Retinal dysfunction of contrast processing in major depression also apparent in cortical activity.

Area of Science:

• Neuroscience
• Ophthalmology
• Psychiatry

Background:

• Depressive disorder is associated with altered visual perception.
• Growing evidence suggests the visual system's involvement in depression pathophysiology.
• Previous research found reduced retinal contrast response in major depression patients using pattern electroretinogram (PERG).

Purpose of the Study:

• To investigate if the reduced retinal contrast response in major depression has a cortical correlate.
• To analyze the visual evoked potential (VEP) in the occipital cortex of patients with depressive disorder.

Main Methods:

• Analyzed VEP in 40 patients with depressive disorder and 28 healthy controls.
• Used checkerboard stimuli (0.51° check size, 12.5 Hz, 3-80% contrast).
• Compared VEP amplitude versus contrast transfer function and correlated with depression severity scales (HDRS, BDI).

Main Results:

• Patients with major depression showed significantly reduced VEP amplitudes across all contrast levels (p = 0.029).
• VEP amplitude correlated with depression severity.
• VEP contrast transfer function was reduced to 75% in depressed patients, compared to a ≈50% reduction in PERG.

Conclusions:

• Depression impacts cortical visual responses, but to a lesser extent than retinal responses.
• Modified contrast adaptation in the lateral geniculate nucleus or cortex may moderate retinal processing losses in depression.