Neural sequences: deductive principles and rules

A neural sequence is set not only by deterministic, but also by chaotic rules. The former are, mainly, recency effects, while the latter intervene in the early stage of the performance. Chaotic-like sequences can be recognized by the presence, within them, of greater variations. Factors producing accelerations or decelerations of temporal parameters, i.e. inter-stimulus intervals (ISIs) and reaction latencies, and changes in other parameters, i.e. numbers of pauses, freezings and errors, depend on two orders of variability, a neural order (here we refer to degrees of excitability of different cortical and subcortical systems and temporal dissociations between their activities), and a psychological order (levels of attention, expectation, habituation and fatigue).