The Journal of Neuroscience, April 15, 2003, 23(8):3100
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 neocortex, local excitation spreads over large distances via the long-range horizontal connections in layer 2/3 and may spread over an
entire cortical area if excitatory polysynaptic pathways are also
activated. Therefore, a balance between local excitation and surround
inhibition 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
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