Response Latencies of Visually Sensitive Neurons in Area 21a of the Cortex

The paper presents the results of a study on the duration of latent periods (LP) of responses from single neurons in region 21a after their receptive fields (RF) are triggered by stationary flashing visual stimuli. Neurons exhibiting only ON or OFF responses demonstrate markedly reduced fluctuations in LP duration, and the mean LP duration in these neurons is much lower compared to those with ON-OFF responses. A reduced fluctuation in LP duration was noted in neurons exhibiting a tonic response pattern, which also displayed the shortest average LP duration. The most significant variations in LP durations and the highest average values were seen in ON–OFF neurons exhibiting a phasic response pattern. In only one-third of the examined neurons, the length of LP remains constant across the whole RF area; in the majority of neurons, it fluctuates based on the stimulus’s location inside the RF. The disparity in LP duration within a single RF can attain a factor of three or greater. It was also determined that the majority of neurons exhibit a significant degree of independence in the variations of LP ON and OFF components of ON–OFF responses. The acquired results suggest that the majority of RF neurons 21a area possess not only a complicated spatial organization but also an inhomogeneous discrete temporal structure.