inner brow raiser: deep dive

inner brow raiser wrong

The following post is about AU1/inner brow raiser/frontalis, pars medialis. It covers: anatomical variation, common mistakes, and some clean references. Scroll down to view clean examples.

AU1 – inner brow raiser
frontalis, pars medialis

Inner brow raiser is one of the most difficult facial actions to find clean references for. Many sources fail to find actors who can separate their inner brow raiser from other facial actions such as outer brow raiser (from frontalis, pars lateralis) and brow lowerer (from corrugator).

I recently critiqued a set of FACS shapes for a client and noticed his inner brow raiser shape had some corrugator (from brow lowerer) mistakenly mixed in.

client’s inner brow raiser + my review notes:

inner brow raiser with brow lowerer mistake
FACS shape of “inner brow raiser” by Derrick Sesson

Adding corrugator to inner brow raiser is a very common mistake. This commonality is partly due to the fact that: Good references are hard to find!

Even my client – an established industry artist with a great portfolio and CV – unknowingly added corrugator features to his model, because he trusted a tainted reference. The reference he used was from a prominent anatomy and facial expression book: Anatomy of Facial Expressions. Many art students and professionals use this textbook. It is a great textbook, but some of its FACS shapes are incorrect.

inner brow raiser reference used by client:

See the vertical and wavy lines in the center of the forehead in the images below? Those vertical lines are from corrugator. Corrugator should not be activated for the inner brow raiser base shape. Corrugator should only be present when one is intentionally combining inner brow raiser with brow lowerer.

inner brow raiser wrong

To view some clean examples of AU1, observe the GIFs below. Read about the primary and secondary effects of inner brow raiser as well as how its features can vary across individuals.

some clean AU1 (inner brow raiser) examples

AU 1 - inner brow raiser
AU1 i

AU1 - inner brow raiser
AU1 ii

AU 1 - inner brow raiserAU1 iii

primary effects
  • contracts inner portions of the frontalis muscle – the pars medialis section
  • pulls up the inner brow area

secondary effects

  • stretches inner portion of the upper eyelid skin
  • stretches skin near inner eye cover fold (eye cover fold: where the upper eyelid skin folds into the eye socket)
  • even if eye cover fold is not present (monolid or hooded eyelids), skin above tear duct is still stretched and pulled up
  • skin around sides of nose (near tear duct) is also stretched


  • due to variation in human frontalis shapes, the inner brow raiser pull looks different on different individuals
    • some inner brow raiser pulls occur at the innermost edge of the inner brow tip (AU1 iii)
    • other inner brow raiser pulls take place half an inch away from the inner brow tip (or further), landing near the middle of the brow (AU1 i and AU1 ii)
  • inner brow raiser wrinkles also vary significantly across individuals
    • some have no wrinkles (AU1 i and AU1 ii)
    • some have straight wrinkles concentrated in the center of the forehead (AU1 iii)
    • some have curved wrinkles concentrated in the center of the forehead, with a raised hump in the middle
    • some have horizontally wavy wrinkles (think “M”-shape) concentrated in the center of the forehead with two humps and a slight dip in the middle of the wrinkles (Emilia Clarke has this type.)

examples i-iii explained

AU1 i
AU 1 - inner brow raiser

    • asymmetric raise
    • pull is stronger on screen left
    • pull on screen left takes place closer to the middle of the brow than the pull on screen right (which is closer to the inner brow tip)
    • pull on screen right is lower in intensity and closer to inner brow tip
    • no wrinkles

AU1 ii
AU1 - inner brow raiser

  • asymmetric raise
  • pull on screen right takes place closer to the middle of the brow than the pull on screen left (which is closer to the inner brow tip)
  • overall, the raise on this face does not have much range
  • no wrinkles

AU1 iii
AU 1 - inner brow raiser

    • very symmetric
    • high range raise
    • raise occurs at the innermost tips of the brow
    • really good example of an exaggerated, cartoony inner brow raise

For more information on inner brow raiser, see: the secret life of inner brow raiser.


One thought on “inner brow raiser: deep dive

  1. Pingback:  ARKit to FACS Translation – Face the FACS

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