[Verse 1] Talk about the perforant path, the two-lane bridge Layer two's the courier running straight off the ridge Dumps its cargo in dentate gyrus, granule cell bin Then CA3 catches the echo, lets the pattern spin Layer three's a different courier, different route to run Skips the dentate detour, goes straight to CA1 Temporoammonic highway, subiculum too Same building, different floors, different work to do [Chorus] Two in, one out, that's the entorhinal deal Layer two and three keep the memory wheel Dorsolateral rides the dorsal train Ventromedial ships to ventral terrain Perforant path punches through, mnemonic hit Two feeds the bin, three feeds CA one, get it [Verse 2] Topography ain't random, it's a map you can trust Dorsolateral MEC, dorsal hippocampus, must Handle the fine-grain grid, the small-scale spatial code Ventromedial slides on down the ventral road Broader scale, wider fields, coarser zone Same six-layer structure, different postal home Witter mapped the wiring back in 2007 Fibers perforating through like a needle, keen and even [Chorus] Two in, one out, that's the entorhinal deal Layer two and three keep the memory wheel Dorsolateral rides the dorsal train Ventromedial ships to ventral terrain Perforant path punches through, mnemonic hit Two feeds the bin, three feeds CA one, get it [Verse 3] Now flip the tape, the loop don't dead-end at CA1 Subiculum and CA1 ship output, work is done Climbing back to layer five, the deep return address Layer five sends out to neocortex, clears the mess But layer five ain't finished, got one more errand yet Feeds right back to layers two and three, no debt unmet That's the loop sealed tight, recurrent, self-renewed Cortex whispers to hippocampus, hippocampus answers too [Bridge] Direct path: layer three straight to CA one, comparing lanes Indirect: layer two through dentate, trisynaptic chains Suh eleven showed us — novelty lights the indirect line Direct path handles matching, the familiar sign Compare what's new against what's old, that's the CA1 chore Two routes converge on one cell, novelty at the door [Verse 4] Complete the graph from module six, add the labeled edge Layer two, arrow dentate, arrow CA3, the ledge Layer three, arrow CA one, arrow subiculum too Five, arrow cortex, five, arrow two and three, loop renews Draw it clean, six layers, arrows pointing right Perforant path's the highway, edge connected to edge [Chorus] Two in, one out, that's the entorhinal deal Layer two and three keep the memory wheel Dorsolateral rides the dorsal train Ventromedial ships to ventral terrain Perforant path punches through, mnemonic hit Two feeds the bin, three feeds CA one, get it [Outro] Two feeds the bin, three feeds the one Five sends it home when the circuit's done Dorsal to dorsal, ventral to ventral flow Close the loop, that's the entorhinal show
← Module 6 — Inputs to the Entorhinal Cortex | Module 8 — Grid Cells →