Many technological, biological, social, and information networks fall into the broad class of 'small-world' networks: they have tightly interconnected clusters nodes, a shortest mean path length that is similar to matched random graph (same number nodes edges). This semi-quantitative definition leads categorical distinction ('small/not-small') rather than quantitative, continuous grading networks, can lead uncertainty about network's small-world status. Moreover, systems described by are...

Recently, it has been demonstrated that several complex systems may have simple graph-theoretic characterizations as so-called 'small-world' and 'scale-free' networks. These networks also applied to the gross neural connectivity between primate cortical areas nervous system of Caenorhabditis elegans. Here, we extend this work a specific circuit vertebrate brain--the medial reticular formation (RF) brainstem--and, in doing so, made three key contributions. First, constitutes first model (and...

The basal ganglia (BG) have long been implicated in both motor function and dysfunction. It has proposed that the BG form a centralized action selection circuit, resolving conflict between multiple neural systems competing for access to final common pathway. We present new spiking neuron model of circuitry test this proposal, incorporating all major features many physiologically plausible details. include following: effects dopamine subthalamic nucleus (STN) globus pallidus (GP),...

ORIGINAL RESEARCH article Front. Neurosci., 06 February 2012Sec. Decision Neuroscience https://doi.org/10.3389/fnins.2012.00009

Operant learning requires that reinforcement signals interact with action representations at a suitable neural interface. Much evidence suggests this occurs when phasic dopamine, acting as prediction error, gates plasticity cortico-striatal synapses, and thereby changes the future likelihood of selecting action(s) coded by striatal neurons. But hypothesis faces serious challenges. First, is inexplicably complex, depending on spike timing, dopamine level, receptor type. Second, there credit...

Behavior in spatial navigation is often organized into map-based (place-driven) vs. map-free (cue-driven) strategies; behavior operant conditioning research goal-directed habitual strategies. Here we attempt to unify the two. We review one powerful theory for distinct forms of learning during instrumental conditioning, namely model-based (maintaining a representation world) and model-free (reacting immediate stimuli) algorithms. extend these lines argument propose an alternative taxonomy...

Local supra-linear summation of excitatory inputs occurring in pyramidal cell dendrites, the so-called dendritic spikes, results independent spiking sub-units, which turn neurons into two-layer neural networks capable computing linearly non-separable functions, such as exclusive OR. Other neuron classes, interneurons, may possess only a few or passive dendrites where input is purely sub-linear, and sub-units are saturating. To determine if can also compute we enumerate, for given parameter...

Identifying similar spike-train patterns is a key element in understanding neural coding and computation. For single neurons, spike evoked by stimuli are evidence of common coding. Across multiple trains indicate potential cell assemblies. As recording technology advances, so does the urgent need for grouping methods to make sense large-scale datasets trains. Existing require specifying number groups advance, limiting their use exploratory analyses. I derive new method from network theory...

Loss of dopamine from the striatum can cause both profound motor deficits, as in Parkinsons's disease, and disrupt learning. Yet effect on striatal neurons remains a complex controversial topic, is need comprehensive framework. We extend reduced model medium spiny neuron (MSN) to account for dopaminergic modulation its intrinsic ion channels synaptic inputs. tune our D1 D2 receptor MSN models using data recent large-scale compartmental model. The new capture input-output relationships...

We previously proposed that the basal ganglia (BG) play a crucial role in action selection. Quantitative analysis and simulation of computational model intrinsic BG demonstrated its output was consistent with this proposition. Here we build on by embedding it into wider circuit containing motor thalamocortical loop thalamic reticular nucleus (TRN). Simulation extended showed additions gave five main results which are desirable selection/switching mechanism. First, low salience actions (i.e....

A system's wiring constrains its dynamics, yet modelling of neural structures often overlooks the specific networks formed by their neurons. We developed an approach for constructing anatomically realistic and reconstructed GABAergic microcircuit medium spiny neurons (MSNs) fast-spiking interneurons (FSIs) adult rat striatum. grew dendrite axon models these extracted probabilities presence neurites as a function distance from soma. From these, we found intersection between two given...

Deep brain stimulation (DBS) is a remarkably successful treatment for the motor symptoms of Parkinson's disease. High-frequency subthalamic nucleus (STN) within basal ganglia main clinical target, but physiological mechanisms therapeutic STN DBS at cellular and network level are unclear. We set out to begin address hypothesis that mixture responses in output nuclei, combining regularized firing inhibition, key contributor effectiveness DBS. used our computational model complete circuit show...

Investigating how, when, and what subjects learn during decision-making tasks requires tracking their choice strategies on a trial-by-trial basis. Here, we present simple but effective probabilistic approach to at trial resolution using Bayesian evidence accumulation. We show this identifies both successful learning the exploratory used in decision performed by humans, non-human primates, rats, synthetic agents. Both when rules change of win-stay lose-shift, often considered complementary,...

The search for the neural substrate of vertebrate action selection has focused on structures in forebrain and midbrain, particularly group sub-cortical nuclei known as basal ganglia. Yet, behavioural repertoire decerebrate neonatal animals suggests existence a relatively self-contained brainstem. We propose that medial reticular formation (mRF) is substrate's main component review evidence showing mRF's inputs, outputs intrinsic organization are consistent with requirements an...

Although the basal ganglia have been widely studied and implicated in signal processing action selection, little information is known about active role striatal microcircuit plays selection ganglia-thalamo-cortical loops. To address this knowledge gap we use a large scale three dimensional spiking model of striatum, combined with rate coded loop, to asses computational striatum selection. We identify robust transient phenomena generated by microcircuit, which temporarily enhances difference...

The joint activity of neural populations is high dimensional and complex. One strategy for reaching a tractable understanding circuit function to seek the simplest dynamical system that can account population activity. By imaging Aplysia’s pedal ganglion during fictive locomotion, here we show its population-wide arises from low-dimensional spiral attractor. Evoking locomotion moved into low-dimensional, periodic, decaying orbit - in which it behaved as true attractor, converging same when...

If spikes are the medium, what is message? Answering that question driving development of large-scale, single neuron resolution recordings from behaving animals, on scale thousands neurons. But these data inherently high-dimensional, with as many dimensions neurons - so how do we make sense them? For answer to reduce number dimensions. Here I argue can distinguish weak and strong principles neural dimension reduction. The principle reduction a convenient tool for making complex data. shows...

Abstract Calcium imaging is a powerful tool for capturing the simultaneous activity of large populations neurons. Here we determine extent to which our inferences neural population activity, correlations, and coding depend on choice whether how deconvolve calcium time-series into spike-driven events. To this end, use range deconvolution algorithms create nine versions same data obtained from barrel cortex during pole-detection task. Seeking suitable values algorithms’ parameters, optimise...