AU1 – inner brow raiser
frontalis, pars medialis
FRONTALIS ANATOMICAL DIVERSITY: A major factor often out of many anatomical references is the variability of frontalis shape, size, and structure. Despite its diversity, the frontalis muscle is often presented homogeneously. It is presented as a muscle spanning across most of the forehead with a split (bifurcation) in the upper portion of the muscle (as shown in the image above). However, in reality, this bifurcation is not always present. Some portion of people have an uninterrupted frontalis (no split). Others have a frontalis fully split (does not meet together in the medial area) into two sections. Even within the cases where there is a bifurcation, the split varies in terms of where it occurs along the frontalis as well as how deep it goes. All of these factors – and more – affect the way in which the brows move as well as how a particular individual’s wrinkles form. Read more here.
- Difficult to perform voluntarily
- Commonly combines with AU 2 to create full brow raise (AUs 1+2)
- Full brow raise is a signature marker in speech for word emphasis, attentiveness, and punctuation
- It is also a major component of the surprise emotion prototype, which features AU 5 and 25+26 (lips parted with jaw drop, respectively)
- Combines with AU 4 to create prototypic brow configuration for sadness (AUs 1+4)
- Also combines with AUs 2 and 4 for fear emotion brow prototypes (AUs 1+2+4)
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.)
- Compare AU1 to a full brow raise (1+2). Observe image below.