Facial expression processing after amygdalotomy

Facial expression processing impairments were studied in D.R., a 51-year-old woman with a partial bilateral amygdalotomy. D.R. was poor at recognising emotional facial expressions, both in static and moving stimuli. In identity matching tasks (same vs different person) and expression matching tasks (same vs different expression), D.R. was impaired at expression matching with simultaneously or successively presented faces; she experienced difficulties whenever the faces' identities were discrepant with their expressions. For identity matching, she also had problems when simultaneously presented images showed the same face with two different expressions; her deficit in interpreting facial expressions could lead her to mistake differences in expression for a difference in identity. In imagery tasks, D.R. was able to answer questions about the appearance of familiar people, yet she was very poor at imaging facial expressions of emotion. We suggest that her problems in processing facial expressions included impaired knowledge of the patterning of facial features in each emotion; without this, remembering or reconstructing what emotional facial expressions look like is as impaired as perceptual recognition. These findings are consistent with the hypothesis of a role for the amygdala in social behaviour.

Left hemisphere representations of emotional facial expressions

Researchers have suggested that the right hemisphere is superior at processing emotional facial expressions because it contains stored perceptual 'templates' of facial expressions. We tested each hemisphere of a split-brain patient on two tasks involving emotional facial expressions. Both hemispheres performed equally well and significantly above chance matching facial expressions with emotion words. The subject's right hemisphere consistently performed well judging whether two facial expressions were the same or different. His left hemisphere performed poorly on this discrimination task at first, but showed a sharp improvement when the instructions were changed slightly, emphasizing verbal labels for the facial expressions. Results suggest that 'facial expression templates' may not be stored only on the right.

Face perception and within-category discrimination in prosopagnosia

Prosopagnosics are impaired at face recognition, but unimpaired, or relatively less impaired, at common object recognition. It has been suggested that this dissociation results simply from the greater difficulty of face recognition compared to object recognition, or from the greater need to discriminate visually similar members of a single category in face recognition compared to object recognition. We tested these hypotheses using the performance of normal subjects in an 'old/new' recognition paradigm to establish the true relative difficulty of face and object recognition, and required both normal subjects and a prosopagnosic subject to discriminate both faces and visually similar exemplars of nonface object categories. In two different experiments, the prosopagnosic patient performed disproportionately poorly with faces. These results disconfirm the hypotheses described above, and imply that prosopagnosia is an impairment of a specialized form of visual recognition that is necessary for face recognition and is not necessary, or less necessary, for the recognition of common objects.

A Neuroethological Framework for the Representation of Minds

The cognition that constructs mental features such as intention, disposition, and character is an aspect of theory of mind. This aspect of representation of minds, which inherently has valence, is viewed from cognitive, evolutionary, and neural perspectives. It is proposed that this cognition is modular, and that it normally operates in association with a valence-free cognition able to represent mental states such as belief. Examples of neural activity capable of supporting the social representations macaque monkeys are believed to possess (understanding of affective displays, purposeful movement, and elemental social interactions) are presented.

Savings in Relearning Face—Name Associations as Evidence for “Covert Recognition” in Prosopagnosia

Prosopagnosic patients appear to be impaired at recognizing faces. However, recent evidence for “covert recognition” in prosopagnosia has been taken to suggest that the impairment is not in face recognition per se, but rather in conscious access to face recognition. The most widely used test for covert recognition of faces in prosopagnosia is the face-name relearning task, in which some prosopagnosics have been found to learn correct names for previously familiar faces more easily than incorrect names. Although this phenomenon is consistent with face recognition operating normally but out of reach of conscious awareness, it may also be consistent with an impairment in face recognition per se. Perhaps savings in relearning is sufficiently sensitive to the residual information contained in degraded face representations that are not detectable by overt measures of recognition. If so, then we should expect to observe this same savings in relearning when overt recognition is obliterated for reasons other than brain damage. In the present study, we used forgetting of face-name associations in normal subjects as a way of degrading recognition ability. We found the same dissociation between overt recognition performance and savings in relearning as observed in prosopagnosic patients. This implies that the performance of prosopagnosic patients in these tasks does not demand explanation in terms other than an impairment in face recognition per se.

Neuropsychological impairment of face recognition units

Despite the absence of "conscious", overt identification, some patients with face recognition impairments continue covertly to process information regarding face familiarity. The fact that by no means all patients show these covert effects has led to the suggestion that indirect recognition tasks may help in identifying different types of face recognition impairment. The present report describes a number of experiments with the patient NR, who, after a closed head injury, has been severely impaired at recognizing familiar faces. Investigations mostly failed to show overt or covert face recognition, but NR performed at an above-chance level in selecting the familiar face on a task requiring a forced-choice between a familiar and an unfamiliar face. This discrepancy between a degree of rudimentary overt recognition and absence of covert effects on most indirect tests was addressed using a cross-domain identity priming paradigm. This examined separately the possibility of preserved recognition for faces that NR consistently chose correctly in a forced-choice familiarity decision and those on which he performed at chance level. Priming effects were apparent only for the faces that were consistently chosen as "familiar" in forced-choice. We suggest that NR's stored representations of familiar faces are degraded, so that face recognition is possible only via a limited set of relatively preserved representations able to support a rudimentary form of overt recognition and to facilitate performance in matching and priming tasks.