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Brief Communication Imaging Spatiotemporal Dynamics of Surround Inhibition in
 

Summary: Brief Communication
Imaging Spatiotemporal Dynamics of Surround Inhibition in
the Barrels Somatosensory Cortex
Dori Derdikman, Rina Hildesheim, Ehud Ahissar, Amos Arieli, and Amiram Grinvald
Department of Neurobiology, The Weizmann Institute of Science, Rehovot 76100, Israel
Sensory processing and its perception require that local information would also be available globally. Indeed, in the mammalian neocor-
tex, local excitation spreads over large distances via the long-range horizontal connections in layer 2/3 and may spread over an entire
corticalareaifexcitatorypolysynapticpathwaysarealsoactivated.Therefore,abalancebetweenlocalexcitationandsurroundinhibition
is required. Here we explore the spatiotemporal aspects of cortical depolarization and hyperpolarization of rats anesthetized with
urethane. New voltage-sensitive dyes (VSDs) were used for high-resolution real-time visualization of the cortical responses to whisker
deflections and cutaneous stimulations of the whisker pad. These advances facilitated imaging of ongoing activity and evoked responses
even without signal averaging. We found that the motion of a single whisker evoked a cortical response exhibiting either one or three
phases. During a triphasic response, there was first a cortical depolarization in a small cortical region the size of a single cortical barrel.
Subsequently, this depolarization increased and spread laterally in an oval manner, preferentially along rows of the barrel field. During
the second phase, the amplitude of the evoked response declined rapidly, presumably because of recurrent inhibition. Subsequently, the
third phase exhibiting a depolarization rebound was observed and clear, and 16 Hz oscillations were detected. Stimulus conditions
revealing a net surround hyperpolarization during the second phase were also found. By using new, improved VSD, the present findings
shed new light on the spatial parameters of the intricate spatiotemporal cortical interplay of inhibition and excitation.
Key words: barrel cortex; cortical dynamics; cortical populations; cutaneous stimulation; depolarization; excitation; hyperpolarization;
inhibition; oscillations; somatosensory cortex; voltage sensitive dyes

  

Source: Ahissar, Ehud - Department of Neurobiology, Weizmann Institute of Science
Grinvald, Amiram - Department of Neurobiology, Weizmann Institute of Science

 

Collections: Biology and Medicine