After-images

After-images are the visual persistence of a stimulus — its outline, brightness, or color — that lingers in perception after the source is removed or the gaze shifts.

As a drug effect they are acute and dose-proportional, fading as the substance wears off; this separates them from persistent post-substance visual phenomena. They range from faint ghost-trails on moving objects at low doses to vivid superimposed echoes that follow every shift in gaze.

After-images are a common visual effect across several psychoactive classes. They are most commonly induced at moderate to high doses under psychedelics such as LSD, psilocybin mushrooms, and MDA, and under deliriants such as Datura, Amanita muscaria, and benzydamine; they also appear under dissociatives like dextromethorphan and memantine, and are reported under depressants such as alcohol, GHB, and GBL.

After-images are felt as the visual world leaving traces of itself: wherever the gaze shifts, the outline or color of a recently viewed object remains briefly superimposed on the new scene. Bright sources — windows, lamps, flames — linger longest, often filling with complementary hues. The effect is passive and arrives uninvited.

Attending to it sharpens it; deliberately tracking a moving object amplifies the trail. At high doses, particularly under psychedelics and deliriants, the echoes compound and stack across the visual field.

After-images arise through different pathways depending on the drug class:

• Psychedelics — act on 5-HT2A receptors, disrupting cortical suppression of visual persistence so that activated representations linger beyond their normal window.
• Deliriants — block muscarinic acetylcholine receptors, destabilizing the visual system's ability to clear between successive inputs.
• Dissociatives — antagonize NMDA receptors, impairing the temporal gating that ordinarily resets visual processing between moments.
• Depressants — broadly depress central activity, slowing the clearance of residual visual representations.

How much each pathway contributes in a given case is not fully understood.

Who experiences it, and how strongly, varies widely. Dose is the primary driver — after-images are rarely noticed at low doses and become pronounced at high ones. A bright, visually busy environment amplifies them; a dim, static setting produces fewer.

People with prior psychedelic experience or existing visual sensitivity tend to notice them more readily. Expectation also plays a role — entering a session already watching for visual trailing makes it easier to find, and harder to dismiss once found.