It is well-established that synapse formation involves highly selective chemospecific mechanisms, but how neuron arbors are positioned before synapse formation remains unclear. Using 3D reconstructions of 298 neocortical cells of different types (including nest basket, small basket, large basket, bitufted, pyramidal, and Martinotti cells), we constructed a structural model of a cortical microcircuit, in which cells of different types were independently and randomly placed. We compared the positions of physical appositions resulting from the incidental overlap of axonal and dendritic arbors in the model (statistical structural connectivity) with the positions of putative functional synapses (functional synaptic connectivity) in 90 synaptic connections reconstructed from cortical slice preparations. Overall, we found that statistical connectivity predicted an average of 74 ± 2.7% (mean ± SEM) synapse location distributions for nine types of cortical connections. This finding suggests that chemospecific attractive and repulsive mechanisms generally do not result in pairwise-specific connectivity. In some cases, however, the predicted distributions do not match precisely, indicating that chemospecific steering and aligning of the arbors may occur for some types of connections. This finding suggests that random alignment of axonal and dendritic arbors provides a sufficient foundation for specific functional connectivity to emerge in local neural microcircuits.
I’d like to know where “accuracy ranging from 75 percent to 95 percent” in the press release came from.
Looking at the paper, I’m guessing it’s the histogram intersection (HI) measurement, which actually ranged from 50% to 95% with an average of 75%, so that’s one glaring error I could find in the first few minutes of looking at a paper in a field that I know next to nothing about. (A further guess is that the journalist thought 75% accuracy didn’t sound all that impressive, and so went on a hunt for a grander number, hitting on the 95%.)
Maybe I’m all wet, but what I’m taking from the paper is that it’s actually a null result? As in, some other researchers had theorized that the fine structure of synaptic connections was somehow “guided” by chemical signals, but the simulation in fact suggests that “randomly bumping into each other” is closer to the truth. This does seem to (maybe decisively) settle a debate which the authors say has gone on for decades; I’m wondering if the term “breakthrough” is warranted though.
Just released.
Abstract:
Thanks!
I’d like to know where “accuracy ranging from 75 percent to 95 percent” in the press release came from.
Looking at the paper, I’m guessing it’s the histogram intersection (HI) measurement, which actually ranged from 50% to 95% with an average of 75%, so that’s one glaring error I could find in the first few minutes of looking at a paper in a field that I know next to nothing about. (A further guess is that the journalist thought 75% accuracy didn’t sound all that impressive, and so went on a hunt for a grander number, hitting on the 95%.)
Maybe I’m all wet, but what I’m taking from the paper is that it’s actually a null result? As in, some other researchers had theorized that the fine structure of synaptic connections was somehow “guided” by chemical signals, but the simulation in fact suggests that “randomly bumping into each other” is closer to the truth. This does seem to (maybe decisively) settle a debate which the authors say has gone on for decades; I’m wondering if the term “breakthrough” is warranted though.