Impaired pre-attentive change detection in major depressive disorder patients revealed by auditory mismatch negativity.

Patients with major depressive disorder (MDD) show deficits in cognitive functions. However, the neural mechanisms underlying the pre-attentive information processing in MDD patients are poorly understood. The present study investigated whether MDD patients have impairments in pre-attentive information processing indexed by auditory mismatch negativity (MMN). The deviant-standard reverse oddball paradigm was used to obtain the memory-comparison-based duration auditory MMN in 24 MDD patients and 24 healthy control subjects. Over the frontal-central area, MDD patients exhibited decreased MMN amplitudes only for the increment condition (150-ms MMN), whereas the temporal MMN did not differ between MDD patients and healthy subjects, regardless of the increment or decrement (50-ms MMN) condition. The MMN amplitudes were not correlated with depression symptoms. In addition, the peak latency of MMN amplitudes was longer in the MDD patients than the control subjects. These data indicate that pre-attentive information processing is impaired in MDD patients. This dysfunction may represent a trait of MDD patients rather than a state-dependent phenomenon.