Salelkar Siddhesh, Somasekhar Gowri Manohari, Ray Supratim
IISc Mathematics Initiative, Department of Mathematics, Indian Institute of Science , Bangalore , India.
Centre for Neuroscience, Indian Institute of Science , Bangalore , India.
J Neurophysiol. 2018 Aug 1;120(2):681-692. doi: 10.1152/jn.00807.2017. Epub 2018 Apr 25.
Local field potential (LFP) recorded with a microelectrode reflects the activity of several neural processes, including afferent synaptic inputs, microcircuit-level computations, and spiking activity. Objectively probing their contribution requires a design that allows dissociation between these potential contributors. Earlier reports have shown that the primate lateral geniculate nucleus (LGN) has a higher temporal frequency (drift rate) cutoff than the primary visual cortex (V1), such that at higher drift rates inputs into V1 from the LGN continue to persist, whereas output ceases, permitting partial dissociation. Using chronic microelectrode arrays, we recorded spikes and LFP from V1 of passively fixating macaques while presenting sinusoidal gratings drifting over a wide range. We further optimized the gratings to produce strong gamma oscillations, since recent studies in rodent V1 have reported LGN-dependent narrow-band gamma oscillations. Consistent with earlier reports, power in higher LFP frequencies (above ~140 Hz) tracked the population firing rate and were tuned to preferred drift rates similar to those for spikes. Significantly, power in the lower (up to ~40 Hz) frequencies increased transiently in the early epoch after stimulus onset, even at high drift rates, and had preferred drift rates higher than for spikes/high gamma. Narrow-band gamma (50-80 Hz) power was not strongly correlated with power in high or low frequencies and had much lower preferred temporal frequencies. Our results demonstrate that distinct frequency bands of the V1 LFP show diverse tuning profiles, which may potentially convey different attributes of the underlying neural activity. NEW & NOTEWORTHY In recent years the local field potential (LFP) has been increasingly studied, but interpreting its rich frequency content has been difficult. We use a stimulus manipulation that generates different tuning profiles for low, gamma, and high frequencies of the LFP, suggesting contributions from potentially different sources. Our results have possible implications for design of better neural prosthesis systems and brain-machine interfacing applications.
用微电极记录的局部场电位（LFP）反映了多种神经活动过程，包括传入突触输入、微电路水平的计算以及动作电位发放活动。客观地探究它们的作用需要一种能够区分这些潜在作用因素的设计。早期报告表明，灵长类动物的外侧膝状体核（LGN）比初级视觉皮层（V1）具有更高的时间频率（漂移率）截止值，以至于在更高的漂移率下，从LGN输入到V1的信号持续存在，而输出停止，从而实现部分区分。我们使用慢性微电极阵列，在呈现大范围漂移的正弦光栅时，记录被动注视猕猴V1区的动作电位和LFP。由于最近在啮齿动物V1区的研究报道了依赖LGN的窄带伽马振荡，我们进一步优化了光栅以产生强烈的伽马振荡。与早期报告一致，较高LFP频率（高于约140Hz）的功率跟踪群体放电率，并被调整到与动作电位类似的偏好漂移率。值得注意的是，即使在高漂移率下，较低频率（高达约40Hz）的功率在刺激开始后的早期阶段也会短暂增加，并且其偏好漂移率高于动作电位/高伽马频率。窄带伽马（50 - 80Hz）功率与高频或低频功率没有强烈相关性，并且其偏好时间频率要低得多。我们的结果表明，V1区LFP的不同频段显示出不同的调谐曲线，这可能潜在地传达了基础神经活动的不同属性。新发现与值得关注之处近年来，局部场电位（LFP）受到越来越多的研究，但解释其丰富的频率内容一直很困难。我们使用一种刺激操作，为LFP的低频、伽马和高频产生不同的调谐曲线，表明可能来自不同来源的贡献。我们的结果可能对更好的神经假体系统和脑机接口应用的设计具有启示意义。
