Jürgen M. Kaufmann

Human brain potential correlates of repetition priming in face and name recognition

We investigated repetition priming in the recognition of famous people by recording event-related brain potentials (ERPs) and reaction times (RTs). Participants performed speeded two-choice responses depending on whether or not a stimulus showed a famous person. In Experiment 1, a facilitation was found in RTs to famous (but not to unfamiliar) faces when primed by the same face shown in an earlier priming phase of the experiment. In ERPs, an influence of repetition priming was observed neither for the N170 nor for a temporal N250 component which in previous studies had been shown to be sensitive to immediate face repetitions. ERPs to primed unfamiliar faces were more negative over right occipitotemporal areas than those to unprimed faces, but this effect was specific for repetitions of the same image, consistent with recent findings. In contrast, ERPs to primed familiar faces were more positive than those to unprimed faces at parietal sites from 500-600 ms after face onset, and these priming effects were comparable regardless of whether the same or a different image of the celebrity had served as prime. In Experiment 2, similar results were found for name recognition-a facilitation in RTs to primed familiar but not unfamiliar names, and a parietal positivity to primed names around 500-600 ms. ERP repetition effects showed comparable topographies for faces and names, consistent with the idea of a common underlying source. With reference to current models of face recognition, we suggest that these ERP repetition effects for familiar stimuli reflect a change in post-perceptual representations for people, rather than a neural correlate of recognition at a perceptual level.

N250 erp correlates of the acquisition of face representations across different images

We used ERPs to investigate neural correlates of face learning. At learning, participants viewed video clips of unfamiliar people, which were presented either with or without voices providing semantic information. In a subsequent face-recognition task (four trial blocks), learned faces were repeated once per block and presented interspersed with novel faces. To disentangle face from image learning, we used different images for face repetitions. Block effects demonstrated that engaging in the face-recognition task modulated ERPs between 170 and 900 msec poststimulus onset for learned and novel faces. In addition, multiple repetitions of different exemplars of learned faces elicited an increased bilateral N250. Source localizations of this N250 for learned faces suggested activity in fusiform gyrus, similar to that found previously for N250r in repetition priming paradigms [Schweinberger, S. R., Pickering, E. C., Jentzsch, I., Burton, A. M., & Kaufmann, J. M. Event-related brain potential evidence for a response of inferior temporal cortex to familiar face repetitions. Cognitive Brain Research, 14, 398–409, 2002]. Multiple repetitions of learned faces also elicited increased central–parietal positivity between 400 and 600 msec and caused a bilateral increase of inferior–temporal negativity (>300 msec) compared with novel faces. Semantic information at learning enhanced recognition rates. Faces that had been learned with semantic information elicited somewhat less negative amplitudes between 700 and 900 msec over left inferior–temporal sites. Overall, the findings demonstrate a role of the temporal N250 ERP in the acquisition of new face representations across different images. They also suggest that, compared with visual presentation alone, additional semantic information at learning facilitates postperceptual processing in recognition but does not facilitate perceptual analysis of learned faces.

Expression Influences the Recognition of Familiar Faces

Face recognition has been assumed to be independent of facial expression. We used familiar and unfamiliar faces that were morphed from a happy to an angry expression within a given identity. Participants performed speeded two-choice decisions according to whether or not a face was familiar. Consistent with earlier findings, reaction times for classifications of unfamiliar faces were independent of facial expressions. In contrast, expression clearly influenced the recognition of familiar faces, with fastest recognition for moderately happy expressions. This suggests that representations of familiar faces for recognition preserve some information about typical emotional expressions.

Auditory Adaptation in Voice Perception

Perceptual aftereffects following adaptation to simple stimulus attributes (e.g., motion, color) have been studied for hundreds of years. A striking recent discovery was that adaptation also elicits contrastive aftereffects in visual perception of complex stimuli and faces [1-6]. Here, we show for the first time that adaptation to nonlinguistic information in voices elicits systematic auditory aftereffects. Prior adaptation to male voices causes a voice to be perceived as more female (and vice versa), and these auditory aftereffects were measurable even minutes after adaptation. By contrast, crossmodal adaptation effects were absent, both when male or female first names and when silently articulating male or female faces were used as adaptors. When sinusoidal tones (with frequencies matched to male and female voice fundamental frequencies) were used as adaptors, no aftereffects on voice perception were observed. This excludes explanations for the voice aftereffect in terms of both pitch adaptation and postperceptual adaptation to gender concepts and suggests that contrastive voice-coding mechanisms may routinely influence voice perception. The role of adaptation in calibrating properties of high-level voice representations indicates that adaptation is not confined to vision but is a ubiquitous mechanism in the perception of nonlinguistic social information from both faces and voices.

Hearing facial identities.

While audiovisual integration is well known in speech perception, faces and speech are also informative with respect to speaker recognition. To date, audiovisual integration in the recognition of familiar people has never been demonstrated. Here we show systematic benefits and costs for the recognition of familiar voices when these are combined with time-synchronized articulating faces, of corresponding or noncorresponding speaker identity, respectively. While these effects were strong for familiar voices, they were smaller or nonsignificant for unfamiliar voices, suggesting that the effects depend on the previous creation of a multimodal representation of a persons identity. Moreover, the effects were reduced or eliminated when voices were combined with the same faces presented as static pictures, demonstrating that the effects do not simply reflect the use of facial identity as a “cue” for voice recognition. This is the first direct evidence for audiovisual integration in person recognition.

Arguments Against a Configural Processing Account of Familiar Face Recognition.

Face recognition is a remarkable human ability, which underlies a great deal of people’s social behavior. Individuals can recognize family members, friends, and acquaintances over a very large range of conditions, and yet the processes by which they do this remain poorly understood, despite decades of research. Although a detailed understanding remains elusive, face recognition is widely thought to rely on configural processing, specifically an analysis of spatial relations between facial features (so-called second-order configurations). In this article, we challenge this traditional view, raising four problems: (1) configural theories are underspecified; (2) large configural changes leave recognition unharmed; (3) recognition is harmed by nonconfigural changes; and (4) in separate analyses of face shape and face texture, identification tends to be dominated by texture. We review evidence from a variety of sources and suggest that failure to acknowledge the impact of familiarity on facial representations may have led to an overgeneralization of the configural account. We argue instead that second-order configural information is remarkably unimportant for familiar face recognition.

Brain responses to repetitions of human and animal faces, inverted faces, and objects — An MEG study

Recent studies have identified a prominent face-selective ERP response to immediate repetitions of faces approximately 250 ms (N250r) which was strongly attenuated or eliminated for control stimuli (Schweinberger, Huddy, and Burton 2004, NeuroReport, 15, 1501-1505). In the present study we used a 148-channel whole head neuromagnetometer to investigate event-related magnetic fields (ERMFs) elicited by repetitions of exemplars of human faces, inverted human faces, primate faces, and car fronts. Participants counted rare pictures of butterflies interspersed in a series of pairs of one of these categories. The second stimulus of each pair could either be a repetition or a non-repetition of the first stimulus. We observed prominent M100 (90-140 ms) and M170 (140-220 ms) responses. Both M100 and M170 were insensitive to repetition and showed little differences between stimulus categories, except for a slight increase and delay of M170 to inverted faces. By contrast, we observed a repetition-sensitive M250r response (220-330 ms). This M250r was larger for upright human and primate faces when compared to both inverted human faces and cars, a finding that was specific for right hemispheric sensors. Source localization suggested different generators for M170 and M250r in occipitotemporal and fusiform areas, respectively. These findings suggest that repetition-sensitive brain activity approximately 250 ms reflects the transient activation of object representations, with largest responses for upright faces, in the right hemisphere.

Atypical organisation of the auditory cortex in dyslexia as revealed by MEG

Neuroanatomical and -radiological studies have converged to suggest an atypical organisation in the temporal bank of the left-hemispheric Sylvian fissure for dyslexia. Against the background of this finding, we applied high temporal resolution magnetoencephalography (MEG) to investigate functional aspects of the left-hemispheric auditory cortex in 11 right-handed dyslexic children (aged 8-13 years) and nine matched normal subjects (aged 8-14 years). Event-related field components during a passive oddball paradigm with pure tones and consonant-vowel syllables were evaluated. The first major peak of the auditory evoked response, the M80, showed identical topographical distributions in both groups. In contrast, the generating brain structures of the later M210 component were located more anterior to the earlier response in children with dyslexia only. Control children exhibited the expected activation of more posterior source locations of the component that appeared later in the processing stream. Since the group difference in the relative location of the M210 source seemed to be independent of stimulus category, it is concluded that dyslexics and normally literate children differ as to the organisation of their left-hemispheric auditory cortex.

The faces you remember: caricaturing shape facilitates brain processes reflecting the acquisition of new face representations.

We report two experiments on the influence of spatial caricaturing on face learning and recognition. In the learning phase of Experiment 1, participants learned unfamiliar faces, half of which were caricatured at an exaggeration level of 30%. During learning we found increased N170, N250 and LPC and decreased P200 for caricatures. At test we observed better generalization to non-identical exemplars for faces learned as caricatures. At test, N250 was larger for caricatures. In Experiment 2, using more and stronger levels of caricaturing (0%=veridical, 35% and 70%), we replicated and extended main findings of Experiment 1 and found a clear learning advantage for caricatures. ERP and performance effects were directly related to the level of caricaturing. Overall, the present results suggest that (i) distinctive shape information is particularly informative to form new face representations for unfamiliar faces, and (ii) this formation of new representations is reflected by an increase in occipito-temporal negativity that is most prominent in the time range of the P200 and N250 components.

Distortions in the brain? ERP effects of caricaturing familiar and unfamiliar faces.

We report two experiments in which participants classified familiarity and rated best-likeness of photorealistic spatial caricatures and anti-caricatures (up to a distortion level of 30%) in comparison to veridical pictures of famous faces (Experiment 1) and personally familiar faces (Experiment 2). In both experiments there was no evidence for a caricature advantage in the behavioural data. In line with previous research, caricatures were perceived as worse likenesses than veridical pictures and moderate anti-caricatures. In Experiment 2, ERPs for familiar faces were largely unaffected by spatial caricaturing, whereas clear effects of caricaturing were observed for unfamiliar faces, for which caricaturing elicited increased occipito-temporal N170 and N250 responses. Whereas increases in N170 amplitude were limited to the first half of the experiment, increases in N250 were largest after a number of stimulus repetitions in the second half of the experiment. In the second half, ERPs to caricatured unfamiliar faces became more similar to ERPs to familiar faces, whereas ERP differences between familiar and unfamiliar faces remained prominent for veridicals and anti-caricatures. In the context of previous reports of caricature effects for line-drawings, these results imply that non-spatial (e.g., texture) information plays a prominent role for familiar face recognition, whereas spatial caricaturing may be particularly important for the recognition of unfamiliar faces, by increasing their distinctiveness.