FACS – cheat sheet

AU1 – inner brow raiser 

frontalis, pars medialis

for a deeper dive on AU1:

• The Secret Life of Inner Brow Raiser
  
  • This post and video will walk you through the variations in inner brow raiser and how to identify each person’s unique inner brow raising style – including your own! 
  • (If you are not a subscriber, the free version of this video is on YouTube) 
• Inner Brow Raiser Deep Dive
  • This  post covers fundamental features of inner brow raiser.
  • It also goes over common misconceptions regarding inner brow raiser and how to recognize incorrect inner brow raiser references. (Spoiler alert: There are a lot of them.)
• Frontalis Variation
  • This  post covers under-researched topics in frontalis muscle structure. 
  • It covers anatomical differences of the frontalis muscle and how these differences look as well as what implications they may have in the areas of:
    • face tracking
    • mocap
    • EMG recording
    • FACS-based facial coding
• Compare AU1 to a full brow raise (1+2). Observe image below.
  

  

AU2 – outer brow raiser 

frontalis, pars lateralis

for a deeper dive on AU2:

• In the context of AU1 vs. AU2:  The Secret Life of Inner Brow Raiser (If you are not a subscriber, the free version of this video is on YouTube)
  • While this post and video is primarily focused on AU1 (inner brow raiser), there is valuable information on AU2 here as well.
• Frontalis Variation
  • This  post covers under-researched topics in frontalis muscle structure. 
  • It covers anatomical differences of the frontalis muscle and how these differences look as well as what implications they may have in the areas of:
    • face tracking
    • mocap
    • EMG recording
    • FACS-based facial coding
• Compare AU2 to a full brow raise (1+2). Observe image below.
  

AU4 – brow lowerer 

corrugator supercilii, depressor glabellae,  depressor supercilii

for a deeper dive on AU4:

• • The 3 muscles that make up AU4 can move independently.

1. corrugator

• • • • tends to push the brows toward each other
      • can be referred to as “knitting” the brows
      • causes vertical wrinkles above the nose

2. depressor glabellae

• • • • technically considered a nasal muscle
      • tends to push the down the medial portion of the brows, above the nose
      • causes horizontal wrinkle above nasal root

3. depressor supercilii

• • • • technically considered an eye muscle
      • debated whether this muscle is its own distinct muscle or part of orbicularis oculi
        
        ***Many surgeons, dermatologists, ophthalmologists, and plastic surgeons argue strongly that depressor supercilii is a distinct muscle with its own movement. I’m with them on this one. I believe I have identified depressor supercilii action occurring in isolation (or near isolation); however, I was not able to find any depressor supercilii references to compare to. I am happy to hear feedback from anatomists and surgeons. See GIF below.
        
        
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      GIFs     

AU1 – inner brow raiser 

AU2 – outer brow raiser 

AU4 – brow lowerer 

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      still images