Functional MRI evidence for a role of ventral prefrontal cortex in tinnitus

Abstract

It has long been known that subjective tinnitus, a constant or intermittent phantom sound perceived by 10 to 15 % of the adult population, is not a purely auditory phenomenon but is also tied to limbic-related brain regions. Supporting evidence comes from data indicating that stress and emotion can modulate tinnitus, and from brain imaging studies showing functional and anatomical differences in limbic-related brain regions of tinnitus patients and controls. Recent studies from our lab revealed altered blood oxygen level-dependent (BOLD) responses to stimulation at the tinnitus frequency in the ventral striatum (specifically, the nucleus accumbens) and gray-matter reductions (i.e. anatomical changes) in ventromedial prefrontal cortex (vmPFC), of tinnitus patients compared to controls. The present study extended these findings by demonstrating functional differences in vmPFC between 20 tinnitus patients and 20 age-matched controls. Importantly, the observed BOLD response in vmPFC was positively correlated with tinnitus characteristics such as subjective loudness and the percent of time during which the tinnitus was perceived, whereas correlations with Tinnitus Handicap Inventory scores and other variables known to be affected in tinnitus (e.g. depression, anxiety, noise sensitivity, hearing loss) were weaker or absent. This suggests that the observed group differences are indeed related to the tinnitus percept and not to an affective reaction to tinnitus. The results further corroborate vmPFC as a region of high interest for tinnitus research.

Association of Chronic Subjective Tinnitus with Neuro-Cognitive Performance

“…The results of the present study on these cognitive tasks suggest that tinnitus interferes with the nonauditory processing 10,35 as the patients performed poorly on digit span, verbal comprehension, mental balance, attention & concentration, immediate recall, visual recognition and visual-motor gestalt subtests. The correlation between different cognitive performances with tinnitus loudness and onset duration, indicated their association as hypothesized in other studies 10,20 .…”

“…Observed negative correlation of onset-duration and loudness with performance on VAIS shows that longer the duration, poorer the performance similarly greater the tinnitus loudness poorer the performance, especially for information subtest. This association indicates that the subjective tinnitus loudness and/or duration might had influenced cortical modifications 20,42 , also associated with deviated functional connectivity between frontaltemporal-occipital cortices in the tinnitus group 10 .…”

“…Andersson and McKenna reported that tinnitus had an interfering effect on cognitive functions, observed in those subjects who attend to the tinnitus (Andersson and McKenna, 2006), association of nonverbal performance with the duration further in present study emphasize the non-auditory areas modification. It was also suggested by fronto-occipital cortical areas (functional) connectivity in the tinnitus patients 10,20,42 . The performance of the tinnitus patients on memory test (PGIMS) was affected on subtests: mental balance (72% patients), attention & concentration (52%), immediate recall (68%), remote memory (44%), retention of dissimilar pairs (44%) and visual recognition of pictures (40%).…”

“…The performance might be altered due to deviated attention 43,44 for auditory 15,39 and nonauditory sensory processing 45 , poor working memory 46 , word recall, plan execution 47 , remote memory or/and autobiographical memory 48 . It can be hypothesized that in tinnitus patients due the reduction of gray matter in the ventromedial prefrontal cortex that participates in auditory gating 20 there is disruption in the processing of information and working memory system 46 , the attention is focused to tinnitus 43 leading to cognitive inefficiency 15 .…”

“…Inclusion criteria for selection in the study were: patients with consistent idiopathic subjective tinnitus, tinnitus onset since 10 weeks or more (≥ 2.5 months), and those who gave their written consent for the study, before starting their tinnitus management. Onset duration ≥ 2.5 months was considered as chronic tinnitus in concordance with neuro-cognitive studies 19,20 and chronic pain definition in ICD10. Exclusion criteria were: patients having any external or middle ear pathology, suspected of Meniere's disease or otosclerosis, having acoustic neuroma or vestibular schwanomma, with history of ototoxicity, sudden hearing loss, ear trauma, noise induced hearing loss, having any systemic disorders, and/ or any other organic neurological or psychiatric disease.…”