To summarize the evidence on how brain functional connectivity (FC) and its daily fluctuations differ across morning and evening chronotypes.

Chronotype reflects an individual’s natural preference for activity in the morning or evening. FC measures communication between brain regions and how it changes throughout the day. However, it remains unclear how chronotype and time-of-day influence these brain network patterns.

We conducted a literature review on PubMed to identify studies examining the relationship between brain FC and chronotype. Studies published in the last ten years were included, with no restrictions on age or language. Methodological quality and risk of bias were evaluated using both the JBI Critical Appraisal Checklist for Analytical Cross-Sectional Studies (to assess internal validity) and the AXIS tool (to evaluate reporting quality and transparency).

Nine studies met inclusion criteria: six with repeated-measures designs conducted at different times of day and three cross-sectional studies. Sample sizes ranged from 16-192 participants, mostly healthy adults in their late 20s. Across chronotypes, stronger thalamo-sensory connectivity was observed in the morning and reduced visual–motor coupling by evening (p = 0.031). Somatomotor network connectivity increased in the evening (p < 0.01), whereas ventral attention and visual networks were more dominant in the morning (p < 0.05). Evening chronotypes exhibited decreased default mode network (DMN) connectivity associated with lower attention task performance (p < 0.05), stronger precuneus–medial prefrontal cortex coupling (p = 0.002) linked to poorer sleep quality (p = 0.009) and reduced anterior cingulate cortex and insular connectivity (p < 0.05) compared to morning types. Both JBI and AXIS assessments indicated a low to moderate risk of bias across studies.

Evening chronotypes showed decreased connectivity across several brain networks compared to morning chronotypes. Lower FC in the DMN across evening types was associated with reduced attention task performance and increased fatigue.