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Aina Puce

Publications and source records attributed to Aina Puce.

16 recordsLinked to original sources
PubMed2007

Neural responses elicited to face motion and vocalization pairings.

During social interactions our brains continuously integrate incoming auditory and visual input from the movements and vocalizations of others. Yet, the dynamics of the neural events elicited to these multisensory stimuli remain largely uncharacterized. Here we recorded audiovisual scalp event-related potentials (ERPs) to dynamic human faces with associated human vocalizations. Audiovisual controls were a dynamic monkey face with a species-appropriate vocalization, and a house with opening front door with a creaking door sound. Subjects decided if audiovisual stimulus trials were congruent (e.g. human face-human sound) or incongruent (e.g. house image-monkey sound). An early auditory ERP component, N140, was largest to human and monkey vocalizations. This effect was strongest in the presence of the dynamic human face, suggesting that species-specific visual information can modulate auditory ERP characteristics. A motion-induced visual N170 did not change amplitude or latency across visual motion category in the presence of sound. A species-specific incongruity response consisting of a late positive ERP at around 400 ms, P400, was selectively larger only when human faces were mismatched with a non-human sound. We also recorded visual ERPs at trial onset, and found that the category-specific N170 did not alter its behavior as a function of stimulus category-somewhat unexpected as two face types were contrasted with a house image. In conclusion, we present evidence for species-specificity in vocalization selectivity in early ERPs, and in a multisensory incongruity response whose amplitude is modulated only when the human face motion is paired with an incongruous auditory stimulus.

Acoustic Stimulation↗
PubMed2006

Neural correlates of imagined and synaesthetic colours.

The experience of colour is a core element of human vision. Colours provide important symbolic and contextual information not conveyed by form alone. Moreover, the experience of colour can arise without external stimulation. For many people, visual memories are rich with colour imagery. In the unusual phenomenon of grapheme-colour synaesthesia, achromatic forms such as letters, words and numbers elicit vivid experiences of colour. Few studies, however, have examined the neural correlates of such internally generated colour experiences. We used functional magnetic resonance imaging (fMRI) to compare patterns of cortical activity for the perception of external coloured stimuli and internally generated colours in a group of grapheme-colour synaesthetes and matched non-synaesthetic controls. In a voluntary colour imagery task, both synaesthetes and non-synaesthetes made colour judgements on objects presented as grey scale photographs. In a synaesthetic colour task, we presented letters that elicited synaesthetic colours, and asked participants to perform a localisation task. We assessed the neural activity underpinning these two different forms of colour experience that occur in the absence of chromatic sensory input. In both synaesthetes and non-synaesthetes, voluntary colour imagery activated the colour-selective area, V4, in the right hemisphere. In contrast, the synaesthetic colour task resulted in unique activity for synaesthetes in the left medial lingual gyrus, an area previously implicated in tasks involving colour knowledge. Our data suggest that internally generated colour experiences recruit brain regions specialised for colour perception, with striking differences between voluntary colour imagery and synaesthetically induced colours.

Adolescent↗
PubMed2006

Human MT/V5 activity on viewing eye gaze changes in others: A magnetoencephalographic study.

The present study used magnetoencephalography (MEG) to investigate human MT/V5 activity when observing changes in eye gaze. Subjects viewed a face in which the eyes changed to look either directly at (BACK) or away from (AWAY) the subject in a series of apparent motion conditions. BACK involved 2 directions, from left to center (LC) and from right to center (RC). Likewise, AWAY involved 2 directions, from center to left (CL) and from center to right (CR). A clear MEG component, 1M, was elicited with all eye gaze changes. Mean peak latency was 157 ms and was unaffected by stimulus condition. The equivalent current dipole (ECD) was localized to human MT/V5. Two main effects were noted: (1) ECD moment was significantly larger for BACK than for AWAY; and (2) 1M ECD locations were more posterior for AWAY than for BACK. Gaze direction, with LEFT involving CL and RC and RIGHT involving CR and LC, showed no significant effects. These data indicate that MT/V5 responds to gaze direction rather than eye position, and that eye movements directed at the viewer elicit the strongest effects. Processing of gaze change is NOT sensitive to eye direction per se but rather is modulated by eye gaze relative to the viewer.

Adult↗
PubMed2005

Configural processing of biological motion in human superior temporal sulcus.

Observers recognize subtle changes in the movements of others with relative ease. However, tracking a walking human is computationally difficult, because the degree of articulation is high and scene changes can temporarily occlude parts of the moving figure. Here, we used functional magnetic resonance imaging to test the hypothesis that the superior temporal sulcus (STS) uses form cues to aid biological movement tracking. The same 10 healthy subjects detected human gait changes in a walking mannequin in two experiments. In experiment 1, we tested the effects of configural change and occlusion. The walking mannequin was presented intact or with the limbs and torso apart in visual space and either unoccluded or occluded by a set of vertical white bars. In experiment 2, the effects of inversion and occlusion were investigated, using an intact walking mannequin. Subjects reliably detected gait changes under all stimulus conditions. The intact walker produced significantly greater activation in the STS, inferior temporal sulcus (ITS), and inferior parietal cortex relative to the apart walker, regardless of occlusion. Interestingly, STS and ITS activation to the upright versus inverted walker was not significantly different. In contrast, superior parietal lobule and parieto-occipital cortex showed greater activation to the apart relative to intact walker. In the absence of an intact body configuration, parietal cortex activity increased to the independent movements of the limbs and torso. Our data suggest that the STS may use a body configuration-based model to process biological movement, thus forming a representation that survives partial occlusion.

Adult↗
PubMed2004

No about face on houses in the fusiform face area!

Yovel and Kanwisher (this issue of Neuron) altered upright and inverted face and house characteristics during a same-different task. The right fusiform face area (FFA) was more active to faces than houses but, unlike behavior, was unaffected by spatial configuration or parts manipulations. These data raise interesting questions regarding the relationship of brain activation to observed behavior.

Brain↗
PubMed2004

Magnetoencephalographic study of occipitotemporal activity elicited by viewing mouth movements.

OBJECTIVE: We studied the temporal and spatial characteristics of neural responses elicited by viewing mouth movements using magnetoencephalography. METHODS: We focused on differences in responses to mouth opening and closing movements by apparent motion, using an averting eyes condition as a control. RESULTS: A large clear MEG component, 1 M (mean peak latency of approximately 160 ms), was elicited by both mouth movements. We modeled the neural sources using a brain electric source analysis (BESA) method and placed the sources around: (1) the occipitotemporal border at human MT/V5, (2) the primary visual cortex (V1), and (3) fusiform gyrus. The calculated activity of Source (1) was large whereas the activity of the others was small or negligible. Source (1), as calculated separately for mouth closing and opening movements and eye movement, showed no significant different amplitude and locations. We did not find any activity in the superior temporal sulcus (STS). CONCLUSIONS: Our results indicate that human MT/V5 is active in the perception of both mouth and eye motions. Viewing mouth and eye movements elicits no significant differences in MT/V5 activity, indicating that the perception of movement of facial parts is probably processed in the same manner. SIGNIFICANCE: Characteristic activities in the human MT/V5 elicited by viewing mouth movement were clarified by MEG.

Adult↗
PubMed2004

Digit representation is more than just hand waving.

Lip-reading and interpreting hand gestures help provide nonverbal information that aids speech comprehension in noisy environments and places emphasis on certain key utterances. In this fMRI study, we examined if viewing the similar semantic information presented by either finger movements or lip movements was processed by common or discrete brain regions. Subjects viewed videos of a hand conveying number information via finger movements and a face whose lip movements conveyed the same numerical information. Control stimuli consisted of meaningless finger and lip movements. Lip-reading numbers activated left posterior superior temporal sulcus (STS), while identifying numbers presented by fingers activated the intraparietal region (IPR) bilaterally. Conjunction analysis highlighted common activation in right IPR to numbers presented via fingers and lips. Our data indicate that left hemisphere decodes human movements conveying semantic information, although the specific brain region that is engaged may depend on the body part that is moving.

Adolescent↗
PubMed2004

Viewing the motion of human body parts activates different regions of premotor, temporal, and parietal cortex.

Activation of premotor and temporoparietal cortex occurs when we observe others movements, particularly relating to objects. Viewing the motion of different body parts without the context of an object has not been systematically evaluated. During a 3T fMRI study, 12 healthy subjects viewed human face, hand, and leg motion, which was not directed at or did not involve an object. Activation was identified relative to static images of the same human face, hand, and leg in both individual subject and group average data. Four clear activation foci emerged: (1) right MT/V5 activated to all forms of viewed motion; (2) right STS activated to face and leg motion; (3) ventral premotor cortex activated to face, hand, and leg motion in the right hemisphere and to leg motion in the left hemisphere; and (4) anterior intraparietal cortex (aIP) was active bilaterally to viewing hand motion and in the right hemisphere leg motion. In addition, in the group data, a somatotopic activation pattern for viewing face, hand, and leg motion occurred in right ventral premotor cortex. Activation patterns in STS and aIP were more complex--typically activation foci to viewing two types of human motion showed some overlap. Activation in individual subjects was similar; however, activation to hand motion also occurred in the STS with a variable location across subjects--explaining the lack of a clear activation focus in the group data. The data indicate that there are selective responses to viewing motion of different body parts in the human brain that are independent of object or tool use.

Adolescent↗
PubMed2004

Is the fusiform face area specialized for faces, individuation, or expert individuation?

Several brain imaging studies have identified a region of fusiform gyrus (FG) that responds more strongly to faces than common objects. The precise functional role of this fusiform face area (FFA) is, however, a matter of dispute. We sought to distinguish among three hypotheses concerning FFA function: face specificity, individuation, and expert individuation. According to the face-specificity hypothesis, the FFA is specialized for face processing. Alternatively, the FFA may be specialized for individuating visually similar items within a category (the individuation hypothesis) or for individuating within categories with which a person has expertise (the expert-individuation hypothesis). Our results from two experiments supported the face-specificity hypothesis. Greater FFA activation to faces than Lepidoptera, another homogeneous object class, occurred during both free viewing and individuation, with similar FFA activation to Lepidoptera and common objects (Experiment 1). Furthermore, during individuation of Lepidoptera, 83% of activated FG voxels were outside the face FG region and only 15% of face FG voxels were activated. This pattern of results suggests that distinct areas may individuate faces and Lepidoptera. In Experiment 2, we tested Lepidoptera experts using the same experimental design. Again, the results supported the face-specificity hypothesis. Activation to faces in the FFA was greater than to both Lepidoptera and objects with little overlap between FG areas activated by faces and Lepidoptera. Our results suggest that distinct populations of neurons in human FG may be tuned to the features needed to individuate the members of different object classes, as has been reported in monkey inferotemporal cortex, and that the FFA contains neurons tuned for individuating faces.

Adolescent↗
PubMed2003

Electrophysiology and brain imaging of biological motion.

The movements of the faces and bodies of other conspecifics provide stimuli of considerable interest to the social primate. Studies of single cells, field potential recordings and functional neuroimaging data indicate that specialized visual mechanisms exist in the superior temporal sulcus (STS) of both human and non-human primates that produce selective neural responses to moving natural images of faces and bodies. STS mechanisms also process simplified displays of biological motion involving point lights marking the limb articulations of animate bodies and geometrical shapes whose motion simulates purposeful behaviour. Facial movements such as deviations in eye gaze, important for gauging an individual's social attention, and mouth movements, indicative of potential utterances, generate particularly robust neural responses that differentiate between movement types. Collectively such visual processing can enable the decoding of complex social signals and through its outputs to limbic, frontal and parietal systems the STS may play a part in enabling appropriate affective responses and social behaviour.

Animals↗
PubMed2003

The human temporal lobe integrates facial form and motion: evidence from fMRI and ERP studies.

Physiological studies in humans and monkeys indicate that the posterior temporal cortex is active when viewing the movements of others. Here we tested the premise that this region integrates form and motion information by presenting both natural and line-drawn displays of moving faces and motion controls where motion was continuously presented in the same part of the visual field. The cortex in and near the STS and on the fusiform gyrus (FG) responded to both types of face stimuli, but not to the controls, in a functional magnetic resonance imaging study in 10 normal subjects. The response in the STS to both types of facial motion was equal in magnitude, whereas in the FG the natural image of the face produced a significantly greater response than that of the line-drawn face. In a subsequent recording session, the electrical activity of the brain was recorded in the same subjects to the same activation task. Significantly larger event-related potentials (ERPs) to both types of moving faces were observed over the posterior temporal scalp compared to the motion controls at around 200 ms postmotion onset. Taken together, these data suggest that regions of temporal cortex actively integrate form and motion information-a process largely independent of low-level visual processes such as changes in local luminance and contrast.

Adult↗
PubMed2003

The functional magnetic resonance imaging hemodynamic response to faces remains stable until the ninth decade.

The effects of aging on blood oxygen level dependent signal changes and the hemodynamic response (HDR) remain controversial. Using functional magnetic resonance (MR) imaging, we examined the HDR properties and activated voxel counts in striate and extrastriate cortex in 18 healthy elderly subjects in response to a simple visual paradigm. Subjects of equal number and gender were prospectively separated into groups from the seventh, eighth, and ninth decades. Activation data were compared with those of 6 healthy subjects aged 30-39 under the same conditions. We found no systematic difference in HDR amplitude, shape, or latency across these groups. However, increasing age over 60 was associated with a significant decline in activated voxel counts, relative to the young controls. The results are discussed in comparison with previously published studies and in the context of the effects of aging on MR signal change. While robust activation can be produced in the striate and extrastriate cortices until the end of the ninth decade, caution should be exercised when comparing data from subjects in different decades. As functional magnetic resonance imaging is increasingly being used to examine patients with stroke and dementia, these results emphasize the importance of careful selection and age matching of control subjects when comparing with a patient population affected by disease processes associated with aging.

Adult↗
PubMed2002

Should bad workmen always blame their tools?

In this issue of Neuron, differentiated brain regions in humans that are selectively responsive to viewing motion: (1) of humans, (2) of tools/utensils, and (3) in general. Active regions were the superior temporal sulcus, middle temporal gyrus, and MT/V5, respectively. This study provides impetus for future work in motion perception and its relationship to apraxia.

Animals↗
PubMed2002

Category-sensitive excitatory and inhibitory processes in human extrastriate cortex.

Single-cell recordings from the temporal lobe of monkeys viewing stimuli show that cells may be highly selective, responding for example to particular objects such as faces. However, stimulus-selective cells may be inhibited by nonpreferred stimuli. Can such inhibitory mechanisms be detected in human visual cortex? In previous recordings from the surface of human ventral extrastriate cortex, we found that specific categories of stimuli such as faces and words generate category-specific negative event-related potentials (ERPs) with a peak latency of about 200 ms (N200). Laminar recordings in animal cortex suggest that the human N200 reflects excitatory depolarizing potentials in apical dendrites of pyramidal cells. In this study we found that, at about half of word-specific N200 sites, faces generated a positive ERP (P200); conversely, at about half of face-specific sites, words generated P200s. The electrogenesis of N200 implies that P200 ERPs reflect hyperpolarizing inhibition of apical dendrites. These recordings, together with the prior animal recordings, provide strong circumstantial evidence that in human cortex populations of cells responsive to one stimulus category (such as faces) inhibit cells responsive to another category (such as words), probably by a type of lateral inhibition. Of the stimulus categories studied quantitatively, face-specific cells are maximally inhibited by words and vice versa, but other categories of stimuli may generate smaller P200s, suggesting that inhibition of category-specific cells by nonpreferred stimuli is a general feature of human extrastriate cortex involved in object recognition.

Dendrites↗
PubMed2002

Differential functional magnetic resonance imaging language activation in twins discordant for a left frontal tumor.

Eight-year-old twins, one with a left frontal tumor and aphasic seizures, the other neurologically normal, underwent serial assessment of expressive language with functional magnetic resonance imaging and neuropsychology. The affected twin showed a significant amount of right hemisphere activation coincident with behavioral deterioration in expressive language and late growth in the tumor. This pattern of language dysfunction and the left language dominance of her co-twin suggested that the affected twin was also left dominant for language, and the significance of her right activation is discussed. We postulate that the right hemisphere activation represents a stabilizing mechanism in the context of a developmental and progressive lesion in language cortex rather than language transfer per se.

Brain Neoplasms↗