With a 0.5 ms relay delay, fitted synaptic delays permitted earlier inhibition in three of 25 mouse V1 triplets

A connection map does not give response order. We tested direct excitation and a two-synapse inhibitory route in Allen Synaptic Physiology release r2.1. The selected sample had 25 mouse V1 triplets in 19 slice recordings. Three fitted timing budgets were 0.862, 0.964, and 1.471 ms. These budgets permit indirect inhibition before direct excitation if the relay fires within the budget. All accepted fit combinations kept these three budgets above an assumed relay delay of 0.5 ms. Two candidates also had voltage-clamp fits on all three edges. At the same relay delay, an added error bound of 0.1 ms per edge left two candidates with a positive lower margin. A 0.2 ms bound left one. None of 13 comparison triplets through an excitatory relay had a point budget above 0.5 ms. We provide derived tables, a timing-bound tool, figures, source hashes, and complete repeat instructions. The study is exploratory. Shared manual onset limits can make accepted fits agree. Relay spikes and intact-circuit response order were not measured. The result gives conditional timing hypotheses, not evidence that inhibition actually came first.

synaptic delay · feedforward inhibition · circuit motifs · mouse visual cortex · interval bounds · synaptic physiology