PVALB and Alpers syndrome: Interestingly, calretinin+ interneurons were the least affected interneuron subtype, and were only significantly reduced in the occipital cortex of patients with Alpers' syndrome relative to controls at the group level (P < 0.05, Figure 2) but were preserved in many patient tissues (z > −2), even within cortex affected by focal lesions with a total loss of parvalbumin+ interneurons (Figure 1B).