title: Intratympanic manganese administration revealed sound intensity and frequency dependent functional activity in rat auditory pathway.
abstract: The cochlear plays a vital role in the sense and sensitivity of hearing; however, there is currently a lack of knowledge regarding the relationships between mechanical transduction of sound at different intensities and frequencies in the cochlear and the neurochemical processes that lead to neuronal responses in the central auditory system. In the current study, we introduced manganese-enhanced MRI (MEMRI), a convenient in vivo imaging method, for investigation of how sound, at different intensities and frequencies, is propagated from the cochlear to the central auditory system. Using MEMRI with intratympanic administration, we demonstrated differential manganese signal enhancements according to sound intensity and frequencies in the ascending auditory pathway of the rat after administration of intratympanic MnCl2.Compared to signal enhancement without explicit sound stimuli, auditory structures in the ascending auditory pathway showed stronger signal enhancement in rats who received sound stimuli of 10 and 40 kHz. In addition, signal enhancement with a stimulation frequency of 40 kHz was stronger than that with 10 kHz. Therefore, the results of this study seem to suggest that, in order to achieve an effective response to high sound intensity or frequency, more firing of auditory neurons, or firing of many auditory neurons together for the pooled neural activity is needed.
authors: Department of Medical & Biological Engineering, Kyungpook National University, Dongduk-Ro, Jung-Gu, Daegu, Korea.
authors: Seong-Uk
authors: SU
authors: Jin
authors: Jae-Jun
authors: JJ
authors: Lee
authors: Kwan Soo
authors: KS
authors: Hong
authors: Mun
authors: M
authors: Han
authors: Jang-Woo
authors: JW
authors: Park
authors: Hui Joong
authors: HJ
authors: Lee
authors: Sangheun
authors: S
authors: Lee
authors: Kyu-Yup
authors: KY
authors: Lee
authors: Kyung Min
authors: KM
authors: Shin
authors: Jin Ho
authors: JH
authors: Cho
authors: Chaejoon
authors: C
authors: Cheong
authors: Yongmin
authors: Y
authors: Chang
mesh_terms: D000818:Animals; D001306:Auditory Pathways / Q000187:drug effects* / Q000473:pathology*; D001696:Biomechanical Phenomena; D001933:Brain Stem / Q000473:pathology; D002712:Chlorides / Q000737:chemistry*; D003051:Cochlea / Q000502:physiology; D006309:Hearing; D008279:Magnetic Resonance Imaging; D008297:Male; D017895:Manganese Compounds / Q000737:chemistry*; D009474:Neurons / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013016:Sound; D014432:Tympanic Membrane / Q000187:drug effects
chemical_list: D002712:Chlorides; D017895:Manganese Compounds; C025340:manganese chloride
keywords: Auditory pathway; MEMRI; Sound frequency; Sound intensity