The effect of dopamine on the comprehension of spectrally-shifted noise-vocoded speech: a pilot study

Peripheral hearing in Parkinson's disease: a systematic review

OBJECTIVE

To investigate the implications of Parkinson's disease (PD) in the peripheral auditory system, a systematic survey of the scientific literature was conducted.

DESIGN

Systematic review.

STUDY SAMPLE

An electronic search of the non-gray literature in the last decade was conducted using the digital databases MEDLINE® (PubMed interface), LILACS® (Virtual Health Library), Web of Science® (CAPES publications portal), and SciELO®. Studies addressing peripheral auditory function as part of the range of nonmotor PD symptoms were selected for analysis.

RESULTS

Pure tone audiometry data suggested that sensorineural hearing loss was more severe in the PD population than in the control groups. The effects of PD on cochlear function were evidenced by a decrease in the levels of otoacoustic emissions.

CONCLUSIONS

Sensorineural hearing loss and cochlear impairment are more severe in the PD population than in the control groups. Additional studies are recommended to further understand the characteristics of the peripheral auditory system in PD patients, which constitutes an emerging subject in the scientific literature.

Processing of Degraded Speech in Brain Disorders

The speech we hear every day is typically "degraded" by competing sounds and the idiosyncratic vocal characteristics of individual speakers. While the comprehension of "degraded" speech is normally automatic, it depends on dynamic and adaptive processing across distributed neural networks. This presents the brain with an immense computational challenge, making degraded speech processing vulnerable to a range of brain disorders. Therefore, it is likely to be a sensitive marker of neural circuit dysfunction and an index of retained neural plasticity. Considering experimental methods for studying degraded speech and factors that affect its processing in healthy individuals, we review the evidence for altered degraded speech processing in major neurodegenerative diseases, traumatic brain injury and stroke. We develop a predictive coding framework for understanding deficits of degraded speech processing in these disorders, focussing on the "language-led dementias"-the primary progressive aphasias. We conclude by considering prospects for using degraded speech as a probe of language network pathophysiology, a diagnostic tool and a target for therapeutic intervention.