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Matthew Colonnese; Rapid Development of Feed Forward Inhibition Drives Emergence of Visual Alertness. Journal of Vision 2013;13(9):279. doi: 10.1167/13.9.279.
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© ARVO (1962-2015); The Authors (2016-present)
The generation of appropriate cortical network states is a key regulator of visual perception and plasticity, but their role during development is poorly characterized. We have shown that human preterm infants and pre-eye opening rats undergo a rapid maturation of network states just before the onset of visual experience. This change results in a massive down regulation of visual responses, shifting them from all-or-none oscillatory bursts, to graded responses capable of processing visual input. Here we test the hypothesis that this maturation is the rapid emergence of cortical activation, or ‘active’, states. Using in vivo current clamp and polytrode recordings in visual cortex of awake, head-fixed neonatal and infant rats, we find that cortical activation, defined by persistent membrane depolarization during waking, emerges suddenly 1-2 days before eye-opening. The amplitude of activation remained constant between emergence and adulthood, though stability and duration of depolarization gradually increased. This switch in network properties was responsible for the down-regulation of visual responses as light began to evoke active states rather than supra-theshold plateau potentials observed before the switch. Reducing GABAA currents just after the switch eliminates activation and reverts activity to immature patterns. Measurement of the timing and amplitude of inhibitory and excitatory currents by voltage clamp showed the rapid development of fast feed-forward inhibition at this time. In total we have identified, for the first time, a specific role for changes in inhibitory circuitry in the developmental regulation of cortical activity. This change effectively divides visual cortex development into two clear phases--an early pre-visual period concurrent with spontaneous retinal waves and the establishment of retinal topography, and a late period linked to the onset of pattern vision, visual exploration and the onset of experience-dependent plasticity—that each have unique computational characteristics.
Meeting abstract presented at VSS 2013
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