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[evol-psych] Cerebral cortex cells may pulse electrical rhythm through the brain

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  • Ian Pitchford
    FOR RELEASE: 3 NOVEMBER 1999 AT 14:00 ET US Brown University http://www.brown.edu/Administration/News_Bureau Cerebral cortex cells may pulse electrical rhythm
    Message 1 of 1 , Nov 3, 1999
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      FOR RELEASE: 3 NOVEMBER 1999 AT 14:00 ET US
      Brown University
      http://www.brown.edu/Administration/News_Bureau

      Cerebral cortex cells may pulse electrical rhythm through the brain

      Like the steady synchronized blink of a string of holiday lights, certain types
      of nerve cells in the cerebral cortex communicate with each other through
      electrical connections, forming a new type of brain circuitry described in the
      current Nature.

      Until now, scientists thought nerve cells in the cerebral cortex, the sinuous
      bumps on top of the brain, communicated only through chemical signals.

      The cerebral cortex contains two types of nerve cells ­ excitatory or
      inhibitory. Each neuron ­ a nerve cell in the brain ­ communicates with other
      neurons through chemical connections that fire off a tiny bit of chemical that
      either inhibits or excites the next neuron. These connections between neurons
      are called synapses.

      While studying the chemical synaptic connections in the cerebral cortex of
      rats, Brown University researchers found that two separate types of inhibitory
      neurons were also using electrical synaptic connections to communicate, but
      only within their specific groups.

      The cerebral cortex is the biggest part of the brain. This large and
      complicated neural circuit is involved in most of the brain's highest
      functions, such as memory, language and sight. Within each type of excitatory
      or inhibitory cell, circuitry keeps neurons interconnected and communicating to
      keep overall brain activity in balance. Too much excitation and too little
      inhibition, for example, may lead to seizures. The opposite may lead to a loss
      of consciousness, coma or death.

      The presence of electrical synapses in the cerebral cortex allows each network
      of inhibitory neurons to fire in a highly coordinated and direct way, as if
      there were a wire directly connecting the cells, said Barry Connors, professor
      of neuroscience and senior author of the study. "We think the inhibitory cells
      are coordinating their activity through the electrical synapses," he said. The
      result is synchrony similar to the steady blinking of Christmas lights.

      One of the two circuits, dubbed LTS neurons, may be involved in preventing
      runaway excitation among nerve cells in the cerebral cortex, Connors said. The
      electrical synapses may allow these neurons to generate activity over a large
      area of the brain, he said.

      "It appears this one group is especially suited to regulating cortical
      function," he said. "Most of the time it is not doing anything. But it becomes
      active when the brain's activity increases to a high level. This network of
      inhibitory neurons may act like the governor on the engine of the cortex,
      keeping excitability from running away and becoming an epileptic seizure."

      Some scientists have suggested that inhibitory neurons generate the brain's
      electrical rhythms. These rhythms offer clues to the brain's state. Rhythms are
      smaller and faster when one is awake and slower and larger during sleep. LTS
      neurons may be the rhythms' source.

      "As we continue this research, we do suspect that this group of inhibitory
      cells may be the 'pacemaker' for generating some of the brain's rhythmic
      electrical activity, the kind measured by an EEG," Connors said.

      The other electrical network of inhibitory neurons described in the study,
      called FS neurons, seems to be more directly involved in the processing of
      sensory information, he said.

      Connors and colleagues study epilepsy, an illness often controlled by drugs
      that steady the brain's chemical signals to keep cellular networks in balance.
      Discovery of electrical interconnections among cells in the cerebral cortex may
      one day provide another pathway for the treatment of brain-based illnesses.

      The study's lead author is Jay Gibson, postdoctoral fellow. The other author is
      graduate student Michael Beierlein. The National Institutes of Health funded
      the research.
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