Given a simple noun such as apple, and a question such as is it edible?, what processes take place in the human brain? More specifically, given the stimulus, what are the interactions between (groups of) neurons (also known as functional connectivity) and how can we automatically infer those interactions, given measurements of the brain activity? Furthermore, how does this connectivity differ across different human subjects?In this work we present a simple, novel good-enough brain model, or GEBM in short, and a novel algorithm SPARSE-SYSID, which are able to effectively model the dynamics of the neuron interactions and infer the functional connectivity. Moreover, GEBM is able to simulate basic psychological phenomena such as habituation and priming (whose definition we provide in the main text).We evaluate GEBM by using both synthetic and real brain data. Using the real data, GEBM produces brain activity patterns that are strikingly similar to the real ones, and the inferred functional connectivity is able to provide neuroscientific insights towards a better understanding of the way that neurons interact with each other, as well as detect regularities and outliers in multi-subject brain activity measurements.
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KeywordsBrain Activity Analysis; System Identification; Brain Functional Connectivity; Control Theory; Neuroscience Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from permissions@acm.org. real GeBM CCA) brain activity for a particular voxel (results by LS and CCA are similar to the one in Fig. 2 for all voxels). By minimizing the sum of squared errors, both algorithms that solve for MODEL 0 resort to a simple line that increases very slowly over time, thus having a minimal squared error, given linearity assumptions. Comparison of true brain activity and brain activity generated using the LS, and CCA solutions to MODEL 0 . Clearly, MODEL 0 is not able to capture the trends of the brain activity, and to the end of minimizing the squared error, produces an almost straight line that dissects the real brain activity waveform.
Proposed approach: GeBMFormulating the problem as MODEL 0 is not able to meet the requirements for our desired solution. However, we have not exhausted the space of possible formulations that live within our set of simplifying assumptions. In this section, we describe GEBM, our proposed approach which, under the assumptions that we have already made in Section 2, is able to meet our requirements remarkably well.In order to come up with a more accurate m...