mise à jour du
16 février 2007
Ann Anat
EMG study of the anterior, superior and
posterior auricular muscles in man
Berzin F, Fortinguerra CR
Departamento de Morfologia, Piracicaba, Brazil


Anterior, superior and posterior auricular muscles were studied electromyographically by means of wire electrodes. During ear movement the three muscles acted as a group and the movement was always directed upwards and backwards. The highest electrical activities were observed during natural smiling and yawning. Mouth opening without the drawing backwards of the comissura labiorum and the displacement of galea aponeurotica also produced electrical activity by the auricular muscles, with however, less intensity and in only 50% of the cases studied.
Very little has been published on the cutaneous musculature. As far as the extrinsic muscles of the ear (anterior auricularis, superior auricularis and posterior auricularis) are concerned, we only found the work of Serra et al. (1986), who studied the posterior auricularis muscle in lesions of the facial nerve but did not focus on its kinesiology.
The anatomy textbooks tell us that the anterior auricularis muscle draws the ear forward, the superior auricularis muscle draws it upward and the posterior auricularis muscle draws it backward. However, most of the authors considered them in humans as rudimentary muscles of little or no importance (Testut and Latarjet 1929; Gardner et al. 1960; Rouviere 1970; Orts Llorca 1970). Lockhart et al. (1965) stated that the auricular muscles act together, but only to a limited extension. Chiarugi (1948), Gray (1973) and Goss (1977) described them as acting as a group together with the occipitofrontalis muscle.
Since the specific literature on this subject is insufficient and the descriptions of their actions in textbooks conflicting, we have decided to study the anterior, superior and posterior auricular muscles in man electromyographycally.
Material and methods
The anterior, superior and posterior right auricular muscles (a.m.) of 30 male volunteers, from 19 to 25 years old, were the subjects of our EMG study.
The potential of the muscular activity was recorded with wire electrodes, according to Sumitsuji et al. (1965). Such electrodes consist of steel wires (full hard) with a diameter of 0.08 mm and a length of 15 cm which were introduced manually through the skin into the muscle being studied. This procedure was facilitated by the absence of a fascia in the mimic muscles. The electrode was connected to the electromyograph by a special spring connector for fine-wire electrodes (Basmajian et al. 1966).
The three auricular muscles were analysed while earring of the following facial movements or assuming the expressions described:
  1. moving the ear: upward, backward and forward
  2. smiling naturally
  3. yawning
  4. opening the mouth to maximum extent without drawing in the comissura labioruin.
  5. closing the eyelids: naturally and forcefully
  6. opening the eyelids: naturally and forcefully
  7. making vertical wrinkles on the forehead.
  8. displacing the galea aponeurotica posteriorly by attempting to contract the venter occipitalis
  9. displacing the ga/eu aponeurotica anteriorly by attempting to contract the venter frontalis
  10. lowering the eyebrows
  11. blinking the eyes.
Displacement of the ga/eu aponeurorica was detected by gently placing the observer's fingertips on this region.
Among 30 volunteers, only 16 could move their ears when asked, of whom only 6 achieved it from a rest position and 10 just managed to move the auricle after lifting the eyebrows. The ear was always displaced upward and backward; at the same time in 10 volunteers, the movement was more upward than backward and in 6, more backward than upward. In al 16 cases the action potentials were strong, concomitant and equivalent in the three muscles regardless of whether the ear moved in a more backward or more upward direction.
Action potentials were observed in all 3 auricular muscles during natural smiling and yawning.
Very tiny displacements of the ear backward and upward, with slight predominance of the latter, were observed in 28 volunteers during natural smiling.
The displacement of the galea aponeurotica backward was achieved by only 16 volunteers, and in 13 of these cases a strong simultaneous electrical potential could be recorded from the auricular muscles.
It is noteworthy that the volunteers always tended to raise their eyebrows before trying to execute movements of the ear or of the galea aponeurolica.
Isolated movements of the ear upward, forward and backward, as described in anatomy textbooks, have not been observed. In 16 volunteers, small combined displacements in an upward and backward direction were observed concomitantly, and in these cases the three auricular muscles acted as a group. This agrees partially with Lockhart et al. (1965) but in contrast to him we found high action potentials with some movements in spite of the limited displacement of the ear.
The synchronised upward and backward movement of the ear could be explained by the combined action of the three auricular muscles (am.). The contractions produce three forces applied simultaneously to the ear, as can be seen in Fig. 1. Since F1 (anterior a.m.) and F3 (posterior a.m.) are approximately in the same plane but act in opposite directions they tend to cancel each other out if they are exerting the same force, thus living only the action of F2 (superior a.m.). The resultant of these forces would then tend to displace the ear upward. But if F3 is slightly stronger than F1 the resultant would pull the ear upward and backward.
Originally we intended to study electromyographically only the muscular actions suggested in the literature. Nevertheless, during the experimental procedures, unforeseen spontaneous movements with strong action potential in the three auricular muscles were observed during natural smiling and yawning.
Activity of the auricular muscles was also observed in 50% of the individuals studied when the galea aponeurotica was displaced forwards. These results agree with Chiarugi, Gray and Goss, suggesting an interaction between the occipital muscle and the extrinsic auricular muscles.
In conclusion, the results presented showed that the a.m. are not just rudiments, since they show marked action potentials in relation to certain movements of the ear and face.