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Yao Chen, Zengguang Ma, Pengjia Cao, Pengcheng Sun, Xinyu Chai; Antagonistic Cortical Activation Evoked by Transcorneal Electrical Stimulation: Study by Intrinsic Optical Imaging and Electrophysiological Recording. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):776.
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© ARVO (1962-2015); The Authors (2016-present)
Revealing the hemodynamic changes in visual cortex occurred after electrical stimulation can contribute to comprehension of neurophysiological underpinnings underlying prosthetic vision. Our previous work found transcorneal electrical stimulation (TcES) through an ERG-jet corneal electrode could consistently elicit response areas in cats’ visual cortex, using optical imaging of intrinsic signals (OIS) (IOVS, 2014). These OIS activation regions were mainly located in cortical areas representing peripheral visual field. Both the extent of activation areas and the strength of intrinsic signals were increased with higher current intensities and longer pulse widths. Furthermore, we found an antagonistic spatial pattern of positive and negative OIS response (POR and NOR) evoked by TcES. This phenomenon was similar to the pervasive negative blood oxygenation level-dependent (BOLD) response reported in functional magnetic resonance imaging (fMRI) study. The purpose of this study was to investigate the spatialtemporal patterns of cortical antagonistic OIS response and its relationship to local neuronal activity.
Multiwavelength OIS response was recorded from area 17/18 in cats to investigate the cortical responses to TcES through an ERG-jet contact lens electrode. Multiunit activity (MUA) and local field potentials (LFPs) were recorded from the 96-channels Utah microelectrode array placed in positive and negative OIS response regions. Linear microelectrode array was also used to measure the laminar neuronal activity throughout the depth of the cortex.
The regions of POR were mainly located in cortical areas representing peripheral visual field while the NOR regions were corresponding to visual centre. Similar to the positive OIS response, the amplitude and activated areas of negative OIS response were also related to electrical stimulation. Furthermore, the POR regions exhibited stronger LFP and MUA responses. Spectral power analysis showed that the power of electrophysiological signal in ranges 30-130 Hz (LFP) and 300-2500 Hz (MUA) from the POR regions were significantly higher than those from the NOR regions (Mann-Whitney test, P < 0.005, n = 7 cats).
This work provides evidence that the negative hemodynamic response may not due to the decreased neuronal activity in that region.
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