Thread by @JMGrohNeuro

We have a new #preprint out! It’s about what happens in your ears when your eyes move. A #tweeprint about @Stephschlebusch, @cindyking40, David L.K. Murphy et al. 1/

https://twitter.com/biorxivpreprint/status/1597066596635185152?s=20&t=bG2N1mVWc9JdTpBhgvWlwg

First some background: A couple years ago, we (Gruters, Murphy et al.) discovered that your ears *make* tiny sounds when your eyes move. See theatlantic.com/science/archiv… by @edyong209 2/

@edyong209 And the original paper here, open access: pnas.org/doi/abs/10.107… 3/

How can your ears make sounds? Everyone’s ears contain little muscles – middle ear muscles – and other cells that behave like muscles – the so called “outer hair cells” in the cochlea. 4/

When they move, they push or pull on the various inner workings of the ear, such as the basilar membrane in the cochlea and the tiny bones that connect the eardrum to the cochlea. 5/

Because all these inner parts are mechanically connected to one another, the actions of outer hair cells or middle ear muscles end up causing the eardrums to move, like the brain is banging on a little tiny drum. Presto! the brain creates sound 6/

So far, this is all previously known. What we discovered a couple years ago is that the brain is sending signals to these little muscles/muscle-like cells in connection with movements of the eye! That's what's described in pnas.org/doi/abs/10.107… 7/

In the current paper, we start asking why it does this? What kind of signals is the brain sending to these muscles, and what would they be good for? Our general idea is that they relate to a central problem the brain has to solve – connecting what we hear with what we see. 8/

This requires very specific information about the movements of the eyes – so the brain can be ready to attribute sounds to the matching locations in the visual scene. 9/

More technically, the problem involves reference frames – visual spatial information originates in retinal coordinates, whereas auditory spatial information is detected in head-centered coordinates. Movements of the eyes shift these axes with respect to one another. 10/

In the current paper we show that EMREOs are precise & parametric enough to allow reconstruction of what visual target the eyes are moving to from recording in the ears with a microphone! 11/

E.g. the black dots are where the saccade targets were and the red are where they are reconstructed to be from the ear canal microphone recordings. Not perfect, but not bad! 12/

There’s a lot we still don’t know! (This is an exciting problem to work on!) We still don’t know *how* the information in EMREOs is used – what impact the mechanisms that cause EMREOs have on responses to incoming sound, or even exactly what those underlying mechanism(s) are 13/

But with this paper we can say that the fingerprints are there of a process by which the brain begins making the necessary adjustments to link what we hear with what we see regardless of where we are looking 14/

Finally thanks again to this great team effort led by @Stephschlebusch @cindyking40 and David L. K. Murphy @DukeU @DukeBrain @DukePsychNeuro @DukeNeuro with key contributions from Rachel Landrum and our valued collaborator Christopher Shera at @USC 15/15

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