Immune cells in the brain influence high-order cognitive function but increase the risk of neuropsychiatric disorders.
The dorsolateral prefrontal cortex is a functional region of the brain that mediates complex cognitive functions. It is unique to primates. Findings from a recent study suggest that specialized immune cells called microglia are present in the dorsolateral prefrontal cortex of humans only, setting them apart in terms of cognitive abilities but making them more vulnerable to language and neuropsychiatric disorders.
Microglia are the brain’s resident immune cells. Their acute activation modulates inflammation and neurotoxicity, but chronic activation promotes brain inflammation and damage. Evidence suggests that microglia activation influences mood.
Researchers profiled the expression of genes in more than 600,000 cells found in the dorsolateral prefrontal cortices of four primate groups, including humans, macaques, chimpanzees, and marmosets. They identified 109 cell types that were conserved across the four species and five that were species-specific.
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Of the species-specific cell types, they noted that one type of microglia was only found in humans, while another was found in both humans and chimpanzees. They also found that microglia express a gene called FOXP2, which is involved in language disorders, schizophrenia, and autism.
These findings suggest that microglia play critical roles in establishing higher-order cognitive function in humans, but they may also increase humans' risk for language and neuropsychiatric disorders.