Faces and Feelings
The face is the most expressive part of the body, available for all to see. Ekman identified seven facial expressions of emotion that are found in all human groups: anger, happiness, fear, surprise, disgust, sadness and contempt. Emotional facial expressions are mostly involuntary, but some can be simulated or faked. An observer learns about the inner state of another by observing facial expressions. Humans do best at evaluating the sincerity of another person when they talk face to face. There must be a congruence of expression and verbal content before the speaker is believable. A spontaneous smile involves the whole face; a contrived smile uses only the lower facial muscles that uplift the corners of the mouth.
Adolph’s et al suggested that the recognition of emotional facial expression depends on discrete regions of right sensory cortices and that the recognition of specific emotions depends on subsets of these cortical regions. They tested 37 subjects with focal brain damage, asking subjects to recognize facial expressions of six basic emotions: happiness, surprise, fear, anger, disgust, and sadness. They mapped task performance scores onto images of brain activity. All subjects recognized happy expressions but some subjects were impaired in recognizing negative emotions, especially fear and sadness. The cortical regions that best correlated with impaired recognition of emotion were in the right inferior parietal cortex and in the right anterior infracalcarine cortex. They did not find impairments in recognizing any emotion in subjects with lesions restricted to the left hemisphere.
The idea of a modular brain extends to specialization of object recognition. From a dense field of objects, events and sensory information that is always changing, we recognize and identify objects of importance.
For example, Ishai and colleagues described specialized cortical areas for the recognition of pictures of faces, houses and chairs: “Recently, we identified, using fMRI, three bilateral regions in the ventral temporal cortex that responded preferentially to faces, houses, and chairs …Here, we report differential patterns of activation, similar to those seen in the ventral temporal cortex, in the bilateral regions of the ventral occipital cortex. We also found category-related responses in the dorsal occipital cortex and in the superior temporal sulcus. Moreover, rather than activating discrete, segregated areas, each category was associated with its own differential pattern of response across a broad expanse of cortex. The distributed patterns of response were similar across tasks (passive viewing, delayed matching) and presentation formats (photographs, line drawings). We propose that the representation of objects in the ventral visual pathway, including both occipital and temporal regions, is not restricted to small, highly selective patches of cortex but, instead, is a distributed representation of information about object form. Within this distributed system, the representation of faces appears to be less extensive as compared to the representations of non-face objects. “
Tsao et al noted that primates have specialized occipital-temporal areas specialized to the visual analysis of faces and used functional magnetic resonance imaging in alert macaques to identify three other regions of face-selective cortex in ventral prefrontal cortex, one of which was strongly lateralized to the right hemisphere.