Bradley Duchaine

TMS Evidence for the Involvement of the Right Occipital Face Area in Early Face Processing

Extensive research has demonstrated that several specialized cortical regions respond preferentially to faces. One such region, located in the inferior occipital gyrus, has been dubbed the occipital face area (OFA). The OFA is the first stage in two influential face-processing models, both of which suggest that it constructs an initial representation of a face, but how and when it does so remains unclear. The present study revealed that repetitive transcranial magnetic stimulation (rTMS) targeted at the right OFA (rOFA) disrupted accurate discrimination of face parts but had no effect on the discrimination of spacing between these parts. rTMS to left OFA had no effect. A matched part and spacing discrimination task that used house stimuli showed no impairment. In a second experiment, rTMS to rOFA replicated the face-part impairment but did not produce the same effect in an adjacent area, the lateral occipital cortex. A third experiment delivered double pulses of TMS separated by 40 ms at six periods after stimulus presentation during face-part discrimination. Accuracy dropped when pulses were delivered at 60 and 100 ms only. These findings indicate that the rOFA processes face-part information at an early stage in the face-processing stream.

Human face recognition ability is specific and highly heritable

Compared with notable successes in the genetics of basic sensory transduction, progress on the genetics of higher level perception and cognition has been limited. We propose that investigating specific cognitive abilities with well-defined neural substrates, such as face recognition, may yield additional insights. In a twin study of face recognition, we found that the correlation of scores between monozygotic twins (0.70) was more than double the dizygotic twin correlation (0.29), evidence for a high genetic contribution to face recognition ability. Low correlations between face recognition scores and visual and verbal recognition scores indicate that both face recognition ability itself and its genetic basis are largely attributable to face-specific mechanisms. The present results therefore identify an unusual phenomenon: a highly specific cognitive ability that is highly heritable. Our results establish a clear genetic basis for face recognition, opening this intensively studied and socially advantageous cognitive trait to genetic investigation.

Triple Dissociation of Faces, Bodies, and Objects in Extrastriate Cortex

Neuroscientists have long debated whether focal brain regions perform specific cognitive functions [1-5], and the issue remains central to a current debate about visual object recognition. The distributed view of cortical function suggests that object discrimination depends on dispersed but functionally overlapping representations spread across visual cortex [6-8]. The modular view claims different categories of objects are discriminated in functionally segregated and specialized cortical areas [9-11]. To test these competing theories, we delivered transcranial magnetic stimulation (TMS) over three adjacent functionally localized areas in extrastriate cortex. In three experiments, participants performed discrimination tasks involving faces, bodies, and objects while TMS was delivered over the right occipital face area (rOFA) [12], the right extrastriate body area (rEBA) [13], or the right lateral occipital area (rLO) [14]. All three experiments showed a task selective dissociation with performance impaired only by stimulation at the site selective for that category: TMS over rOFA impaired discrimination of faces but not objects or bodies; TMS over rEBA impaired discrimination of bodies but not faces or objects; TMS over rLO impaired discrimination of objects but not faces or bodies. The results support a modular account in which category-selective areas contribute solely to discrimination of their preferred categories.

Family resemblance: Ten family members with prosopagnosia and within-class object agnosia

We report on neuropsychological testing done with a family in which many members reported severe face recognition impairments. These 10 individuals were high functioning in everyday life and performed normally on tests of low-level vision and high-level cognition. In contrast, they showed clear deficits with tests requiring face memory and judgements of facial similarity. They did not show deficits with all aspects of higher level visual processing as all tested performed normally on a challenging facial emotion recognition task and on a global–local letter identification task. On object memory tasks requiring recognition of particular cars and guns, they showed significant deficits so their recognition impairments were not restricted to facial identity. These results strongly suggest the existence of a genetic condition leading to a selective deficit of visual recognition.

The role of the occipital face area in the cortical face perception network

Functional magnetic resonance imaging (fMRI) studies have identified spatially distinct face-selective regions in human cortex. These regions have been linked together to form the components of a cortical network specialized for face perception but the cognitive operations performed in each region are not well understood. In this paper, we review the evidence concerning one of these face-selective regions, the occipital face area (OFA), to better understand what cognitive operations it performs in the face perception network. Neuropsychological evidence and transcranial magnetic stimulation (TMS) studies demonstrate the OFA is necessary for accurate face perception. fMRI and TMS studies investigating the functional role of the OFA suggest that it preferentially represents the parts of a face, including the eyes, nose, and mouth and that it does so at an early stage of visual perception. These studies are consistent with the hypothesis that the OFA is the first stage in a hierarchical face perception network in which the OFA represents facial components prior to subsequent processing of increasingly complex facial features in higher face-selective cortical regions.

Diagnosing prosopagnosia: Effects of ageing, sex, and participant-stimulus ethnic match on the cambridge face memory test and cambridge face perception test

The Cambridge Face Memory Test (CFMT) and Cambridge Face Perception Test (CFPT) have provided the first theoretically strong clinical tests for prosopagnosia based on novel rather than famous faces. Here, we assess the extent to which norms for these tasks must take into account ageing, sex, and testing country. Data were from Australians aged 18 to 88 years (N = 240 for CFMT; 128 for CFPT) and young adult Israelis (N = 49 for CFMT). Participants were unselected for face recognition ability; most were university educated. The diagnosis cut-off for prosopagnosia (2 SDs poorer than mean) was affected by age, participant–stimulus ethnic match (within Caucasians), and sex for middle-aged and older adults on the CFPT. We also report internal reliability, correlation between face memory and face perception, correlations with intelligence-related measures, correlation with self-report, distribution shape for the CFMT, and prevalence of developmental prosopagnosia.

Developmental prosopagnosia: a window to content-specific face processing

Developmental prosopagnosia is characterized by severely impaired face recognition. Individuals with this disorder, which often runs in families, have no history of brain damage and intact early visual processing systems. Recent research has also demonstrated that many developmental prosopagnosics have normal or relatively good object recognition, indicating that their impairments are not the result of deficits to a unitary visual recognition mechanism. To investigate the nature of the impaired mechanisms, extensive testing was done on an individual with especially pure face processing deficits. The results ruled out all extant explanations of prosopagnosia except one that proposed that faces are recognized by a content-specific face processing mechanism. fMRI and MEG studies show that there are a variety of neural profiles in developmental prosopagnosia, which is consistent with behavioral studies demonstrating that it is a heterogeneous disorder.

Where cognitive development and aging meet: Face learning ability peaks after age 30

Research on age-related cognitive change traditionally focuses on either development or aging, where development ends with adulthood and aging begins around 55 years. This approach ignores age-related changes during the 35 years in-between, implying that this period is uninformative. Here we investigated face recognition as an ability that may mature late relative to other abilities. Using data from over 60,000 participants, we traced the ability to learn new faces from pre-adolescence through middle age. In three separate experiments, we show that face learning ability improves until just after age 30 - even though other putatively related abilities (inverted face recognition and name recognition) stop showing age-related improvements years earlier. Our data provide the first behavioral evidence for late maturation of face processing and the dissociation of face recognition from other abilities over time demonstrates that studies on adult age development can provide insight into the organization and development of cognitive systems.

Prosopagnosia as an impairment to face-specific mechanisms: Elimination of the alternative hypotheses in a developmental case

For more than 35 years, researchers have debated whether face recognition is carried out by face-specific mechanisms or whether it involves more general mechanisms that are also used for objects. Prosopagnosic patients have furnished powerful evidence for face-specific mechanisms. Yet for each case that has been tested there have always been several untested alternative explanations that could account for the case. As such, each of these individuals has not been sufficiently tested to provide conclusive evidence for face-specific processes. Here we make a stronger argument with a single case of severe developmental prosopagnosia by exhaustively addressing all extant alternatives. We reject each in turn and thus eliminate all alternative accounts. Because this case is developmental in etiology the results also indicate that face recognition involves developmental mechanisms different from those producing other visual recognition mechanisms.

Voxel-based morphometry reveals reduced grey matter volume in the temporal cortex of developmental prosopagnosics

Individuals with developmental prosopagnosia exhibit severe and lasting difficulties in recognizing faces despite the absence of apparent brain abnormalities. We used voxel-based morphometry to investigate whether developmental prosopagnosics show subtle neuroanatomical differences from controls. An analysis based on segmentation of T1-weighted images from 17 developmental prosopagnosics and 18 matched controls revealed that they had reduced grey matter volume in the right anterior inferior temporal lobe and in the superior temporal sulcus/middle temporal gyrus bilaterally. In addition, a voxel-based morphometry analysis based on the segmentation of magnetization transfer parameter maps showed that developmental prosopagnosics also had reduced grey matter volume in the right middle fusiform gyrus and the inferior temporal gyrus. Multiple regression analyses relating three distinct behavioural component scores, derived from a principal component analysis, to grey matter volume revealed an association between a component related to facial identity and grey matter volume in the left superior temporal sulcus/middle temporal gyrus plus the right middle fusiform gyrus/inferior temporal gyrus. Grey matter volume in the lateral occipital cortex was associated with component scores related to object recognition tasks. Our results demonstrate that developmental prosopagnosics have reduced grey matter volume in several regions known to respond selectively to faces and provide new evidence that integrity of these areas relates to face recognition ability.