HuberleL2013 3 E Huberle W Lutzenberger 2013-02-00 67 119–126 NeuroImage Object recognition is a fundamental mechanism of visual processing and requires the extraction of shape information. Early visual areas have been linked to the analysis of local image features, while higher visual areas of the ventral visual pathway rather mediate the perception and recognition of global shapes. Investigations of the spatiotemporal characteristics of shape analysis in the human visual cortex by rapid event-related fMRI adaptation in combination with a region of interest analysis suggested a transient manner of contour integration and shape processing in early visual areas compared to sustained processing in higher visual areas. fMRI adaptation (or repetition suppression) paradigms offer the possibility to enhance the restricted spatial resolution of conventional fMRI by focusing on decreased responses for repeated stimulus presentation. However, improving our understanding of complex neuronal mechanisms in the human brain requires the investigation not only at high spatial but also temporal resolution. A limitation of fMRI adaptation can be found in its poor temporal resolution which EEG- and MEG-techniques can overcome, though at a lower spatial resolution. The present study aimed to investigate temporal characteristics of shape processing in the human brain by adapting the principles of fMRI adaption in a MEG study. In parallel to an earlier fMRI study, the two stimuli of a trial were presented at varied interstimulus intervals. Additional analyses by means of a dipole analysis and co-registration of MEG and fMRI data were conducted. Adaptation was observed for the short as well as the longer interstimulus interval. Interestingly, the latency of the adaptation effects varied with the interstimulus interval. The findings support a late onset of adaption that possibly underlies global discrimination processes and recognition in higher areas of the ventral visual pathway. Further, the present results indicate a useful extension of adaptation paradigms and ‘region of interest’-analyses from fMRI to MEG at a high temporal resolution. no notspecified http://www.kyb.tuebingen.mpg.de/ published -119 15017 15422 RitzingerHK2012 3 B Ritzinger E Huberle H-O Karnath 2012-10-00 10 7 1 7 PLoS One While early and higher visual areas along the ventral visual pathway in the inferotemporal cortex are critical for the recognition of individual objects, the neural representation of human perception of complex global visual scenes remains under debate. Stroke patients with a selective deficit in the perception of a complex global Gestalt with intact recognition of individual objects – a deficit termed simultanagnosia – greatly helped to study this question. Interestingly, simultanagnosia typically results from bilateral lesions of the temporo-parietal junction (TPJ). The present study aimed to verify the relevance of this area for human global Gestalt perception. We applied continuous theta-burst TMS either unilaterally (left or right) or bilateral simultaneously over TPJ. Healthy subjects were presented with hierarchically organized visual stimuli that allowed parametrical degrading of the object at the global level. Identification of the global Gestalt was significantly modulated only for the bilateral TPJ stimulation condition. Our results strengthen the view that global Gestalt perception in the human brain involves TPJ and is co-dependent on both hemispheres. no notspecified http://www.kyb.tuebingen.mpg.de/ published 6 HuberleRLK2012 3 E Huberle P Rupek M Lappe H-O Karnath 2012-08-00 56 6 1 7 Frontiers in Behavioral Neuroscience Over the past 25 years, visual processing has been discussed in the context of the dual stream hypothesis consisting of a ventral (“what”) and a dorsal (“where”) visual information processing pathway. Patients with brain damage of the ventral pathway typically present with signs of visual agnosia, the inability to identify and discriminate objects by visual exploration, but show normal perception of motion perception. A dissociation between the perception of biological motion and non-biological motion has been suggested: perception of biological motion might be impaired when “non-biological” motion perception is intact and vice versa. The impact of object recognition on the perception of biological motion remains unclear. We thus investigated this question in a patient with severe visual agnosia, who showed normal perception of non-biological motion. The data suggested that the patient's perception of biological motion remained largely intact. However, when tested with objects constructed of coherently moving dots (“Shape-from-Motion”), recognition was severely impaired. The results are discussed in the context of possible mechanisms of biological motion perception. no notspecified http://www.kyb.tuebingen.mpg.de/ published 6 HuberleK201 3 E Huberle K-O Karnath 2012-07-00 3 217 735 746 Brain Structure and Function Grouping processes enable the coherent perception of our environment. A number of brain areas has been suggested to be involved in the integration of elements into objects including early and higher visual areas along the ventral visual pathway as well as motion-processing areas of the dorsal visual pathway. However, integration not only is required for the cortical representation of individual objects, but is also essential for the perception of more complex visual scenes consisting of several different objects and/or shapes. The present fMRI experiments aimed to address such integration processes. We investigated the neural correlates underlying the global Gestalt perception of hierarchically organized stimuli that allowed parametrical degrading of the object at the global level. The comparison of intact versus disturbed perception of the global Gestalt revealed a network of cortical areas including the temporo-parietal junction (TPJ), anterior cingulate cortex and the precuneus. The TPJ location corresponds well with the areas known to be typically lesioned in stroke patients with simultanagnosia following bilateral brain damage. These patients typically show a deficit in identifying the global Gestalt of a visual scene. Further, we found the closest relation between behavioral performance and fMRI activation for the TPJ. Our data thus argue for a significant role of the TPJ in human global Gestalt perception. no notspecified http://www.kyb.tuebingen.mpg.de/ published 11 ThomasKHKB2012 3 C Thomas K Kveraga E Huberle H-O Karnath M Bar 2012-05-00 5 135 1578 1585 Brain A fundamental aspect of visual cognition is our disposition to see the ‘forest before the trees’. However, damage to the posterior parietal cortex, a critical brain region along the dorsal visual pathway, can produce a neurological disorder called simultanagnosia, characterized by a debilitating inability to perceive the ‘forest’ but not the ‘trees’ (i.e. impaired global processing despite intact local processing). This impairment in perceiving the global shape persists even though the ventral visual pathway, the primary recognition pathway, is intact in these patients. Here, we enabled global processing in patients with simultanagnosia using a psychophysical technique, which allowed us to bias stimuli such that they are processed predominantly by the intact ventral visual pathway. Our findings reveal that the impairment in global processing that characterizes simultanagnosia stems from a disruption in the processing of low-spatial frequencies through the dorsal pathway. These findings advance our understanding of the relationship between visuospatial attention and perception and reveal the neural mechanism mediating the disposition to see the ‘forest before the trees’. no notspecified http://www.kyb.tuebingen.mpg.de/ published 7 HuberleK2010 3 E Huberle K-O Karnath 2010-08-00 4 204 595 603 Experimental Brain Research Patients with parieto-occipital brain damage may show simultanagnosia, a selective impairment in the simultaneous perception and integration of multiple objects (global perception) with normal recognition of individual objects. Recent findings in patients with simultanagnosia indicate improved global perception at smaller spatial distances between local elements of hierarchical organized complex visual arrays. Global perception thus does not appear to be an all-or-nothing phenomenon but can be modified by the spatial relationship between local elements. The present study aimed to define characteristics of a general principle that accounts for improved global perception of hierarchically organized complex visual arrays in patients with simultanagnosia with respect to the spatial properties of local elements. In detail, we investigated the role of the number and size of the local elements as well as their relationship with each other for the global perception. The findings indicate that global perception increases independently of the size of the global object and depends on the spatial relationship between the local elements and the global object. The results further argue against the possibility of a restriction in the attended or perceived area in simultanagnosia, in the sense that the integration of local elements into a global scene is impaired if a certain spatial “field of view” is exceeded. A possible explanation for these observations might be a shift from global to local saliency in simultanagnosia. no notspecified http://www.kyb.tuebingen.mpg.de/ published 8 KreifeltsEHGW2010 3 B Kreifelts T Ethofer E Huberle W Grodd D Wildgruber 2010-07-00 7 31 979–991 Human Brain Mapping Multimodal integration of nonverbal social signals is essential for successful social interaction. Previous studies have implicated the posterior superior temporal sulcus (pSTS) in the perception of social signals such as nonverbal emotional signals as well as in social cognitive functions like mentalizing/theory of mind. In the present study, we evaluated the relationships between trait emotional intelligence (EI) and fMRI activation patterns in individual subjects during the multimodal perception of nonverbal emotional signals from voice and face. Trait EI was linked to hemodynamic responses in the right pSTS, an area which also exhibits a distinct sensitivity to human voices and faces. Within all other regions known to subserve the perceptual audiovisual integration of human social signals (i.e., amygdala, fusiform gyrus, thalamus), no such linked responses were observed. This functional difference in the network for the audiovisual perception of human social signals indicates a specific contribution of the pSTS as a possible interface between the perception of social information and social cognition. no notspecified http://www.kyb.tuebingen.mpg.de/ published -979 HuberleDK2013 3 E Huberle J Driver H-O Karnath 2010-05-00 6 48 1677–1682 Neuropsychologia Patients with simultanagnosia following bilateral parieto-temporo-occipital brain damage show a characteristic impairment of global gestalt perception, while their perception of individual objects or elements remains intact. For instance, when shown ‘hierarchical’ stimuli comprising a larger global object (e.g. a large letter) made up from smaller components (e.g. multiple small letters), they typically report seeing one of the smaller components but not the global figure. Recent work on simultanagnosia revealed that global perception can be improved if local element spacing is reduced. However, it is still unclear whether the retinal separation or the physical (post-size-constancy) spatial separation is critical. Here, we presented various hierarchical global/local letter stimuli at different viewing distances and sizes to separate the impacts of retinal versus physical size. Our findings indicate a key role for visual angle in determining simultanagnosic perception. We observed that not only retinal spacing (in terms of visual angle) between local elements had a major impact on global perception in simultanagnosia, but also the physical size of the separation between local elements, provided that binocular cues to viewing distance were available. The results indicate both pre-size-constancy retinal influences and binocular-post-constancy influences upon conscious perception in simultanagnosia. no notspecified http://www.kyb.tuebingen.mpg.de/ published -1677 HuberleRLK2009 3 E Huberle P Rupek M Lappe H-O Karnath 2009-01-00 1 29 197–204 European Journal of Neuroscience Patients with bilateral parieto-occipital brain damage may show intact processing of individual objects, while their perception of multiple objects is disturbed at the same time. The deficit is termed ‘simultanagnosia’ and has been discussed in the context of restricted visual working memory and impaired visuo-spatial attention. Recent observations indicated that the recognition of global shapes can be modulated by the spatial distance between individual objects in patients with simultanagnosia and thus is not an all-or-nothing phenomenon depending on spatial continuity. However, grouping mechanisms not only require the spatial integration of visual information, but also involve integration processes over time. The present study investigated motion-defined integration mechanisms in two patients with simultanagnosia. We applied hierarchical organized stimuli of global objects that consisted of coherently moving dots (‘shape-from-motion’). In addition, we tested the patients’ ability to recognize biological motion by presenting characteristic human movements (‘point-light-walker’). The data revealed largely preserved perception of biological motion, while the perception of motion-defined shapes was impaired. Our findings suggest separate mechanisms underlying the recognition of biological motion and shapes defined by coherently moving dots. They thus argue against a restriction in the overall capacity of visual working memory over time as a general explanation for the impaired global shape recognition in patients with simultanagnosia. no notspecified http://www.kyb.tuebingen.mpg.de/ published -197 HuberleK2006 3 E Huberle K-O Karnath 2006-07-00 6 44 905–911 Neuropsychologia Simultanagnosia is a rare deficit that impairs individuals in perceiving several objects at the same time. It is usually observed following bilateral parieto-occipital brain damage. Despite the restrictions in perceiving the global aspect of a scene, processing of individual objects remains unaffected. The mechanisms underlying simultanagnosia are not well understood. Previous findings indicated that the integration of multiple objects into a holistic representation of the environment is not impossible per se, but might depend on the spatial relationship between individual objects. The present study examined the influence of inter-element distances between individual objects on the recognition of global shapes in two patients with simultanagnosia. We presented Navon hierarchical letter stimuli with different inter-element distances between letters at the Local Scale. Improved recognition at the Global Scale was observed in both patients by reducing the inter-element distance. Global shape recognition in simultanagnosia thus seems to be modulated by the spatial distance of local elements and does not appear to be an all-or-nothing phenomenon depending on spatial continuity. The findings seem to argue against a deficit in visual working memory capacity as the primary deficit in simultanagnosia. However, further research is necessary to investigate alternative interpretations. no notspecified http://www.kyb.tuebingen.mpg.de/ published -905 3487 3 Z Kourtzi E Huberle 2005-11-00 2 28 440 452 NeuroImage The integration of local elements to coherent forms is at the core of understanding visual perception. Accumulating evidence suggests that both early retinotopic and higher occipitotemporal areas contribute to the integration of local elements to global forms. However, the spatiotemporal characteristics of form analysis in the human visual cortex remain largely unknown. The aim of this study was to investigate form analysis at different spatial (global vs. local structure) and temporal (different stimulus presentation rates) scales across stages of visual analysis (from V1 to the lateral occipital complex—LOC) in the human brain. We used closed contours rendered by Gabor elements and manipulated either the global contour structure or the orientation of the local Gabor elements. Our rapid event-related fMRI adaptation studies suggest that contour integration and form processing in early visual areas is transient and limited within the local neighborhood of their cells' receptive field. In contrast, higher visual areas appear to process the perceived global form in a more sustained manner. Finally, we demonstrate that these spatiotemporal properties of form processing in the visual cortex are modulated by attention. Attention to the global form maintains sustained processing in occipitotemporal areas, whereas attention to local elements enhances their integration in early visual areas. These findings provide novel neuroimaging evidence for form analysis at different spatiotemporal scales across human visual areas and validate the use of rapid event-related fMRI adaptation for investigating processing across stages of visual analysis in the human brain. no notspecified http://www.kyb.tuebingen.mpg.de/ published 12 15017 15422 15017 15421 HuberleK2004 7 E Huberle Z Kourtzi Tübingen, Germany2004-02-00 136 7th Tübingen Perception Conference (TWK 2004) Coherent visual perception requires the integration of local elements into global shapes. However, the involvement of the various visual areas in the integration of local features into global shapes remains largely unknown.Event-related fMRI was used to test for local and global mechanisms of shape processing in higher visual object related areas. We tested for responses in the Fusiform Face Area (FFA) known to respond selectively to faces [1] and the Parahippocampal Place Area (PPA) known to be involved in the analysis of spatial layout [2]. The stimuli consisted of images of houses or faces (global shapes) rendered by smaller images of stimuli from these categories (local shapes). We tested four conditions: a) global faces rendered by local faces; b) global faces rendered by local houses; c) global houses rendered by local faces and d) global houses rendered by local houses. Subjects were instructed to judge whether global and local shapes where from the same or different categories. Our results showed strong fMRI responses for global faces in the FFA and global houses in the PPA independent of the stimulus category at the local level. Lower category specic responses to the local shapes were observed when the global shapes were from a different category than the local shapes. Further studies tested for fMRI responses at different stimulus scales and attentional shifts. Stronger responses to the local faces in the FFA and local houses in the PPA were observed compared to global faces and global houses. Our results suggest differential processing of global and local shape information in category selective areas. Furthermore, attention and spatial scale inuence the processing of local and global shape information. no notspecified http://www.kyb.tuebingen.mpg.de/ published -136 15017 15422 HuberleK2003 7 E Huberle Z Kourtzi New Orleans, LA, USA2003-11-00 33rd Annual Meeting of the Society for Neuroscience (Neuroscience 2003) Coherent visual perception requires the integration of local elements into global shapes. However, the involvement of the various visual areas in the integration of local features into global shapes remains largely unknown. We used event-related fMRI to test for local and global shape processing in visual areas known to be involved in the processing of shapes. The stimuli consisted of images of houses or faces (global shapes) rendered by smaller images of stimuli from these categories (local shapes). We tested four conditions: a) global faces rendered by local faces; b) global faces rendered by local houses; c) global houses rendered by local faces and d) global houses rendered by local houses. Subjects were instructed to judge whether global and local shapes where from the same or different categories. We tested for responses in the Fusiform Face Area (FFA) known to respond selectively to faces (Kanwisher et al., 1997) and the Parahippocampal Place Area (PPA) known to be involved in the analysis of spatial layout (Epstein et al., 1998). Our results showed strong fMRI responses for global faces in the FFA and global houses in the PPA independent of the stimulus category at the local level. Lower category specific responses to the local shapes were observed when the global shapes were from a different category than the local shapes. These results suggest differential processing of global and local shape information in category selective areas. Further studies will test for the processing of global and local shape information at different stimulus scales. no notspecified http://www.kyb.tuebingen.mpg.de/ published 0 15017 15422 2114 7 E Huberle A Deubelius W Lutzenberger HH Bülthoff Z Kourtzi Sarasota, FL, USA2003-10-00 266 Third Annual Meeting of the Vision Sciences Society (VSS 2003) Recent studies have shown that global information about shapes is processed in both early ventral (i.e. V1, V2, Vp, V4) and higher occipitotemporal visual areas (i.e. Lateral Occipital Complex-LOC). However, the temporal properties of shape processing across visual areas in the human brain are not known. We addressed this question in a combined fMRI and MEG study that made use of the complimentary spatial and temporal resolution of the two techniques. We used an event-related adaptation paradigm in which lower neural responses are observed for two identical than two different consecutively-presented stimuli. The stimuli were closed contours that consisted of collinear Gabor elements. We manipulated the interstimulus interval (ISI: 100 vs. 400 msec) between the two consecutively-presented stimuli. The fMRI results showed adaptation for both the short and the long ISI in the LOC but only for the short ISI in early visual areas. The MEG data showed similar patterns of response amplitude to the fMRI data and differences in latencies for the different ISIs across visual areas. These findings suggest sustained shape processing in higher visual areas compared to more transient visual analysis in early visual areas. Further studies test the analysis of local vs. global shape features across areas with different temporal processing properties. no notspecified http://www.kyb.tuebingen.mpg.de//fileadmin/user_upload/files/publications/pdf2114.pdf published -266 15017 15422 HuberleDLBK2003 7 E Huberle A Deubelius W Lutzenberger HH Bülthoff Z Kourtzi Tübingen, Germany2003-02-00 151 6. Tübinger Wahrnehmungskonferenz (TWK 2003) Recent studies have shown that global information about shapes is processed in both early ventral (i.e. V1, V2, Vp, V4) and higher occipitotemporal visual areas (i.e. Lateral Occipital Complex-LOC). However, the temporal properties of shape processing across visual areas in the human brain are largely unknown. We addressed this question in a combined fMRI and MEG study that made use of the high spatial resolution of fMRI and the temporal resolution of MEG. We used an event-related adaptation paradigm in which lower neural responses are observed for two identical than two different consecutively-presented stimuli. The stimuli were closed contours that consisted of collinear Gabor elements. We manipulated the interstimulus interval (ISI: 100 vs. 400 msec) between the two consecutively-presented stimuli in each trial. To ensure comparability between fMRI and MEG results, subjects participated in both parts of the study. The fMRI results for 11 subjects showed adaptation for both the short and the long ISI in the LOC but only for the short ISI in early visual areas. The MEG data showed similar patterns of response amplitude to the fMRI data and dierences in latencies for the dierent ISIs across visual areas ranging between 70 and 160 ms. These ndings suggest sustained shape processing in higher visual areas compared to more transient visual analysis in early visual areas. Further studies test the analysis of local vs. global shape features across areas with dierent temporal processing properties. no notspecified http://www.kyb.tuebingen.mpg.de/ published -151 15017 1542215017 15421