Positron Emission Tomography Imaging Reveals Auditory and Frontal Cortical Regions Involved with Speech Perception and Loudness Adaptation

• Published in: PloS one Vol. 10; no. 6; p. e0128743
• Main Authors: Berding, Georg, Wilke, Florian, Rode, Thilo, Haense, Cathleen, Joseph, Gert, Meyer, Geerd J, Mamach, Martin, Lenarz, Minoo, Geworski, Lilli, Bengel, Frank M, Lenarz, Thomas, Lim, Hubert H
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 05.06.2015; Public Library of Science (PLoS)
• Subjects: Acoustic Stimulation; Activation; Adaptation; Adaptation, Physiological; Adult; Aged; Auditory Cortex - pathology; Auditory Cortex - physiopathology; Auditory Cortex - surgery; Auditory system; Brain Mapping; Brain stem; Brain Stem - pathology; Brain Stem - physiopathology; Brain Stem - surgery; Cerebral cortex; Cochlea; Cochlea - pathology; Cochlea - physiopathology; Cochlea - surgery; Cochlear Implantation; Cochlear Implants; Cortex (auditory); Cortex (frontal); Deactivation; Deafness; Electrodes; Emissions; Female; Frontal Lobe - pathology; Frontal Lobe - physiopathology; Frontal Lobe - surgery; Health physics; Hearing loss; Hearing Loss, Bilateral - pathology; Hearing Loss, Bilateral - physiopathology; Hearing Loss, Bilateral - surgery; Humans; Implants; Loudness; Male; Medical imaging; Medical schools; Mesencephalon; Microprocessors; Middle Aged; Neuroimaging; NMR; Nuclear magnetic resonance; Nuclear medicine; Otolaryngology; Patients; Perception; Positron emission; Positron emission tomography; Prefrontal cortex; Recovery of Function; Rehabilitation; Restoration; Sensory stimulation; Speech; Speech perception; Speech Perception - physiology; Studies; Tinnitus; Tomography; Transplants & implants; New York; United States > US; Germany
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0128743

Considerable progress has been made in the treatment of hearing loss with auditory implants. However, there are still many implanted patients that experience hearing deficiencies, such as limited speech understanding or vanishing perception with continuous stimulation (i.e., abnormal loudness adaptation). The present study aims to identify specific patterns of cerebral cortex activity involved with such deficiencies. We performed O-15-water positron emission tomography (PET) in patients implanted with electrodes within the cochlea, brainstem, or midbrain to investigate the pattern of cortical activation in response to speech or continuous multi-tone stimuli directly inputted into the implant processor that then delivered electrical patterns through those electrodes. Statistical parametric mapping was performed on a single subject basis. Better speech understanding was correlated with a larger extent of bilateral auditory cortex activation. In contrast to speech, the continuous multi-tone stimulus elicited mainly unilateral auditory cortical activity in which greater loudness adaptation corresponded to weaker activation and even deactivation. Interestingly, greater loudness adaptation was correlated with stronger activity within the ventral prefrontal cortex, which could be up-regulated to suppress the irrelevant or aberrant signals into the auditory cortex. The ability to detect these specific cortical patterns and differences across patients and stimuli demonstrates the potential for using PET to diagnose auditory function or dysfunction in implant patients, which in turn could guide the development of appropriate stimulation strategies for improving hearing rehabilitation. Beyond hearing restoration, our study also reveals a potential role of the frontal cortex in suppressing irrelevant or aberrant activity within the auditory cortex, and thus may be relevant for understanding and treating tinnitus.