Sensitive period for a multimodal response in human visual motion area MT/MST.

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Sensory Processing

Background:

• The middle temporal complex (MT/MST) is a brain region typically specialized for visual motion perception.
• Following long-standing blindness, MT/MST can exhibit auditory responses, suggesting cross-modal plasticity.
• The developmental timing of this sensory plasticity in MT/MST remains largely unknown.

Purpose of the Study:

• To investigate the sensitive period for visual specialization in the middle temporal complex (MT/MST).
• To compare the functional response of MT/MST to auditory stimuli in individuals with congenital blindness, late-onset blindness, and sighted controls.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was employed to assess MT/MST activity and functional connectivity.
• Participants included adults with congenital blindness, late-onset blindness, and sighted controls.
• Analysis focused on MT/MST responses to auditory stimuli and its connectivity with visual and prefrontal regions.

Main Results:

• MT/MST responded to sound in congenitally blind adults but not in late-blind or sighted adults.
• A critical sensitive period for visual specialization in MT/MST was identified, with no auditory response in individuals losing vision between ages 2-3.
• Reduced functional connectivity between MT/MST and visual areas was observed in all blind groups, while increased connectivity with prefrontal areas was noted in the congenitally blind.

Conclusions:

• A sensitive period exists for the visual specialization of the middle temporal complex (MT/MST).
• Early visual experience is crucial for establishing and maintaining the typical visual dominance of MT/MST.
• Once established, the visual response profile of MT/MST is resistant to alteration by long-standing blindness, highlighting the critical role of early sensory input.