Vision in mice with neuronal redundancy due to inhibition of developmental cell death

Transgenic mice overexpressing bcl-2, due to inhibition of naturally occurring cell death, have much larger brains and optic nerves as compared to wild-type mice. Since developmental cell death is believed to exert a crucial role in establishing the mature neural circuitry and function, we asked the question of whether basic aspects of vision were altered in bcl-2 mice. Local visually evoked potentials (VEPs) in response to patterned stimuli were recorded from the primary visual cortex. The representation of the vertical meridian was displaced by about 15% in the bcl-2 mouse, accounting for brain expansion. However, visual acuity, contrast threshold, and response latency were normal, indicating that compensatory mechanisms can ensure normal basic properties of vision in spite of marked neuronal redundancy.