Sentence:  Important as these differences <WSD>are</WSD> , they should not obscure the basic fact that by shifting the hypothalamic balance sufficiently to the parasympathetic side , we produce depressions , whereas a shift in the opposite direction causes excitatory effects and , eventually , maniclike changes . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)