Related Experiment Video
Updated: Aug 6, 2026
09:25
Assessment of Ultrasonic Vocalizations During Drug Self-administration in Rats
Published on: July 22, 2010
A Subtype of Ultrasonic Vocalizations during Palatable Food Consumption in Rats Identified by Machine
Koshi Murata1,2, Yuki Ikedo3, Takashi Ryoke3,4
1Division of Brain Structure and Function, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan kmurata@u-fukui.ac.jp yugo@u-fukui.ac.jp.
Eneuro
|July 17, 2026
Summary
Researchers identified a new type of ultrasonic vocalization (USV) in rats, the 40-kHz inverted-U, specifically linked to eating palatable food like chocolate. This discovery offers a new way to study animal emotions and reward systems.
Area of Science:
- Neuroscience and Animal Behavior
- Bioacoustics and Machine Learning Applications
Background:
- Ultrasonic vocalizations (USVs) in rats are linked to emotional states but their diversity during rewarding experiences is poorly understood.
- Investigating USVs can provide insights into the neural basis of positive emotions and reward processing in animals.
Purpose of the Study:
- To explore the acoustic features of rat USVs during the consumption of palatable food, specifically chocolate.
- To identify and characterize novel USV subtypes associated with rewarding feeding behaviors.
- To investigate the role of the endogenous opioid system in modulating these vocalizations.
Main Methods:
- Male rats were recorded for USVs during chocolate consumption.
- A machine learning-assisted logistic regression model was used to classify USV subtypes based on spectrogram features.
- The effect of naloxone (opioid receptor antagonist) on USV emission was assessed.
- USV frequencies were compared between chocolate and standard food pellet consumption.
Main Results:
- A distinct USV subtype, termed the 40-kHz inverted-U, was selectively identified during chocolate consumption and tightly time-locked to feeding.
- Naloxone administration significantly reduced the emission of 40-kHz inverted-U USVs.
- 40-kHz inverted-U USVs were significantly more frequent during chocolate intake compared to standard food pellets, while 40-kHz flat USVs were comparable.
Conclusions:
- The 40-kHz inverted-U USV subtype likely reflects internal states associated with palatable food consumption and is modulated by the endogenous opioid system.
- Machine learning provides an effective tool for objective and high-throughput classification of USV subtypes.
- Specific USVs serve as promising behavioral readouts for studying the neurobiology of positive emotions, reward, and communication in rats.
