Classical discussions locate or associate reason with the heart, brain or rational soul, depending on the school and the kind of evidence being considered.
References to the heart in scriptural and devotional language express important claims about understanding and inner responsibility, but do not automatically amount to a complete anatomical map. Observations about brain injury or cognition raise a different set of questions.
Disagreement about the seat of reason does not by itself defeat the claim that humans can know truths through valid reasoning.