Differential Rapid Plasticity in Auditory and Visual Responses in the Primarily Multisensory Orbitofrontal Cortex

Abstract

Given the connectivity of orbitofrontal cortex (OFC) with the sensory areas and areas involved in goal execution, it is likely that OFC, along with its function in reward processing, also has a role to play in perceptionbased multisensory decision-making. To understand mechanisms involved in multisensory decision-making, it is important to first know the encoding of different sensory stimuli in single neurons of the mouse OFC. Ruling out effects of behavioral state, memory, and others, we studied the anesthetized mouse OFC responses to auditory, visual, and audiovisual/multisensory stimuli, multisensory associations and sensory-driven input organization to the OFC. Almost all, OFC single neurons were found to be multisensory in nature, with sublinear to supralinear integration of the component unisensory stimuli. With a novel multisensory oddball stimulus set, we show that the OFC receives both unisensory as well as multisensory inputs, further corroborated by retrograde tracers showing labeling in secondary auditory and visual cortices, which we find to also have similar multisensory integration and responses. With long audiovisual pairing/association, we show rapid plasticity in OFC single neurons, with a strong visual bias, leading to a strong depression of auditory responses and effective enhancement of visual responses. Such rapid multisensory association driven plasticity is absent in the auditory and visual cortices, suggesting its emergence in the OFC. Based on the above results, we propose a hypothetical local circuit model in the OFC that integrates auditory and visual information which participates in computing stimulus value in dynamic multisensory environments.

Choice-dependent cross-modal interaction in the medial prefrontal cortex of rats

“…Cross-modal enhancement appears not to be the default integrative mode for mPFC neurons of awake rats because most of them failed to show it in the choice-free task (Task 3). Similar results were found in other studies [67][68][69]. However, this result is quite different from earlier studies conducted in the superior colliculus and other sensory cortical areas that primarily showed enhanced multisensory responses to spatiotemporally congruent cues [3,4,70,71].…”

Modulation of auditory responses by visual inputs in the mouse auditory cortex

“…We found that most units responded robustly to the auditory stimulus and of these, ∼73% did not respond to the visual stimulus. Based on the latency of peak response to visual and auditory stimulus and the post-hoc Nissl staining of the sliced brain (Sharma and Bandyopadhyay, 2020), we claim that all of our electrodes were in the ACX. Thus, we claim the existence of inhibitory and excitatory neurons in layer 5/6 of the ACX as potential direct and indirect source that may drive hyperpolarization of neurons in layer2/3.…”

“…This percent can be explained by AuD’s proximity with secondary visual areas. AuD previously has been shown to be multisensory, responding to both auditory and visual stimuli (Sharma and Bandyopadhyay, 2020). Another point to notice here is that in the type MAV population, not all cells showed significant change on multisensory presentation (85%) and all those that did majority of them showed suppression (Fig.5A, Table 1).…”

“…We recorded responses to visual and auditory stimulus from layer 5/6 of the ACX using a 4 by 4 array of electrodes (data also published in the paper (Sharma and Bandyopadhyay, 2020)). We separated the recorded neurons into inhibitory and excitatory neurons based on the spike shapes (Fig.…”

“…This percent can be explained by AuD's proximity with secondary visual areas. AuD previously has been shown to be multisensory, responding to both auditory and visual stimuli (Sharma and Bandyopadhyay, 2020).…”