Philipp Sterzer

A structural neural deficit in adolescents with conduct disorder and its association with lack of empathy

The goal of this study was to determine whether brain regions implicated in emotion processing show structural alterations in adolescents with conduct disorder (CD). Using an optimized voxel-based morphometry protocol, we compared grey matter volume in 12 patients with CD and 12 age-, sex-, and intelligence-matched control subjects. Grey matter volume in bilateral anterior insular cortex and the left amygdala was significantly reduced in CD patients compared to healthy control subjects. The insular grey matter abnormalities could be attributed to aggressive behaviour. Moreover, bilateral anterior insular grey matter volume in CD patients correlated significantly with empathy scores. These novel findings point at a joint neuroanatomical substrate underpinning aggressive behaviour and impaired capacity of empathy and suggest a critical role for the anterior insula in regulating social behaviour.

Delusions and the Role of Beliefs in Perceptual Inference

Delusions are unfounded yet tenacious beliefs and a symptom of psychotic disorder. Varying degrees of delusional ideation are also found in the healthy population. Here, we empirically validated a neurocognitive model that explains both the formation and the persistence of delusional beliefs in terms of altered perceptual inference. In a combined behavioral and functional neuroimaging study in healthy participants, we used ambiguous visual stimulation to probe the relationship between delusion-proneness and the effect of learned predictions on perception. Delusional ideation was associated with less perceptual stability, but a stronger belief-induced bias on perception, paralleled by enhanced functional connectivity between frontal areas that encoded beliefs and sensory areas that encoded perception. These findings suggest that weakened lower-level predictions that result in perceptual instability are implicated in the emergence of delusional beliefs. In contrast, stronger higher-level predictions that sculpt perception into conformity with beliefs might contribute to the tenacious persistence of delusional beliefs.

Rapid Fear Detection Relies on High Spatial Frequencies

Signals of threat—such as fearful faces—are processed with priority and have privileged access to awareness. This fear advantage is commonly believed to engage a specialized subcortical pathway to the amygdala that bypasses visual cortex and processes predominantly low-spatial-frequency information but is largely insensitive to high spatial frequencies. We tested visual detection of low- and high-pass-filtered fearful and neutral faces under continuous flash suppression and sandwich masking, and we found consistently that the fear advantage was specific to high spatial frequencies. This demonstrates that rapid fear detection relies not on low- but on high-spatial-frequency information—indicative of an involvement of cortical visual areas. These findings challenge the traditional notion that a subcortical pathway to the amygdala is essential for the initial processing of fear signals and support the emerging view that the cerebral cortex is crucial for the processing of ecologically relevant signals.

Unconscious processing under interocular suppression: getting the right measure.

In order to demonstrate unconscious visual processing, researchers need to select a technique for rendering stimuli invisible and a measure reflecting the processing of these stimuli. The most popular techniques are backward masking, in which the visibility of a very brief stimulus is degraded by the presentation of a succeeding visual pattern (Breitmeyer and Ogmen, 2006), and interocular suppression, where a stimulus shown to one eye degrades the visibility of a stimulus presented to the other eye (Lin and He, 2009). Recently, much work has been carried out using continuous flash suppression (CFS; Tsuchiya and Koch, 2005), a particularly potent interocular suppression technique. In CFS, a train of high-contrast patterns flashed into one eye can suppress the visibility of a stationary stimulus shown to the other eye for up to several seconds (Figure ​(Figure1).1). Because CFS allows for extended periods of reliable invisibility of complex stimuli, this technique has sparked a surge of interest in unconscious visual processing. Figure 1 Competing models of the processes mediating detection performance in the b-CFS paradigm. (A) The single-process model posits that both the CFS and the control condition measure differences between stimuli in accessing awareness that exist independent ... Ideally, research aimed at delineating the scope and limits of visual processing without awareness should adopt the technique that is most sensitive to unconscious processing. This is because a failure to find evidence for a certain unconscious effect could always be due to constraints imposed by the specific technique rather than to the genuine absence of unconscious processing (Faivre et al., 2012). However, since the extent to which a technique allows for unconscious processing is difficult to determine, and due to a lack of general consensus on valid measures of unconscious processing, no definite criteria exist for choosing the most sensitive technique.

Eye gaze adaptation under interocular suppression

The perception of eye gaze is central to social interaction in that it provides information about another persons goals, intentions, and focus of attention. Direction of gaze has been found to reflexively shift the observers attention in the corresponding direction, and prolonged exposure to averted eye gaze adapts the visual system, biasing perception of subsequent gaze in the direction opposite to the adapting face. Here, we tested the role of conscious awareness in coding eye gaze directions. To this end, we measured aftereffects induced by adapting faces with different eye gaze directions that were presented during continuous flash suppression, a potent interocular suppression technique. In some trials the adapting face was rendered fully invisible, whereas in others it became partially visible. In Experiment 1, the adapting and test faces were presented in identical sizes and to the same eye. Even fully invisible faces were capable of inducing significant eye gaze aftereffects, although these were smaller than aftereffects from partially visible faces. When the adapting and test faces were shown to different eyes in Experiment 2, significant eye gaze aftereffects were still observed for the fully invisible faces, thus showing interocular transfer. Experiment 3 disrupted the spatial correspondence between adapting and test faces by introducing a size change. Under these conditions, aftereffects were restricted to partially visible adapting faces. These results were replicated in Experiment 4 using a blocked adaptation design. Together, these findings indicate that size-dependent low-level components of eye gaze can be represented without awareness, whereas object-centered higher-level representations of eye gaze directions depend on visual awareness.

Hemispheric Asymmetry for Affective Stimulus Processing in Healthy Subjects–A fMRI Study

Background While hemispheric specialization of language processing is well established, lateralization of emotion processing is still under debate. Several conflicting hypotheses have been proposed, including right hemisphere hypothesis, valence asymmetry hypothesis and region-specific lateralization hypothesis. However, experimental evidence for these hypotheses remains inconclusive, partly because direct comparisons between hemispheres are scarce. Methods The present fMRI study systematically investigated functional lateralization during affective stimulus processing in 36 healthy participants. We normalized our functional data on a symmetrical template to avoid confounding effects of anatomical asymmetries. Direct comparison of BOLD responses between hemispheres was accomplished taking two approaches: a hypothesis-driven region of interest analysis focusing on brain areas most frequently reported in earlier neuroimaging studies of emotion; and an exploratory whole volume analysis contrasting non-flipped with flipped functional data using paired t-test. Results The region of interest analysis revealed lateralization towards the left in the medial prefrontal cortex (BA 10) during positive stimulus processing; while negative stimulus processing was lateralized towards the right in the dorsolateral prefrontal cortex (BA 9 & 46) and towards the left in the amygdala and uncus. The whole brain analysis yielded similar results and, in addition, revealed lateralization towards the right in the premotor cortex (BA 6) and the temporo-occipital junction (BA 19 & 37) during positive stimulus processing; while negative stimulus processing showed lateralization towards the right in the temporo-parietal junction (BA 37,39,42) and towards the left in the middle temporal gyrus (BA 21). Conclusion Our data suggests region-specific functional lateralization of emotion processing. Findings show valence asymmetry for prefrontal cortical areas and left-lateralized negative stimulus processing in subcortical areas, in particular, amygdala and uncus.

Tactile and visual motion direction processing in hMT+/V5

The human motion complex hMT+/V5 is activated not only by visual motion, but also by tactile and auditory motion. Whilst direction-selectivity has been found within this complex for visual and auditory stimuli, it is unknown whether hMT+/V5 also contains direction-specific information from the tactile modality. In the current study, we sought to investigate whether hMT+/V5 contains direction-specific information about visual/tactile moving stimuli. Leftward and rightward moving stimuli were presented in the visual and tactile modalities in an event-related fMRI design. Using region-of-interest-based multivariate pattern analysis we could decode the two motion directions for both tactile and visual stimuli in hMT+/V5. The activity patterns of the two modalities differed significantly, indicating that motion direction information from different modalities may be carried by distinct sets of neuronal populations. Our findings show that hMT+/V5 contains specific information about the direction of a moving stimulus in both the tactile and visual modalities, supporting the theory of hMT+/V5 being a multimodal motion area.

Probing principles of large-scale object representation: Category preference and location encoding

Knowledge about the principles that govern large‐scale neural representations of objects is central to a systematic understanding of object recognition. We used functional magnetic resonance imaging (fMRI) and multivariate pattern classification to investigate two such candidate principles: category preference and location encoding. The former designates the preferential activation of distinct cortical regions by a specific category of objects. The latter refers to information about where in the visual field a particular object is located. Participants viewed exemplars of three object categories (faces, bodies, and scenes) that were presented left or right of fixation. The analysis of fMRI activation patterns revealed the following. Category‐selective regions retained their preference to the same categories in a manner tolerant to changes in object location. However, category preference was not absolute: category‐selective regions also contained location‐tolerant information about nonpreferred categories. Furthermore, location information was present throughout high‐level ventral visual cortex and was distributed systematically across the cortical surface. We found more location information in lateral‐occipital cortex than in ventral‐temporal cortex. Our results provide a systematic account of the extent to which the principles of category preference and location encoding determine the representation of objects in the high‐level ventral visual cortex. Hum Brain Mapp, 2013.

Attentional modulation of reward processing in the human brain

Although neural signals of reward anticipation have been studied extensively, the functional relationship between reward and attention has remained unclear: Neural signals implicated in reward processing could either reflect attentional biases towards motivationally salient stimuli, or proceed independently of attentional processes. Here, we sought to disentangle reward and attention‐related neural processes by independently modulating reward value and attentional task demands in a functional magnetic resonance imaging study in healthy human participants. During presentation of a visual reward cue that indicated whether monetary reward could be obtained in a subsequent reaction time task, participants either attended to the reward cue or performed an unrelated attention‐demanding task at two different levels of difficulty. In ventral striatum and ventral tegmental area, neural responses were modulated by reward anticipation irrespective of attentional demands, thus indicating attention‐independent processing of reward cues. By contrast, additive effects of reward and attention were observed in visual cortex. Critically, reward‐related activations in right anterior insula strongly depended on attention to the reward cue. Dynamic causal modelling revealed that the attentional modulation of reward processing in insular cortex was mediated by enhanced effective connectivity from ventral striatum to anterior insula. Our results provide evidence for distinct functional roles of the brain regions involved in the processing of reward‐indicating information: While subcortical structures signal the motivational salience of reward cues even when attention is fully engaged elsewhere, reward‐related responses in anterior insula depend on available attentional resources, likely reflecting the conscious evaluation of sensory information with respect to motivational value. Hum Brain Mapp 35:3036–3051, 2014.

Own-race and own-age biases facilitate visual awareness of faces under interocular suppression

The detection of a face in a visual scene is the first stage in the face processing hierarchy. Although all subsequent, more elaborate face processing depends on the initial detection of a face, surprisingly little is known about the perceptual mechanisms underlying face detection. Recent evidence suggests that relatively hard-wired face detection mechanisms are broadly tuned to all face-like visual patterns as long as they respect the typical spatial configuration of the eyes above the mouth. Here, we qualify this notion by showing that face detection mechanisms are also sensitive to face shape and facial surface reflectance properties. We used continuous flash suppression (CFS) to render faces invisible at the beginning of a trial and measured the time upright and inverted faces needed to break into awareness. Young Caucasian adult observers were presented with faces from their own race or from another race (race experiment) and with faces from their own age group or from another age group (age experiment). Faces matching the observers’ own race and age group were detected more quickly. Moreover, the advantage of upright over inverted faces in overcoming CFS, i.e., the face inversion effect (FIE), was larger for own-race and own-age faces. These results demonstrate that differences in face shape and surface reflectance influence access to awareness and configural face processing at the initial detection stage. Although we did not collect data from observers of another race or age group, these findings are a first indication that face detection mechanisms are shaped by visual experience with faces from one’s own social group. Such experience-based fine-tuning of face detection mechanisms may equip in-group faces with a competitive advantage for access to conscious awareness.