Functional delineation of the human occipito-temporal areas related to face and scene processing. A PET study.
(1/65)
By measuring regional cerebral blood flow using PET, we delineated the roles of the occipito-temporal regions activated by faces and scenes. We asked right-handed normal subjects to perform three tasks using facial images as visual stimuli: in the face familiar/unfamiliar discrimination (FF) task, they discriminated the faces of their friends and associates from unfamiliar ones; in the face direction discrimination (FD) task, they discriminated the direction of each unfamiliar face; in the dot location discrimination (DL) task, they discriminated the location of a red dot on a scrambled face. The activity in each task was compared with that in the control fixation (CF) task, in which they fixated on the centre of a display without visual stimuli. The DL task activated the occipital cortices and posterior fusiform gyri bilaterally. During the FD task, the activation extended anteriorly in the right fusiform gyrus and laterally to the right inferior temporal cortex. The FF task further activated the right temporal pole. To examine whether the activation due to faces was face-specific, we used a scene familiar/unfamiliar discrimination (SF) task, in which the subjects discriminated familiar scenes from unfamiliar ones. Our results suggest that (i) the occipital cortices and posterior fusiform gyri non-selectively respond to faces, scrambled faces and scenes, and are involved mainly in the extraction of physical features of complex visual images; (ii) the right inferior temporal/fusiform gyrus responds selectively to faces but not to non-face stimuli and is involved in the visual processing related to face perception, whereas the bilateral parahippocampal gyri and parieto-occipital junctions respond selectively to scenes and are involved in processing related to scene perception; and (iii) the right temporal pole is activated during the discrimination of familiar faces and scenes from unfamiliar ones, and is probably involved in the recognition of familiar objects. (+info)
Selective sparing of face learning in a global amnesic patient.
(2/65)
OBJECTIVE: To test the hypothesis that visual memory for faces can be dissociated from visual memory for topographical material. METHOD: A patient who developed a global amnesic syndrome after acute carbon monoxide poisoning is described. A neuroradiological examination documented severe bilateral atrophy of the hippocampi. RESULTS: Despite a severe anterograde memory disorder involving verbal information, abstract figures, concrete objects, topographical scenes, and spatial information, the patient was still able to learn previously unknown human faces at a normal (and, in some cases, at a higher) rate. CONCLUSIONS: Together with previous neuropsychological evidence documenting selective sparing of topographical learning in otherwise amnesic patients, this case is indicative of the fact that the neural circuits involved in face recognition are distinct from those involved in the recognition of other visuoperceptual material (for example, topographical scenes). (+info)
Face recognition in age related macular degeneration: perceived disability, measured disability, and performance with a bioptic device.
(3/65)
AIMS: (1) To explore the relation between performance on tasks of familiar face recognition (FFR) and face expression difference discrimination (FED) with both perceived disability in face recognition and clinical measures of visual function in subjects with age related macular degeneration (AMD). (2) To quantify the gain in performance for face recognition tasks when subjects use a bioptic telescopic low vision device. METHODS: 30 subjects with AMD (age range 66-90 years; visual acuity 0.4-1.4 logMAR) were recruited for the study. Perceived (self rated) disability in face recognition was assessed by an eight item questionnaire covering a range of issues relating to face recognition. Visual functions measured were distance visual acuity (ETDRS logMAR charts), continuous text reading acuity (MNRead charts), contrast sensitivity (Pelli-Robson chart), and colour vision (large panel D-15). In the FFR task, images of famous people had to be identified. FED was assessed by a forced choice test where subjects had to decide which one of four images showed a different facial expression. These tasks were repeated with subjects using a bioptic device. RESULTS: Overall perceived disability in face recognition did not correlate with performance on either task, although a specific item on difficulty recognising familiar faces did correlate with FFR (r = 0.49, p<0.05). FFR performance was most closely related to distance acuity (r = -0.69, p<0.001), while FED performance was most closely related to continuous text reading acuity (r = -0.79, p<0.001). In multiple regression, neither contrast sensitivity nor colour vision significantly increased the explained variance. When using a bioptic telescope, FFR performance improved in 86% of subjects (median gain = 49%; p<0.001), while FED performance increased in 79% of subjects (median gain = 50%; p<0.01). CONCLUSION: Distance and reading visual acuity are closely associated with measured task performance in FFR and FED. A bioptic low vision device can offer a significant improvement in performance for face recognition tasks, and may be useful in reducing the handicap associated with this disability. There is, however, little evidence for a correlation between self rated difficulty in face recognition and measured performance for either task. Further work is needed to explore the complex relation between the perception of disability and measured performance. (+info)
Slowly progressive defect in recognition of familiar people in a patient with right anterior temporal atrophy.
(4/65)
We report the case of a patient (C.O.) who showed a selective defect in the recognition of familiar people, with very mild disease progression during a period of 30 months resulting from focal atrophy of the right temporal lobe. On formal neuropsychological testing, C.O. obtained high scores on tests of general intelligence, episodic memory, language, executive functions, selective attention, visual recognition and visual-spatial abilities. On more specific tasks of familiar and unfamiliar face recognition, C.O. scored above the controls' means on perceptual tests, but obtained highly pathological results on amnesic-associative tests. His disorder of recognition of familiar people was not due to loss of person-specific information, since he obtained highly abnormal naming scores when presented with photographs of famous people but borderline or mildly abnormal scores in a tasks in which he had to name celebrities from verbal definitions. On the other hand, C.O.'s recognition disorder could not be considered to be a form of 'associative prosopagnosia' since a similar defect was observed when he was requested to access information about famous persons through their voice rather than their face. Two alternative interpretations are advanced to explain C.O.'s inability to access his relatively spared person-specific knowledge not only through the person's face but also through the person's voice. The first hypothesis is that, before accessing the person-specific information, unimodal recognition channels must converge into a multimodal, non-verbal person-recognition system and that the right anterior temporal cortices play a crucial role in this integrative activity. The second hypothesis is that the face-recognition units have privileged access to person-specific semantic knowledge and that other recognition subsystems require coactivation of the face-recognition units in order to access person-specific semantic information. (+info)
Hyperfamiliarity for unknown faces after left lateral temporo-occipital venous infarction: a double dissociation with prosopagnosia.
(5/65)
Right hemisphere dominance in face processing is well established and unilateral right inferior temporo-occipital damage can result in prosopagnosia. Here, we describe a 21-year-old right-handed woman with acute impairment in face recognition that selectively concerned unfamiliar faces, following a focal left lateral temporo-occipital venous infarct. She was severely impaired in discerning that unknown people seen in everyday life were unfamiliar, although she had no difficulty recognizing familiar people. Thus, she had no prosopagnosia, but abnormal 'hyperfamiliarity' for unknown faces. Her difficulty was not accompanied by delusions or deficits in discrimination, identification or memory for faces. Standard neuropsychological testing showed that her recognition of familiar faces was entirely normal. By contrast, her sense of personally knowing faces was severely impaired when unknown faces evoked weak signals of familiarity based on spurious cues, to the extent that she would misattribute fame to faces that were unknown but to which she had been incidentally exposed on a prior occasion. Priming experiments also revealed that, unlike normal subjects, she made familiarity judgements without accessing semantic identity representations. Moreover, in face recognition tests, she generally showed bias in that she relied more on right-hemisphere strategies to identify global traits and less on left-hemisphere processes compared with healthy subjects. This case provides novel evidence for a differential contribution of the two hemispheres to face recognition. Hyperfamiliarity for unknown faces might arise from an imbalance between reciprocal hemispheric functions in face recognition, with relative hypoactivation of left hemisphere processes but hyperactivation of right-hemisphere processes for retrieving stored associations about people, linking seen faces to representations of affective and personal relevance. Hence, abnormal bias in attributing some personal meaning to unknown faces could be evoked by spurious signals of familiarity based on irrelevant affective associations in the right hemisphere. (+info)
A network of occipito-temporal face-sensitive areas besides the right middle fusiform gyrus is necessary for normal face processing.
(6/65)
Neuroimaging studies have identified at least two bilateral areas of the visual extrastriate cortex that respond more to pictures of faces than objects in normal human subjects in the middle fusiform gyrus [the 'fusiform face area' (FFA)] and, more posteriorly, in the inferior occipital cortex ['occipital face area' (OFA)], with a right hemisphere dominance. However, it is not yet clear how these regions interact which each other and whether they are all necessary for normal face perception. It has been proposed that the right hemisphere FFA acts as an isolated ('modular') processing system for faces or that this region receives its face-sensitive inputs from the OFA in a feedforward hierarchical model of face processing. To test these proposals, we report a detailed neuropsychological investigation combined with a neuroimaging study of a patient presenting a deficit restricted to face perception, consecutive to bilateral occipito-temporal lesions. Due to the asymmetry of the lesions, the left middle fusiform gyrus and the right inferior occipital cortex were damaged but the right middle fusiform gyrus was structurally intact. Using functional MRI, we disclosed a normal activation of the right FFA in response to faces in the patient despite the absence of any feedforward inputs from the right OFA, located in a damaged area of cortex. Together, these findings show that the integrity of the right OFA is necessary for normal face perception and suggest that the face-sensitive responses observed at this level in normal subjects may arise from feedback connections from the right FFA. In agreement with the current literature on the anatomical basis of prosopagnosia, it is suggested that the FFA and OFA in the right hemisphere and their re-entrant integration are necessary for normal face processing. (+info)
Impaired configurational processing in a case of progressive prosopagnosia associated with predominant right temporal lobe atrophy.
(7/65)
F.G., a 71-year-old right-handed man, presented with a slowly progressive deterioration in his ability to recognize faces of familiar and famous persons, contrasting with the relative preservation of other cognitive domains. His primary face perception skills were intact. Along with his face-recognition deficit, F.G. also exhibited a mild visual agnosia. A more detailed analysis of his performance on visuoperceptual tests revealed a selective deficit in retrieving the configurational representation of complex visual entities and an over-reliance on analysing individual features. Quantitative volumetric measurements of his temporal lobe structures showed a prevalent atrophy of the right fusiform gyrus and parahippocampal cortex. The results of the present study suggest that a right temporal variant of frontotemporal lobar degeneration may be characterized over a period of several years by an impaired configurational processing of visually complex entities in the absence of any semantic deficit. (+info)
A modulatory role for facial expressions in prosopagnosia.
(8/65)
Brain-damaged patients experience difficulties in recognizing a face (prosopagnosics), but they can still recognize its expression. The dissociation between these two face-related skills has served as a keystone of models of face processing. We now report that the presence of a facial expression can influence face identification. For normal viewers, the presence of a facial expression influences performance negatively, whereas for prosopagnosic patients, it improves performance dramatically. Accordingly, although prosopagnosic patients show a failure to process the facial configuration in the interest of face identification, that ability returns when the face shows an emotional expression. Accompanying brain-imaging results indicate activation in brain areas (amygdala, superior temporal sulcus, parietal cortex) outside the occipitotemporal areas normally activated for face identification and lesioned in these patients. This finding suggests a modulatory role of these areas in face identification that is independent of occipitotemporal face areas. (+info)