[Verse 1] Back in ninety-two, Goodale and Milner saw Two streams of vision with a different call Not just "where" and "what" like we thought before But "how" and "what" - they opened up the door Dorsal stream computes for action's need Ventral builds the world that we perceive [Chorus] What versus how, the brain divides the load Vision for perception down the ventral road Vision for action takes the dorsal way Two separate systems working night and day What versus how, remember this refrain Double dissociation proves they're not the same [Verse 2] Meet patient D.F., carbon monoxide's curse Damaged ventral stream, but here's what's perverse She cannot tell you if a slot runs straight Or recognize the size upon her plate But watch her hand move with perfect grace Threading cards through slots she cannot trace [Chorus] What versus how, the brain divides the load Vision for perception down the ventral road Vision for action takes the dorsal way Two separate systems working night and day What versus how, remember this refrain Double dissociation proves they're not the same [Verse 3] Optic ataxia tells the flip side tale Parietal damage makes their reaching fail They'll name each object, know it crystal clear But grasp for coffee cups that aren't quite there Perception's perfect, action goes astray When dorsal pathways lose their guiding way [Verse 4] Temporal cortex for the what we know Parietal lobe for how our actions flow Online control versus conscious sight One works in darkness, one needs the light Evolution's answer to survive and thrive Keep these systems functionally alive [Bridge] Egocentric coordinates for grasping motion Allocentric maps for recognition's potion Real-time guidance versus memory's store Two parallel worlds behind perception's door Cleanest evidence that neuroscience has found Functional separation, safe and sound [Chorus] What versus how, the brain divides the load Vision for perception down the ventral road Vision for action takes the dorsal way Two separate systems working night and day What versus how, remember this refrain Double dissociation proves they're not the same [Outro] So when you reach out for your morning brew Remember streams of vision, split in two Goodale and Milner showed us something true The brain's not one, but systems numbering two
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