What term describes the visual impression left by a stimulus?

The term that best describes the visual impression left by a stimulus is "icon." Icons refer to the brief and very clear mental images that occur as a result of stimuli, typically lasting only a fraction of a second. This concept is closely related to the idea of sensory memory, where an impression from the environment is held momentarily before it fades.

The other terms have distinct meanings: "memory trace" refers to the long-term representation of information stored in the brain after an experience, rather than the immediate visual impression. "Image" can imply a more general concept of a visual representation but does not specifically capture the fleeting nature of the impression from a stimulus. "Representation" broadly encompasses any method of conveying meaning or information, which does not specifically denote the transient visual impression linked to stimuli.

Therefore, the correct answer emphasizes the specific and ephemeral nature of visual impressions left by external stimuli as captured by the term "icon."