 As of 2012, efforts to determine differences in neurotransmitter receptor expression or for function in the brains of people with MDD using positron emission tomography (PET) had shown inconsistent results.Using the PET imaging technology and reagents available as of 2012, it appeared that the D1 receptor may be underexpressed in the striatum of people with MDD.5-HT1A receptor binding literature is inconsistent; however, it leans towards a general decrease in the mesiotemporal cortex.