Introduction

Abstract

The human face is not always symmetrical with respect to the vertical midline; observation has revealed asymmetries in the resting face, as well as while emoting or speaking. Such deviations from symmetry have always been noticed in the faces of patients suffering from specific damage to the nervous system (i.e., facial paralysis), and more recently in the faces of normal individuals while involved in communication (i.e., facial asymmetry). The documentation and meaning of these asymmetries is the topic of this special issue. As an introduction, the neuroanatomy of the facial nerve will be delineated and the facial musculature described. Experimental studies with normals on facial asymmetry observed during emotional communication and speech output will be presented. Clinical studies of patients with facial paralysis of peripheral and central origin will be described, and treatment and diagnostic procedures for such patients will be evaluated. The issue is concluded with a methodological critique of the studies presented and a theoretical evaluation of the research in this area from a cognitive and information processing perspective.