Optoelectronic Synapses Based on MXene/Violet Phosphorus van der Waals Heterojunctions for Visual‑Olfactory Crossmodal Perception

The crossmodal interaction of different senses,which is an important basis for learning and memory in the human brain,is highly desired to be mimicked at the device level for developing neuromorphic crossmodal perception,but related researches are scarce.Here,we demonstrate an optoelectronic synapse for vision-olfactory crossmodal perception based on MXene/violet phosphorus(VP)van der Waals heterojunctions.Benefiting from the efficient separation and transport of photogenerated carriers facilitated by conductive MXene,the photoelectric responsivity of VP is dramatically enhanced by 7 orders of magnitude,reaching up to 7.7 A W^(−1).Excited by ultraviolet light,multiple synaptic functions,including excitatory postsynaptic currents,pairedpulse facilitation,short/long-term plasticity and“learning-experience”behavior,were demonstrated with a low power consumption.Furthermore,the proposed optoelectronic synapse exhibits distinct synaptic behaviors in different gas environments,enabling it to simulate the interaction of visual and olfactory information for crossmodal perception.This work demonstrates the great potential of VP in optoelectronics and provides a promising platform for applications such as virtual reality and neurorobotics.

Excitatory Crossmodal Input to a Widespread Population of Primary Sensory Cortical Neurons

Crossmodal information processing in sensory cortices has been reported in sparsely distributed neurons under normal conditions and can undergo experience-or activity-induced plasticity.Given the potential role in brain function as indicated by previous reports,crossmodal connectivity in the sensory cortex needs to be further explored.Using perforated whole-cell recording in anesthetized adult rats,we found that almost all neurons recorded in the primary somatosensory,auditory,and visual cortices exhibited significant membrane-potential responses to crossmodal stimulation,as recorded when brain activity states were pharmacologically down-regulated in light anesthesia.These crossmodal cortical responses were excitatory and subthreshold,and further seemed to be relayed primarily by the sensory thalamus,but not the sensory cortex,of the stimulated modality.Our experiments indicate a sensory cortical presence of widespread excitatory crossmodal inputs,which might play roles in brain functions involving crossmodal information processing or plasticity.

AB056. Multisensory stochastic facilitation: effect of thresholds and reaction times

Background:The concept of stochastic facilitation suggests that the addition of precise amounts of white noise can improve the perceptibility of a stimulus of weak amplitude.We know from previous research that tactile and auditory noise can facilitate visual perception,respectively.Here we wanted to see if the effects of stochastic facilitation generalise to a reaction time paradigm,and if reaction times are correlated with tactile thresholds.We know that when multiple sensory systems are stimulated simultaneously,reaction times are faster than either stimulus alone,and also faster than the sum of reaction times(known as the race model).Methods:Five participants were re-tested in five blocks each of which contained a different background noise levels,randomly ordered across sessions.At each noise level,they performed a tactile threshold detection task and a tactile reaction time task.Results:Both tactile threshold and tactile reaction times were significantly affected by the background white noise.While the preferred amplitude for the white noise was different for every participant,the average lowest threshold was obtained with white noise presented binaurally at 70 db.The reaction times were analysed by fitting an ex-Gaussian,the sum of a Gaussian function and an exponential decay function.The white noise significantly affected the exponential parameter(tau)in a way that is compatible with the facilitation of thresholds.Conclusions:We therefore conclude that multisensory reaction time facilitation can,at least in part,be explained by stochastic facilitation of the neural signals.

Cross-Modal Interaction and Integration Through Stimulus-Specific Adaptation in the Thalamic Reticular Nucleus of Rats

Stimulus-specific adaptation(SSA),defined as a decrease in responses to a common stimulus that only partially generalizes to other rare stimuli,is a widespread phenomenon in the brain that is believed to be related to novelty detection.Although cross-modal sensory processing is also a widespread phenomenon,the interaction between the two phenomena is not well understood.In this study,the thalamic reticular nucleus(TRN),which is regarded as a hub of the attentional system that contains multi-modal neurons,was investigated.The results showed that SSA existed in an interactive oddball stimulation,which mimics stimulation changes from one modality to another.In the bimodal integration,SSA to bimodal stimulation was stronger than to visual stimulation alone but similar to auditory stimulation alone,which indicated a limited integrative effect.Collectively,the present results provide evidence for independent cross-modal processing in bimodal TRN neurons.