stills     

click tabs for GIFs & further info

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.

  

the secret life of inner brow raiser

inner brow raiser: deep dive

frontalis variation

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, procerus,  depressor supercilii

for a deeper dive on AU4:

• • The 3 muscles that make up AU4 can move independently.
    • • corrugator supercilii
      • depressor supercilii
      • procerus

1. corrugator supercilii

GIF above shows posed. isolated (or mostly isolated) corrugator supercilii activation at mild/medium intensity.

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

2. depressor supercilii

GIF above shows spontaneous. isolated (or mostly isolated) depressor supercilii activation at mild intensity.
GIF above shows posed. isolated (or mostly isolated) depressor supercilii activation at mild/medium intensity. NOTE 1: In the posed version, I was unable to symmetrically activate depressor supercilii, and it is dominant on the left side (screen right). NOTE 2: In the posed version, I activate nostril compressor, which accounts for the movement on the lower parts of the nose. Please ignore this movement, as it is not a part of depressor supercilii movement. Reference the spontaneous pose to see action without added movement from nostril compression.

• • • • 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.

3. procerus

GIF above shows posed full brow raise (frontalis) + procerus activation. I cannot activate procerus without strong corrugator supercilii unless I raise my brows. Even in this example, besides the full brow raise, there appears to be mild to moderate intensity depressor supercilii and potentially mild corrugator supercilii; however, the strongest and most obvious AU4 action here comes from procerus, which you can observe creating U-shaped wrinkles in the medial area of the forehead. When occurring without brow raise, procerus wrinkles are typically straight and horizontal.

• • • • 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