Tanya Chapter 16, Class 5 (126).

Tanya Chapter 16, Class 5 (126).
The heart is considered physical and even “Chumri” (crude) and the mind (brain) is considered spiritual, as though it was “out of body” (see Chapter [33,] 35)
Accordingly, what the heart feels compels the body, but what the mind knows and feels does not
If not… for the fact that הקב”ה מצרפה למעשה Hashem ties the brain “feeling” and the action so it is פרחה לעילא.