Bilateral coupling in learned blinking: side superiority, synchrony and temporal coordination in normal cats

In order to study interocular temporal coupling in the initiation of learned symmetrical blinking, experiments were carried out on cats trained to blink in response to a 500-ms tone paired with 100-ms airpuffs randomly delivered to either eye (alternate airpuff; 6 animals) or simultaneously directed to both eyes (bilateral airpuff; 4 animals) 400 ms after tone onset. In spite of the fact that differences in conditioned response (CR) latencies of the right and left eye varied in a wide range between positive and negative values in all subjects, a statistically significant difference between the mean CR latencies of the two eyes (further called side superiority) was found in 6 animals, of which 4 were trained by alternate airpuff and 2 by bilateral airpuff. Superiority of the right eye was found in 3 animals and the opposite was observed in the other 3. Analysis of the differences between CR latencies of the two eyes showed that side superiority was not due to the ability of one eye to give CRs consistently shorter than those of the other eye, but it crucially depended on the higher proportion of trials in which the superior eye led. The ability to give simultaneous CRs by the two eyes was found inversely related to the mean CR latency per session and subject. Regression analysis showed that power equations best described these relationships. In all animals, the frequency distribution of simultaneous CRs paralleled the frequency distribution of all CRs. In spite of a considerable trial-by-trial variability in the temporal relationships between CR latencies of the two eyes, clear-cut linear correlations were found by plotting the mean CR latencies of the right and left eye per both session and subject. The results reviewed in this paper are best accounted for by suggesting that blink onset of the two eyes is independently controlled by two distinct command signals and is modulated by bilaterally-balanced and lateralized influences.