In recent years, hybrid brain-computer interfaces (BCIs) have gained significant attention due to their demonstrated advantages in increasing the number of targets and enhancing robustness of the systems. However, Existing studies usually construct BCI systems using intense auditory stimulation and strong central visual stimulation, which lead to poor user experience and indicate a need for improving system comfort. Studies have proved that the use of peripheral visual stimulation and lower intensity of auditory stimulation can effectively boost the user's comfort. Therefore, this study used high-frequency peripheral visual stimulation and 40-dB weak auditory stimulation to elicit steady-state visual evoked potential (SSVEP) and auditory steady-state response (ASSR) signals, building a high-comfort hybrid BCI based on weak audio-visual evoked responses. This system coded 40 targets via 20 high-frequency visual stimulation frequencies and two auditory stimulation frequencies, improving the coding efficiency of BCI systems. Results showed that the hybrid system's averaged classification accuracy was (78.00 ± 12.18) %, and the information transfer rate (ITR) could reached 27.47 bits/min. This study offers new ideas for the design of hybrid BCI paradigm based on imperceptible stimulation.
Brain-Computer Interfaces ; Humans ; Evoked Potentials, Visual/physiology* ; Acoustic Stimulation ; Photic Stimulation ; Electroencephalography ; Evoked Potentials, Auditory/physiology* ; Adult

Rhythm, as a prominent characteristic of auditory experiences such as speech and music, is known to facilitate attention, yet its contribution to working memory (WM) remains unclear. Here, human participants temporarily retained a 12-tone sequence presented rhythmically or arrhythmically in WM and performed a pitch change-detection task. Behaviorally, while having comparable accuracy, rhythmic tone sequences showed a faster response time and lower response boundaries in decision-making. Electroencephalographic recordings revealed that rhythmic sequences elicited enhanced non-phase-locked beta-band (16 Hz-33 Hz) and theta-band (3 Hz-5 Hz) neural oscillations during sensory encoding and WM retention periods, respectively. Importantly, the two-stage neural signatures were correlated with each other and contributed to behavior. As beta-band and theta-band oscillations denote the engagement of motor systems and WM maintenance, respectively, our findings imply that rhythm facilitates auditory WM through intricate oscillation-based interactions between the motor and auditory systems that facilitate predictive attention to auditory sequences.
Humans ; Memory, Short-Term/physiology* ; Male ; Beta Rhythm/physiology* ; Female ; Theta Rhythm/physiology* ; Young Adult ; Auditory Perception/physiology* ; Adult ; Electroencephalography ; Acoustic Stimulation ; Reaction Time/physiology* ; Brain/physiology* ; Attention/physiology*

The ability to localize sound sources rapidly allows human beings to efficiently understand the surrounding environment. Previous studies have suggested that there is an auditory "where" pathway in the cortex for processing sound locations. The neural activation in regions along this pathway encodes sound locations by opponent hemifield coding, in which each unilateral region is activated by sounds coming from the contralateral hemifield. However, it is still unclear how these regions interact with each other to form a unified representation of the auditory space. In the present study, we investigated whether functional connectivity in the auditory "where" pathway encoded sound locations during passive listening. Participants underwent functional magnetic resonance imaging while passively listening to sounds from five distinct horizontal locations (-90°, -45°, 0°, 45°, 90°). We were able to decode sound locations from the functional connectivity patterns of the "where" pathway. Furthermore, we found that such neural representation of sound locations was primarily based on the coding of sound lateralization angles to the frontal midline. In addition, whole-brain analysis indicated that functional connectivity between occipital regions and the primary auditory cortex also encoded sound locations by lateralization angles. Overall, our results reveal a lateralization-angle-based representation of sound locations encoded by functional connectivity patterns, which could add on the activation-based opponent hemifield coding to provide a more precise representation of the auditory space.
Humans ; Sound Localization/physiology* ; Male ; Female ; Magnetic Resonance Imaging ; Young Adult ; Functional Laterality/physiology* ; Adult ; Brain Mapping ; Auditory Cortex/physiology* ; Acoustic Stimulation ; Auditory Pathways/physiology* ; Brain/physiology*

Humans and animals have a fundamental ability to use experiences and environmental information to organize behavior. It often happens that humans and animals make decisions and prepare actions under uncertain situations. Uncertainty would significantly affect the state of animals' minds, but may not be reflected in behavior. How to "read animals' mind state" under different situations is a challenge. Here, we report that neuronal activity in the medial prefrontal cortex (mPFC) of rats can reflect the environmental uncertainty when the task situation changes from certain to uncertain. Rats were trained to perform behavioral tasks under certain and uncertain situations. Under certain situations, rats were required to simply repeat two nose-poking actions that each triggered short auditory tone feedback (single-task situation). Whereas under the uncertain situation, the feedback could randomly be either the previous tone or a short musical rhythm. No additional action was required upon the music feedback, and the same secondary nose-poking action was required upon the tone feedback (dual-task situation); therefore, the coming task was uncertain before action initiation. We recorded single-unit activity from the mPFC when the rats were performing the tasks. We found that in the dual task, when uncertainty was introduced, many mPFC neurons were actively engaged in dealing with the uncertainty before the task initiation, suggesting that the rats could be aware of the task situation change and encode the information in the mPFC before the action of task initiation.
Animals ; Prefrontal Cortex/cytology* ; Uncertainty ; Neurons/physiology* ; Male ; Rats ; Rats, Long-Evans ; Action Potentials/physiology* ; Acoustic Stimulation

Atypical sensory responsivity is widely reported in autistic individuals and is related to elevated functional difficulties. Dynamically, altered initial responses and/or habituation rates could underlie their atypical averaged responses to repeated sensory stimuli. In this study we aimed to measure the arousal level in response to different types of auditory stimuli and the dynamic change of atypical arousal level using pupillometry in autistic children. In Experiment 1, 43 autistic children and 49 neurotypical (NT) children were asked to passively listen to a mild sound and an aversive sound repeatedly. In Experiment 2, 39 autistic children and 44 NT children who went through Experiment 1 listened to a gradually emerging non-startling sound and a suddenly emerging startling sound in a random order. We found that the autistic group showed hyper-arousal in response to the aversive sound and the startling sound as reflected by their larger change in pupil area. In comparison, these autistic children demonstrated normal arousal in response to the mild sound and the non-startling sound. Dynamically, the autistic group had a larger peak pupil area change than the NT group in the first trial and a normal habituation rate to the aversive sound. In summary, our results suggest hyper-arousal to aversive and startling stimuli and the role of larger initial responses in hyper-arousal in autism. Minimizing aversive and startling sensory stimuli or gradually increasing the volume of aversive auditory stimuli to allow autistic children to adapt using the principle of habituation is recommended to reduce the arousal level and problematic behaviors of autistic children.
Humans ; Male ; Child ; Female ; Acoustic Stimulation ; Autistic Disorder/physiopathology* ; Arousal/physiology* ; Pupil/physiology* ; Habituation, Psychophysiologic/physiology* ; Auditory Perception ; Child, Preschool

Integrating multisensory inputs to generate accurate perception and guide behavior is among the most critical functions of the brain. Subcortical regions such as the amygdala are involved in sensory processing including vision and audition, yet their roles in multisensory integration remain unclear. In this study, we systematically investigated the function of neurons in the amygdala and adjacent regions in integrating audiovisual sensory inputs using a semi-chronic multi-electrode array and multiple combinations of audiovisual stimuli. From a sample of 332 neurons, we showed the diverse response patterns to audiovisual stimuli and the neural characteristics of bimodal over unimodal modulation, which could be classified into four types with differentiated regional origins. Using the hierarchical clustering method, neurons were further clustered into five groups and associated with different integrating functions and sub-regions. Finally, regions distinguishing congruent and incongruent bimodal sensory inputs were identified. Overall, visual processing dominates audiovisual integration in the amygdala and adjacent regions. Our findings shed new light on the neural mechanisms of multisensory integration in the primate brain.
Animals ; Macaca ; Acoustic Stimulation ; Auditory Perception/physiology* ; Visual Perception/physiology* ; Amygdala/physiology* ; Photic Stimulation

The anterior auditory field (AAF) is a core region of the auditory cortex and plays a vital role in discrimination tasks. However, the role of the AAF corticostriatal neurons in frequency discrimination remains unclear. Here, we used c-Fos staining, fiber photometry recording, and pharmacogenetic manipulation to investigate the function of the AAF corticostriatal neurons in a frequency discrimination task. c-Fos staining and fiber photometry recording revealed that the activity of AAF pyramidal neurons was significantly elevated during the frequency discrimination task. Pharmacogenetic inhibition of AAF pyramidal neurons significantly impaired frequency discrimination. In addition, histological results revealed that AAF pyramidal neurons send strong projections to the striatum. Moreover, pharmacogenetic suppression of the striatal projections from pyramidal neurons in the AAF significantly disrupted the frequency discrimination. Collectively, our findings show that AAF pyramidal neurons, particularly the AAF-striatum projections, play a crucial role in frequency discrimination behavior.
Acoustic Stimulation/methods* ; Neurons/physiology* ; Auditory Cortex/physiology* ; Auditory Perception ; Pyramidal Cells

The classical auditory oddball paradigm is a commonly used experimental paradigm for evoking event related potentials (ERPs). The present study was aimed to explore the auditory cognitive processing mechanism of space perception of human brain. We employed an auditory oddball paradigm of binaural unbiased and biased sound intensity to compare and analyze the response characteristics of ERP. By focusing on the spatial lateralization characteristics of P300 and mismatch negativity (MMN) components, we analyzed their lateralization trends according to the laterality index. We found that both P300 and MMN components showed right-hemisphere lateralization phenomenon under the stimulation of asymmetric intensity of auditory acoustic. The results suggested that the right hemisphere of human brain played a key role in spatial information processing. The results also indicated that the hemispherical characteristics of the brain were not related to the actual spatial direction of the auditory stimulus, but were determined by the hemispherical functions of the brain. Furthermore, the results suggested that the MMN components induced by spatial differences were stronger in females than those in males.
Acoustic Stimulation ; Auditory Perception/physiology* ; Brain Mapping ; Electroencephalography ; Evoked Potentials ; Evoked Potentials, Auditory/physiology* ; Female ; Humans ; Male

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.
Acoustic Stimulation ; Animals ; Auditory Perception/physiology* ; Geniculate Bodies ; Rats ; Rats, Wistar ; Thalamic Nuclei/physiology*

OBJECTIVE: To investigate the auditory response patterns of mouse primary auditory cortex (A1) neurons. METHODS: In vivo cell-attached recordings and neural network modeling were performed to detect the changes in response patterns of A1 neurons of awake C57BL/6J mice to sound stimulation with varying lengths. A1 neuron signals were recorded for 216 neurons in 20 awake mice using a target sound stimulation sequence, and the classification and response characteristics of A1 neuron response patterns were examined using post-stimulus spike time histograms. To simulate the diversity of the A1 neuron response patterns, an A1 neuron model was established based on the Wilson-Cowan model and integral-firing model. The neuron connection weight parameters in the model were calculated by examining the micro loop structure of the pyramidal neurons, parvalbumin neurons, and somatostatin neurons in the A1 region, and the A1 neural network information coding model was constructed. RESULTS: The Onset response neurons only had fast spike response within 10 to 40 ms after the beginning of noise stimulation (122 neurons). The Sustained response neurons had spike response continuously during the noise stimulation (26 neurons). The On-off response neurons had fast spike response after the beginning and the end of noise stimulation (40 neurons). The Offset response neurons only had fast spike response within 10 to 40 ms after the end of noise stimulation (22 neurons). In the neural network model, the Onset peak neural activities of A1 pyramidal neurons, parvalbumin neurons, and somatostatin neurons were 0.7483, 0.5236 and 0.9427, respectively, and their response half peak widths were 18.5 ms, 12 ms and 31 ms during the 100 ms noise stimulation, respectively. By changing the feedforward excitation and synaptic inhibition time constants in the model, the neurons generated numerous different types of spike train. CONCLUSION The auditory response of mouse A1 neurons to sound stimuli shows mainly the Onset, Sustained, On-off, and Offset response patterns.
Acoustic Stimulation ; Animals ; Auditory Cortex/physiology* ; Mice ; Mice, Inbred C57BL ; Parvalbumins ; Somatostatin