Running Head: Sex Differences in Cerebral Laterality Cardiovascular Reactivity to Speech Processing and Cold Pressor Stress: Evidence for Sex Differences in Functional Cerebral Laterality

Traditionally, brain asymmetry has been demonstrated using behavioral measures of laterality. Foremost among these measures has been the evidence for language lateralization to the left hemisphere [14]. The left and right cerebral hemispheres also appear to differ in their parasympathetic and sympathetic nervous system roles, perhaps having direct implications for cardiovascular and cardiopulmonary functioning [14]. The evidence supports a right hemispheric role in activation of the sympathetic nervous system, whereas the left hemisphere is primarily associated with activation of the parasympathetic nervous system. In the present project, sex differences in functional cerebral laterality for processing dichotic speech sounds were examined by measuring cardiovascular reactivity and dichotic listening performance in response to a cold pressor stressor. Men demonstrated a significant increase in systolic blood pressure (SBP) when focusing on sounds at the left ear and in response to the cold pressor stressor. However, the dichotic listening task significantly decreased SBP in men, but not in women. Women demonstrated a unique ability to increase accuracy at the targeted ear and identified significantly more speech sounds at the left ear relative to men. The findings contribute to the literature on sex differences in brain lateralization for language and autonomic nervous system functions that are potentially relevant to differences in cardiovascular risk.