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Neurochemical Mechanisms of Perceptual Deficits in Schizophrenic Patients – A Spiking Neural Network Approach

Christoph Metzner1, 2*, Achim Schweikard1 and Bartosz Zurowski3
  • 1 University of Luebeck, Institute for Robotics and Cognitive Systems, Germany
  • 2 Graduate School for Computing in Medicine and Life Sciences, Germany
  • 3 University Clinics Schleswig-Holstein, Department of Psychiatry, Germany

Schizophrenia is a mental disorder which is characterized by positive symptoms (psychosis, hallucinations and paranoia) and negative symptoms (flattened affect, anhedonia) as well as cognitive and perceptual deficits [1]. Dakin et al. [2] report that schizophrenic patients are less vulnerable to 'contrast-contrast' illusions ( 'surround suppression', i.e. the mutual inhibition of a focal visual stimulus and its surrounding). This weaker contextual suppression can be interpreted in terms of reduced GABAergic inhibition [3]. Recently, research in schizophrenia has focused on GABAergic inhibitory neural circuits [4]. However, the exact neural basis and perceptual consequences of a compromised GABAergic system remain unclear.

We modeled the effects of manipulating particular aspects of GABAergic neurotransmission (altered decay times at GABAergic synapses, reduced availability of GABA and decreased density of GABAergic interneurons [4]) on surround suppression strength. Therefore, we built a model of primary visual cortex based on anatomical and physiological data, using the neuron model from Izhikevich [5].

The model exhibits surround suppression, i.e. shows reduced activity to stimuli mimicking a high-contrast surrounding than compared to stimuli mimicking a uniform surrounding.
Furthermore, increased decay times at GABAergic synapses lead to a reduction in surround suppression in our network model. This suggests one possible factor of altered perception in schizophrenia and is in agreement with previous modeling studies, e.g. in the auditory system [6].

Acknowledgements

This work was partially supported by the Graduate School for Computing in Medicine and Life Sciences funded by Germany's Excellence Initiative [DFG GSC 235/1].

References

References
1. Butler PD et al.: Visual perception and its deficits in schizophrenia. Biological Psychiatry, 2008, 64(1):40-47.
2. Dakin S et al.: Weak suppression of visual context in chronic schizophrenia. Current Biology, 2005, 15:822-824.
3. Yoon et al.: GABA concentration is reduced in visual cortex in schizophrenia and correlates with orientation-specific surround suppression. J Neurosci, 2010, 30(10):3777-3781.
4. Lisman JE et al.: Circuit-based framework for understanding neurotransmitter and risk gene interactions in schizophrenia. Trends Neurosci, 2008, 31(5):234-242.
5. Izhikevich EM: Simple model of spiking neurons. IEEE Trans. Neural Netw., 2003, 14(6):1569-1572.
6. Vierling-Claassen D et al.: Modeling GABA alterations in schizophrenia: A link between impaired inhibition and altered gamma and beta range auditory entrainment. J Neurophysiol, 2008, 99: 2656-2671.

Keywords: brain disease, network dysfunction and intervention, Schizophrenia, spiking neural networks, surround suppression

Conference: BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011, Freiburg, Germany, 4 Oct - 6 Oct, 2011.

Presentation Type: Poster

Topic: brain disease, network dysfunction and intervention (please use "brain disease, network dysfunction and intervention" as keyword)

Citation: Metzner C, Schweikard A and Zurowski B (2011). Neurochemical Mechanisms of Perceptual Deficits in Schizophrenic Patients – A Spiking Neural Network Approach. Front. Comput. Neurosci. Conference Abstract: BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011. doi: 10.3389/conf.fncom.2011.53.00110

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Received: 23 Aug 2011; Published Online: 04 Oct 2011.

* Correspondence: Mr. Christoph Metzner, University of Luebeck, Institute for Robotics and Cognitive Systems, Luebeck, Germany, christoph.metzner@gmail.com