Extrageniculostriate vision in the monkey. VIII. Critical structures for spatial localization

Area of Science:

• Neuroscience
• Primate Vision
• Visual System Anatomy

Background:

• The geniculostriate pathway is traditionally considered crucial for visual perception.
• The role of subcortical structures like the superior colliculus in spatial localization remains an area of investigation.

Purpose of the Study:

• To investigate the necessity of the striate cortex and superior colliculus for spatial localization in monkeys (Macaca mulatta).
• To determine the functional contribution of these visual structures in visually guided reaching tasks.

Main Methods:

• Monkeys underwent ablations of the striate cortex, superior colliculus, or both, with histological verification.
• Animals were trained on a spatial localization task involving reaching for a target under varying conditions.
• Performance was assessed based on accuracy and trials to criterion.

Main Results:

• Monkeys with superior colliculus removal were unimpaired in spatial localization.
• Monkeys with striate cortex removal showed deficits, particularly with larger and smaller targets.
• Combined ablations resulted in a complete failure to perform the task.

Conclusions:

• The superior colliculus plays a critical role in spatial localization when the striate cortex is absent.
• The geniculostriate system is primary for spatial localization, but subcortical pathways contribute significantly.
• Findings challenge a strict dichotomy between distinct visual processing streams.