does striatum support competitive dynamics a test of this hypothesis using a biologically realistic model of the striatal microcircuit

Bio Med CentralPage 1 of 2 page number not for citation purposes BMC Neuroscience Open Access Poster presentation Does striatum support competitive dynamics?. A test of this hypothesis

Bio Med Central

Page 1 of 2

(page number not for citation purposes)

BMC Neuroscience

Open Access

Poster presentation

Does striatum support competitive dynamics? A test of this

hypothesis using a biologically realistic model of the striatal

microcircuit

Richard Wood*, Mark D Humphries and Kevin Gurney

Address: Psychology Department, University of Sheffield, Sheffield, S10 2TP, UK

Email: Richard Wood* - ric.wood@sheffield.ac.uk

* Corresponding author

Introduction

The striatum is the man input structure of the basal

gan-glia and consists principally of medium spiny neurons

(MSNs) The remaining neurons comprise several species

of interneuron, including the GABAergic fast spiking

interneuron (FSIs) Both neuron species are highly

inter-connected (including a network of gap junctions between

the FSIs) and both are modulated by dopamine

Under-standing this complex microcircuit is therefore very

chal-lenging Previous computational hypotheses have

suggested that the inhibitory collaterals between MSNs

lead to a strong competitive dynamic [1] In contrast,

Koós and Tepper [2] suggest that feed-forward inhibition

from the FSIs is the dominant force in the control of

MSNs We have developed a detailed, biologically

con-strained model of the striatal microcircuit aimed at

resolv-ing these issues and discoverresolv-ing the computations

performed in this critical brain area

Methods

The model incorporates dopamine modulated MSNs and

FS interneurons, and we used a novel technique in

com-putational anatomy to develop realistic connection

statis-tics for all known pathways in this circuit The response of

the model to realistic in vivo background input was

ana-lyzed using a novel multiple spike-train analysis

tech-nique to find groups of synchronized neurons (as

observed experimentally) Predicated on the hypothesis

that the basal ganglia is performing action selection, we

then used these groups to define "channels" in a series of selection experiments We hypothesized that, if there were naturally emerging clusters of MSNs in the network, these might serve to compete well with each other We repeated these experiments with channels comprised of randomly selected neurons

Results

Using realistic parameter values for the input glutamater-gic spike trains, and for the GABAerglutamater-gic and gap junction conductances, we found little evidence for selection in the model Removing the FSI input to the MS neurons also failed to reveal any competition via the MSN collaterals, suggesting that FSN input was not imposing another dynamic Varying the level of dopamine in the simulation also failed to show any significant change in the networks selective ability Increasing the conductance of the MSN collateral synapses by a factor of ten, however, did force the network to show signs of competition between com-peting channels No significant difference was observed when using channels of randomly selected neurons, com-pared to channels defined by the multiple spike-train analysis method We conclude that the striatum does not support competitive dynamics using the circuits compris-ing MSNs and FSIs within a range of realistic parameter settings

from Eighteenth Annual Computational Neuroscience Meeting: CNS*2009

Berlin, Germany 18–23 July 2009

Published: 13 July 2009

BMC Neuroscience 2009, 10(Suppl 1):P317 doi:10.1186/1471-2202-10-S1-P317

<supplement> <title> <p>Eighteenth Annual Computational Neuroscience Meeting: CNS*2009</p> </title> <editor>Don H Johnson</editor> <note>Meeting abstracts – A single PDF containing all abstracts in this Supplement is available <a href="http://www.biomedcentral.com/content/files/pdf/1471-2202-10-S1-full.pdf">here</a>.</note> <url>http://www.biomedcentral.com/content/pdf/1471-2202-10-S1-info.pdf</url> </supplement>

This abstract is available from: http://www.biomedcentral.com/1471-2202/10/S1/P317

© 2009 Wood et al; licensee BioMed Central Ltd

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Acknowledgements

This work was supported by EPSRC grant EP/C516303/1 and EU FP7 grant

ICEA.

References

1. Koós T, Tepper JM: Inhibitory control of neostriatal projection

neurons by GABAergic interneurons Nat Neurosci 1999,

2:467-472.

2. Wickens J: Basal ganglia: Structure and computations Network

Computation in Neural Systems 1997, 8:77-109.