Question

Which of the following outcomes would you expect from monocular deprivation at 2 weeks in primates compared to monocular deprivation at 20 weeks (select all that apply)?

a) An ocular dominance shift in layer IV of the primary visual cortex such that all neurons primarily receive inputs from both eyes
b) An ocular dominance shift in layer IV of the primary visual cortex such that input is primarily received from the eye that was not deprived
c) An ocular dominance shift in layer IV of the primary visual cortex such that there are highly segregated, evenly distributed strips of neurons receiving input from a single eye
d) An ocular dominance shift in layer IV of the primary visual cortex such that input is primarily received from the deprived eye
e) An ocular dominance shift in layer III of the primary visual cortex such that input is primarily received from the eye that was not deprived

Answer 1

Monocular deprivation at 2 weeks in primates shifts ocular dominance in layer IV of the primary visual cortex heavily towards the non-deprived eye. Later deprivation at 20 weeks leads to less profound changes due to the visual system's reduced plasticity past the critical period.

Step-by-step explanation:

In the context of ocular dominance and cortical plasticity, monocular deprivation during the critical period of visual development has significant effects on the organization of the visual cortex. If a primate is subjected to monocular deprivation at 2 weeks of age, the neural connections in the primary visual cortex adapt, resulting in a shift in ocular dominance. Consequently, the neurons in layer IV of the visual cortex will be more responsive to the input from the non-deprived eye (b), thus reducing the influence of the deprived eye and preventing a symmetrical distribution of input from both eyes.

Moreover, sensory input during critical periods is crucial for proper neural development. When one eye is deprived of sensory input early on, the corresponding neuronal connections weaken or may get repurposed for other functions. If monocular deprivation occurs significantly later, at around 20 weeks, the degree of ocular dominance shifting and neural plasticity would be much less profound due to the reduced susceptibility of the visual system to changes past the critical period. As such, the organization of visual cortex input would not be as strongly affected. Thus, deprivation at 20 weeks would not result in a dominant input from the non-deprived eye as strongly as it would at 2 weeks, making b) the best answer compared to c), d), and e), which would either not occur or have less of an effect.