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ABSTRACT: Face processing can be modified by bottom-up and top-down influences, but it is unknown how these processes interact in patients with face-recognition impairments (prosopagnosia). We investigated a prosopagnosic with lesions in right occipital and left fusiform cortex but whose right fusiform gyrus is intact and still activated during face-processing tasks. P.S., a patient with a well-established and selective agnosia for faces, was instructed to detect the presence of either faces or houses in pictures with different amounts of noise. The right fusiform face area (FFA) showed reduced responses to face information when visual images were degraded with noise. However, her right FFA still activated to noise-only images when she was instructed to detect faces. These results reveal that fusiform activation is still selectively modulated by task demands related to the anticipation of a face, despite severe face-recognition deficits and the fact that no reliable stimulus-driven response is evoked by actual facial information. Healthy controls showed stimulus-driven responses to faces in fusiform, and in right but not left occipital cortex, suggesting that the latter area alone might provide insufficient facial information in P.S. These results provide a novel account for residual activation of the FFA and underscore the importance of controlling task demands during functional magnetic resonance imaging.
Cerebral Cortex 11/2009; 20(8):1878-90. · 6.54 Impact Factor
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ABSTRACT: Adult attachment style refers to individual personality traits that strongly influence emotional bonds and reactions to social partners. Behavioral research has shown that adult attachment style reflects profound differences in sensitivity to social signals of support or conflict, but the neural substrates underlying such differences remain unsettled. Using functional magnetic resonance imaging (fMRI), we examined how the three classic prototypes of attachment style (secure, avoidant, anxious) modulate brain responses to facial expressions conveying either positive or negative feedback about task performance (either supportive or hostile) in a social game context. Activation of striatum and ventral tegmental area was enhanced to positive feedback signaled by a smiling face, but this was reduced in participants with avoidant attachment, indicating relative impassiveness to social reward. Conversely, a left amygdala response was evoked by angry faces associated with negative feedback, and correlated positively with anxious attachment, suggesting an increased sensitivity to social punishment. Secure attachment showed mirror effects in striatum and amygdala, but no other specific correlate. These results reveal a critical role for brain systems implicated in reward and threat processing in the biological underpinnings of adult attachment style, and provide new support to psychological models that have postulated two separate affective dimensions to explain these individual differences, centered on the ventral striatum and amygdala circuits, respectively. These findings also demonstrate that brain responses to face expressions are not driven by facial features alone but determined by the personal significance of expressions in current social context. By linking fundamental psychosocial dimensions of adult attachment with brain function, our results do not only corroborate their biological bases but also help understand their impact on behavior.
PLoS ONE 02/2008; 3(8):e2868. · 4.09 Impact Factor
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ABSTRACT: 22q11.2 deletion syndrome (22q11DS) is a neurogenetic syndrome associated with a high rate of psychiatric disorders. Previous research has revealed distinctive cognitive deficits, including impaired face processing. However, the neuro-functional substrates underlying these deficits have not been explored. Our aim was to investigate facial and emotional processing in 22q11DS.
During event-related functional magnetic resonance imaging, 15 individuals with 22q11DS were compared with age- and gender-matched healthy control subjects on a simple visual categorization task (faces or houses). Each stimulus was presented twice, and faces had either neutral or emotional (fearful) expressions.
Abnormal responses to faces were observed in 22q11DS, including a lack of normal face-selectivity in fusiform gyrus. By contrast, responses to houses were comparable across groups, with preserved selectivity in parahippocampal gyrus. Results also revealed a repetition-suppression effect for fearful faces in the right amygdala, which arose in healthy control subjects only, suggesting a lack of amygdala modulation by fear expression in 22q11DS.
Our results demonstrate selective anomalies in several brain regions critically implicated in visual and social function in 22q11DS. These findings suggest important new avenues for studying emotional processing and social deficits frequently observed in psychotic patients and establishing their relation to specific phenotypic manifestations in 22q11DS.
Biological psychiatry 02/2008; 63(1):49-57. · 8.93 Impact Factor
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ABSTRACT: The manipulation of numbers required during calculation is known to rely on working memory (WM) resources. Here, we investigated the respective contributions of verbal and/or spatial WM manipulation brain networks during the addition of four numbers performed by adults, using functional magnetic resonance imaging (fMRI). Both manipulation and maintenance tasks were proposed with syllables, locations, or two-digit numbers. As compared to their maintenance, numbers manipulation (addition) elicited increased activation within a widespread cortical network including inferior temporal, parietal, and prefrontal regions. Our results demonstrate that mastery of arithmetic calculation requires the cooperation of three WM manipulation systems: an executive manipulation system conjointly recruited by the three manipulation tasks, including the anterior cingulate cortex (ACC), the orbital part of the inferior frontal gyrus, and the caudate nuclei; a left-lateralized, language-related, inferior fronto-temporal system elicited by numbers and syllables manipulation tasks required for retrieval, selection, and association of symbolic information; and a right superior and posterior fronto-parietal system elicited by numbers and locations manipulation tasks for spatial WM and attentional processes. Our results provide new information that the anterior intraparietal sulcus (IPS) is involved in tasks requiring a magnitude processing with symbolic (numbers) and nonsymbolic (locations) stimuli. Furthermore, the specificity of arithmetic processing is mediated by a left-hemispheric specialization of the anterior and posterior parts of the IPS as compared to a spatial task involving magnitude processing with nonsymbolic material.
Neuropsychologia 02/2008; 46(9):2403-14. · 3.64 Impact Factor
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ABSTRACT: Internal senses of the position of the eye in the orbit may influence the cognitive processes that take into account gaze and limb positioning for movement or guiding actions. Neuroimaging studies have revealed eye position-dependent activity in the extrastriate visual, parietal, and frontal areas, but, at the earliest vision stage, the role of the primary visual area (V1) in these processes remains unclear. Functional MRI (fMRI) was used to investigate the effect of eye position on V1 activity evoked by a quarter-field stimulation using a visual checkerboard. We showed that the amplitude of V1 activity was modulated by the position of the eye, the activity being maximal when both the eye and head positions were aligned. Previous studies gave impetus to the emerging view that V1 activity is a cortical area in which contextual influences take place. The present study suggests that eye position may affect an early stage of visual processing.
Human Brain Mapping 08/2007; 28(7):673-80. · 5.88 Impact Factor
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ABSTRACT: Previous neuroimaging studies of oddball tasks and other paradigms measuring attention processes support right hemisphere dominance for attentional processes. Using an auditory selective attention task, we studied the functional asymmetry of the human brain in response to attended or unattended deviant tones. Secondly, we examined whether a congruency or a discrepancy between audio-spatial and visuo-spatial cued attentional resources may influence the activity elicited by an auditory selective attention task.
We used event-related functional magnetic resonance imaging (fMRI) to study healthy adults as they performed an auditory oddball task in which a spatial-cued instruction indicated the ear to attend a monaural deviant tone. We addressed the question of congruency/discrepancy between attentional resources by using three different eye positions during the performance of the auditory oddball task.
Relative to standard tones, both attended and unattended deviant tones (DTs) presented to either ear elicit the activation of a widespread bilaterally distributed cortical and subcortical network. A subset of this network, essentially frontal and temporal areas, showed not only greater right than left activity but an enhancement of this rightward asymmetry in response to attended DTs. The only cortical region that showed a leftward asymmetry in response to attended DTs overlapped Heschl gyrus and planum temporale, unmasking a left hemisphere preference of both primary and secondary auditory cortex for processing simple attended monaural stimuli. Questioning the impact of eye position during auditory oddball task, we observed a lesser activity in right integrative crossmodal areas (superior temporal sulcus, opercular part of the inferior frontal gyrus, pre-SMA) when the eye positions were contralateral to detected DTs. These regions may be tuned to best respond when both visuo-spatial and audio-spatial attentional resources work together.
These results support the assumption that the right hemisphere is preferentially engaged in processing audio-spatial attentional resources and underline the interest to study the crossmodal integration of attentional resources by the mean of the detection of DTs in different eye positions.
Restorative neurology and neuroscience 02/2007; 25(3-4):211-25. · 2.51 Impact Factor
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ABSTRACT: To reach and grasp an object in space on the basis of its image cast on the retina requires different coordinate transformations that take into account gaze and limb positioning. Eye position in the orbit influences the image's conversion from retinotopic (eye-centered) coordinates to an egocentric frame necessary for guiding action. Neuroimaging studies have revealed eye position-dependent activity in extrastriate visual, parietal and frontal areas that is along the visuo-motor pathway. At the earliest vision stage, the role of the primary visual area (V1) in this process remains unclear. We used an experimental design based on pattern-onset visual evoked potentials (VEP) recordings to study the effect of eye position on V1 activity in humans.
We showed that the amplitude of the initial C1 component of VEP, acknowledged to originate in V1, was modulated by the eye position. We also established that putative spontaneous small saccades related to eccentric fixation, as well as retinal disparity cannot explain the effects of changing C1 amplitude of VEP in the present study.
The present modulation of the early component of VEP suggests an eye position-dependent activity of the human primary visual area. Our findings also evidence that cortical processes combine information about the position of the stimulus on the retinae with information about the location of the eyes in their orbit as early as the stage of primary visual area.
BMC Neuroscience 10/2004; 5:35. · 3.04 Impact Factor
