Forebrain neural patterns associated with sex differences in autonomic and cardiovascular function during...

Area of Science:

• Neuroscience
• Cardiovascular Physiology
• Human Physiology

Background:

• Women generally exhibit smaller autonomic and cardiovascular reactions to stress compared to men.
• The underlying mechanisms for these sex-dependent differences in stress response remain unclear, with potential involvement of baroreflex sensitivity.
• Previous research identified a cortical network linked to cardiovascular responses to baroreceptor unloading in men.

Purpose of the Study:

• To investigate sex-related differences in neural activity patterns within a specific forebrain network.
• To determine if these neural differences correlate with sex-specific physiological responses to lower body negative pressure (LBNP).

Main Methods:

• Functional magnetic resonance imaging (fMRI) with blood oxygen level-dependent (BOLD) contrast was used to measure forebrain activity in healthy men and women.
• Physiological data including stroke volume (SV), heart rate (HR), and muscle sympathetic nerve activity (MSNA) were collected separately.
• Participants underwent lower body negative pressure (LBNP) at 5, 15, and 35 mmHg.

Main Results:

• Men exhibited larger decreases in stroke volume and greater increases in heart rate and muscle sympathetic nerve activity during 35 mmHg LBNP compared to women.
• Significant sex differences in BOLD signal changes were observed in forebrain regions, including the insula, anterior cingulate cortex, amygdala, and medial prefrontal cortex.
• Men showed greater increases in BOLD signal in the right insula and dorsal anterior cingulate cortex, and greater reductions in the right amygdala, left insula, ventral anterior cingulate, and ventral medial prefrontal cortex.

Conclusions:

• Sex-specific differences in forebrain activity patterns are associated with distinct cardiovascular and sympathetic responses to stress.
• The observed greater changes in forebrain activity in men may contribute to their elevated heart rate and sympathetic responses during LBNP.
• These findings highlight the neural basis for sex differences in autonomic cardiovascular regulation during stress.