Publications by authors named "Christian Gerlach"

30 Publications

  • Page 1 of 1

Object recognition and visual object agnosia.

Handb Clin Neurol 2021 ;178:155-173

Department of Psychology, University of Copenhagen, Copenhagen, Denmark.

The term visual agnosia is used to refer to recognition disorders that are confined to the visual modality, that are not due to an impairment in sensory functions, and that cannot be explained by other cognitive deficits or by general reduction in intellectual ability. Here, we describe the different types of visual agnosia that have been reported (form agnosia, integrative agnosia, associative agnosia, transformational and orientation agnosia as well as category-specific impairments such as pure alexia and prosopagnosia) and how they relate to the current understanding of visual object recognition. Together with related disorders such as simultanagnosia, texture agnosia, aphantasia, and optic aphasia, these visual perceptual impairments can have severe consequences for those affected. We suggest how in-depth assessment can be carried out to determine the type and the extent of these impairments. In the context of clinical assessment, a step-by-step approach reflecting a posterior to anterior gradient in visual object recognition, from more perceptual to more memory-related processes, is suggested. Individually tailored interventions targeting the identified impairments can be initiated based on the results of the assessment.
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http://dx.doi.org/10.1016/B978-0-12-821377-3.00008-8DOI Listing
January 2021

Patterns of perceptual performance in developmental prosopagnosia: An in-depth case series.

Cogn Neuropsychol 2021 Feb 17;38(1):27-49. Epub 2021 Jan 17.

Department of Psychology, University of Copenhagen, Copenhagen, Denmark.

Developmental prosopagnosia (DP) is a syndrome characterized by lifelong impairment in face recognition in the absence of brain damage. A key question regarding DP concerns which process(es) might be affected to selectively/disproportionally impair face recognition. We present evidence from a group of DPs, combining an overview of previous results with additional analyses important for understanding their pattern of preserved and impaired perceptual abilities. We argue that for most of these individuals, the common denominator is a deficit in (rapid) processing of global shape information. We conclude that the deficit in this group of DPs is not face-selective, but that it may appear so because faces are more visually similar-and recognized at a more fine-grained level-than objects. Indeed, when the demand on perceptual differentiation and visual similarity are held constant for faces and objects, we find no evidence for a disproportionate deficit for faces in this group of DPs.
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http://dx.doi.org/10.1080/02643294.2020.1869709DOI Listing
February 2021

Face recognition in developmental dyslexia: evidence for dissociation between faces and words.

Cogn Neuropsychol 2021 Feb 26;38(1):107-115. Epub 2020 Nov 26.

Department of Psychology, University of Copenhagen, Copenhagen, Denmark.

Developmental dyslexia is primarily a reading disorder, but recent studies have indicated that face processing problems may also be present. Using a case-series approach, we tested face recognition and visual word recognition in 24 high school students diagnosed with developmental dyslexia. Contrary to previous findings, no face recognition problems were found on the group-level. Rather, a significant classical dissociation with impaired word reading and normal face recognition was demonstrated on a group-level and for six individuals with developmental dyslexia. However, four individuals with dyslexia did show face recognition problems. Thus, while problems in face recognition can be present in developmental dyslexia, the dissociation strongly suggests that face recognition can also be preserved. Combined with previously reported dissociations between face and word recognition in developmental prosopagnosia, this constitutes a double dissociation.
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http://dx.doi.org/10.1080/02643294.2020.1847060DOI Listing
February 2021

Left hemisphere abnormalities in developmental prosopagnosia when looking at faces but not words.

Brain Commun 2019 20;1(1):fcz034. Epub 2019 Dec 20.

Department of Psychology, University of Copenhagen, Copenhagen DK-1353, Denmark.

Developmental prosopagnosia is a disorder characterized by profound and lifelong difficulties with face recognition in the absence of sensory or intellectual deficits or known brain injury. While there has been a surge in research on developmental prosopagnosia over the last decade and a half, the cognitive mechanisms behind the disorder and its neural underpinnings remain elusive. Most recently it has been proposed that developmental prosopagnosia may be a manifestation of widespread disturbance in neural migration which affects both face responsive brain regions as well as other category-sensitive visual areas. We present a combined behavioural and functional MRI study of face, object and word processing in a group of developmental prosopagnosics ( = 15). We show that developmental prosopagnosia is associated with reduced activation of core ventral face areas during perception of faces. The reductions were bilateral but tended to be more pronounced in the left hemisphere. As the first study to address category selectivity for word processing in developmental prosopagnosia, we do not, however, find evidence for reduced activation of the visual word form area during perception of orthographic material. We also find no evidence for reduced activation of the lateral occipital complex during perception of objects. These imaging findings correspond well with the behavioural performance of the developmental prosopagnosics, who show severe impairment for faces but normal reading and recognition of line drawings. Our findings suggest that a general deficit in neural migration across ventral occipito-temporal cortex is not a viable explanation for developmental prosopagnosia. The finding of left hemisphere involvement in our group of developmental prosopagnosics was at first surprising. However, a closer look at existing studies shows similar, but hitherto undiscussed, findings. These left hemisphere abnormalities seen in developmental prosopagnosia contrasts with lesion and imaging studies suggesting primarily right hemisphere involvement in acquired prosopagnosia, and this may reflect that the left hemisphere is important for the development of a normal face recognition network.
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http://dx.doi.org/10.1093/braincomms/fcz034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7425287PMC
December 2019

Who's got the global advantage? Visual field differences in processing of global and local shape.

Cognition 2020 02 12;195:104131. Epub 2019 Nov 12.

Université de Paris, LaPsyDÉ, CNRS, F-75005 Paris, France; Institut Universitaire de France (IUF), France.

Much evidence suggests that we first perceive the overall layout of a scene or object followed later by the details. This coarse-to-fine temporal dynamic in visual processing is also found in Navon's classical paradigm where information at the global level of compound stimuli is processed faster than information at the local level (global precedence effect), and where information at the global level has larger effects on local level responses than local level information has on global level responses (asymmetric interference effects). Traditionally, global shape primacy in Navon's paradigm has been linked with a right hemisphere preference (left visual field advantage) for global shape processing, and a left hemisphere preference (right visual field advantage) for local shape processing. This link, however, has been based on measures which confound global precedence and interference effects. Indeed, when these measures are de-confounded, we find no evidence for larger global precedence effects in the left compared with the right visual field in a large sample of participants (N = 337). In comparison, global-to-local interference effects are found to be stronger in the left than in the right visual field. We argue that these findings can be accounted for by assuming that the right hemisphere plays a special role in integrating shape information across spatial scales, that is, without assuming the existence of a right hemisphere preference for global shape processing per se.
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http://dx.doi.org/10.1016/j.cognition.2019.104131DOI Listing
February 2020

The good, the bad, and the average: Characterizing the relationship between face and object processing across the face recognition spectrum.

Neuropsychologia 2019 02 4;124:274-284. Epub 2018 Dec 4.

Department of Psychology, University of Southern Denmark, Odense, Denmark. Electronic address:

Face recognition skills vary considerably both in the normal population and in various clinical groups, and understanding the cognitive mechanisms contributing to this variability is important. In the present study, we investigate whether a group of good face recognizers (high performers; HPs) perform qualitatively differently from a control group on tests of face, object and word recognition, and also compare them to a group of developmental prosopagnosics (DPs). Through a series of experiments, we (i) examine whether HPs are better than control subjects in face and object recognition, (ii) investigate if any dissociations among face, object, and word processing tasks can be demonstrated in the HPs, and (iii) compare the performance of the HPs to a group of poor face recognizers namely a group of DPs. Data from this DP group have previously been reported, but the analyses presented here are new. We find that HPs were significantly better than matched control subjects on tests of face and object recognition including a reading task, but they did not show significantly larger inversion effects on typical tests of face processing (the CFMT and the CFPT). There was no evidence of dissociations between face and object processing in the HPs when compared to controls, indicating superior performance across visual domains. In the DP group, however, we found significant dissociations between face and object recognition performance on a group level, indicating that face processing is disproportionally affected. On this basis, we propose that superior face processing in HPs rely on more general cognitive or perceptual processes shared with object processing. Hence, while face processing in DPs seems qualitatively different from the normal population, there is no such difference between average and high performing face recognizers. Thus, what underlies superior face processing in HPs might also underlie their superior performance with other stimulus classes and might be conceived as a general factor in the visual domain, a VG-factor, akin to the G factor in intelligence.
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http://dx.doi.org/10.1016/j.neuropsychologia.2018.11.016DOI Listing
February 2019

Delayed processing of global shape information is associated with weaker top-down effects in developmental prosopagnosia.

Cogn Neuropsychol 2018 12 11;35(8):471-478. Epub 2018 Sep 11.

b Department of Psychology , University of Copenhagen , København , Denmark.

In previous studies we have shown that a group of individuals with developmental prosopagnosia (DP): (i) were impaired at recognizing objects when presented as silhouettes or fragmented forms; stimuli which place particular demands on global shape processing, (ii) that these impairments correlated with their face recognition deficit, (iii) that they showed a reduced global precedence effect in Navon's paradigm, and (iv) that the magnitude of their global precedence effect correlated with their face and object recognition performance. This pattern of deficits points towards a delay in the processing of global shape information; a delay that may weaken top-down influences on recognition performance. Here we show that the DPs show reduced real object superiority effects (faster responses to real objects than nonobjects) compared with controls. Given that real object superiority effects reflect top-down processing, these findings support the notion of impaired global shape based top-down processing in DP.
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http://dx.doi.org/10.1080/02643294.2018.1519505DOI Listing
December 2018

On defining and interpreting dissociations.

Cogn Neuropsychol 2018 Feb - Mar;35(1-2):66-69

b Department of Psychology , University of Copenhagen , Copenhagen , Denmark.

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http://dx.doi.org/10.1080/02643294.2017.1414692DOI Listing
February 2019

Inversion effects for faces and objects in developmental prosopagnosia: A case series analysis.

Neuropsychologia 2018 05 26;113:52-60. Epub 2018 Mar 26.

Department of Psychology, University of Southern Denmark, Denmark.

The disproportionate face inversion effect (dFIE) concerns the finding that face recognition is more affected by inversion than recognition of non-face objects; an effect assumed to reflect that face recognition relies on special operations. Support for this notion comes from studies showing that face processing in developmental prosopagnosia (DP) is less affected by inversion than it is in normal subjects, and that DPs may even display face inversion superiority effects, i.e. better processing of inverted compared to upright faces. To date, however, there are no reports of direct comparisons between inversion effects for faces and objects, investigating whether the altered inversion effect in DP is specific to faces. We examined this question by comparing inversion effects for faces and cars in two otherwise identical recognition tasks in a group of DPs (N = 16) and a matched control group, using a case series design. Although both groups showed inversion effects for both faces and cars, only the control group exhibited a significant dFIE, i.e. a larger inversion effect for faces than cars. In comparison, the DPs were not significantly more affected by inversion than the control group when assessed with a face processing task that did not require recognition. Importantly, in both settings the DPs are better with upright than with inverted faces, and on the individual level no DP was found to perform significantly better with inverted than with upright faces. In fact, the DPs are impaired relative to the control group with both upright and inverted faces and to a less extent also with upright and inverted cars. These results yield no evidence of inversion superiority in DP but rather suggest that their face recognition problem is not limited to operations specialized for upright faces.
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http://dx.doi.org/10.1016/j.neuropsychologia.2018.03.026DOI Listing
May 2018

Global precedence effects account for individual differences in both face and object recognition performance.

Psychon Bull Rev 2018 08;25(4):1365-1372

Department of Psychology, University of Copenhagen, Copenhagen, Denmark.

There has been an increase in studies adopting an individual difference approach to examine visual cognition and in particular in studies trying to relate face recognition performance with measures of holistic processing (the face composite effect and the part-whole effect). In the present study we examine whether global precedence effects, measured by means of non-face stimuli in Navon's paradigm, can also account for individual differences in face recognition and, if so, whether the effect is of similar magnitude for faces and objects. We find evidence that global precedence effects facilitate both face and object recognition, and to a similar extent. Our results suggest that both face and object recognition are characterized by a coarse-to-fine temporal dynamic, where global shape information is derived prior to local shape information, and that the efficiency of face and object recognition is related to the magnitude of the global precedence effect.
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http://dx.doi.org/10.3758/s13423-018-1458-1DOI Listing
August 2018

Reading in developmental prosopagnosia: Evidence for a dissociation between word and face recognition.

Neuropsychology 2018 02;32(2):138-147

Department of Psychology, University of Southern Denmark.

Objective: Recent models suggest that face and word recognition may rely on overlapping cognitive processes and neural regions. In support of this notion, face recognition deficits have been demonstrated in developmental dyslexia. Here we test whether the opposite association can also be found, that is, impaired reading in developmental prosopagnosia.

Method: We tested 10 adults with developmental prosopagnosia and 20 matched controls. All participants completed the Cambridge Face Memory Test, the Cambridge Face Perception test and a Face recognition questionnaire used to quantify everyday face recognition experience. Reading was measured in four experimental tasks, testing different levels of letter, word, and text reading: (a) single word reading with words of varying length,(b) vocal response times in single letter and short word naming, (c) recognition of single letters and short words at brief exposure durations (targeting the word superiority effect), and d) text reading.

Results: Participants with developmental prosopagnosia performed strikingly similar to controls across the four reading tasks. Formal analysis revealed a significant dissociation between word and face recognition, as the difference in performance with faces and words was significantly greater for participants with developmental prosopagnosia than for controls.

Conclusions: Adult developmental prosopagnosics read as quickly and fluently as controls, while they are seemingly unable to learn efficient strategies for recognizing faces. We suggest that this is due to the differing demands that face and word recognition put on the perceptual system. (PsycINFO Database Record
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http://dx.doi.org/10.1037/neu0000428DOI Listing
February 2018

Navon's classical paradigm concerning local and global processing relates systematically to visual object classification performance.

Sci Rep 2018 01 10;8(1):324. Epub 2018 Jan 10.

LaPsyDÉ, UMR 8240, CNRS, Université Paris Descartes, Université Caen Normandie, Paris, France.

Forty years ago David Navon tried to tackle a central problem in psychology concerning the time course of perceptual processing: Do we first see the details (local level) followed by the overall outlay (global level) or is it rather the other way around? He did this by developing a now classical paradigm involving the presentation of compound stimuli; large letters composed of smaller letters. Despite the usefulness of this paradigm it remains uncertain whether effects found with compound stimuli relate directly to visual object recognition. It does so because compound stimuli are not actual objects but rather formations of elements and because the elements that form the global shape of compound stimuli are not features of the global shape but rather objects in their own right. To examine the relationship between performance on Navon's paradigm and visual object processing we derived two indexes from Navon's paradigm that reflect different aspects of the relationship between global and local processing. We find that individual differences on these indexes can explain a considerable amount of variance in two standard object classification paradigms; object decision and superordinate categorization, suggesting that Navon's paradigm does relate to visual object processing.
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http://dx.doi.org/10.1038/s41598-017-18664-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5762637PMC
January 2018

Delayed processing of global shape information in developmental prosopagnosia.

PLoS One 2017 20;12(12):e0189253. Epub 2017 Dec 20.

Department of Psychology, University of Copenhagen, Copenhagen, Denmark.

There is accumulating evidence suggesting that a central deficit in developmental prosopagnosia (DP), a disorder characterized by profound and lifelong difficulties with face recognition, concerns impaired holistic processing. Some of this evidence comes from studies using Navon's paradigm where individuals with DP show a greater local or reduced global bias compared with controls. However, it has not been established what gives rise to this altered processing bias. Is it a reduced global precedence effect, changes in susceptibility to interference effects or both? By analyzing the performance of 10 individuals with DP in Navon's paradigm we find evidence of a reduced global precedence effect: The DPs are slower than controls to process global but not local shape information. Importantly, and in contrast to previous studies, we demonstrate that the DPs perform normally in a comprehensive test of visual attention, showing normal: visual short-term memory capacity, speed of visual processing, efficiency of top-down selectivity, and allocation of attentional resources. Hence, we conclude that the reduced global precedence effect reflects a perceptual rather than an attentional deficit. We further show that this reduced global precedence effect correlates both with the DPs' face recognition abilities, as well as their ability to recognize degraded (non-face) objects. We suggest that the DPs' impaired performance in all three domains (Navon, face and object recognition) may be related to the same dysfunction; delayed derivation of global relative to local shape information.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0189253PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5738059PMC
January 2018

Different Measures of Structural Similarity Tap Different Aspects of Visual Object Processing.

Front Psychol 2017 17;8:1404. Epub 2017 Aug 17.

Department of Psychology, University of Southern Denmark OdenseOdense, Denmark.

The structural similarity of objects has been an important variable in explaining why some objects are easier to categorize at a superordinate level than to individuate, and also why some patients with brain injury have more difficulties in recognizing natural (structurally similar) objects than artifacts (structurally distinct objects). In spite of its merits as an explanatory variable, structural similarity is not a unitary construct, and it has been operationalized in different ways. Furthermore, even though measures of structural similarity have been successful in explaining task and category-effects, this has been based more on implication than on direct empirical demonstrations. Here, the direct influence of two different measures of structural similarity, and , on object individuation (object decision) and superordinate categorization performance is examined. Both measures can account for performance differences across objects, but in different conditions. It is argued that this reflects differences between the measures in whether they tap: (i) global or local shape characteristics, and (ii) between- or within-category structural similarity.
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http://dx.doi.org/10.3389/fpsyg.2017.01404DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5563126PMC
August 2017

Topographic processing in developmental prosopagnosia: Preserved perception but impaired memory of scenes.

Cogn Neuropsychol 2016 Oct - Dec;33(7-8):405-413. Epub 2016 Dec 30.

a Department of Psychology , University of Southern Denmark , Odense , Denmark.

Anecdotal evidence suggests a relation between impaired spatial (navigational) processing and developmental prosopagnosia. To address this formally, we tested two aspects of topographic processing - that is, perception and memory of mountain landscapes shown from different viewpoints. Participants included nine individuals with developmental prosopagnosia and 18 matched controls. The group with developmental prosopagnosia had no difficulty with topographic perception, but was reliably poorer in the retention of topographic information. Additional testing revealed that this did not reflect a general deficit in visual processing or visual short-term memory. Interestingly, a classical dissociation could be demonstrated between impaired face memory and preserved topographic memory in two developmental prosopagnosics. We conclude that impairments in topographic memory tend to co-occur with developmental prosopagnosia, although the underlying functions are likely to be independent.
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http://dx.doi.org/10.1080/02643294.2016.1267000DOI Listing
September 2017

Gender differences in category-specificity do not reflect innate dispositions.

Cortex 2016 12 15;85:46-53. Epub 2016 Oct 15.

Center for Neuropsychological Research and Department of Neurosciences, Institute of Neurology Policlinico Gemelli, Catholic University of Rome, Italy; Department of Clinical and Behavioral Neurology, IRCCS Fondazione Santa Lucia, Rome, Italy.

It is well established that certain categories of objects are processed more efficiently than others in specific tasks; a phenomenon known as category-specificity in perceptual and conceptual processing. In the last two decades there have also been several reports of gender differences in category-specificity. In the present experiments we test the proposition that such gender differences have an evolutionary origin. If they do, we would expect them to emerge even when the population tested comprises young individuals raised in a gender-equality oriented society. Contrary to this expectation we find no evidence of gender differences in category-specificity in a relatively large sample (N = 366) drawn from such a population; and this despite the fact that both tasks applied (object decision and superordinate categorization) gave rise to reliable category-effects. We suggest that a plausible account of this discrepancy is that previous reports of gender differences may have reflected differences in familiarity originating from socially-based gender roles.
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http://dx.doi.org/10.1016/j.cortex.2016.09.022DOI Listing
December 2016

On the Relation between Face and Object Recognition in Developmental Prosopagnosia: No Dissociation but a Systematic Association.

PLoS One 2016 28;11(10):e0165561. Epub 2016 Oct 28.

Department of Psychology, University of Copenhagen, Copenhagen, Denmark.

There is an ongoing debate about whether face recognition and object recognition constitute separate domains. Clarification of this issue can have important theoretical implications as face recognition is often used as a prime example of domain-specificity in mind and brain. An important source of input to this debate comes from studies of individuals with developmental prosopagnosia, suggesting that face recognition can be selectively impaired. We put the selectivity hypothesis to test by assessing the performance of 10 individuals with developmental prosopagnosia on demanding tests of visual object processing involving both regular and degraded drawings. None of the individuals exhibited a clear dissociation between face and object recognition, and as a group they were significantly more affected by degradation of objects than control participants. Importantly, we also find positive correlations between the severity of the face recognition impairment and the degree of impaired performance with degraded objects. This suggests that the face and object deficits are systematically related rather than coincidental. We conclude that at present, there is no strong evidence in the literature on developmental prosopagnosia supporting domain-specific accounts of face recognition.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0165561PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5085057PMC
June 2017

Category-Specific Visual Recognition and Aging from the PACE Theory Perspective: Evidence for a Presemantic Deficit in Aging Object Recognition.

Exp Aging Res 2016 Oct-Dec;42(5):431-446

a Laboratoire de psychologie EA4139 , Université Victor Segalen-Bordeaux 2 , Bordeaux , France.

Background/Study Context: The objective of this study was to investigate the object recognition deficit in aging. Age-related declines were examined from the presemantic account of category effects (PACE) theory perspective (Gerlach, 2009, Cognition, 111, 281-301). This view assumes that the structural similarity/dissimilarity inherent in living and nonliving objects, respectively, can account for a wide range of category-specific effects.

Methods: In two experiments on object recognition, young (36 participants, 18-27 years) and older (36 participants, 53-69 years) adult participants' performances were compared.

Results: The young adults' results corroborate the PACE theory expectations. The results of the older adults showed an impairment in recognition of structurally similar objects irrespective of semantic category.

Conclusion: The two sets of results suggest that a deficit in the selection stage of the PACE theory (visual long-term memory matching) could be responsible for these impairments. Indeed, the older group showed a deficit when this stage was most relevant. This article emphasize on the critical need for taking into account structural component of the stimuli and type of tasks in further studies.
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http://dx.doi.org/10.1080/0361073X.2016.1224634DOI Listing
June 2017

Structural similarity exerts opposing effects on perceptual differentiation and categorization: an FMRI study.

J Cogn Neurosci 2015 May 12;27(5):974-87. Epub 2014 Nov 12.

University of Southern Denmark.

We manipulated the degree of structural similarity between objects that had to be matched either according to whether they represented the same object (perceptual matching) or belonged to the same category (conceptual matching). Behaviorally, performance improved as a linear function of increased structural similarity during conceptual matching but deteriorated as a linear function of increased structural similarity during perceptual matching. These effects were mirrored in fMRI recordings where activation in several ventral posterior areas exhibited a similar interaction between match type and structural similarity. Our findings provide direct support for the notion that structural similarity exerts opposing effects on classification depending on whether objects are to be perceptually differentiated or categorized-a notion that has been based on rather circumstantial evidence. In particular, the finding that structural similarity plays a major role in categorization of instances according to taxonomy challenges the view that the organization of superordinate categories is not driven by shared structural features.
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http://dx.doi.org/10.1162/jocn_a_00748DOI Listing
May 2015

Same, same—but different: on the use of Navon derived measures of global/local processing in studies of face processing.

Acta Psychol (Amst) 2014 Nov 1;153:28-38. Epub 2014 Oct 1.

Department of Psychology, University of Southern Denmark.

Some studies have reported a significant correlation between face discrimination/recognition ability and indexes of global/local processing derived from the Navon paradigm. Other studies, however, have failed to find such a relationship. In this paper we examine three aspects related to the Navon paradigm that may have contributed to this discrepancy but which have been largely neglected: (i) the use of different types of compound stimuli across studies, (ii) differences between studies in the type of index derived from the Navon paradigm, and (iii) the reliability of these indexes. In a Navon experiment comparing performance with compound letters and compound shapes in normal participants, we find little consistency both within and across participants in how they perform with these stimulus types, despite the fact that both stimulus types give rise to the typical effects. In addition we find that many of the Navon derived indexes of global/local effects used in studies examining face processing have low reliability and do not measure the same aspects of global/local processing. Echoing the results from the normal participants, we also find little consistency in how a congenital prosopagnosic performs in the Navon paradigm. With compound letters, she responds much faster to local than to global aspects of the stimuli; a pattern not seen in a single of the normal participants. With compound shapes, however, she exhibits no such abnormality. These findings question the validity of the conclusions in studies relating Navon derived indexes of global/local processing to face processing.
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http://dx.doi.org/10.1016/j.actpsy.2014.09.004DOI Listing
November 2014

White matter microstructure in superior longitudinal fasciculus associated with spatial working memory performance in children.

J Cogn Neurosci 2011 Sep 22;23(9):2135-46. Epub 2010 Oct 22.

MR-Department, Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital, Hvidovre, Denmark.

During childhood and adolescence, ongoing white matter maturation in the fronto-parietal cortices and connecting fiber tracts is measurable with diffusion-weighted imaging. Important questions remain, however, about the links between these changes and developing cognitive functions. Spatial working memory (SWM) performance improves significantly throughout the childhood years, and several lines of evidence implicate the left fronto-parietal cortices and connecting fiber tracts in SWM processing. Here we report results from a study of 76 typically developing children, 7 to 13 years of age. We hypothesized that better SWM performance would be associated with increased fractional anisotropy (FA) in a left fronto-parietal network composed of the superior longitudinal fasciculus (SLF), the regional white matter underlying the dorsolateral pFC, and the posterior parietal cortex. As hypothesized, we observed a significant association between higher FA in the left fronto-parietal network and better SWM skills, and the effect was independent of age. This association was mainly accounted for by variability in left SLF FA and remained significant when FA measures from global fiber tracts or right SLF were included in the model. Further, the effect of FA in left SLF appeared to be mediated primarily by decreasing perpendicular diffusivity. Such associations could be related to individual differences among children in the architecture of fronto-parietal connections and/or to differences in the pace of fiber tract development. Further studies are needed to determine the contributions of intrinsic and experiential factors to the development of functionally significant individual differences in fiber tract structure.
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http://dx.doi.org/10.1162/jocn.2010.21592DOI Listing
September 2011

Response inhibition is associated with white matter microstructure in children.

Neuropsychologia 2010 Mar 10;48(4):854-62. Epub 2009 Nov 10.

Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital, Hvidovre, Denmark.

Cognitive control of thoughts, actions and emotions is important for normal behaviour and the development of such control continues throughout childhood and adolescence. Several lines of evidence suggest that response inhibition is primarily mediated by a right-lateralized network involving inferior frontal gyrus (IFG), presupplementary motor cortex (preSMA), and subthalamic nucleus. Though the brain's fibre tracts are known to develop during childhood, little is known about how fibre tract development within this network relates to developing behavioural control. Here we examined the relationship between response inhibition, as measured with the stop-signal task, and indices of regional white matter microstructure in typically-developing children. We hypothesized that better response inhibition performance would be associated with higher fractional anisotropy (FA) in fibre tracts within right IFG and preSMA after controlling for age. Mean FA and diffusivity values were extracted from right and left IFG and preSMA. As hypothesized, faster response inhibition was significantly associated with higher FA and lower perpendicular diffusivity in both the right IFG and the right preSMA, possibly reflecting faster speed of neural conduction within more densely packed or better myelinated fibre tracts. Moreover, both of these effects remained significant after controlling for age and whole brain estimates of these DTI parameters. Interestingly, right IFG and preSMA FA contributed additively to the prediction of performance variability. Observed associations may be related to variation in phase of maturation, to activity-dependent alterations in the network subserving response inhibition, or to stable individual differences in underlying neural system connectivity.
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http://dx.doi.org/10.1016/j.neuropsychologia.2009.11.001DOI Listing
March 2010

Visual processing in pure alexia: a case study.

Cortex 2010 Feb 16;46(2):242-55. Epub 2009 Apr 16.

Department of Psychology, Center for Visual Cognition, University of Copenhagen, Denmark.

Whether pure alexia is a selective disorder that affects reading only, or if it reflects a more general visual disturbance, is highly debated. We have investigated the selectivity of visual deficits in a pure alexic patient (NN) using a combination of psychophysical measures, mathematical modelling and more standard experimental paradigms. NN's naming and categorization of line drawings were normal with regards to both errors and reaction times (RTs). Psychophysical experiments revealed that NN's recognition of single letters at fixation was clearly impaired, and recognition of single digits was also affected. His visual apprehension span was markedly reduced for letters and digits. His reduced visual processing capacity was also evident when reporting letters from words. In an object decision task with fragmented pictures, NN's performance was abnormal. Thus, even in a pure alexic patient with intact recognition of line drawings, we find evidence of a general visual deficit not selective to letters or words. This finding is important because it raises the possibility that other pure alexics might have similar non-selective impairments when tested thoroughly. We argue that the general visual deficit in NN can be accounted for in terms of inefficient build-up of sensory representations, and that this low level deficit can explain the pattern of spared and impaired abilities in this patient.
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http://dx.doi.org/10.1016/j.cortex.2009.03.013DOI Listing
February 2010

Category-specificity in visual object recognition.

Cognition 2009 Jun 25;111(3):281-301. Epub 2009 Mar 25.

Learning Lab Denmark, University of Arhus, Copenhagen NV, Denmark.

Are all categories of objects recognized in the same manner visually? Evidence from neuropsychology suggests they are not: some brain damaged patients are more impaired in recognizing natural objects than artefacts whereas others show the opposite impairment. Category-effects have also been demonstrated in neurologically intact subjects, but the findings are contradictory and there is no agreement as to why category-effects arise. This article presents a pre-semantic account of category-effects (PACE) in visual object recognition. PACE assumes two processing stages: shape configuration (the binding of shape elements into elaborate shape descriptions) and selection (among competing representations in visual long-term memory), which are held to be differentially affected by the structural similarity between objects. Drawing on evidence from clinical studies, experimental studies with neurologically intact subjects and functional imaging studies, it is argued that PACE can account for category-effects at both behavioural and neural levels in patients and neurologically intact subjects. The theory also accounts for the way in which category-effects are affected by different task parameters (the degree of perceptual differentiation called for), stimulus characteristics (whether stimuli are presented as silhouettes, full line-drawings, or fragmented forms), stimulus presentation (stimulus exposure duration and position) as well as interactions between these parameters.
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http://dx.doi.org/10.1016/j.cognition.2009.02.005DOI Listing
June 2009

A review of functional imaging studies on category specificity.

J Cogn Neurosci 2007 Feb;19(2):296-314

Learning Lab Denmark, The Danish University of Education, Tuborgvej 164, 2400 Copenhagen NV, Denmark.

A review of 20 functional imaging studies that compared visual processing of natural objects and artifacts in normal subjects is presented. The studies included fulfilled three criteria: (i) they used pictures as stimuli, (ii) they were based on direct contrasts between categories, and (iii) they reported findings in Talairach space. Not a single area is consistently activated for a given category across all studies. In contrast, 11 out of 29 regions are reported activated by both artifacts and natural objects. It is argued that the inconsistency is unlikely to reflect differences between studies in task requirements alone. Rather, the most likely causes of the inconsistency are: (i) adoption of liberal statistical thresholds that may yield false-positive activations, (ii) limited sensitivity due to few observations, and (iii) failure to match categories on confounding variables such as familiarity and visual complexity. Of the most consistent activations found, none appear to be selective for natural objects or artifacts. The findings reviewed are compatible with theories of category specificity that assume a widely distributed conceptual system not organized by category.
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http://dx.doi.org/10.1162/jocn.2007.19.2.296DOI Listing
February 2007

The visual what for area: words and pictures in the left fusiform gyrus.

Neuroimage 2007 Mar 18;35(1):334-42. Epub 2007 Jan 18.

Center for Visual Cognition, Department of Psychology, University of Copenhagen, Linnesgade 22, DK-1361 Copenhagen K, Denmark.

An area in the left fusiform gyrus labelled the Visual Word Form Area (VWFA) is claimed to be especially, or even selectively, responsive to words. We explored how stimulus type and task demands affect activity in this area by conducting a PET experiment where words and pictures were presented in two conditions that differed in demands on shape processing: colour decision and categorization. The subjects also performed an object decision task with pictures only. The imaging data revealed a main effect of stimulus type: rCBF was higher during word compared with picture processing. When compared individually for colour decision and categorization, the difference between words and pictures was only significant during colour decision, although a trend was present during categorization also. rCBF in the VWFA was highest during the object decision task, where only pictures were presented. Our findings indicate that the putative VWFA is activated more by written words than pictures, but only under certain circumstances. As demands on shape processing increase, the difference in activation between words and pictures decreases and can even be abolished. We suggest that activation in the VWFA could reflect shape configuration-the integration of shape elements into elaborate shape descriptions corresponding to whole objects or words. This process may be required to different degrees for pictures and words depending on task demands.
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http://dx.doi.org/10.1016/j.neuroimage.2006.12.003DOI Listing
March 2007

Shape configuration and category-specificity.

Neuropsychologia 2006 14;44(7):1247-60. Epub 2005 Nov 14.

The Neurobiology Research Unit, N9201, Department of Clinical Physiology & Nuclear Medicine, Copenhagen University Hospital, Denmark.

We examined the neural correlates of visual shape configuration, the binding of local shape characteristics into wholistic object descriptions, by comparing the regional cerebral blood flow associated with recognition of outline drawings and fragmented drawings. We found no areas that responded more to fragmented drawings than to outline drawings even though fragmentation had a clear impact on recognition performance. Instead, a region extending from the inferior occipital gyri to the middle parts of the fusiform gyri was activated during shape configuration of both outline drawings and fragmented drawings. We also examined whether fragmentation had different impact on the recognition of natural objects and artefacts and found that recognition of artefacts was more affected by fragmentation than recognition of natural objects. Thus, the usual finding of an advantage for artefacts in difficult object decision tasks, which is also found in the present experiments with outlines, is reversed when the stimuli are fragmented. This interaction between category (natural versus artefacts) and stimulus type (outlines versus fragmented forms) is in accordance with predictions derived from a recent account of category-specificity and lends support to the notion that category-specific impairments can occur for both natural objects and artefacts following damage to pre-semantic stages in visual object recognition. The implications of the present findings are discussed in relation to theories of perceptual organization, visual object recognition and category-specificity.
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http://dx.doi.org/10.1016/j.neuropsychologia.2005.09.010DOI Listing
October 2006

Structural similarity and category-specificity: a refined account.

Neuropsychologia 2004 ;42(11):1543-53

The Neurobiology Research Unit, N9201, Department of Clinical Physiology & Nuclear Medicine, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen, Denmark.

It has been suggested that category-specific recognition disorders for natural objects may reflect that natural objects are more structurally (visually) similar than artefacts and therefore more difficult to recognize following brain damage. On this account one might expect a positive relationship between blood flow and structural similarity in areas involved in visual object recognition. Contrary to this expectation we report a negative relationship in that identification of articles of clothing cause more extensive activation than identification of vegetables/fruit and animals even though items from the categories of animals and vegetables/fruit are rated as more structurally similar than items from the category of articles of clothing. Given that this pattern cannot be explained in terms of a tradeoff between activation and accuracy, we interpret these findings within a model where the matching of visual forms to memory incorporates two operations: (i) the integration of stored object features into whole object representations (integral units), and (ii) the competition between activated integral units for selection (i.e. identification). In addition, we suggest that these operations are differentially affected by structural similarity in that high structural similarity may be beneficial for the integration of stored features into integral units, thus explaining the greater activation found with articles of clothing, whereas it may be harmful for the selection process proper because a greater range of candidate integral units will be activated and compete for selection, thus explaining the higher error rate associated with animals. We evaluate the model based on previous evidence from both normal subjects and patients with category-specific disorders and argue that this model can help reconcile otherwise conflicting data.
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http://dx.doi.org/10.1016/j.neuropsychologia.2004.03.004DOI Listing
September 2004

When action turns into words. Activation of motor-based knowledge during categorization of manipulable objects.

J Cogn Neurosci 2002 Nov;14(8):1230-9

Copenhagen University Hospital, Denmark.

Functional imaging studies have demonstrated that processing of man-made objects activate the left ventral premotor cortex, which is known to be concerned with motor function. This has led to the suggestion that the comprehension of man-made objects may rely on motor-based knowledge of object utilization (action knowledge). Here we show that the left ventral premotor cortex is activated during categorization of "both" fruit/vegetables and articles of clothing, relative to animals and nonmanipulable man-made objects. This observation suggests that action knowledge may not be important for the processing of man-made objects per se, but rather for the processing of manipulable objects in general, whether natural or man-made. These findings both support psycholinguistic theories suggesting that certain lexical categories may evolve from, and the act of categorization rely upon, motor-based knowledge of action equivalency, and have important implications for theories of category specificity. Thus, the finding that the processing of vegetables/fruit and articles of clothing give rise to similar activation is difficult to account for should knowledge representations in the brain be truly categorically organized. Instead, the data are compatible with the suggestion that categories differ in the weight they put on different types of knowledge.
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http://dx.doi.org/10.1162/089892902760807221DOI Listing
November 2002

[The working brain--how does it look like?].

Ugeskr Laeger 2002 Apr;164(17):2267-75

Numerous brain functions, such as awareness of surroundings, control of movements, thoughts, and memory have always been a kind of mystery, which has provoked human curiosity and thus inspired research in many areas. The present paper gives an overview on imaging research of the human brain's functions. The historical progress is briefly reviewed with the emphasis on major Danish contributions. The major methods of mapping brain functions and their biological basis are mentioned. These methods are positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). They are highly technological and generate enormous amounts of data. Thus, data analysis will per se be a research area in brain imaging. Finally, several examples of the authors' results on functional activation are dealt with. These examples aim to illustrate the research area and its contribution to our increased knowledge of the working brain.
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April 2002