Abstract
Auditory steady-state responses (ASSRs) represent the electrophysiological activity of the auditory nervous system in response to a periodic acoustic stimulus. Spectrogram analysis can reveal the frequency and phase information entrained in ASSRs. Clinically, the ASSR is used to detect abnormalities in electroencephalographs obtained from schizophrenia patients, who show reduced power and phase locking of ASSRs. The neonatal ventral hippocampal lesion (NVHL) rat is a widely used model to investigate the neurodevelopmental mechanisms of schizophrenia. It has been established that NVHL rats exhibit several schizophrenia-like behavioral and molecular abnormalities. However, no clear abnormalities in ASSRs have been reported to date. The present study compared ASSRs of adult NVHL and sham-operated rats. We inserted microelectrodes into the primary auditory cortex (A1) or posterior auditory field (PAF) and recorded the local field potential (LFP) in response to 40- and 80-Hz click train stimuli. Spectrogram analysis was performed to obtain the mean trial power (MTP) and phase-locking factor (PLF) of the click train-evoked LFPs. We found that in the control animals, A1 showed a stronger MTP and PLF of ASSR than PAF, and NVHL operation mainly impaired the ASSR in PAF. Analysis of spike activity also indicated that NVHL operation extended the duration of tone-evoked responses in PAF neurons. Our results reveal, for the first time, that NVHL may distinctly influence the neural activities of primary and non-primary fields of the auditory cortex.
Highlights
The disruption of neural synchronization and information integration is considered a key pathological characteristic of schizophrenia [1]
PPI of the acoustic startle response is disrupted in neonatal ventral hippocampal lesion (NVHL) rats The 6 NVHL rats used in this study showed a significant decrease in PPI compared with the 6 sham rats (Fig 2; p = 0.04, t test; Cohen’s d effect size = 1.33)
We found that the NVHL rat model exhibits a significantly reduced auditory steady state response (ASSR), a common phenomenon observed in electrophysiological examinations of schizophrenia patients
Summary
The disruption of neural synchronization and information integration is considered a key pathological characteristic of schizophrenia [1]. ASSRs in patients with schizophrenia are typically reduced in power or phase synchronization in response to a 40-Hz stimulation ASSR deficits in the 40-Hz range suggest the function of auditory cortex (AC) is disturbed in schizophrenia [9]. Individuals with schizophrenia commonly show auditory symptoms including auditory hallucinations. Magnetic resonance imaging studies have attributed the auditory symptoms in schizophrenia to the altered activation of the AC [10,11,12,13]. Loss of dendritic spines and alterations of synaptic signaling have been observed in the AC of schizophrenia patients [14,15]. The AC is a worthy subject of schizophrenia research
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