Influence of the cardiac phase on the latency of a motor response to a visual stimulus in the blowfly

The main feature of heart activity in the blowfly, Calliphora vomitoria, is the regular alternation of phases of forward and backward beating. It is known that forward beats are inhibited by sensory stimulation and locomotor activity. In the present study it is shown that the latency of a motor response to a moving visual stimulus is significantly longer when the releasing stimulus is applied in the course of forward beating (0.90 ± 0.07 sec) than during backward beating (0.70 ± 0.06 sec). A facilitatory influence of backward beating of the heart on motor activity is thus demonstrated. This finding is discussed with reference to the biological significance of heart-beat reversal in insects and a possible role for sensory-induced cardiac responses as preparatory for motor behaviour.