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Mismatch Negativity and Ear Laterality in Alzheimer's Disease and in Mild Cognitive Impairment
Esma Idrizbegovic1,2, Christina Hederstierna1,2, Ulf Rosenhall1,2
1Department of Audiology and Neurotology, Karolinska University Hospital, Stockholm, Sweden.
Background:
Cortical auditory event-related potentials (ERPs) were studied in order to measure mismatch negativity (MMN). Three groups of subjects were studied: patients with Alzheimer's disease (AD, n = 32), mild cognitive impairment (MCI, n = 44), and subjective memory complaints without cognitive decline (SMC, n = 27). A bottom up strategy was applied, and the right and left ears were stimulated monaurally.
Objective:
To investigate MMN in AD and MCI, and in a clinical reference group.
Methods:
ERPs were carried out with 500 tone pulses at 80 dBnHL. Each sequence included 80% standard tones (500 Hz) (f), and 20% deviant tones (1000 Hz) (r). MMN measurements were carried out by comparing the amplitudes of (f) and (r) recordings and to calculate the amplitude difference in μV for each group. The right and the left ears were analyzed separately.
Results:
A left ear advantage (LEA) of MMN amplitude was demonstrated in the two groups with better cognition (the MCI and the SMC groups), but not in the AD group.
Discussion:
The absence of MMN asymmetry in the AD group is possibly caused by a dysfunction to apprehend changes of tonal stimuli.
Insights
Mismatch negativity (MMN) auditory event-related potentials show a left ear advantage in mild cognitive impairment and subjective memory complaints, but not in Alzheimer's disease patients. This suggests impaired auditory change detection in Alzheimer's disease.
Area of Science:
- Neuroscience
- Auditory Neuroscience
- Cognitive Neuroscience
Background:
- Cortical auditory event-related potentials (ERPs) are used to measure mismatch negativity (MMN).
- Studies included patients with Alzheimer's disease (AD), mild cognitive impairment (MCI), and subjective memory complaints (SMC).
- A bottom-up strategy with monaural stimulation of right and left ears was employed.
Purpose of the Study:
- To investigate MMN in AD and MCI patients compared to a clinical reference group (SMC).
- To assess auditory processing differences in neurodegenerative conditions.
Main Methods:
- Auditory ERPs were elicited using sequences of standard (500 Hz) and deviant (1000 Hz) tones.
- MMN amplitude was calculated by comparing responses to standard and deviant tones.
- Analysis was performed separately for right and left ear stimulation.
Main Results:
- A significant left ear advantage (LEA) in MMN amplitude was observed in the MCI and SMC groups.
- This LEA was absent in the Alzheimer's disease (AD) group.
- The findings indicate altered auditory processing in AD.
Conclusions:
- The absence of MMN asymmetry in AD patients may indicate a dysfunction in processing auditory change detection.
- MMN analysis could serve as a potential biomarker for early detection of auditory processing deficits in AD.
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