Multisensory Interactions in the Lateral Geniculate Nucleus

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DESCRIPTION (provided by applicant): The aim of the proposed research is to explore the radical idea that the primary information received by the visual cortex from the lateral geniculate nucleus (LGN) is not purely visual but rather visual information that has already been primed by information from other sensory modalities. For more than a century, the predominant view among neuroscientists has been that sensations are built into perceptions in a serial progression. According to this scheme, sensory "relay nuclei" of the thalamus such as the LGN simply provide a passive image of the world as captured by each sense organ to the first order neurons of the corresponding sensory cerebral cortex. Those first order neurons of the cortex add a bit more, the second order neurons still more and the percept is gradually built up through the cortical hierarchy and thereafter reaches multisensory association areas. In this proposal we hypothesize that the primate brain achieves fast and accurate decision-making in part due its ability to focus, right from the beginning, on relevant aspects of inputs from all sense organs without appreciating all the details presented by each sense organ. We propose that the brain compromises detailed representation and analysis of each sensory world for an overall "view" of the world that is versatile, reliable and highly informative to guide behavior. This requires a multimodal modulation of the primary information received by each sensory cortex. We present preliminary evidence to support this view. We argue that several recent reports showing cross-modal modulation of the activity of early cortical neurons also support this hypothesis. In this pilot effort we will explore the existence of (1) passive stimulus mixing (2) exogenous attention driven and (3) endogenous attention driven cross-modal interactions in the LGN and systematically characterize them. Our specific hypothesis is that cross-modal interactions occur in the earliest structures of the sensory pathway such as the LGN in a task dependent manner. In this pilot project, we will investigate whether these auditory-visual interactions are spatiotemporally precise, how the position of the eye relative to the head influences this interaction, and whether the modulation of visual responses is tuned for auditory parameters. Finally, we will explore whether endogenous crossmodal attentional effects can be obtained either for competing, cooperating, or both types of cross-modal cues. If we are able to support our preliminary results and begin to determine how multisensory interactions occur in sensory thalamus we could radically change current views of how information is processed at the earliest stages in the brain. PUBLIC HEALTH RELEVANCE When one sense, such as hearing, is lost due to disease, accident, or ageing, we must cope with the remaining senses, but the loss of one sense could impact the remaining senses also. This research will reveal how auditory neurons in the brain influence the performance of visual neurons and, therefore, how hearing loss could impact vision or how inappropriate integration between vision and audition could lead to schizophrenic symptoms. This will lead to more effective therapies.