brain is, in one sense, a system of opponent processors. In other words, it contains mutually opposed elements whose contrary influence make possible finely calibrated responses to complex situations.
Two parts working together to resolve a single preferential/more balanced effect. But note footnote eleven (below this highlight) that up-down and forward-back differ relationally to left-right in that the former relate sequentially whilst the latter relate in parralel (reflecting their evolutionary development, either is series or simultaneously).
