A Knoblauch

A Morrison

Andreas Knoblauch

C Clopath

F Hauser

Florian Hauser

S Song

TJ Teyler

English

PubMed

Springer - Publisher Connector

POSTER PRESENTATION Open Access
STDP, Hebbian cell assemblies, and temporal
coding by spike synchronization
Andreas Knoblauch1*, Florian Hauser2
From Twentieth Annual Computational Neuroscience Meeting: CNS*2011
Stockholm, Sweden. 23-28 July 2011
The question whether neural activity follows a rate code
or a temporal code is still an unsolved issue in neu-
roscience. Recent theoretical works have suggested that
realistic models of spike-timing-dependent-plasticity
(STDP) in recurrent networks could resolve this issue
because they observed a seemingly unique relation
between the neural code and the resulting pattern of
synaptic connections [1]. In particular, these works
argue that temporal coding would be inconsistent with
bidirectional synaptic connectivity as observed in visual
cortex [2] and expected for Hebbian cell assemblies
(“what fires together wires together”). This conclusion is
based on two assumptions, first, that simple STDP
based on spike doublets would be generally unable to
produce bidirectional synaptic connectivity (see refer-
ences in [1]) and, second, that realistic voltage-based
STDP would be able to produce bidirectional synaptic
connectivity only for rate coding where signals are
coded by cell ensembles jointly elevating firing rates on
a time scale of hundreds of milliseconds [1].
We have disproved both assumptions. In particular, here
we show that already simple STDP models can easily grow
bidirectional connections for a temporal code based on
spike synchronization unless synchronization is extremely
precise (see [3] for disproving the second assumption). To
this end we present simulation results for various STDP
models [4] including all-to-all (AA) doublet STDP, near-
est-neighbor (NN) doublet STDP, and various triplet
STDP model variants with parameters fitted to experimen-
tal data and including realistic propagation delays. It turns
out that all model variants can grow functional cell assem-
blies as reflected by strong bidirectional connectivity and
tested within an associative memory framework [5]. This
requires coarsely synchronized inputs such that spikes of
the neurons within a cell assembly get synchronized on a
time scale of 5 to 50 milliseconds, whereas more precise
synchronization leads to depression of synaptic weights
and, thus, destruction of the cell assembly. For NN doub-
let STDP and triplet STDP synaptic potentiation is
boosted by increasing the rate of synchronized inputs,
whereas high rates destroy cell assemblies for AA doublet
STDP.
Thus, both rate coding and temporal coding based on
coarse synaptic synchronization can account for the
bidirectional connectivity observed, for example, in visual
cortex [2]. However, we argue that the temporal code
will be much more energy efficient for learning because
it allows to grow and preserve cell assemblies at low
mean firing rates at the level of spontaneous activity,
whereas a rate code (based on uncorrelated Poissonian
firing) can grow cell assemblies only by maintaining high
firing rates over longer time intervals. Moreover, addi-
tional simulation experiments demonstrate how STDP
can quickly grow multiple independent cell assemblies
reflecting the spike timing relations of simultaneously
active input neurons. We speculate that such a multiplex-
ing mechanism may play a role both for working memory
and long-range communication where “copies” or
“indices” [6] of cell assemblies could easily be transmitted
between cortical areas.
Author details
1Honda Research Institute EU, 63073 Offenbach/Main, Germany. 2Institute of
Neural Information Processing, Ulm University, 89069 Ulm, Germany.
Published: 18 July 2011
References
1. Clopath C, Büsing L, Vasilaki E, Gerstner W: Connectivity reflects coding: a
model of voltage-based STDP with homeostasis. Nature Neuroscience
2010, 13:344-352.
* Correspondence: andreas.knoblauch@honda-ri.de
1Honda Research Institute EU, 63073 Offenbach/Main, Germany
Full list of author information is available at the end of the article
Knoblauch and Hauser BMC Neuroscience 2011, 12(Suppl 1):P142
http://www.biomedcentral.com/1471-2202/12/S1/P142
© 2011 Knoblauch and Hauser; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
2. Song S, Sjöström PJ, Reigl M, Nelson S, Chklovskii DB: Highly nonrandom
features of synaptic connectivity in local cortical circuits. PLOS Biology
2005, 3:507-519.
3. Hauser F, Palm G, Knoblauch A: Different neural codes result in
bidirectional connectivity formed by the same model of spike-timing-
dependent plasticity. BMC Neuroscience 2011, same supplement.
4. Morrison A, Diesmann M, Gerstner W: Phenomenological models of
synaptic plasticity based on spike timing. Biological Cybernetics 2008,
98:459-478.
5. Knoblauch A, Palm G: Pattern separation and synchronization in spiking
associative memories and visual areas. Neural Networks 2001, 14:763-780.
6. Teyler TJ, Rudy JW: The hippocampal indexing theory and episodic
memory: Updating the index. Hippocampus 2007, 17:1158-1169.
doi:10.1186/1471-2202-12-S1-P142
Cite this article as: Knoblauch and Hauser: STDP, Hebbian cell
assemblies, and temporal coding by spike synchronization. BMC
Neuroscience 2011 12(Suppl 1):P142.
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Knoblauch and Hauser BMC Neuroscience 2011, 12(Suppl 1):P142
http://www.biomedcentral.com/1471-2202/12/S1/P142
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STDP, Hebbian cell assemblies, and temporal coding by spike synchronization

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A: Different neural codes result in bidirectional connectivity formed by the same model of spike-timingdependent plasticity. BMC Neuroscience 2011, same supplement.

Connectivity reflects coding: a model of voltage-based STDP with homeostasis. Nature Neuroscience

Pattern separation and synchronization in spiking associative memories and visual areas. Neural Networks

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Submit your next manuscript to BioMed Central and take full advantage of: • Convenient online submission • Thorough peer review • No space constraints or color ﬁgure charges • Immediate publication on acceptance

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STDP, Hebbian cell assemblies, and temporal coding by spike synchronization

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