Arousal origin of the mouse thalamocortical audiovisual responses
To what extent thalamic activity contributes to multisensory integration at cortical level is unclear. To explore this, we used the mouse narrowband gamma oscillations (NBG), which arise from the lateral geniculate nucleus (LGN) and from upstream retinal inputs, as a tool to investigate potential thalamic transfer of audiovisual information to the primary visual cortex (V1). We found that audiovisual stimuli increased the power of V1 NBG and that this effect occurred independently of primary auditory cortex activation. Recordings from the LGN revealed that the majority of its neurons exhibited audiovisual properties consistent with those observed in the cortex. While neural data suggests a new role for the LGN as a multisensory integration and relay center, audiovisual responses align with changes in animal’s arousal, namely an increase in pupil diameter and a tachypneic response. Therefore, as recently reported by others, neural activity with apparent multisensory characteristics may simply arise from signals linked to the animal's internal state.
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