Functional Imaging of Auditory Cortex in Adult Cats using High-field fMRI

Trecia A. Brown; Joseph S. Gati; Sarah M. Hughes; Pam L. Nixon; Ravi S. Menon; Stephen G. Lomber

doi:10.3791/50872

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Method Article

Functional Imaging of Auditory Cortex in Adult Cats using High-field fMRI

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DOI:

10.3791/50872

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February 19th, 2014

Trecia A. Brown¹^,⁶ , Joseph S. Gati⁵ , Sarah M. Hughes⁵ , Pam L. Nixon¹^,⁶ , Ravi S. Menon³^,⁴^,⁵ , Stephen G. Lomber¹^,²^,⁴^,⁵^,⁶^,⁷

¹Department of Physiology and Pharmacology, University of Western Ontario, ²Department of Psychology, University of Western Ontario, ³Department of Medical Biophysics, University of Western Ontario, ⁴Brain and Mind Institute, University of Western Ontario, ⁵Centre for Functional and Metabolic Mapping, Robarts Research Institute, University of Western Ontario, ⁶Cerebral Systems Laboratory, University of Western Ontario, ⁷National Centre for Audiology, University of Western Ontario

Summary

Functional studies of the auditory system in mammals have traditionally been conducted using spatially-focused techniques such as electrophysiological recordings. The following protocol describes a method of visualizing large-scale patterns of evoked hemodynamic activity in the cat auditory cortex using functional magnetic resonance imaging.

Abstract

Current knowledge of sensory processing in the mammalian auditory system is mainly derived from electrophysiological studies in a variety of animal models, including monkeys, ferrets, bats, rodents, and cats. In order to draw suitable parallels between human and animal models of auditory function, it is important to establish a bridge between human functional imaging studies and animal electrophysiological studies. Functional magnetic resonance imaging (fMRI) is an established, minimally invasive method of measuring broad patterns of hemodynamic activity across different regions of the cerebral cortex. This technique is widely used to probe sensory function in the human brain, is a useful tool in linking studies of auditory processing in both humans and animals and has been successfully used to investigate auditory function in monkeys and rodents. The following protocol describes an experimental procedure for investigating auditory function in anesthetized adult cats by measuring stimulus-evoked hemodynamic changes in auditory cortex using fMRI. This method facilitates comparison of the hemodynamic responses across different models of auditory function thus leading to a better understanding of species-independent features of the mammalian auditory cortex.

Introduction

Current understanding of auditory processing in mammals is mainly derived from invasive electrophysiological studies in monkeys^1-5, ferrets^6-10, bats^11-14, rodents^15-19, and cats^20-24. Electrophysiological techniques commonly utilize extracellular microelectrodes to record the activity of single and multiple neurons within a small area of neural tissue surrounding the electrode tip. Established functional imaging methods, such as optical imaging and functional magnetic resonance imaging (fMRI), serve as useful complements to extracellular recordings by providing a macroscopic perspective of simultaneous driven act....