Compensatory and transneuronal plasticity after early collicular ablation.

Area of Science:

• Neuroscience
• Developmental Biology
• Visual System Plasticity

Background:

• The developing visual system exhibits plasticity.
• Unilateral superior collicular (SC) ablation in early postnatal development serves as a model for studying visual system compensation.
• Understanding compensatory mechanisms is crucial for visual neuroscience.

Purpose of the Study:

• To investigate visual system plasticity in the quokka wallaby after early unilateral superior collicular (SC) ablation.
• To assess the impact of SC ablation on retinal ganglion cell (RGC) projections and numbers.
• To determine if the visual system maintains a set volume of arborization post-injury.

Main Methods:

• Unilateral SC ablation in quokka wallabies at postnatal days 8-10.
• Tracing of retinal ganglion cell (RGC) projections at maturity (P100).
• Estimation of total RGC numbers in both eyes.

Main Results:

• Significant bilateral increases in the absolute volume of visual projections were observed.
• Minor anomalous projections formed in surviving SC layers and via midline crossing.
• Total RGC numbers were reduced in one eye but increased in the other, maintaining overall numbers.
• No significant difference in total projection volume between partial and complete ablations, or compared to normal.

Conclusions:

• The quokka wallaby's visual system compensates for unilateral injury by maintaining a set arborization volume, with minor anomalous projections.
• Transneuronal compensation, indicated by increased RGC numbers ipsilateral to the lesion, helps maintain total projecting neurons.
• The visual system acts in concert to preserve RGC terminal arbors and cell bodies following unilateral injury.