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Bin Zhang, Ye Wang, Xiaofeng Tao, Guofu Shen, Janice Marie Wensveen, Earl L Smith, Yuzo M Chino; Spiking Noise in V2 Neurons in Infants Monkeys. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5955. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The spiking of neurons in visual area V2 of amblyopic monkeys raised with monocular defocus is noisy. There is increased irregularity of spike intervals at high contrast and elevated trial-to-trial fluctuation of spike counts at low contrast. However, it is not clear whether this noisy spiking is resulted from active disruptions of developing cortical connections due to abnormal visual experience, or from passive freezing of the immature state of cortical connections in infant. Therefore, in this study, therefore, we analyzed the spike trains of V2 neurons in 4- and 8-week-old normal infant monkeys.
Single unit recording was performed in visual area 2 of anesthetized monkeys. We recorded 178 neurons from infant monkeys and 224 neurons from adult monkeys. We quantified the spiking noise (variability) in response to brief (640 ms) sine wave gratings that were optimized for orientation and spatial frequency for each unit and varied for contrast between 5% and 80%. To assess spiking noise, we quantified the irregularity in spike interval by calculating the square of the coefficient of variation (CV2) and the trial-to-trial variability of the spike count by calculating the mean-matched Fano factor (FF) for individual neurons.
The spiking noise of V2 neurons in infant monkeys was significantly lower than that of the normal adult monkeys. Both the magnitude of spiking irregularity (CV2) and the trial-to-trial fluctuation (m-FF) was lower in spike trains of V2 neurons in infant monkeys than those in normal adult monkeys for all stimulus contrasts.
Our results suggest that the increased spiking noise in V2 neurons of amblyopic adult monkeys does not reflect an arrested development of the infant visual cortex. Instead, the interocular decorrelations of cortical inputs by experiencing chronic monocular defocus shortly after birth actively disrupts the normal maturation of cortical circuitry in V2.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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