title: Mismatch negativity (MMN) reveals inefficient auditory ventral stream function in chronic auditory comprehension impairments.
abstract: BACKGROUND
  Auditory discrimination is significantly impaired in Wernicke's aphasia (WA) and thought to be causatively related to the language comprehension impairment which characterises the condition. This study used mismatch negativity (MMN) to investigate the neural responses corresponding to successful and impaired auditory discrimination in WA.
  
  
  METHODS
  Behavioural auditory discrimination thresholds of consonant-vowel-consonant (CVC) syllables and pure tones (PTs) were measured in WA (n = 7) and control (n = 7) participants. Threshold results were used to develop multiple deviant MMN oddball paradigms containing deviants which were either perceptibly or non-perceptibly different from the standard stimuli. MMN analysis investigated differences associated with group, condition and perceptibility as well as the relationship between MMN responses and comprehension (within which behavioural auditory discrimination profiles were examined).
  
  
  RESULTS
  MMN waveforms were observable to both perceptible and non-perceptible auditory changes. Perceptibility was only distinguished by MMN amplitude in the PT condition. The WA group could be distinguished from controls by an increase in MMN response latency to CVC stimuli change. Correlation analyses displayed a relationship between behavioural CVC discrimination and MMN amplitude in the control group, where greater amplitude corresponded to better discrimination. The WA group displayed the inverse effect; both discrimination accuracy and auditory comprehension scores were reduced with increased MMN amplitude. In the WA group, a further correlation was observed between the lateralisation of MMN response and CVC discrimination accuracy; the greater the bilateral involvement the better the discrimination accuracy.
  
  
  CONCLUSIONS
  The results from this study provide further evidence for the nature of auditory comprehension impairment in WA and indicate that the auditory discrimination deficit is grounded in a reduced ability to engage in efficient hierarchical processing and the construction of invariant auditory objects. Correlation results suggest that people with chronic WA may rely on an inefficient, noisy right hemisphere auditory stream when attempting to process speech stimuli.
authors.affiliation: University of Reading, UK.
authors.forename: Holly
authors.initials: H
authors.lastname: Robson
authors.affiliation: University of Manchester, UK.
authors.forename: Lauren
authors.initials: L
authors.lastname: Cloutman
authors.affiliation: University of Reading, UK.
authors.forename: James L
authors.initials: JL
authors.lastname: Keidel
authors.affiliation: University of Manchester, UK.
authors.forename: Karen
authors.initials: K
authors.lastname: Sage
authors.affiliation: Cardiff University, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Drakesmith
authors.affiliation: University of Manchester, UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: Welbourne
mesh_terms: D000161:Acoustic Stimulation; D000368:Aged; D001041:Aphasia, Wernicke / Q000503:physiopathology*; D001306:Auditory Pathways / Q000503:physiopathology*; D001307:Auditory Perception / Q000502:physiology*; D001309:Auditory Threshold / Q000502:physiology; D002540:Cerebral Cortex / Q000503:physiopathology*; D032882:Comprehension / Q000502:physiology*; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D011930:Reaction Time / Q000502:physiology
keywords: EEG; MMN; Mismatch negativity; Stroke; Wernicke's aphasia