Is a Simple Sensorimotor Reaction Really Simple?

The simple sensorimotor reaction (SSR) is widely used in psychophysiological research. It was previously shown, that the SSR latency is not constant. We studied changes in the SSR latency as a function of the waiting time from the moment of the previous response to the moment of the start of the stimulation. We performed the stimulation using light, sound and air impulse. As a response, we used a "labial sound", a finger touch and blinking of the eyes. In all cases, where the objects of the study were humans, the SSR latency had constant and variable components. The constant SSR component was the shortest in response to closing the eyes to sound (120 ms). For "lip reaction" and finger response to sound it was 174-178 ms and 178-182 ms, respectively, but for "lip reaction" and finger response to light it was 220-226 ms. The variable SSR component represented exponential latency decay with an increase in the waiting time interval. In this case, the decay consisted of at least two components, with an apparent relaxation time in the range 30-150 ms and 600-1300 ms. Alternating stimulation of paired organs of the reception or alternating fingers reduced the apparent relaxation time of the SSR latency decay. Moreover, the latency of the human corneal reflex during eye stimulation with an air pulse also had the latency decay with three components of apparent relaxation time 9.5, 68.2 and 1,086 ms and the constant latency of 34.2 ms. The latency of the corneal reflex in a young cat was constant and had a value of 14.6 ms. Thus, it has been shown, that the SSR latency has a complex structure and, like any conditioned reflex, is strongly influenced by the cortex. We believe that a choice is made in the centers for analysis of receiving signals from reception organs and centers sending signals to reacting organs, i.e. essentially, the SSR is also a choice reaction.