Vision in mice with neuronal redundancy due to inhibition of developmentalcell death

Transgenic mice overexpressing bcl-2, due to inhibition of naturally occurr ing cell death, have much larger brains and optic nerves as compared to wil d-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. Lo cal visually evoked potentials (VEPs) in response to patterned stimuli were recorded from the primary visual cortex. The representation of the vertica l meridian was displaced by about 15% in the bcl-2 mouse, accounting for br ain expansion. However, visual acuity, contrast threshold, and response lat ency were normal, indicating that compensatory mechanisms can ensure normal basic properties of vision in spite of marked neuronal redundancy.