Anterior cingulate cortex pathology in schizophrenia and bipolar disorder

Area of Science:

• Neuroscience
• Psychiatry
• Neuropathology

Background:

• The anterior cingulate cortex (ACC), particularly its dorsal and subgenual parts (areas 24 and 24sg), is implicated in mood disorders and schizophrenia.
• Morphological abnormalities in these ACC regions may underlie the pathophysiology of these psychiatric conditions.

Purpose of the Study:

• To investigate morphological differences in the dorsal and subgenual ACC in individuals with schizophrenia, bipolar disorder, and major depression compared to controls.
• To examine neuron density, size, cortical thickness, and specific protein levels (MAP2, MAP1b, tau) in these ACC subregions.

Main Methods:

• Quantitative postmortem study utilizing stereological counting for neuron density and size estimation.
• Immunocytochemistry and quantitative immunodot assay to assess microtubule-associated proteins (MAP2, MAP1b) and tau protein distribution and density.
• Analysis of drug-naïve or short-term psychotropic medication exposure cases to minimize confounding medication effects.

Main Results:

• Schizophrenia cases showed significant reductions in cortical thickness and pyramidal neuron size in areas 24 and 24sg.
• Bipolar disorder cases exhibited decreased laminar thickness and neuron densities in specific layers (III, V, VI) of the subgenual area 24.
• Bipolar disorder patients had significantly lower levels of MAP2 and MAP1b proteins, while schizophrenia and major depression patients did not show these protein changes.

Conclusions:

• Morphological alterations in the dorsal and subgenual ACC are distinct in schizophrenia and bipolar disorder.
• Reduced neuronal parameters and specific protein deficits in bipolar disorder suggest unique neuropathological mechanisms.
• These findings contribute to understanding the neuroanatomical basis of schizophrenia and bipolar disorder, particularly the role of area 24 and 24sg.