The Face: Will and Expression

Two more out-takes from Beethoven’s Anvil, both about the face, control of facial muscles, and the expression of emotion. We’ve all at one time or another struggled to control our face, attempting “hide” something that’s trying to “break out”. How is such a conflict physically possible?

The first section of the post is about the facial nerve and how it has two components, each mediating a different aspect of behavior and driven by different brain systems. The second indicates some consequences of that division. Other posts related to this general subject:

• A Jazzman Prepares
• Emotion in the Body: James-Lange
• Will in the Nervous System, and Its Consequences

The Facial Nerve

Let us consider a particular anatomical case, the facial nerve. The facial nerve is one of twelve pairs of cranial nerves that connect the brain to the sensors and muscles of the face and neck. (The spinal nerves do the same for the rest of the body. Taken together the cranial and spinal nerves constitute the peripheral nervous system.) It has both a sensory and a motor component. It is the motor component which is of interest to us now, for it controls muscles involved with facial expression.

If the motor component of the facial nerve is damaged in one region your ability to control your lower facial muscles in voluntary activity is weakened or lost. For example, it will be difficult to purse your lips or to hold food in your mouth while eating. But the muscles still respond to emotion. Conversely, damage in a different region will destroy emotional expression, but not voluntary use. Similarly Paul Ekman has noted that spontaneous smiles are different from voluntary ones. Thus we have one set of muscles subject to two different sources of control. The impulse to emotional expression would reflect one source of control--most likely located in the limbic system in the hypothalamus, the basal ganglia, and/or the cingulate gyrus--while the capacity for voluntary control--located in the motor cortex--would reflect a different source of control. When the facial muscles are strongly stimulated by both of these sources you might well have a conflict, for they might be moving those muscles in different ways.

These examples, of course, involve more than control of the facial muscles. They involve control of the voice. In addition to the facial muscles, that involves the tongue, larynx (vocal cords), and respiratory system. However, we know that the vocal system is subject to the same kind of dual control, though a wider set of neural structures is involved. The mammalian vocal system is controlled by cortical and subcortical mechanisms in the limbic system. In order for language to develop it was necessary for our ancestors to gain neocortical control over the vocal system, a matter discussed by Terrence Deacon in his recent account of human evolution, The Symbolic Species: The Co-evolution of Language and the Brain.

Facial Expression

One interesting consequence of this organization is illustrated by an experiment conducted by Paul Ekman. Ekman instructed subjects to move their facial muscles in certain ways, ways characteristic of emotional expression, though the subjects were not told this. When they had done as directed the subjects reported feeling, for example, “happiness” or “anger,” as appropriate to the expression on their face.

Ekman thus rather cleverly managed to put false information into one channel of the nervous system, using one division of the nervous system (the willed, the voluntary division) to fool the other (involuntary). The subjects would have used neocortical motor centers to deliberately compose their facial expressions as Ekman directed, not the limbic centers responsible for emotional modulation of the motor system. However, the cortical systems that assess the state of the musculo-skeletal system interpret the resulting expressions as they would interpret normal expressions and, accordingly, the subjects experienced the appropriate feeling....

Question: Given that both voluntary and involuntary impulses originate within the same brain, why make THAT distinction between them? “Who” or “what” in the brain—or is it the mind?—is making this judgment?

We might thus formulate a principle:

External Circuit: The same expressive acts which signal one’s inner state to others also signal that state to oneself. Cortical brain centers thus routinely get information about the activities of subcortical centers through a channel which is external to the nervous system itself.

This “zone of emotional expression” is thus a behavioral “space” that is both inside the organism, for it expresses inner state in a way that communicates it from one part of the brain to another, and outside, for it is available to others.

Thus one’s emotional feelings involve both the inner and outer environments of the central nervous system and the neural signals that track those environments. For the cortical systems which monitor the state of the motor system—positions of the joints, tension in the muscles—do so through the somatic channels of the peripheral nervous system, not the autonomic channels. Those systems are thus oriented toward the external world, not the inner world. Izard’s and Ekman’s research indicate that they learn of the inner world indirectly, through muscle feedback, in addition to any information they may get through the central nervous system itself.

Question: What does this “crossing” of inner and outer, where higher brain centers are alerted to activity in lower centers through a channel, facial expression, that is visible to others, what does this imply about the phenomenological structure of those public events where strong emotion is expressed in the presence of others?