Group 1 Prof. Wolf Singer

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

On the search for the Neural Codes

Outline

1. In feature binding in the retina

2. In ongoing activity

3. In perceptual awareness

4. In hallucinations

Role of oscillations, synchronous activity and temporal patterns

Unresolved issues

Neuenschwander & Singer, Nature, 1996

Feature binding in the retina

Unresolved issues: feature binding in the retina ?

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

Ongoing activity

Roelfsema et al., Nature, 1997

Unresolved issues:

•What triggers gamma oscillations in the cortex ?

•Neural encoding of expectancies (multi-electrode recording)

•Interaction between external stimulus and ongoing activity

Dominant Non-dominant

(Fries et al, PNAS, 1997)

Perceptual awareness

Neural correlates of visual awareness in V4: (Leopold & Logothetis, Nature 1996)

Unresolved issues:

•What triggers perceptual switch: is it neuron fatigue ?

•Does synchronization have a causal role in perception: disruption of oscillations in olfactory system.

Hallucinations

Hallucination in SchizophreniaGamma 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)

Unresolved questions

• Why do pathological oscillations occur? How do they differ from Singer’s standard oscillations.

• Can stimulations of specific cell assemblies trigger specific hallucinations, or even specific thoughts