Samonds Jason M, Bonds A B
Department of Electrical Engineering, Vanderbilt University, 255 Featheringill Hall, 400 24th Ave. South, Nashville, TN 37212, USA.
J Neurophysiol. 2005 Jan;93(1):223-36. doi: 10.1152/jn.00548.2004. Epub 2004 Jul 28.
Visual cortical cells demonstrate both oscillation and synchronization, although the underlying causes and functional significance of these behaviors remain uncertain. We simultaneously recorded single-unit activity with microelectrode arrays in supragranular layers of area 17 of cats paralyzed and anesthetized with propofol and N(2)O. Rate-normalized autocorrelograms of 24 cells reveal bursting (100%) and gamma oscillation (63%). Renewal density analysis, used to explore the source of oscillation, suggests a contribution from extrinsic influences such as feedback. However, a bursting refractory period, presumably membrane-based, could also encourage oscillatory firing. When we investigated the source of synchronization for 60 cell pairs we found only moderate correlation of synchrony with bursts and oscillation. We did, nonetheless, discover a possible functional role for oscillation. In all cases of cross-correlograms that exhibited oscillation, the strength of the synchrony was maintained throughout the stimulation period. When no oscillation was apparent, 75% of the cell pairs showed decay in their synchronization. The synchrony between cells is strongly dependent on similar response onset latencies. We therefore propose that structured input, which yields tight organization of latency, is a more likely candidate for the source of synchronization than oscillation. The reliable synchrony at response onset could be driven by spatial and temporal correlation of the stimulus that is preserved through the earlier stages of the visual system. Oscillation then contributes to maintenance of the synchrony to enhance reliable transmission of the information for higher cognitive processing.
视觉皮层细胞表现出振荡和同步现象,尽管这些行为的潜在原因和功能意义仍不明确。我们使用微电极阵列,在丙泊酚和N₂O麻醉并瘫痪的猫的17区颗粒上层同时记录单神经元活动。对24个细胞的速率归一化自相关图分析显示,所有细胞(100%)均存在爆发活动,63%的细胞存在伽马振荡。用于探索振荡源的更新密度分析表明,诸如反馈等外在影响起到了一定作用。然而,一个可能基于细胞膜的爆发不应期,也可能促使振荡发放。当我们研究60对细胞的同步源时,发现同步性与爆发活动和振荡之间仅有适度的相关性。尽管如此,我们确实发现了振荡可能具有的功能作用。在所有呈现振荡的互相关图案例中,同步性强度在整个刺激期内保持稳定。当无明显振荡时,75%的细胞对其同步性出现衰减。细胞间的同步性强烈依赖于相似的反应起始潜伏期。因此,我们提出,相较于振荡,能够产生潜伏期紧密组织的结构化输入更有可能是同步源。反应起始时可靠的同步性可能由刺激的空间和时间相关性驱动,这种相关性在视觉系统的早期阶段得以保留。然后,振荡有助于维持同步性,以增强信息向更高认知处理过程的可靠传递。