Enhancement of temporal and spatial synchronization of entorhinal gamma activity by phase reset

Clayton T. Dickson, Marco De Curtis

Research output: Contribution to journalArticle

Abstract

The synchronization of cortical gamma oscillatory activity (25-80 Hz) is thought to coordinate neuronal assemblies in the processing and storage of information. The mechanism by which independently oscillating and distantly located cortical zones become synchronized is presumed to involve activity in corticocortical connections, although evidence supporting this conjecture has only been indirect. In the present study, we show that activation of synaptic inputs within and to the medial entorhinal cortex (mEC) of the in vitro isolated guinea pig brain preparation resets the phase of ongoing gamma activity induced by muscarinic receptor agonism with carbachol (frequency: 24 ± 2 Hz at 32°C). Phase reset was associated with a transient enhancement of the synchronization of gamma activity recorded at distant (> 1 mm) mEC sites, across which low coherence (>0.75) was observed before stimulation. This increase in synchronization, as measured by cross-correlation analysis, was restricted to a maximal period of 200 ms after either local mEC or CA1 afferent stimulation. The results provide direct evidence that synaptic activation can enhance the rhythmic synchronization of spatially remote, independently oscillating neuronal assemblies in the mEC through a mechanism of synaptically evoked phase reset. Dynamic functional grouping of oscillatory discharges across long distances in the mEC may underlie coding processes involved in the integration and storage of incoming information and thus may be important for the role of this region in memory processes.

Original languageEnglish
Pages (from-to)447-456
Number of pages10
JournalHippocampus
Volume12
Issue number4
DOIs
Publication statusPublished - 2002

Keywords

  • 40-Hz oscillation/rhythm
  • Binding
  • Cholinergic
  • Guinea pig
  • Isolated whole-brain

ASJC Scopus subject areas

  • Neuroscience(all)

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