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Editors Selection IGR 16-4

Basic Reseach: Cortex and IOP

Comment by Yeni Yucel on:

12537 Differential behavior of simple and complex cells in visual cortex during a brief IOP elevation, Chen X; Liang Z; Shen W et al., Investigative Ophthalmology and Visual Science, 2005; 46: 2611-2619

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Chen et al. (439) describe changes in evoked activity of neurons in the cat primary visual cortex following short-term elevation of intraocular pressure (IOP). The cortical neurons that are studied consist of simple and complex cells with distinct functional characteristics based on single cell recording. The authors show an effect on cortical neurons after four minutes of IOP increased from 45 mmHg to 80 mmHg following a visual stimulus. The present study demonstrates a preferential effect on simple cortical cells compared to complex cortical cells.

It would have been interesting had the authors also reported changes in cortical spontaneous activity measured in response to elevated IOP alone, as these changes in spontaneous neuronal activity might play an important role in IOP-related visual dysfunction. The authors observed recovery of some of the visual functions in cats with elevated IOP after acute systemic hypertension induced by metaraminol bitartrate injection. Based on these limited experiments, the authors concluded that functional recovery of cortical cells was due to the normalization of retinal perfusion pressure, as calculated by the difference between blood pressure and IOP. The direct effect of metaraminol bitartrate on the retina and the cortex might also be considered in the interpretation of the results. (Lightman S, et al. Hypertension 1987; 10: 390-395)

Further experiments are needed to understand the pathological effects of single or repetitive exposure to short-term IOP elevation in the visual cortex.

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