Recovery of function in cat visual cortex following prolonged deprivation

Area of Science:

• Neuroscience
• Ophthalmology
• Developmental Biology

Background:

• The visual cortex has a critical period for development, typically thought to end in early life.
• Previous studies suggest neural plasticity in the visual cortex is limited to the first few months of life.

Purpose of the Study:

• To investigate if cortical neurons retain plasticity in adult cats after prolonged visual deprivation.
• To determine if visual experience in adulthood can alter neural response characteristics and ocular alignment.

Main Methods:

• Cats were reared in total darkness or strobe light for the first year, followed by normal visual exposure.
• Electrophysiological recordings assessed cortical unit responses and orientation/direction selectivity.
• Ocular alignment was examined to assess for strabismus.

Main Results:

• Cortical neurons in visually deprived cats showed limited orientation selectivity.
• Cats with subsequent normal vision exhibited intermediate orientation selectivity.
• Direction selectivity was rare in 'recovery' cats, unlike normally-reared cats.
• Adult cats showed a convergent strabismus, contrasting with the divergent strabismus seen in younger, deprived animals.

Conclusions:

• Cortical plasticity persists in adult cats long after the proposed critical period.
• Visual experience in adulthood can modify neural properties and ocular alignment.
• These findings challenge the notion of a strictly limited critical period for visual cortex development.