AATRN Networks Seminar, May 5 at 5pm CEST by Arvind Kumar

[Henri Riihimäki]

Dear AATRN Networks Seminar members,

Our next online seminar will be on Tuesday, 5th May, at 17:00 CEST / 11:00 ET.

Speaker: Arvind Kumar

Title: Effect of second order connectivity motifs on structure and activity of biological neural networks

Abstract: How the structure of network connectivity shapes the network activity is a classical problem in neuroscience. The network structure in the brain depends on the spatial scale of our observations and brain regions. Traditionally it was assumed that within 1mm distance connectivity can be approximated as an Erdös-Renyi type network. However, accumulating data now shows that just pairwise connection probability is not enough to capture the network structure even at microscopic scales. That is, we should consider higher-order statistics of connectivity. For instance, we should count the distribution of different types of subnetworks involving 3 neurons. Data suggests that 3-neuron motifs such as convergent, divergent and chain type motifs are either under- or overrepresented in cortical connectivity. Because in 3-neuron motifs we count joint probability of two connections, these motifs are also referred to as second-order motifs. In my talk I will focus on second-order motifs and  discuss how overrepresentation of such motifs may affect the network activity dynamics. Using numerical simulations of biological neural networks we found that second-order motifs (chain and convergent) among excitatory neurons induce very high synchrony which is inconsistent with the data. Next, we found that the hypersynchrony induced by excitatory motifs can be quenched by inhibitory motifs. To better understand the emergence of synchrony and quenching of synchrony by second-order motifs we measured several global properties of the whole network. This analysis revealed that second-order motifs lead to a heavy-tailed degree distribution and in- and out-degrees of neurons become correlated. That is, these motifs render a network with heterogeneous connectivity. This observation not only provided a natural explanation of how second-order motifs induce synchrony but also suggested a better way to think of the impact of higher-order motifs on network activity. Finally, I will discuss the consequence of connection heterogeneity in networks where neurons are wired in a distance-dependent manner. In particular, I will show that connection heterogeneity results in several hot-spots in the network whose stimulation can be used to control network activity.

We will meet in the following coordinates:

https://stockholmuniversity.zoom.us/j/65622268279?pwd=YUsxeGNEeEFKRDFsaTRzRzh2VVMzQT09

Meeting ID: 656 2226 8279

Passcode: 557173

Our seminar usually occurs on the first Tuesday of every month, and you can follow our future planned list of speakers on our website sites.google.com/view/aatrn-networks-seminar.

You may also be interested in adding AATRN’s Google calendar (link), which contains other seminar information.

Best,

The AATRN Networks Seminar organisers

Daniela Egas Santander, Henri Riihimäki, Jason Smith

https://www.youtube.com/@aatrn1