Pharmacopsychiatry 2007; 40: S78-S84
DOI: 10.1055/s-2007-990304
Original Paper

© Georg Thieme Verlag KG Stuttgart · New York

Statistical Fluctuations in Attractor Networks Related to Schizophrenia

M. Loh 1 , E. T. Rolls 2 , G. Deco 1 , 3
  • 1Department of Technology, Universitat Pompeu Fabra, Computational Neuroscience, Barcelona, Spain
  • 2Department of Experimental Psychology, University of Oxford, Oxford, UK
  • 3Institució Catalana de Recerca i Estudis Avançats (ICREA)
Further Information

Publication History

Publication Date:
17 December 2007 (online)

Abstract

We present a hypothesis of how the positive, negative, and cognitive symptoms of schizophrenia could be related to alterations in the stability of cortical networks which lead to a reduced signal-to-noise ratio. We analyze using integrate-and-fire simulations of attractor networks how some of the symptoms of schizophrenia could be related to a reduced depth of basins of attraction, produced by for example a decrease in the NMDA receptor conductances, and to statistical fluctuations caused by stochastic spike firing of neurons. Both of these processes contribute to instability in short term memory, attentional, and semantic neuronal networks. The cognitive symptoms such as distractibility, working memory deficits or poor attention could be caused by this instability of attractor states in prefrontal cortical networks. Lower firing rates are also produced, and in the orbitofrontal and anterior cingulate cortex could account for the negative symptoms including a reduction of emotions. If the decrease in NMDA conductances, and the statistical fluctuations, are combined with a reduction of GABA conductances, this causes the network to switch between the attractor states, and to jump from spontaneous activity into one of the attractors. We relate this to the positive symptoms of schizophrenia including delusions, paranoia, and hallucinations, which may arise because the basins of attraction are shallow and there is instability in temporal lobe semantic memory networks, leading thoughts to move too freely round the attractor energy landscape.

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Correspondence

Dr. M. Loh

Universitat Pompeu Fabra

Computational Neuroscience

Passeig de Circumval.lació 8

08003 Barcelona

Spain

Phone: +34/93/542 23 62

Fax: +34/93/542 24 51

Email: marco.loh@upf.edu