Song, Jun Ho Lucaci, Diana Calangiu, Ioana Brown, Matthew T. C. Park, Jin Sung Kim, Jinhyun Brickley, Stephen G. Chadderton, Paul 2024-01-19T22:04:42Z 2024-01-19T22:04:42Z 2021-09-03 2018-07-24 2211-1247 https://pubs.kist.re.kr/handle/201004/121139 We have applied optogenetics and mGRASP, a light microscopy technique that labels synaptic contacts, to map the number and strength of defined corticocollicular (CC) connections. Using mGRASP, we show that CC projections form small, medium, and large synapses, and both the number and the distribution of synapse size vary among the IC regions. Using optogenetics, we show that low-frequency stimulation of CC axons expressing channelrhodopsin produces prolonged elevations of the CC miniature EPSC (mEPSC) rate. Functional analysis of CC mEPSCs reveals small-, medium-, and large-amplitude events that mirror the synaptic distributions observed with mGRASP. Our results reveal that descending ipsilateral projections dominate CC feedback via an increased number of large synaptic contacts, especially onto the soma of IC neurons. This study highlights the feasibility of combining microscopy (i.e., mGRASP) and optogenetics to reveal synaptic weighting of defined projections at the level of single neurons, enabling functional connectomic mapping in diverse neural circuits. English CELL PRESS INFERIOR COLLICULUS AUDITORY-CORTEX SYNAPTIC CONNECTIVITY SYNAPSES LOCALIZATION NUMBER AREA Combining mGRASP and Optogenetics Enables High-Resolution Functional Mapping of Descending Cortical Projections Article 10.1016/j.celrep.2018.06.076 1 CELL REPORTS, v.24, no.4, pp.1071 - 1080 CELL REPORTS 24 4 1071 1080 scie scopus 000439589900025 2-s2.0-85049906367 Cell Biology Cell Biology Article INFERIOR COLLICULUS AUDITORY-CORTEX SYNAPTIC CONNECTIVITY SYNAPSES LOCALIZATION NUMBER AREA corticofugal functional connectomics synapse synaptic integration