Which type of visual cortex cell requires a specific orientation for activation?

The type of visual cortex cell that requires a specific orientation for activation is the simple cell. Simple cells are found in the primary visual cortex and are characterized by their orientation selectivity. They respond primarily to stimuli such as lines or edges that are oriented in a specific direction.

These cells have receptive fields that are organized in an on-center/off-surround arrangement. The activation of a simple cell occurs when an elongated bar of light, oriented at the appropriate angle to its receptive field, is presented. This is in contrast to other types of cells, like the complex and end-stopped cells, which can respond to more complex stimuli and do not strictly require a specific orientation for activation. Additionally, horizontal cells are involved in lateral inhibition and do not play a direct role in orientation selectivity regarding visual stimuli.

Thus, the defining feature of simple cells—their requirement for a specific orientation—highlights their crucial role in processing visual information related to edges and orientation in the visual field.