04 — music

Music

Right superior temporal gyrus + Heschl's gyrus

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Heschl's gyrus holds primary auditory cortex, sound's first cortical stop. The right auditory cortex leans toward pitch and melody, the left toward rapid changes in sound; music uses both.

This isn't a recording of my brain listening. It's a simulation, drawn over my structural MRI and styled after fMRI. The song is split into layers (kick, snare, hats, bass, chords, lead, air and overall intensity), and each highlighted region follows one of them in that layer's color. Two default-mode hubs work the other way: those regions tend to quiet down when attention turns outward, so here they glow when the music goes quiet.

Some pairings follow music-cognition research, like the beat in the putamen and supplementary motor area, and the melody on the right; others are closer to artistic license. Real fMRI signals trail the sound by several seconds; these land on the beat. Activity is weighted toward gray matter and swells with how loud its layer is, and the three slices move through the brain along a path choreographed to the track.

The track is Aegleseeker by Silentroom vs Frums, from the mobile rhythm game Arcaea, and it's where this site gets its name. I used to play Arcaea seriously. At one point I was in the global top 100, and I had a Pure Memory (every note hit in the tightest timing window) on every song's Future chart in the game at the time. I posted plays on YouTube, including this one on Aegleseeker. I still follow the mobile rhythm game scene, mostly Arcaea and Phigros, and still listen to a lot of its music.

Most layers come from splitting the recording into percussive and harmonic parts, then into frequency bands. The lab panel below has the tuning controls, and it can also run the visualizer live on an audio file of your own.

›labtuning · live analysis · diagnostics

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live analysis

network · layer → regions

  • kick

    • smaSupplementary motor area locks to the beat.
    • putamen_lLeft putamen, beat perception and groove.
    • putamen_rRight putamen, beat perception and groove.

  • snare

    • hg_lLeft primary auditory cortex resolves fast transients like the snare crack.
    • pmd_lLeft dorsal premotor cortex entrains to the backbeat.
    • pmd_rRight dorsal premotor cortex entrains to the backbeat.
    • pt_lLeft planum temporale, the auditory-motor interface for rhythm.

  • hats

    • crus_lLeft lateral cerebellum times fast subdivisions.
    • crus_rRight lateral cerebellum times fast subdivisions.
    • stg_lLeft superior temporal gyrus tracks high transients.

  • bass

    • insula_lLeft insula, the interoceptive response to low end.
    • insula_rRight insula, the interoceptive response to low end.

  • chords

    • ifg_rRight inferior frontal gyrus processes harmonic syntax.
    • ifg_lLeft inferior frontal gyrus (Broca's area), sequence and structure.
    • stg_rRight superior temporal gyrus follows harmonic contour.
    • dlpfc_lLeft dorsolateral prefrontal cortex holds the progression in mind.

  • lead

    • hg_rRight primary auditory cortex favours pitch: the melody.
    • pt_rRight planum temporale, melodic and spectral detail.
    • dlpfc_rRight dorsolateral prefrontal cortex, tonal working memory.

  • air

    • hippocampus_lLeft hippocampus, memory and familiarity under the sustained wash.
    • hippocampus_rRight hippocampus, memory and familiarity under the sustained wash.

  • intensity

    • naccNucleus accumbens, the reward peak; builds through intense passages.
    • ofcMedial orbitofrontal cortex, reward valuation.
    • accAnterior cingulate, arousal and salience.
    • amygdala_lLeft amygdala, emotional response.
    • amygdala_rRight amygdala, emotional response.
    • caudate_lLeft caudate, anticipation ahead of peaks.
    • caudate_rRight caudate, anticipation ahead of peaks.
    • thalamusThalamus (medial geniculate), the auditory relay; tracks loudness quickly.

  • rest

    • precuneusPrecuneus, default-mode hub; active when the music is quiet.
    • pccPosterior cingulate, default-mode hub; active when the music is quiet.

In the key, dimmed layers have nothing visible in the current slices: they are quiet, or playing in regions the slices don't cut.

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