Sound frequency dependence of duration mismatch negativity recorded from awake rats

Abstract

Aims The brain function that detects deviations in the acoustic environment can be evaluated with mismatch negativity (MMN). MMN to sound duration deviance has recently drawn attention as a biomarker for schizophrenia. Nonhuman animals, including rats, also exhibit MMN‐like potentials. Therefore, MMN research in nonhuman animals can help to clarify the neural mechanisms underlying MMN production. However, results from preclinical MMN studies on duration deviance have been conflicting. We investigated the effect of sound frequency on MMN‐like potentials to duration deviance in rats. Methods Event‐related potentials were recorded from an electrode placed on the primary auditory cortex of free‐moving rats using an oddball paradigm consisting of 50‐ms duration tones (standards) and 150‐ms duration tones (deviants) at a 500‐ms stimulus onset asynchrony. The sound frequency was set to three conditions: 3, 12, and 50 kHz. Results MMN‐like potentials that depended on the short‐term stimulus history of background regularity were only observed in the 12‐kHz tone frequency condition. Conclusions MMN‐like potentials to duration deviance are subject to tone frequency of the oddball paradigm in rats, suggesting that rats have distinct sound duration recognition ability.

The dopamine D2 agonist quinpirole impairs frontal mismatch responses to sound frequency deviations in freely moving rats

“…Surgery and electrode placement were performed as described previously 25–27 . Rats (11‐12 weeks old) were anesthetized by intraperitoneal injection of a combination anesthetic containing 0.375‐mg/kg medetomidine (Kyoritsu Seiyaku), 2‐mg/kg midazolam (Sandoz), and 2.5‐mg/kg butorphanol (Meiji Seika Pharma), and positioned in a stereotaxic frame (SR‐5R‐HT; Narishige).…”

“…ECoG recording was performed as described previously 26,27 . Rats were handled for five consecutive days and acclimatized to a recording chamber prior to the commencement of ECoG recording.…”

“…Rats were handled for five consecutive days and acclimatized to a recording chamber prior to the commencement of ECoG recording. ECoG recording occurred in a dimly lit room (0.1 lx) during the dark cycle, which is the active phase in rats 25–27,36 . Each awake rat was placed in the transparent electrically shielded plastic box (dimensions 18 × 36 × 30 cm) during acclimation (15 min) and subsequent stimulation sessions.…”

“…In the equiprobable condition, all nondeviant epochs were extracted. Epochs containing amplitudes exceeding ± 500 μV at either electrode were rejected as artifacts 26,27 . The mean (±SEM) number of epochs used for the calculations as follows: pre‐administration (vehicle‐deviant, 185.90 ± 2.34; vehicle‐nondeviant, 183.00 ± 5.28; quinpirole‐deviant, 179.90 ± 4.05; quinpirole‐nondeviant, 182.60 ± 4.24); post‐administration (vehicle‐deviant, 178.60 ± 5.54; vehicle‐nondeviant, 185.60 ± 3.49; quinpirole‐deviant, 185.80 ± 3.04; quinpirole‐nondeviant, 187.80 ± 5.55).…”

“…Small rodents, such as mice and rats show MMN‐like responses that closely resemble that of humans 24–27 . These animals, which are available for interventional studies, are useful in revealing the molecular and neural bases of MMN 28,29 .…”