Browsing by Author "Doerschner, Katja"
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Item Open Access Abnormal subcortical activity in congenital mirror movement disorder with RAD51 mutation(Turkish Society of Radiology, 2018) Demirayak, Pınar; Onat, Onur Emre; Gevrekci, A. Ö.; Gülsüner, S.; Uysal, H.; Bilgen, R.; Doerschner, Katja; Özçelik, Tayfun; Boyacı, HüseyinPURPOSE Congenital mirror movement disorder (CMMD) is characterized by unintended, nonsuppressible, homologous mirroring activity contralateral to the movement on the intended side of the body. In healthy controls, unilateral movements are accompanied with predominantly contralateral cortical activity, whereas in CMMD, in line with the abnormal behavior, bilateral cortical activity is observed for unilateral motor tasks. However, task-related activities in subcortical structures, which are known to play critical roles in motor actions, have not been investigated in CMMD previously. METHODS We investigated the functional activation patterns of the motor components in CMMD patients. By using linkage analysis and exome sequencing, common mutations were revealed in seven affected individuals from the same family. Next, using functional magnetic resonance imaging (fMRI) we investigated cortical and subcortical activity during manual motor actions in two right-handed affected brothers and sex, age, education, and socioeconomically matched healthy individuals. RESULTS Genetic analyses revealed heterozygous RAD51 c.401C>T mutation which cosegregated with the phenotype in two affected members of the family. Consistent with previous literature, our fMRI results on these two affected individuals showed that mirror movements were closely related to abnormal cortical activity in M1 and SMA during unimanual movements. Furthermore, we have found previously unknown abnormal task-related activity in subcortical structures. Specifically, we have found increased and bilateral activity during unimanual movements in thalamus, striatum, and globus pallidus in CMMD patients. CONCLUSION These findings reveal further neural correlates of CMMD, and may guide our understanding of the critical roles of subcortical structures for unimanual movements in healthy individuals.Item Open Access Attention modulates neuronal correlates of interhemispheric integration and global motion perception(Association for Research in Vision and Ophthalmology Inc., 2014) Akin, B.; Ozdem, C.; Eroglu, S.; Keskin, D. T.; Fang, F.; Doerschner, Katja; Kersten, D.; Boyacı, HüseyinIn early retinotopic areas of the human visual system, information from the left and right visual hemifields (VHFs) is processed contralaterally in two hemispheres. Despite this segregation, we have the perceptual experience of a unified, coherent, and uninterrupted single visual field. How exactly the visual system integrates information from the two VHFs and achieves this perceptual experience still remains largely unknown. In this study using fMRI, we explored candidate areas that are involved in interhemispheric integration and the perceptual experience of a unified, global motion across VHFs. Stimuli were two-dimensional, computergenerated objects with parts in both VHFs. The retinal image in the left VHF always remained stationary, but in the experimental condition, it appeared to have local motion because of the perceived global motion of the object. This perceptual effect could be weakened by directing the attention away from the global motion through a demanding fixation task. Results show that lateral occipital areas, including the medial temporal complex, play an important role in the process of perceptual experience of a unified global motion across VHFs. In early areas, including the lateral geniculate nucleus and V1, we observed correlates of this perceptual experience only when attention is not directed away from the object. These findings reveal effects of attention on interhemispheric integration in motion perception and imply that both the bilateral activity of higher-tier visual areas and feedback mechanisms leading to bilateral activity of early areas play roles in the perceptual experience of a unified visual field.Item Open Access The color appearance of curved transparent objects(Association for Research in Vision and Ophthalmology, 2021-05) Ennis, Robert; Doerschner, KatjaStudies on colored transparent objects have elucidated potential mechanisms, but these studies have mainly focused on flat filters overlaying flat backgrounds. While they have provided valuable insight, these studies have not captured all aspects of transparency, like caustics, specular reflections/highlights, and shadows. Here, we investigate color-matching experiments with curved transparent objects for different matching stimuli: a uniform patch and a flat filter. Two instructions were tested: simply match the color of the glass object and the test element (patch and flat filter) or match the color of the dye that was used to tint the transparent object (patch). Observers’ matches differed from the mean, the most frequent, and the most saturated color of the transparent stimuli, whereas the brightest regions captured the chromaticity, but not the lightness, of patch matches. We applied four models from flat filter studies: the convergence model, the ratios of either the means (RMC) or standard deviations (RSD) of cone excitations, and a robust ratio model. The original convergence model does not fully generalize but does not perform poorly, and with modifications, we find that curved transparent objects cause a convergence of filtered colors toward a point in color space, similar to flat filters. Considering that, the RMC and robust ratio models generalized more than the RSD, with the RMC performing best across the stimuli we tested. We conclude that the RMC is probably the strongest factor for determining the color. The RSD seems instead to be related to the perceived “clarity” of glass objects.Item Open Access Cortical connectivity in the face of congenital structural changes—A case of homozygous LAMC3 mutation(John Wiley & Sons Ltd., 2021-08) Demirayak, P.; Oğuz, Kader Karlı; Üstün, Fatma Seyhun; Ürgen, Buse Merve; Topaç, Yasemin; Gilani, İrtiza; Kansu, T.; Saygı, S.; Özçelik, Tayfun; Boyacı, Hüseyin; Doerschner, KatjaThe homozygous LAMC3 gene mutation is associated with severe bilateral smoothening and thickening of the lateral occipital cortex . Despite this and further significant changes in gray matter structure, a patient harboring this mutation exhibited a range of remarkably intact perceptual abilities . One possible explanation of this perceptual sparing could be that the white matter structural integrity and functional connectivity in relevant pathways remained intact. To test this idea, we used diffusion tensor and functional magnetic resonance imaging to investigate functional connectivity in resting-state networks in major structural pathways involved in object perception and visual attention and corresponding microstructural integrity in a patient with homozygous LAMC3 mutation and sex, age, education, and socioeconomically matched healthy control group. White matter microstructural integrity results indicated widespread disruptions in both intra- and interhemispheric structural connections except inferior longitudinal fasciculus. With a few exceptions, the functional connectivity between the patient's adjacent gray matter regions of major white matter tracts of interest was conserved. In addition, functional localizers for face, object, and place areas showed similar results with a representative control, providing an explanation for the patient's intact face, place, and object recognition abilities. To generalize this finding, we also compared functional connectivity between early visual areas and face, place, and object category-selective areas, and we found that the functional connectivity of the patient was not different from the control group. Overall, our results provided complementary information about the effects of LAMC3 gene mutation on the human brain including intact temporo-occipital structural and functional connectivity that are compatible with preserved perceptual abilities.Item Open Access Disentangling simultaneous changes of surface and illumination(Elsevier, 2019) Ennis, R.; Doerschner, KatjaRetinally incident light is an ambiguous product of spectral distributions of light in the environment and their interactions with reflecting, absorbing, and transmitting materials. An ideal color constant observer would unravel these confounded sources of information and account for changes in each factor. Scene statistics have been proposed as a way to compensate for changes in the illumination, but few theories consider changes of 3- dimensional surfaces. Here, we investigated the visual system’s capacity to deal with simultaneous changes in illumination and surfaces. Spheres were imaged with a hyperspectral camera in a white box and their colors, as well as that of the illumination were varied along “red-green” and “blue-yellow” axes. Both the original hyperspectral images and replica scenes rendered with Mitsuba were used as stimuli, including rendered scenes with Glavens (Acta Psychologica, 2009, 132, 259–266). Observers viewed sequential, random pairs of our images, with either the whole scene, only the object, or only a part of the background being present. They judged how much the illuminant and object color changed on a scale of 0–100%. Observers could extract simultaneous illumination and reflectance changes when provided with a view of the whole scene, but global scene statistics did not fully account for their behavior, while local scene statistics improved the situation. There was no effect of color axis, shape, or simulated vs. original hyperspectral images. Observers appear to be making use of various sources of local information to complete the task.Item Open Access Expectations affect the perception of material properties(Association for Research in Vision and Ophthalmology, 2020) Alley, L. M.; Schmid, A. C.; Doerschner, KatjaMany objects that we encounter have typical material qualities: spoons are hard, pillows are soft, and Jell-O dessert is wobbly. Over a lifetime of experiences, strong associations between an object and its typical material properties may be formed, and these associations not only include how glossy, rough, or pink an object is, but also how it behaves under force: we expect knocked over vases to shatter, popped bike tires to deflate, and gooey grilled cheese to hang between two slices of bread when pulled apart. Here we ask how such rich visual priors affect the visual perception of material qualities and present a particularly striking example of expectation violation. In a cue conflict design, we pair computer-rendered familiar objects with surprising material behaviors (a linen curtain shattering, a porcelain teacup wrinkling, etc.) and find that material qualities are not solely estimated from the object's kinematics (i.e., its physical [atypical] motion while shattering, wrinkling, wobbling etc.); rather, material appearance is sometimes “pulled” toward the “native” motion, shape, and optical properties that are associated with this object. Our results, in addition to patterns we find in response time data, suggest that visual priors about materials can set up high-level expectations about complex future states of an object and show how these priors modulate material appearance.Item Open Access From hate to love: how learning can change affective responses to touched materials(Springer Science and Business Media Deutschland GmbH, 2020) Cavdan, M.; Freund, A.; Trieschmann, A.-K.; Doerschner, Katja; Drewing, K.; Nisky, I.; Hartcher-O’Brien, J.; Wiertlewski, M.; Smeets, J.People display systematic affective reactions to specific properties of touched materials. For example, granular materials such as fine sand feel pleasant, while rough materials feel unpleasant. We wondered how far such relationships between sensory material properties and affective responses can be changed by learning. Manipulations in the present experiment aimed at unlearning the previously observed negative relationship between roughness and valence and the positive one between granularity and valence. In the learning phase, participants haptically explored materials that are either very rough or very fine-grained while they simultaneously watched positive or negative stimuli, respectively, from the International Affective Picture System (IAPS). A control group did not interact with granular or rough materials during the learning phase. In the experimental phase, participants rated a representative diverse set of 28 materials according to twelve affective adjectives. We found a significantly weaker relationship between granularity and valence in the experimental group compared to the control group, whereas roughness-valence correlations did not differ between groups. That is, the valence of granular materials was unlearned (i.e., to modify the existing valence of granular materials) but not that of rough materials. These points to differences in the strength of perceptuo-affective relations, which we discuss in terms of hard-wired versus learned connections.Item Open Access Gloss and speed judgments yield different fine tuning of saccadic sampling in dynamic scenes(Sage Publications, 2019-12) Toscani, M.; Yücel, Ezgi I.; Doerschner, KatjaImage motion contains potential cues about the material properties of objects. In earlier work, we proposed motion cues that could predict whether a moving object would be perceived as shiny or matte. However, whether the visual system uses these cues is still uncertain. Herein, we use the tracking of eye movements as a tool to understand what visual information observers use when engaged in material perception. Observers judged either the gloss or the speed of moving blobby shapes in an eye tracking experiment. Results indicate that during glossiness judgments, participants tend to look at gloss-diagnostic dynamic features more than during speed judgments. This suggests a fine tuning of the visual system to properties of moving stimuli: Task relevant information is actively singled out and processed in a dynamically changing environment.Item Open Access Hand explorations are determined by the characteristics of the perceptual space of real-world materials from silk to sand(Nature Research, 2022-08-30) Dövencioǧlu, Dicle N.; Üstün, F. Seyhun; Doerschner, Katja; Drewing, KnutPerceiving mechanical properties of objects, i.e., how they react to physical forces, is a crucial ability in many aspects of life, from choosing an avocado to picking your clothes. There is, a wide variety of materials that differ substantially in their mechanical properties. For example, both, silk and sand deform and change shape in response to exploration forces, but each does so in very different ways. Studies show that the haptic perceptual space has multiple dimensions corresponding to the physical properties of textures, however in these experiments the range of materials or exploratory movements were restricted. Here we investigate the perceptual dimensionality in a large set of real materials in a free haptic exploration task. Thirty-two participants actively explored deformable and non-deformable materials with their hands and rated them on several attributes. Using the semantic differential technique, video analysis and linear classification, we found four haptic dimensions, each associated with a distinct set of hand and finger movements during active exploration. Taken together our findings suggest that the physical, particularly the mechanical, properties of a material systematically affect how it is explored on a much more fine-grained level than originally thought. © 2022, The Author(s).Item Open Access Haptic discrimination of different types of soft materials(Springer Science and Business Media Deutschland GmbH, 2022-05-20) Cavdan, Müge; Doerschner, Katja; Drewing, KnutWe interact with different types of soft materials on a daily basis such as salt, hand cream, etc. Recently we have shown that soft materials can be described using four perceptual dimensions which are deformability, granularity, viscosity, and surface softness [1]. Here, we investigated whether humans can actually perceive systematic differences in materials that selectively vary along one of these four dimensions as well as how judgments on the different dimensions are correlated to softness judgments. We selected at least two material classes per dimension (e.g., hair gel and hand cream for viscosity) and varied the corresponding feature (e.g., the viscosity of hair gel). Participants ordered four to ten materials from each material class according to their corresponding main feature, and in addition, according to their softness. Rank orders of materials according to the main feature were consistent across participants and repetitions. Rank orders according to softness were correlated either positively or negatively with the judgments along the associated four perceptual dimensions. These findings support our notion of multiple softness dimensions and demonstrate that people can reliably discriminate materials which are artificially varied along each of these softness dimensions. © 2022, The Author(s).Item Open Access Homozygosity mapping and targeted genomic sequencing reveal the game responsible for cerebellar hypoplasia and quadrupedal locomotion in a consanguineous kindred(Cold Spring Harbor Laboratory Press, 2011) Gulsuner, Süleyman; Tekinay, Ayşe Begüm; Doerschner, Katja; Boyaci, Hüseyin; Bilguvar, K.; Ünal, Hilal; Örs, Aslıhan; Onat, O. Emre; Atalar, Ergin; Basak, A. N.; Topaloglu, H.; Kansu, T.; Tan, M.; Tan, U.; Gunel, M.; Özçelik, TayfunThe biological basis for the development of the cerebro-cerebellar structures required for posture and gait in humans is poorly understood. We investigated a large consanguineous family from Turkey exhibiting an extremely rare phenotype associated with quadrupedal locomotion, mental retardation, and cerebro-cerebellar hypoplasia, linked to a 7.1-Mb region of homozygosity on chromosome 17p13.1-13.3. Diffusion weighted imaging and fiber tractography of the patients' brains revealed morphological abnormalities in the cerebellum and corpus callosum, in particular atrophy of superior, middle, and inferior peduncles of the cerebellum. Structural magnetic resonance imaging showed additional morphometric abnormalities in several cortical areas, including the corpus callosum, precentral gyrus, and Brodmann areas BA6, BA44, and BA45. Targeted sequencing of the entire homozygous region in three affected individuals and two obligate carriers uncovered a private missense mutation, WDR81 p.P856L, which cosegregated with the condition in the extended family. The mutation lies in a highly conserved region of WDR81, flanked by an N-terminal BEACH domain and C-terminal WD40 beta-propeller domains. WDR81 is predicted to be a transmembrane protein. It is highly expressed in the cerebellum and corpus callosum, in particular in the Purkinje cell layer of the cerebellum. WDR81 represents the third gene, after VLDLR and CA8, implicated in quadrupedal locomotion in humans.Item Open Access Homozygous LAMC3 mutation links to structural and functional changes in visual attention networks(Elsevier, 2019) Ürgen, Buse M.; Topaç, Yasemin; Üstün, F. Seyhun; Demirayak, Pınar; Oğuz, Kader K.; Kansu, T.; Saygı, S.; Özçelik, Tayfun; Boyacı, Hüseyin; Doerschner, KatjaThe occipital lobe contains a substantial part of the neural machinery involved in visual perception. Mutations in the LAMC3 gene have recently been shown to cause complex bilateral occipital cortical gyration abnormalities. However, to what extent these structural changes impact visual behavior is not known. We recorded responses for two screening test batteries targeting visual function (Leuven - Perceptual Organization Screening Test, Cortical Vision Screening Test) and measured eye fixation performance in a visual attention experiment from a patient with homozygous LAMC3 gene mutation. Using voxel-based morphometry (VBM) we quantitatively assessed the extent of structural changes brought on by the genetic mutation by comparing mean cortical curvature, cortical thickness, and gray matter volume in 34 cortical areas between patient and an age-, sex-, and education-matched control group. Anatomical connectivity between these cortical areas was investigated by a structural covariance analysis. Visual screening-, and behavioral results revealed that the patient's impairments were predominantly in visuo-spatial attention. Consistent with this, VBM and structural connectivity results revealed significant structural changes in cortical regions subserving attentional functions. We conclude that the LAMC3 gene mutation affects cortical areas beyond the occipital lobe and primarily those visual functions that involve heavily distributed networks - such as visuo-spatial attention.Item Open Access Identification of a novel missense mutation in RAD51 in a large family with congenital mirror movements(American Society of Human Genetics, 2012-11) Onat, Onur Emre; Gülsüner, Süleyman; Bilgen, R.; Dal, G. M.; Bilguvar, K.; Boyacı, Hüseyin; Doerschner, Katja; Uysal, H.; Günel, M.; Özçelik, TayfunCongenital mirror movements (CMM) are a rare and heterogeneous group of disorders characterized by involuntary contralateral movements of mainly the upper extremities during intentional movements on the opposite side. Isolated cases are usually familial and suggest autosomal dominant inheritance with incomplete penetrance. In two chromosome 18 linked families, causative mutations were identified in DCC (Science 328:592, 2010; MRMV1; MIM:157600). Here, we describe a three-generation consanguineous Turkish family with six members affected by CMM. Linkage analysis with a dominant model and 90 percent penetrance parameters resulted in peaks on 15q13.3-q21.1, 15q26.2, and 19q12 with maximum multipoint LOD scores of 3.6, 2.6, and 2.6, respectively. However, a region of homozygosity segregating with the phenotype was not observed, and thus excluded the possibility of recessive inheritance of the disease allele in this consanguineous family. Whole-exome sequencing of an affected individual uncovered 7 coding, 33 intronic and 3 intergenic novel variants located within the three linkage intervals, which were filtered against the dbSNP132 dataset. Segregation analysis, population filtering using 1000 genomes and EVS data sets, and conservation considerations using prediction tools revealed a novel missense mutation (c.404C>T [p.T134N], RefSeq accession number NM_002875) in exon 5 of RAD51 (MIM:179617), consistent with the dominant inheritance of the disease allele in the family. The mutation resides in the highly conserved AAA (ATPases associated with diverse cellular activities) domain of the protein, and it was not observed in 436 chromosomes from healthy individuals coming from a geographical matched region. Recently, truncating mutations in RAD51 were identified in two families with CMM (Am J Hum Genet 90:301,2012; MRMV2; MIM:614508). Our findings support the totally unexpected role of RAD51 in neurodevelopment and further suggest that alterations of this gene may lead to neurological phenotypes.Item Open Access Kandinsky or me? How free is the eye of the Beholder in abstract art?(Sage Publications, 2019-09) Braun, D. I.; Doerschner, KatjaWe investigated in “art-naïve” German and Chinese participants the perception of color and spatial balance in abstract art. For color perception, we asked participants (a) to adjust the color of a single element in 24 paintings according to their liking and (b) to indicate whether they preferred their version of the painting or the original. For spatial perception, we asked participants (a) to determine the “balance point” of an artwork and (b) to indicate their preferences for the original or left-right reversed orientation of previously seen and unfamiliar paintings. Results of the color experiments suggest that, even though the interactive task was of a rather open-ended nature, observers’ color adjustments were not random but systematically influenced by each painting’s color palette. Overall, participants liked their own color choices about as much as the original composition. Results of the spatial experiments reveal a remarkable consistency between participants in their balance point settings. The perceived lateral position of the balance point systematically affected the left-right orientation preference for a given painting. We conclude that “art-naïve” observers are sensitive to the composition of colors and spatial structures in abstract art and are influenced by their cultural backgrounds when experiencing abstract paintings.Item Open Access The look and feel of soft are similar across different softness dimensions(Association for Research in Vision and Ophthalmology, 2021-09-28) Cavdan, Müge; Drewing, Knut; Doerschner, KatjaThe softness of objects can be perceived through several senses. For instance, to judge the softness of a cat's fur, we do not only look at it, we often also run our fingers through its coat. Recently, we have shown that haptically perceived softness covaries with the compliance, viscosity, granularity, and furriness of materials (Dovencioglu, Üstün, Doerschner, & Drewing, 2020). However, it is unknown whether vision can provide similar information about the various aspects of perceived softness. Here, we investigated this question in an experiment with three conditions: in the haptic condition, blindfolded participants explored materials with their hands, in the static visual condition participants were presented with close-up photographs of the same materials, and in the dynamic visual condition participants watched videos of the hand-material interactions that were recorded in the haptic condition. After haptically or visually exploring the materials, participants rated them on various attributes. Our results show a high overall perceptual correspondence among the three experimental conditions. With a few exceptions, this correspondence tended to be strongest between haptic and dynamic visual conditions. These results are discussed with respect to information potentially available through the senses, or through prior experience, when judging the softness of materials.Item Open Access A motion feature-based algorithm for the detection of specular objects in natural scenes(Sage Publications, 2012-09) Doerschner, Katja; Yılmaz, ÖzgürSuccessful identification of specularities in an image can be crucial for an artificial vision system when extracting the semantic content of an image or while interacting with the environment. We developed an algorithm that relies on scale and rotation invariant feature extraction techniques and uses motion cues to detect and localize specular surfaces in an office scene. Appearance change in feature vectors is used to quantify the appearance distortion on specular surfaces, which has previously been shown to be a powerful indicator for shininess (Doerschner et al, 2011 Current Biology 21(23), 2010–2016). The algorithm combines epipolar deviations (Swaminathan et al, 2002 ECCV167–172) and appearance distortion cues and succeeds in localizing specular objects across a wide range of camera motions and speeds, object sizes and shapes, and performs well under image noise and blur conditions.Item Open Access Object rigidity and reflectivity identification based on motion analysis(IEEE, 2010) Zang, D.; Schrater P.R.; Doerschner, KatjaRigidity and reflectivity are important properties of objects, identifying these properties is a fundamental problem for many computer vision applications like motion and tracking. In this paper, we extend our previous work to propose a motion analysis based approach for detecting the object's rigidity and reflectivity. This approach consists of two steps. The first step aims to identify object rigidity based on motion estimation and optic flow matching. The second step is to classify specular rigid and diffuse rigid objects using structure from motion and Procrustes analysis. We show how rigid bodies can be detected without knowing any prior motion information by using a mutual information based matching method. In addition, we use a statistic way to set thresholds for rigidity classification. Presented results demonstrate that our approach can efficiently classify the rigidity and reflectivity of an object. © 2010 IEEE.Item Open Access Rapid classification of surface reflectance from image velocities(Springer, Berlin, Heidelberg, 2009) Doerschner, Katja; Kersten, D.; Schrater P.We propose a method for rapidly classifying surface reflectance directly from the output of spatio-temporal filters applied to an image sequence of rotating objects. Using image data from only a single frame, we compute histograms of image velocities and classify these as being generated by a specular or a diffusely reflecting object. Exploiting characteristics of material-specific image velocities we show that our classification approach can predict the reflectance of novel 3D objects, as well as human perception. © 2009 Springer Berlin Heidelberg.Item Open Access Rapid inference of object rigidity and reflectance using optic flow(Springer, Berlin, Heidelberg, 2009) Zang, D.; Doerschner, Katja; Schrater P.R.Rigidity and reflectance are key object properties, important in their own rights, and they are key properties that stratify motion reconstruction algorithms. However, the inference of rigidity and reflectance are both difficult without additional information about the object's shape, the environment, or lighting. For humans, relative motions of object and observer provides rich information about object shape, rigidity, and reflectivity. We show that it is possible to detect rigid object motion for both specular and diffuse reflective surfaces using only optic flow, and that flow can distinguish specular and diffuse motion for rigid objects. Unlike nonrigid objects, optic flow fields for rigid moving surfaces are constrained by a global transformation, which can be detected using an optic flow matching procedure across time. In addition, using a Procrustes analysis of structure from motion reconstructed 3D points, we show how to classify specular from diffuse surfaces. © 2009 Springer Berlin Heidelberg.Item Open Access Recessive LAMC3 mutations cause malformations of occipital cortical development(Nature Publishing Group, 2011) Barak, T.; Kwan, K. Y.; Louvi, A.; Demirbilek, V.; Saygi, S.; Tüysüz, B.; Choi, M.; Boyacı, Hüseyin; Doerschner, Katja; Zhu, Y.; Kaymakçalan, H.; Yilmaz, S.; Bakircioglu, M.; Çağlayan, A. O.; Öztürk, A.K.; Yasuno, K.; Brunken W. J.; Atalar, Ergin; Yalçnkaya, C.; Dinçer, A.; Bronen, R. A.; Mane, S.; Özçelik, Tayfun; Lifton, R. P.; Šestan, N.; Bilgüvar, K.; Günel, M.The biological basis for regional and inter-species differences in cerebral cortical morphology is poorly understood. We focused on consanguineous Turkish families with a single affected member with complex bilateral occipital cortical gyration abnormalities. By using whole-exome sequencing, we initially identified a homozygous 2-bp deletion in LAMC3, the laminin 33 gene, leading to an immediate premature termination codon. In two other affected individuals with nearly identical phenotypes, we identified a homozygous nonsense mutation and a compound heterozygous mutation. In human but not mouse fetal brain, LAMC3 is enriched in postmitotic cortical plate neurons, localizing primarily to the somatodendritic compartment. LAMC3 expression peaks between late gestation and late infancy, paralleling the expression of molecules that are important in dendritogenesis and synapse formation. The discovery of the molecular basis of this unusual occipital malformation furthers our understanding of the complex biology underlying the formation of cortical gyrations.