Phrenologists used to have a monopoly on brain scans: They’d feel around on a patient’s head for bumps and use a map of the skull to diagnose a person’s secretive nature or conscientiousness or even how much they loved their parents. Today, neuroscientists have better guides to our wetware. Using techniques like fluorescent microscopy and electrophysiology, they can trace neural pathways with astonishing precision, turning scans and bits of dissected matter into vibrant images that reveal the structures and signals that make you you.

White Matter

Tracts of white matter transport information between different sections of the brain. Researchers at the Human Connectome Project traced the movement of cells along these pathways, finding that the architecture isn’t just random spaghetti: Fiber bundles largely run left to right (red), back to front (green), or top to bottom (blue).

Neurons

In the past it was hard to tell if a neuron would amplify electrical messages or tamp them down. The Allen Institute for Brain Science zapped cells in a mouse’s visual cortex and recorded their output, mapping loud messages (white) and weaker (yellow) or inhibited ones (red).

Synapse

A single synapse can’t tell you anything about how the whole brain works, but understanding just one neuronal junction can help you understand patterns in the activity of all 100 trillion synapses in your brain. A lab at Harvard created software to diagram individual vesicles—small lipid bubbles (yellow) that hold neuro­transmitters. This one likely contains glutamate, which helps regulate signals throughout the nervous system.

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