The visual cortex is known to contain neurons that respond selectively to the direction of visual motion. The responses of those neurons are said to be 'non-separable' because they cannot be constructed from separate spatial and temporal processes. How neurons compute those responses without resort to explicit time delays is unknown.
Heitmann & Ermentrout (2020) Direction-Selective Motion Discrimination by Traveling Waves in Visual Cortex. PLoS Computational Biology 16(9): e1008164.
Heitmann & Ermentrout (2016) Propagating Waves as a Cortical Mechanism of Direction-Selectivity in V1 Motion Cells. Proc 9th EAI Intl Conf on Bio-inspired Info & Comm Tech. BICT'15. New York.