Remove sausage from casings and brown in skillet, breaking up with wooden spoon until cooked through. Remove from pan and pour off any grease. Brown mushrooms in skillet coated with cooking spray.
Spray slow cooker with cooking spray. Add 1/2 cup sauce to bottom of slow cooker. Layer 6 slices of polenta. Top with half of the sausage and half of the mushrooms. Add half of the zucchini slices and half of the spinach. Spread 1/2 cup of ricotta over top (I used a teaspoon to drop ricotta). Sprinkle 1/4 cup of parmesan cheese, Mrs. Dash and basil. Spread 1 cup of sauce over layers.
Add 6 more slices of polenta, then top with remaining sausage, mushrooms, zucchini, spinach, ricotta and parmesan cheese. Spread 1 cup of sauce over layers. Add remaining 6 slices of polenta and top with remaining sauce.
Cook on LOW for 5-6 hours or on HIGH for 2-3 hours. Lasagna will be hot and bubbly. Turn off slow cooker. Spread mozzarella cheese on top. Cover and allow to rest for 20 minutes before serving.