RECORDING OF NEURONAL NETWORK PROPERTIES WITH NEAR-INFRARED DARK-FIELD MICROSCOPY AND MICROELECTRODES

The function of neuronal networks is determined by system properties l ike coupling of neuronal aggregates by synchronization of spontaneous discharges. In order to study such network properties, recordings of t he spatial properties of neuronal networks are necessary. We investiga ted the possibility of analyzing the functional properties of brain sl ices by optical methods and microelectrodes. Stimulation-induced intri nsic optical signals (IOSs) were monitored using the dark-field config uration of a conventional light microscope. For electrical recordings, glass microelectrodes were placed within the slice. Ion-selective mic roelectrodes were used to measure activity-induced changes in extracel lular potassium concentration. The experiments revealed that electrica l stimulation of the slice induces alterations of IOSs. The IOSs were accompanied by extracellular field potential deflections which are com posed of slow and fast components. At corresponding locations transien t elevations of the extracellular potassium concentration occurred. Re cent experiments revealed that the IOS monitors changes of extracellul ar space volume. This property of IOSs could further be used to demons trate that the brain slice possesses a functionally coupled network of glial cells which serve to transport potassium ions from areas of exc itation into neighbouring brain regions. (C) 1997 Published by Elsevie r Science Ltd.