POm is implicated in the encoding of bilateral tactile events. POm nuclei are mutually connected through the cortex forming a functional POm-POm loop. Structured patterns of sustained activity travelling through the loop O_FIG O_LINKSMALLFIG WIDTH=199 HEIGHT=200 SRC="FIGDIR/small/257667v2_ufig1.gif" ALT="Figure 1"> View larger version (51K): org.highwire.dtl.DTLVardef@217b4forg.highwire.dtl.DTLVardef@26a381org.highwire.dtl.DTLVardef@b88b0eorg.highwire.dtl.DTLVardef@1b15904_HPS_FORMAT_FIGEXP M_FIG C_FIG