Visual Neurons in the Superior Colliculus Discriminate Many Objects by Their Historical Values

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Primate Research

Background:

• The superior colliculus (SC) is crucial for orienting responses to visual stimuli.
• SC neurons process visual features like size, motion, and color.
• It's unknown if SC activity reflects non-visual object features, such as reward value.

Purpose of the Study:

• To investigate if superior colliculus (SC) neuronal activity is modulated by the historical reward value of visual objects.
• To determine if SC neurons can discriminate between objects based on learned reward associations.

Main Methods:

• Monkeys were trained to associate fractal objects with high or low rewards.
• Neuronal recordings were performed in the SC while monkeys fixated.
• Objects were presented visually without associated rewards during recording sessions.

Main Results:

• Approximately 50% of visually responsive SC neurons showed differential responses to high-value ('good') versus low-value ('bad') objects.
• This value discrimination persisted for over a year after reward-association training.
• Neuronal discrimination began ~100 ms after object onset and lasted over 100 ms.

Conclusions:

• SC neurons can discriminate objects based on their long-term learned reward values.
• This value information may originate from basal ganglia structures like the caudate nucleus.
• SC's internal circuits may use this value information for motor output or send it elsewhere for behavioral guidance.