title: Single unit hyperactivity and bursting in the auditory thalamus of awake rats directly correlates with behavioural evidence of tinnitus.
abstract: Tinnitus is an auditory percept without an environmental acoustic correlate. Contemporary tinnitus models hypothesize tinnitus to be a consequence of maladaptive plasticity-induced disturbance of excitation-inhibition homeostasis, possibly convergent on medial geniculate body (MGB, auditory thalamus) and related neuronal networks. The MGB is an obligate acoustic relay in a unique position to gate auditory signals to higher-order auditory and limbic centres. Tinnitus-related maladaptive plastic changes of MGB-related neuronal networks may affect the gating function of MGB and enhance gain in central auditory and non-auditory neuronal networks, resulting in tinnitus. The present study examined the discharge properties of MGB neurons in the sound-exposure gap inhibition animal model of tinnitus. MGB single unit responses were obtained from awake unexposed controls and sound-exposed adult rats with behavioural evidence of tinnitus. MGB units in animals with tinnitus exhibited enhanced spontaneous firing, altered burst properties and increased rate-level function slope when driven by broadband noise and tones at the unit's characteristic frequency. Elevated patterns of neuronal activity and altered bursting showed a significant positive correlation with animals' tinnitus scores. Altered activity of MGB neurons revealed additional features of auditory system plasticity associated with tinnitus, which may provide a testable assay for future therapeutic and diagnostic development.
authors.affiliation: Southern Illinois University School of Medicine Department of Pharmacology, Springfield, IL, USA.
authors.forename: Bopanna I
authors.initials: BI
authors.lastname: Kalappa
authors.affiliation: Southern Illinois University School of Medicine Department of Surgery, Division of Otolaryngology, Springfield, IL, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Brozoski
authors.affiliation: Southern Illinois University School of Medicine Department of Surgery, Division of Otolaryngology, Springfield, IL, USA Department of Psychology-Illinois College, Jacksonville, IL, USA.
authors.forename: Jeremy G
authors.initials: JG
authors.lastname: Turner
authors.affiliation: Southern Illinois University School of Medicine Department of Pharmacology, Springfield, IL, USA Southern Illinois University School of Medicine Department of Surgery, Division of Otolaryngology, Springfield, IL, USA dcaspary@siumed.edu.
authors.forename: Donald M
authors.initials: DM
authors.lastname: Caspary
mesh_terms: D000200:Action Potentials; D000818:Animals; D005829:Geniculate Bodies / Q000166:cytology / Q000503:physiopathology*; D009474:Neurons / Q000502:physiology; D051381:Rats; D020318:Rats, Long-Evans; D014012:Tinnitus / Q000503:physiopathology*; D014851:Wakefulness