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.
Animals ; Auditory Cortex/physiology* ; Neuronal Plasticity/physiology* ; Neurons ; Rats ; Thalamus ; Visual Cortex/physiology*

OBJECTIVE: To explore whether the characteristic responses to sound stimulations of the auditory neurons in the striatum is regulated in different behavioral states. METHODS: The auditory neurons in the striatum of awake C57BL/6J mice were selected for this study. We recorded the auditory response of the striatum to noises over a long period of time by building a synchronous in vivo electrophysiological and locomotion recording system and using glass microelectrode attachment recording. By analyzing the running speed of the mice, the behavioral states of the mice were divided into the quiet state and the active state, and the spontaneous activity and evoked responses of the auditory neurons in the striatum were analyzed in these two states. RESULTS: Compared with those recorded in the quiet state, the spontaneous activity of the auditory neurons in the striatum of the mice increased significantly (37.06±12.02 vs 18.51±10.91, P < 0.001) while the auditory response of the neurons decreased significantly (noise intensity=60 dB, 3.45±2.99 vs 3.04±2.76, P < 0.001) in the active state. CONCLUSION Locomotion has a significant inhibitory effect on the auditory response of the striatum, which may importantly contribute to the decline of sound information recognition ability in the active state.
Acoustic Stimulation ; Animals ; Auditory Cortex/physiology* ; Evoked Potentials, Auditory ; Locomotion/physiology* ; Mice ; Mice, Inbred C57BL ; Neurons

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

Using conventional electrophysiological technique, we investigated the effects of stimulating the medial prefrontal cortex (mPFC) on plasticity of frequency receptive field (RF) in auditory cortical (AC) neurons in rats. When the mPFC was electrically stimulated, the RF plasticity of 51 (27.2%) neurons was not affected and that of 137 neurons (72.8%) was either inhibited (71 neurons, 37.7%) or facilitated (66 neurons, 35.1%). The modulation of RF plasticity by the stimulation of mPFC was dependent upon the time interval between acoustic and electrical stimuli. The best interval time that produced optimal modulation (inhibition or facilitation) ranged from 5 to 30 ms. The inhibitory modulation of mPFC prolonged RF shifting time and shortened RF recovery time. Conversely, the facilitatory modulation of mPFC shortened RF shifting time and prolonged RF recovery time. Our results suggest that the mPFC may affect the plasticity of functional activity in AC neurons, and also may participate in the process of auditory learning and memory.
Animals ; Auditory Cortex ; cytology ; Electric Stimulation ; Neuronal Plasticity ; Neurons ; physiology ; Prefrontal Cortex ; physiology ; Rats

Prepulse inhibition (PPI) refers to a decreased response to a startling stimulus when another weaker stimulus precedes it. Most PPI studies have focused on the physiological startle reflex and fewer have reported the PPI of cortical responses. We recorded local field potentials (LFPs) in four monkeys and investigated whether the PPI of auditory cortical responses (alpha, beta, and gamma oscillations and evoked potentials) can be demonstrated in the caudolateral belt of the superior temporal gyrus (STGcb). We also investigated whether the presence of a conspecific, which draws attention away from the auditory stimuli, affects the PPI of auditory cortical responses. The PPI paradigm consisted of Pulse-only and Prepulse + Pulse trials that were presented randomly while the monkey was alone (ALONE) and while another monkey was present in the same room (ACCOMP). The LFPs to the Pulse were significantly suppressed by the Prepulse thus, demonstrating PPI of cortical responses in the STGcb. The PPI-related inhibition of the N1 amplitude of the evoked responses and cortical oscillations to the Pulse were not affected by the presence of a conspecific. In contrast, gamma oscillations and the amplitude of the N1 response to Pulse-only were suppressed in the ACCOMP condition compared to the ALONE condition. These findings demonstrate PPI in the monkey STGcb and suggest that the PPI of auditory cortical responses in the monkey STGcb is a pre-attentive inhibitory process that is independent of attentional modulation.
Animals ; Auditory Cortex ; physiology ; Evoked Potentials, Auditory ; physiology ; Macaca mulatta ; Male ; Prepulse Inhibition ; physiology ; Temporal Lobe ; physiology

OBJECTIVETo explore the feasibility to evaluate objectively auditory temporal resolution using the iso-modulation depth temporal modulation transfer function (TMTF) derived from the amplitude of evoked response to sinusoidally modulated signals.

METHODSChronic electrodes were implanted in inferior colliculus and auditory cortex of guinea pigs. We recorded the evoked response to sinusoidally modulated tones with modulation frequency being varied from 20 to 400 Hz and modulation depth fixed at 100%. The response amplitude in uV was converted into relative amplitude using the fast Fourier transform (FFT) function provided by Biosig software, and then the iso-modulation depth TMTF was plotted with the relative amplitude changed with modulation frequency. Then we recorded the evoked response to the sinusoidally modulated tones with modulation depth being varied from 100% to 10% and derived the iso-amplitude TMTF comparable to conventional modulation depth threshold TMTF. The derived iso-amplitude TMTF was compared to iso-modulation depth TMTF to determine the validity of iso-modulation depth TMTF.

RESULTSThe iso-modulation-depth TMTF and iso-amplitude TMTF in inferior colliculus and auditory cortex of guinea pigs represented respectively bandpass and lowpass characteristic. The cut-off frequency calculated from the two TMTF methods didn't differ significantly and the cut-off frequency derived from auditory cortex iso-modulation depth TMTF was consistent with behavioral results.

CONCLUSIONSThe TMTF plotted with the response amplitude to sinusoidally modulated tones with the modulation depth fixed at 100% and the modulation frequency was a valid method to evaluate objectively auditory temporal resolution.

Animals ; Auditory Cortex ; physiology ; Electrodes ; Evoked Potentials, Auditory ; physiology ; Fourier Analysis ; Guinea Pigs ; Inferior Colliculi ; physiology ; Reaction Time

Slow vertex response (SVR) is one of long latency auditory evoked potentials. It is a biological and electric response originating from brain cortical neuron evoked by sound stimulus with the latency from 50 to 500 milliseconds. Of all the neuroelectric physiological audiometries, it is the earliest method applied in assessing the function of the auditory neural conduction pathway. The concept, neural generators of SVR have been introduced in this article. Influencing factors on SVR were discussed such as stimulus parameters, consciousness state, age, maturation of the subject. Applications of SVR in clinical and forensic medicine identification were also discussed.
Acoustic Stimulation/methods* ; Audiometry, Evoked Response/methods* ; Auditory Cortex/physiology* ; Auditory Pathways/physiology* ; Auditory Threshold ; Cerebral Cortex/physiology* ; Evoked Potentials, Auditory ; Forensic Medicine/methods* ; Hearing Disorders/diagnosis* ; Humans ; Reaction Time

OBJECTIVETo study the change of synaptic onset latency and threshold in primary auditory cortex (A1) during the development of SD rat.

METHODSExtracellular recording was used to locate A1, followed by transferred to loose-patch and whole-cell patch in vivo to record the spike activity, synaptic onset latency and threshold responses respectively. Rats were divided into 4 groups according to ages, postnatal 12-15 days, 16-18 days, 19-24 days and adult (> 3 months).

RESULTS1. The onset latency of local field potential in A1 of adult rats[(10-20)ms] was shorter than young rats[(20-30)ms]. 2. During development, the onset latency of spikes of a single neuron in response to white noise pulses decreased. And the latency in young rats P12-15 [(40.15 ± 2.67) ms] and P16-18 [(33.86 ± 4.61) ms] were longer than in adults [(22.93 ± 2.94) ms] (ANOVA-test, t = 4.330 and 1.995, P = 0.00 and 0.04) . However, the onset latencies of P19-24 [(24.80 ± 3.63) ms] and adult had no significant difference (P > 0.05). 3.Synaptic onset latencies of both excitation and inhibition were significantly longer in P12-15[ (38.94 ± 1.90) ms, (35.26 ± 2.40) ms] and P16-18[ (32.68 ± 2.52) ms, (30.24 ± 2.18) ms] than in adults [(19.4 ± 1.06) ms, (18.91 ± 0.77) ms] excitation (t = 6.255 and 4.662, P < 0.01) inhibition (t = 8.918 and 4.820, P < 0.01) showed significant difference. Whereas the onset latencies of P19-24[ (23.67 ± 2.46) ms, (21.43 ± 1.80) ms] and adults displayed no prominent difference(P > 0.01). Meanwhile, the difference between the onset latencies of excitation and inhibition became narrower during development[ (3.15 ± 1.02) ms, (2.01 ± 0.73) ms, (1.79 ± 0.85) ms, (0.39 ± 0.48) ms]. P12-15 had notably difference in comparison to adults (t = 1.739, P < 0.01). 4. The thresholds of synaptic response were notably higher in P12-15 (40.0 ± 1.6) dB and P16-18 (41.3 ± 11.6) dB when compared with adults (30.9 ± 0.6) dB (t = 5.284 and 5.867, P < 0.01) . While that of P19-24 (35.0 ± 32.7) dB showed no distinct difference (P > 0.01).

CONCLUSIONSingle neuron spiking activity, synaptic onset latency and threshold evoked by sound stimulus gradually mature during the development in rat A1.

Acoustic Stimulation ; Animals ; Auditory Cortex ; physiology ; Neurons ; physiology ; Rats ; Rats, Sprague-Dawley

Similar to the visual dual-pathway model, neurophysiological studies in non-human primates have suggested that the dual-pathway model is also applicable for explaining auditory cortical processing, including the ventral "what" pathway for object identification and the dorsal "where" pathway for spatial localization. This review summarizes evidence from human neuroimaging studies supporting the dual-pathway model for auditory cortical processing in humans.
Animals ; Auditory Cortex ; anatomy & histology ; physiology ; Auditory Pathways ; anatomy & histology ; physiology ; Auditory Perception ; physiology ; Humans ; Macaca ; anatomy & histology ; physiology ; Models, Neurological ; Neurons ; physiology ; Pitch Discrimination ; physiology ; Sound Localization ; physiology ; Space Perception ; physiology

OBJECTIVETry to observe the plasticity of neuron in primary cortex of rat evoked by conditioned stimulus of different sound level.

METHODSApplying conventional electrophysiological technique of extracellular recording to investigate the plasticity of characteristic frequency (CF) and frequency turning curve (FIC) of neurons in rat auditory cortex (AC) by determining CF shifts of neurons caused by sound stimulus of different sound level.

RESULTSWhen the frequency difference between conditioned stimulus (CS) frequency and the CF of neuron was in 1.0 kHz, the plasticity of CF induced by CS was associated with sound level. The probability of the plasticity of CF evoked by CS of higher sound lever was more than the lower. And the probability was dependent on frequency turning curve (FTC) and almost independent on the sound level of conditioned signal.

CONCLUSIONSound level of conditioned stimulus differs the plasticity of characteristic frequency of neurons in rat auditory cortex.

Acoustic Stimulation ; Animals ; Auditory Cortex ; cytology ; Auditory Perception ; physiology ; Conditioning, Classical ; physiology ; Female ; Male ; Neuronal Plasticity ; physiology ; Neurons ; physiology ; Perceptual Masking ; Rats ; Rats, Sprague-Dawley ; Sound