This is a very common experience, and there's a real neurological + behavioral explanation behind it. A few things are usually happening together:

1. Your brain has been trained to expect novelty and rewards Every time you scroll and see a meme, joke, or short video, you get a small dopamine hit tied to novelty, humor, or social reward (likes, laughs, surprise). Dopamine is the neurotransmitter that drives reward-based learning and reinforces the behaviors that preceded it - so the brain's reward circuitry (nucleus accumbens, mesolimbic pathway) gets conditioned to associate idle moments with "check for stimulation" - Kaplan & Sadock's Comprehensive Textbook of Psychiatry. With repeated exposure, this becomes an automatic loop: boredom or a quiet moment triggers the same circuit that used to fire when you were actively scrolling, so fragments of that content (memes, clips, jokes) pop into your mind unprompted, almost like a conditioned reflex.

2. "Popcorn brain" / cognitive overload from high-density content Short-form content (memes, reels, TikToks) delivers information in rapid, disconnected bursts. A recent review on digital overstimulation ("brain rot") describes how this constant stream creates cognitive overload - the brain tries to process, store, and categorize far more disjointed stimuli than it's built to handle in a day, which leads to mental fatigue, intrusive fragments resurfacing later, and a harder time sustaining focus on single tasks (Demystifying the New Dilemma of Brain Rot in the Digital Era, PMC, 2025). This is sometimes informally called "popcorn brain" - a mind that's become dependent on constant novelty and struggles to settle into slower, single-track thinking.

3. Mind-wandering and intrusive thoughts are normal baseline brain activity Even without social media, the brain's default mode network generates spontaneous, unrelated thoughts during idle time - that's normal. What's changed is the raw material it pulls from. If you spend hours a day consuming memes, your brain's associative memory is saturated with that content, so when it wanders, it surfaces memes instead of, say, memories or plans. This isn't a disorder by itself; it's your mind reflecting what you feed it.

A quick evidence check: a 2025 systematic review in BMC Psychiatry on social media use and "the social brain" (PMID: 39901112) is relevant if you want to dig deeper into the broader cognitive/psychiatric effects of heavy social media use - it didn't contradict anything above, just adds more detail on social-cognitive effects.

None of this points to anything pathological on its own - it sounds like a very normal (if annoying) byproduct of heavy short-form content consumption. If the thoughts become distressing, violent/disturbing in content, or you can't shift attention away from them at all, that would be worth mentioning to a doctor or therapist since it could reflect anxiety or OCD-spectrum patterns rather than simple habit-driven mind-wandering.