Biology subjects

Timothy Verstynen

Publications and source records attributed to Timothy Verstynen.

5 recordsLinked to original sources

bioRxiv2016

Quantifying Differences and Similarities in Whole-brain White Matter Architecture Using Local Connectome Fingerprints

Quantifying differences or similarities in connectomes has been a challenge due to the immense complexity of global brain networks. Here we introduce a noninvasive method that uses diffusion MRI to characterize whole-brain white matter architecture as a single local connectome fingerprint that allows for a direct comparison between structural connectomes. In four independently acquired data sets with repeated scans (total N=213), we show that the local connectome fingerprint is highly specific to an individual, allowing for an accurate self-versus-others classification that achieved 100% accuracy across 17,398 identification tests. The estimated classification error was approximately one thousand times smaller than fingerprints derived from diffusivity-based measures or region-to-region connectivity patterns. The local connectome fingerprint also revealed neuroplasticity within an individual reflected as a decreasing trend in self-similarity across time, whereas this change was not observed in the diffusivity measures. Moreover, the local connectome fingerprint can be used as a phenotypic marker, revealing 12.51% similarity between monozygotic twins, 5.14% between dizygotic twins, and 4.51% between none-twin siblings. This novel approach opens a new door for probing the influence of pathological, genetic, social, or environmental factors on the unique configuration of the human connectome.\n\nAuthor SummaryThe local organization of white matter architecture is highly unique to individuals, making it a tangible metric of connectomic differences. The variability in local white matter architecture is found to be partially determined by genetic factors, but largely plastic across time. This approach opens a new door for probing the influence of pathological, genetic, social, or environmental factors on the unique configuration of the human connectome.

Neuroscience↗

bioRxiv2016

Believer-Skeptic meets Actor-Critic: Rethinking the role basal ganglia pathways in decision-making and reinforcement learning

The flexibility of behavioral control is a testament to the brains capacity for dynamically resolving uncertainty during goal-directed actions. This ability to select actions and learn from immediate feedback is driven by the dynamics of basal ganglia (BG) pathways. A growing body of empirical evidence conflicts with the traditional view that these pathways act as independent levers for facilitating (i.e., direct pathway) or suppressing (i.e., indirect pathway) motor output, suggesting instead that they engage in a dynamic competition during action decisions that computationally captures action uncertainty. Here we discuss the utility of encoding action uncertainty as a dynamic competition between opposing control pathways and provide evidence that this simple mechanism may have powerful implications for bridging neurocomputational theories of decision making and reinforcement learning.

Neuroscience↗

bioRxiv2015

In vivo characterization of the connectivity and subcomponents of the human globus pallidus

Projections from the substantia nigra and striatum traverse through the pallidum on the way to their targets. To date, in vivo characterization of these pathways remains elusive. Here we used high angular resolution diffusion imaging (N=138) to study the characteristics and structural subcompartments of the human pallidum. Our results show that the diffusion orientation distribution at the pallidum is asymmetrically oriented in a dorsolateral direction, consistent with the orientation of underlying fiber systems. Furthermore, compared to the outer pallidal segment, the internal segment has more peaks in the orientation distribution function and stronger anisotropy in the primary fiber direction, consistent with known cellular differences between the underlying nuclei. These differences in orientation, complexity, and degree of anisotropy are sufficiently robust to automatically segment the pallidal nuclei using diffusion properties. Thus the gray matter diffusion signal can be useful as an in vivo measure of the collective nigrostriatal and striatonigral pathways.

Neuroscience↗

bioRxiv2014

Converging structural and functional connectivity of orbitofrontal, dorsolateral prefrontal, and posterior parietal cortex in the human striatum

Modification of spatial attention via reinforcement learning (Lee & Shomstein, 2013) requires the integration of reward, attention, and executive processes. Corticostriatal pathways are an ideal neural substrate for this integration because these projections exhibit a globally parallel (Alexander, De Long, and Strick, 1985), but locally overlapping (Haber, 2003), topographical organization. Here, we explored whether there are unique striatal regions that exhibit convergent anatomical connections from orbitofrontal cortex (OFC), dorsolateral prefrontal cortex (DLPFC), and posterior parietal cortex. Deterministic fiber tractography on diffusion spectrum imaging data from neurologically healthy adults (N=60) was used to map fronto-and parieto-striatal projections. In general, projections from cortex were organized in a rostral-caudal gradient along the striatal nuclei; however, we also identified two bilateral convergence zones--one in the caudate nucleus and another in the putamen--that consisted of voxels with projections from OFC, DLPFC, and parietal regions. The distributed cortical connectivity of these striatal convergence zones was confirmed with follow-up functional connectivity analysis from resting state fMRI data from 55 of the participants, in which a high percentage (62-80%) of structurally connected voxels also showed significant functional connectivity. These results delineate a neurologically plausible network of converging corticostriatal projections that may support the integration of reward, executive control, and spatial attention that occurs during spatial reinforcement learning.

Neuroscience↗

bioRxiv2014

The organization and dynamics of corticostriatal pathways link the medial orbitofrontal cortex to future decisions

Accurately making a decision in the face of incongruent options increases the efficiency of making similar congruency decisions in the future. This adaptive process is modulated by reward, suggesting that ventral corticostriatal circuits may contribute to the process of conflict adaptation. To evaluate this possibility, a group of healthy adults (N = 30) were tested using functional MRI (fMRI) while they performed a color-word Stroop task. In a conflict-related region of the medial orbitofrontal cortex (mOFC), stronger BOLD responses predicted faster response times (RTs) on the next trial. More importantly, the degree of behavioral conflict adaptation on RTs was correlated with the magnitude of mOFC-RT associations on the previous trial, but only after accounting for network-level interactions with prefrontal and striatal regions. This suggests that conflict adaptation may rely on interactions between distributed corticostriatal circuits. The convergence of white matter projections fro ...

Neuroscience↗