Before revision: The main concepts of the hypothesis are that the monoamine neurotransmitters are orthogonal in essence, and the proposed one-to-one relationship between the monoamine neurotransmitters and emotions.
After revision: The main concepts of the hypothesis are that the monoamine neurotransmitters are orthogonal variables, meaning involving independent pairs of neurotransmitters; and secondlyfirstly the proposed one-to-one relationship between the monoamine neurotransmitters and emotions.