What do simple cells in the cortex respond to according to Feature Detection Theory?

Simple cells in the cortex are primarily responsive to specific features of visual stimuli, particularly the orientation and boundaries of objects. According to Feature Detection Theory, these neurons are tuned to detect lines or edges that have a particular angle. This means that they will fire more vigorously when they are presented with visual stimuli that align with their preferred orientations.

This characteristic allows simple cells to play a critical role in the initial processing of visual information, which is necessary for more complex aspects of vision, such as recognizing shapes and forming a coherent visual scene. They essentially act as detectors for fundamental aspects of what we see, laying the groundwork for higher-order visual processing, while other types of cells in the cortex handle different visual features like movement, color, and depth perception.