[Verse 1] Entorhinal cortex, six-layered fortress, Layer two's the courier, never lost or cautious, Punches through the white matter, that's the perforant name, Piercing through the subiculum, entry to the game, Lands in dentate gyrus, granule cells wide awake, Outer molecular layer, lateral's the take, Medial takes the middle, MEC keeps its lane, Same fiber, split targets, no overlap, no strain, Layer two don't stop there, it's got double duty, Fires straight to CA3, no detour, that's the beauty. [Chorus] Two to the dentate, two to CA3, Three to CA1, three to subiculum's bay, Perforant path piercing, poke through the wall, Two entry points, one circuit runs it all, Sparse and strong and squeezed by the inhibitory guard, Pattern separation, keeping memories apart. [Verse 2] Layer three's the sprinter, skips the middleman, Temporoammonic highway, straight to CA1's land, Also kissing subiculum, second stop on the ride, While layer two loops deep down, layer three stays outside, Two separate rivers running through the same canyon, Feedforward, feedforward, no backward companion, Trisynaptic circuit needs both lanes in play, Dentate, CA3, CA1 — that's the classic relay. [Verse 3] Now zoom to the dentate, granule cells packed like sand, Millions sit silent, only a gossamer band Of neurons dare fire — so thin, so few, so bare, That's sparse coding, guarding each memory's share, Basket cells and interneurons clamp down the gate, Heavy inhibition keeps the whole thing sedate, Two patterns look twin-like? Dentate splits them in two, Pattern separation — that's the job it must do. [Bridge] Septal to temporal, dorsal down to the belly, Topography preserved, mapped out like a trellis, Witter, two-thousand-seven, laid the whole thing bare, Grab your pencil, draw the loop, mark both entries there, Layer two's arrow diving, layer three's arrow flat, Trisynaptic circuit — now you know where it's at. [Verse 4] CA3's got mossy fibers, thick and few but mighty, Autoassociative network, recurrent and flighty, Collaterals loop back, feeding on themselves, Pattern completion rising from those tangled shelves, Then Schaffer collaterals carry the call, CA1 receives it, integrates it all, Compares what came direct against what looped around, Match or mismatch — that's how memory's checked and found, CA1 sends output back to deep layers five and six, Closing up the circuit, entorhinal fixed, The loop feeds forward, then it feeds right back again, A hippocampal circuit written in the brain. [Chorus] Two to the dentate, two to CA3, Three to CA1, three to subiculum's bay, Perforant path piercing, poke through the wall, Two entry points, one circuit runs it all, Sparse and strong and squeezed by the inhibitory guard, Pattern separation, keeping memories apart. [Outro] Layer two, layer three, two doors, one hall, Perforant path piercing — now recite it all.
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