Modification of Peak Plasticity Induced by Brief Dark Exposure

Figure 2

The effect on neuron size of a 7-day duration of MD imposed at the peak of the critical period with and without a prior 10-day period of darkness. Schematic at the top of (a1) and (b1) indicate the rearing history and timeline of procedures for each group. The effect of 7 days of MD imposed at postnatal day 30 was obvious upon gross examination of the eye-specific layers of the dLGN (a1), as well as at higher magnification where neurons within deprived-eye (DE) layers were smaller than neurons within non-deprived-eye (NDE) counterpart layers. Stereological quantification of soma size revealed that deprived neurons were rendered 17% smaller than nondeprived neurons, which represented a significant difference. When the same MD was imposed immediately following 10 continuous days of dark exposure started at postnatal day 20, there was an obvious reduction in the staining intensity within deprived-eye layers compared to non-deprived-eye layers (b1). The paler staining within deprived-eye layers was accompanied by a reduction in the size of deprived neurons when compared to nondeprived neurons (b2). Quantification of neuron cross-sectional soma size revealed that deprived neurons were significantly smaller than nondeprived neurons by an average of 22%. Drawing in (a3) represents eye-specific layers of the dLGN with red and blue circles indicating measurements from A and A1 layers, respectively. (1) and 50 μm (2). Arrows in (a1) and (b1) indicate the deprived-eye layer. Asterisks indicate statistical significance at .