Comparison between mismatch negativity amplitude and magnetic mismatch field strength in normal adults

Abnormality of Auditory Mismatch Negativity in Depression and Its Dependence on Stimulus Intensity

Mismatch negativity (MMN) is thought to reveal several abnormalities of cognitive functioning. Although depression often affects cognitive functioning, previous studies concerning MMN in depressed patients provided conflicting results. In recent reports, it has been suggested that depressed patients may show abnormal auditory response to regular auditory stimuli presented with at a relatively high intensity. We thus recorded acoustic MMN in 16 drug-free patients suffering from moderate depression and in 10 healthy subjects at 2 different stimulus intensities. Differences in MMN latency and amplitude between depressed patients and healthy subjects reached the significance level only for high intensity stimulation, and they were consistent with a dysfunction of frontal MMN subcomponents in depressed patients. This finding suggests that consistent MMN abnormalities can be observed in depressed patients by using high-intensity stimulation; moreover, it supports the hypothesis of disturbances of frontal networks in depression even in early stages of disease.

Mismatch negativity in treatment-resistant depression and borderline personality disorder

OBJECTIVE

Cognitive dysfunctions, such as attentional impairment, are central features of both treatment-resistant depression (TRD) and borderline personality disorder (BPD). The treatment failure of TRD due to its comorbidity with BPD is debated in the literature. The mismatch negativity (MMN) of the event-related potentials provides an objective marker of involuntary stimulus selective processing, which might help shed light on this issue and provide an avenue for investigating a possible endophenotypic marker for TRD.

METHOD

We investigated MMN in 22 patients with TRD, 19 with BPD, and 22 with TRD cormorbid with BPD (TRD+BPD), as well as in 32 healthy volunteers, by employing an acoustic frequency deviance paradigm. In addition, we measured the depressive mood using the Plutchik-van Praag (PVP) depression inventory.

RESULTS

There was no significant between-group difference for the N1 latencies/amplitudes, both to the standard and deviant stimuli, and no significant between-group difference for MMN latencies. However, MMN amplitudes were higher in the TRD group than those in the other three groups. PVP scores were highest in TRD+BPD, then TRD, BPD patients, and lowest in healthy subjects. The higher MMN was not correlated with PVP score, nor with the duration of life-long depression, which can be considered as a neurophysiological marker for TRD.

CONCLUSION

An atypical lack of inhibition on the irrelevant stimuli or increased cortical neuronal activity, especially frontal area, or both, might be responsible for the finding.