Group 1 Prof. Wolf Singer

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Group 1 Prof. Wolf Singer
On the search for the Neural Codes
Arnaud Delorme, Salk Institute, San Diego,
CA Claire Martin, ISC Lyon, France Joachim Gross,
Neurology Duesseldorf, Germany Thomas
Klausberger, Univ. of Oxford, UK Stirn Valentina,
Univ. of Frankfort, Germany
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Outline
Role of oscillations, synchronous activity and
temporal patterns

• In feature binding in the retina
• In ongoing activity
• In perceptual awareness
• In hallucinations

? Unresolved issues
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Feature binding in the retina
Neuenschwander Singer, Nature, 1996
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Unresolved issues feature binding in the retina
?

• Gradient of contrast
• Shape
• Motion
• Synchrony of parts
• Continuity of parts

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Ongoing activity
Roelfsema et al., Nature, 1997
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Unresolved issues

• What triggers gamma oscillations in the cortex ?
• Neural encoding of expectancies (multi-electrode
  recording)
• Interaction between external stimulus and ongoing
  activity

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Perceptual awareness
(Fries et al, PNAS, 1997)
Dominant
Non-dominant
Neural correlates of visual awareness in V4
(Leopold Logothetis, Nature 1996)
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Unresolved issues

• What triggers perceptual switch is it neuron
  fatigue ?
• Does synchronization have a causal role in
  perception disruption of oscillations in
  olfactory system.

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Hallucinations
Hallucination in Schizophrenia Gamma burst
increased in sensory areas (EEG) (Kissler et
al., 2000, Clinical Neurophysiology)
Jack Cowan mathematical model Drugs (LSD) ?
depletion of inhibition in V1 ? oscillatory
waves ? moving spiral visual
illusions (Ermentrout Cowan 1979, Biological
Cybernetics)
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Unresolved questions

• Why do pathological oscillations occur? How do
  they differ from Singers standard oscillations.
• Can stimulations of specific cell assemblies
  trigger specific hallucinations, or even specific
  thoughts

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