The effect of visual deprivation upon the basal dendrites of Meynert cells in the striate cortex of the monkey.
The basal dendrites of Meynert cells in the striate cortex have been studied with the Golgi method in the brains of monkeys that had been reared for varying periods with the eyelids closed over one eye. The lengths and arrangement of the dendrites were compared with those in normal brains. In the visually deprived brain almost half of the cells had basal dendrites that were apparently normal with the dendritic fields in the form of an ellipse and the long axes parallel to the direction of the ocular dominance bands. The other cells had dendritic fields that have rarely been seen in normal material and two distinct types could be recognized. The 'lop-sided' cell had an ellipsoidal dendritic field with the major axis parallel to the ocular dominance bands, but the extents of the dendrites along the minor axis were very asymmetric; the ratio of the means of the long and short arms of the minor axis of the 'lop-sided' cell is 2.3:1 compared with 1.1:1 in normal brains. The 'perpendicular' type of cell also had an ellipsoidal dendritic field but the relation of the major and minor axes to the direction of the ocular dominance bands was the reverse of the normal cell, with the long axis of the ellipse being aligned perpendicular to the bands. 'Lop-sided' cells formed approximately 18% of the total of Meynert cells studied and the 'perpendicular' 32%. The proportion of the cells with abnormal basal dendritic fields, and particularly the 'perpendicular', increased with longer durations of eyelid closure. It is suggested that the alterations in the dendritic fields of the 'lop-sided' and 'perpendicular' cells may be correlated with the changes in width of the ocular dominance bands that are known to occur after monocular eyelid suture.