Temporal Organization of Synaptic Input and Intrinsic Excitability Shape Direction Selectivity in the Developing Xenopus laevis Optic Tectum
- 1Brandeis University
Abstract
A moving object passes through locations in visual space in a particular order. To distinguish opposite directions of motion, visual circuits must convert this temporal order into different direction selective neuronal responses. This ability emerges and is refined as visual circuits develop. In Xenopus laevis tadpoles, direction selectivity in the optic tectum sharpens over development. Companion work by Zheng et al (2026) shows that direction selectivity sharpens between stage 45 (approximately 6 to 7 days postfertilization), when the retinotectal circuit is undergoing rapid refinement, and stage 48 (approximately 10 to 16 days postfertilization), when the projection has completed one phase of refinement and visual acuity has improved. The same study shows that, over this period, both the excitatory synaptic input received by tectal neurons and the intrinsic properties of those neurons change. How these synaptic and intrinsic changes work together to produce a sharpening of direction selectivity unclear. Here, we combined visually evoked excitatory postsynaptic current trains recorded at each stage with stage-specific single-compartment conductance-based models. These simulations reproduced the developmental increase in direction selectivity and reduction in spiking at stage 48. Changing intrinsic properties produced only modest changes in spike counts, while reassigning amplitudes among the original event times did not eliminate developmental sharpening. Together, these results suggest that the temporal organization of synaptic input carries much of the directional information, while intrinsic maturation lowers overall spike output, making the existing directional bias in the input more pronounced.
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BibTeX
@misc{mondal2026temporal,
title = {{Temporal Organization of Synaptic Input and Intrinsic Excitability Shape Direction Selectivity in the Developing Xenopus laevis Optic Tectum}},
author = {Y. Mondal and K. Zheng and R. Calabrese and K. G. Pratt},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.23.753923},
url = {https://www.biorxiv.org/content/10.64898/2026.09.23.753923v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Temporal Organization of Synaptic Input and Intrinsic Excitability Shape Direction Selectivity in the Developing Xenopus laevis Optic Tectum
AU - Y. Mondal
AU - K. Zheng
AU - R. Calabrese
AU - K. G. Pratt
PY - 2026
DA - 2026/09/23
PB - bioRxiv
DO - 10.64898/2026.09.23.753923
UR - https://www.biorxiv.org/content/10.64898/2026.09.23.753923v1
AB - A moving object passes through locations in visual space in a particular order. To distinguish opposite directions of motion, visual circuits must convert this temporal order into different direction selective neuronal responses. This ability emerges and is refined as visual circuits develop. In Xenopus laevis tadpoles, direction selectivity in the optic tectum sharpens over development. Companion work by Zheng et al (2026) shows that direction selectivity sharpens between stage 45 (approximately 6 to 7 days postfertilization), when the retinotectal circuit is undergoing rapid refinement, and stage 48 (approximately 10 to 16 days postfertilization), when the projection has completed one phase of refinement and visual acuity has improved. The same study shows that, over this period, both the excitatory synaptic input received by tectal neurons and the intrinsic properties of those neurons change. How these synaptic and intrinsic changes work together to produce a sharpening of direction selectivity unclear. Here, we combined visually evoked excitatory postsynaptic current trains recorded at each stage with stage-specific single-compartment conductance-based models. These simulations reproduced the developmental increase in direction selectivity and reduction in spiking at stage 48. Changing intrinsic properties produced only modest changes in spike counts, while reassigning amplitudes among the original event times did not eliminate developmental sharpening. Together, these results suggest that the temporal organization of synaptic input carries much of the directional information, while intrinsic maturation lowers overall spike output, making the existing directional bias in the input more pronounced.
ER -