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Zum Thema Kategorisierung. Als Einführung relevante Passūs eines Resümées eines eigenen Aufsatzes (zum Thema Wortarten) “As do animals, humans need categories for cognition. Without the existence of such categories, orientation in a manifold and most variegated world would not be possible. Categories allow us to recognize invariance in a highly variable environment. To a large extent, as humans we are free to create such categories – they reflect, among other things, our cultural interests (e.g., categories in law or categories used in noun classification languages). […] Nonetheless, there should be zones of overlap or a common core. It is due to phylogeny. We categorize the observed outside world as for example individuals with intentions and roles, actions with possible states or enunciations that have a relation to reality (thus giving rise to mood as a grammatical category). Partly, this common background is reflected by the ontogeny of acquiring a first language. We have to acquire first the permanence of an object, i.e., the identity existing between seemingly different apparitions of the same object. While this process may be associated with a projection zone of our visual system located in the inferior temporal lobes in both hemispheres of our brain, in a later phase we learn to recognize an identity among different objects or phenomena – that is we learn to truly categorize. This faculty has a strong link to the anterior parts of our frontal lobes. Moreover, all existing evidence suggests that this faculty does not only concern visible or palpable objects like birds, stones or trees. In primates, it also extends to categorization on a more abstract level – for instance of the intentional actions and transitive movements (grasping of an apple) already mentioned. […]” 1: Anim Cogn. 2008 Feb 8 [Epub ahead of print] Ultra-rapid categorisation in non-human primates. Girard P, Jouffrais C, Kirchner CH. Université de Toulouse, CerCo, UPS, 31062, Toulouse, France, [email protected]. The visual system of primates is remarkably efficient for analysing information about objects present in complex natural scenes. Recent work has demonstrated that they perform this at very high speeds. In a choice saccade task, human subjects can initiate a first reliable saccadic eye movement response to a target (the image containing an animal) in only 120 ms after image onset. Such fast responses impose severe time constraints if one considers neuronal responses latencies in high-level ventral areas of the macaque monkey. The question then arises: are non-human primates able to perform the task? Two rhesus macaque monkeys (Macaca mulatta) were trained to perform the same forced-choice categorization task as the one used in humans. Both animals performed the task with a high accuracy and generalized to new stimuli that were introduced everyday: accuracy levels were comparable both with new and well-known images (84% vs. 94%). More importantly, reaction times were extremely fast (minimum reaction time 100 ms and median reaction time 152 ms). Given that typical single units onset times in Inferotemporal cortex (IT) are about as long as the shortest behavioural responses measured here, we conclude that visual processing involved in ultra rapid categorisations might be based on rather simple shape cue analysis that can be achieved in areas such as extrastriate cortical area V4. The present paper demonstrates for the first time, that rhesus macaque monkeys (Macaca mulatta) are able to match human performance in a forced-choice saccadic categorisation task of animals in natural scenes. PMID: 18259787 [PubMed - as supplied by publisher] 2: Neurosci Res. 2008 May;61(1):70-8. Epub 2008 Feb 6. Categorization of biologically significant objects, food and gender, in rhesus monkeys I. Behavioral study. Inoue T, Hasegawa T, Takara S, Lukáts B, Mizuno M, Aou S. Department of Brain Sciences and Engineering, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Kitakyushu, Fukuoka 808-0196, Japan. Macaque monkeys have a highly evolved visual system comparable to that of humans. One of the important visual functions is performing discriminations among biologically significant objects such as food or heterosexual partners. In the present study, we examined whether rhesus monkeys could categorize two-dimensional images related to food or gender using a visual discrimination task. Three rhesus monkeys were trained to make distinctions of food from non-food items, and between male and female monkeys, using 60 or more different pictures of each category. After more than 9 months of training, the monkeys discriminated a variety of foods from non-food and different males from females with more than 80% accuracy, even when the stimuli were used for the first time or presented only once in a session. The proportion of correct responses and response latencies showed better performance in discrimination of food/non-food than that of gender. The results suggest that rhesus monkeys are able to perform visual discrimination of highly abstract biologically significant categories with better performance in a food-related category than a gender-related one, using two-dimensional visual information. PMID: 18329121 [PubMed - in process] 3: Proc Biol Sci. 2007 Sep 7;274(1622):2069-76. Individuation and holistic processing of faces in rhesus monkeys. Dahl CD, Logothetis NK, Hoffman KL. Max Planck Institute for Biological Cybernetics, Tübingen 72012, Germany. Despite considerable evidence that neural activity in monkeys reflects various aspects of face perception, relatively little is known about monkeys' face processing abilities. Two characteristics of face processing observed in humans are a subordinate-level entry point, here, the default recognition of faces at the subordinate, rather than basic, level of categorization, and holistic effects, i.e. perception of facial displays as an integrated whole. The present study used an adaptation paradigm to test whether untrained rhesus macaques (Macaca mulatta) display these hallmarks of face processing. In experiments 1 and 2, macaques showed greater rebound from adaptation to conspecific faces than to other animals at the individual or subordinate level. In experiment 3, exchanging only the bottom half of a monkey face produced greater rebound in aligned than in misaligned composites, indicating that for normal, aligned faces, the new bottom half may have influenced the perception of the whole face. Scan path analysis supported this assertion: during rebound, fixation to the unchanged eye region was renewed, but only for aligned stimuli. These experiments show that macaques naturally display the distinguishing characteristics of face processing seen in humans and provide the first clear demonstration that holistic information guides scan paths for conspecific faces. Publication Types: Research Support, Non-U.S. Gov't PMID: 17609192 [PubMed - indexed for MEDLINE] PMCID: PMC1919404 4: J Neurophysiol. 2007 Jun;97(6):4296-309. Epub 2007 Apr 11. Object category structure in response patterns of neuronal population in monkey inferior temporal cortex. Kiani R, Esteky H, Mirpour K, Tanaka K. Research Group for Brain and Cognitive Sciences, School of Medicine, Shaheed Beheshti University, P.O. Box 19835-181, Tehran, Iran. Our mental representation of object categories is hierarchically organized, and our rapid and seemingly effortless categorization ability is crucial for our daily behavior. Here, we examine responses of a large number (>600) of neurons in monkey inferior temporal (IT) cortex with a large number (>1,000) of natural and artificial object images. During the recordings, the monkeys performed a passive fixation task. We found that the categorical structure of objects is represented by the pattern of activity distributed over the cell population. Animate and inanimate objects created distinguishable clusters in the population code. The global category of animate objects was divided into bodies, hands, and faces. Faces were divided into primate and nonprimate faces, and the primateface group was divided into human and monkey faces. Bodies of human, birds, and four-limb animals clustered together, whereas lower animals such as fish, reptile, and insects made another cluster. Thus the cluster analysis showed that IT population responses reconstruct a large part of our intuitive category structure, including the global division into animate and inanimate objects, and further hierarchical subdivisions of animate objects. The representation of categories was distributed in several respects, e.g., the similarity of response patterns to stimuli within a category was maintained by both the cells that maximally responded to the category and the cells that responded weakly to the category. These results advance our understanding of the nature of the IT neural code, suggesting an inherently categorical representation that comprises a range of categories including the amply investigated face category. Publication Types: Research Support, Non-U.S. Gov't PMID: 17428910 [PubMed - indexed for MEDLINE] 5: J Neurophysiol. 2007 Apr;97(4):2900-16. Epub 2007 Jan 24. Properties of shape tuning of macaque inferior temporal neurons examined using rapid serial visual presentation. De Baene W, Premereur E, Vogels R. Laboratorium voor Neuro- en Psychofysiologie, K.U. Leuven Medical School, Campus Gasthuisberg, Herestraat 49, bus 1021, Leuven, B-3000, Belgium. We used rapid serial visual presentation (RSVP) to examine the tuning of macaque inferior temporal cortical (IT) neurons to five sets of 25 shapes each that varied systematically along predefined shape dimensions. A comparison of the RSVP technique using 100-ms presentations with that using a longer duration showed that shape preference can be determined with RSVP. Using relatively complex shapes that vary along relatively simple shape dimensions, we found that the large majority of neurons preferred extremes of the shape configuration, extending the results of a previous study using simpler shapes and a standard testing paradigm. A population analysis of the neuronal responses demonstrated that, in general, IT neurons can represent the similarities among the shapes at an ordinal level, extending a previous study that used a smaller number of shapes and a categorization task. However, the same analysis showed that IT neurons do not faithfully represent the physical similarities among the shapes. The responses to the two-part shapes could be predicted, virtually perfectly, from the average of the responses to the respective two parts presented in isolation. We also showed that IT neurons adapt to the stimulus distribution statistics. The neural shape discrimination improved when a shape set with a narrower stimulus range was presented, suggesting that the tuning of IT neurons is not static but adapts to the stimulus distribution statistics, at least when stimulated at a high rate with a restricted set of stimuli. Publication Types: Research Support, Non-U.S. Gov't PMID: 17251368 [PubMed - indexed for MEDLINE] 6: J Neurosci. 2006 Oct 11;26(41):10524-35. Related Articles, Links Neuronal responses to object images in the macaque inferotemporal cortex at different stimulus discrimination levels. Suzuki W, Matsumoto K, Tanaka K. Cognitive Brain Mapping Laboratory, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan. We can discriminate visual objects at multiple levels, from coarse categorization to individual identification. It is not known how the brain adapts to the varying levels of discrimination required in different behavioral contexts. In the present study, we investigated whether the stimulus selectivity of neuronal responses in the monkey inferotemporal cortex, which is the final unimodal stage in the ventral visual pathway, changes with the varying levels of discrimination required for different task conditions. Responses of each inferotemporal cell to the same set of nine object images were examined in two different task conditions. The task alternated between coarse and fine discriminations in the first experiment, and the rule alternated between categorization and individual object identification in the second experiment. Despite these changes in the task requirements and the resulting differences in the monkeys' behavior, we found that the responses of inferotemporal cells were largely unchanged in both experiments. Our results suggest that representation of object images in the inferotemporal cortex is stable and rather insensitive to these kinds of shifts in behavioral context. Neuronal adaptations to behavioral context may occur downstream of the inferotemporal cortex. Publication Types: Comparative Study Research Support, Non-U.S. Gov't PMID: 17035537 [PubMed - indexed for MEDLINE] 7: Nature. 2006 Sep 7;443(7107):85-8. Epub 2006 Aug 27. Related Articles, Links Experience-dependent representation of visual categories in parietal cortex. Freedman DJ, Assad JA. Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, Massachusetts 02115, USA. [email protected] Categorization is a process by which the brain assigns meaning to sensory stimuli. Through experience, we learn to group stimuli into categories, such as 'chair', 'table' and 'vehicle', which are critical for rapidly and appropriately selecting behavioural responses. Although much is known about the neural representation of simple visual stimulus features (for example, orientation, direction and colour), relatively little is known about how the brain learns and encodes the meaning of stimuli. We trained monkeys to classify 360 degrees of visual motion directions into two discrete categories, and compared neuronal activity in the lateral intraparietal (LIP) and middle temporal (MT) areas, two interconnected brain regions known to be involved in visual motion processing. Here we show that neurons in LIP--an area known to be centrally involved in visuo-spatial attention, motor planning and decision-making-robustly reflect the category of motion direction as a result of learning. The activity of LIP neurons encoded directions of motion according to their category membership, and that encoding shifted after the monkeys were retrained to group the same stimuli into two new categories. In contrast, neurons in area MT were strongly direction selective but carried little, if any, explicit category information. This indicates that LIP might be an important nexus for the transformation of visual direction selectivity to more abstract representations that encode the behavioural relevance, or meaning, of stimuli. Publication Types: Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't PMID: 16936716 [PubMed - indexed for MEDLINE] Publication Types: Research Support, Non-U.S. Gov't PMID: 16513005 [PubMed - indexed for MEDLINE] 9: Proc Natl Acad Sci U S A. 2004 Mar 2;101(9):3184-9. Epub 2004 Feb 20. Related Articles, Links Categorization in the monkey hippocampus: a possible mechanism for encoding information into memory. Hampson RE, Pons TP, Stanford TR, Deadwyler SA. Department of Physiology and Pharmacology, Wake Forest University School of Medicine, WinstonSalem, NC 27157, USA. The mammalian hippocampus processes sensory information into memory. The neurobiological basis of this representation, as well as the type of information that is encoded, is central to understanding how memories are formed. Normally, there is an infinite amount of information that could be encoded for any given stimulus. Thus, the question arises as to how the hippocampus selects and encodes features of a given stimulus. Here, we show that neurons in the hippocampus of the monkey appear to categorize types of visual stimuli presented in a delayed-match-to-sample memory task. By extracting unique combinations of features, these category cells are able to encode aspects of behaviorally important images instead of encoding all visual details. The subject is then able to rapidly select an appropriate response to that stimulus when distracting stimuli are presented simultaneously, thereby facilitating performance. Moreover, across animals, this specific type of encoding differed considerably. Just as in humans, different monkeys attended to and selected different aspects of the same stimulus image, most likely reflecting different histories, strategies, and expectations residing within individual hippocampal networks. Publication Types: Research Support, U.S. Gov't, Non-P.H.S. Research Support, U.S. Gov't, P.H.S. PMID: 14978264 [PubMed - indexed for MEDLINE] PMCID: PMC365764 10: Behav Brain Res. 2004 Feb 4;149(1):1-7. Related Articles, Links Visual categorization and the inferior temporal cortex. Sigala N. MRC-Cognition and Brain Sciences Unit, 15 Chaucer Road, CB2 2EF, Cambridge, UK. [email protected] We investigated the effects of categorization on the representation of stimulus features in combined psychophysical-electrophysiological experiments. We used parameterized line drawings of faces and fish as stimuli, and we varied the relevance of the different features for the categorization task. The psychophysical and electrophysiological data support an exemplar-based framework for visual object recognition. We recorded from visual neurons in the anterior inferior temporal (IT) cortex of macaque monkeys, while they were performing a categorization task. The visual neurons did not respond selectively to one stimulus set, or to one category. The majority of the anterior IT feature selective neurons were tuned for features that were diagnostic for the categorization task. We argue that this fine-tuning of the neurons reflects the perceptual sensitization to the diagnostic features. Publication Types: Clinical Trial Comparative Study Research Support, Non-U.S. Gov't PMID: 14739004 [PubMed - indexed for MEDLINE] : J Vis. 2008 Feb 22;8(2):9.1-15. Related Articles, Links Object features used by humans and monkeys to identify rotated shapes. Nielsen KJ, Logothetis NK, Rainer G. Max Planck Institute for Biological Cybernetics, Tübingen, Germany. [email protected] Humans and rhesus monkeys can identify shapes that have been rotated in the picture plane. Recognition of rotated shapes can be as efficient as recognition of upright shapes. Here we investigate whether subjects showing view-invariant performance use the same object features to identify upright and rotated versions of a shape. We find marked differences between humans and monkeys. While humans tend to use the same features independent of shape orientation, monkeys use unique features for each orientation. Humans are able to generalize to a greater degree across orientation changes than rhesus monkey observers, who tend to relearn separate problems at each orientation rather than flexibly apply previously learned knowledge to novel problems. Publication Types: Comparative Study Research Support, Non-U.S. Gov't PMID: 18318635 [PubMed - indexed for MEDLINE] 1: Neuron. 2007 Aug 2;55(3):341-4. Related Articles, Links Comment on: Neuron. 2007 Aug 2;55(3):507-20. Appearance isn't everything: news on object representation in cortex. Riesenhuber M. Department of Neuroscience, Georgetown University Medical Center, Research Building Room WP12, 3970 Reservoir Road, Northwest, Washington, D.C. 20007, USA. [email protected] How objects are represented in the visual system is one of the big questions in cognitive neuroscience. In this issue of Neuron, Mahon and colleagues present an intriguing study that suggests that properties of objects other than shape can influence the arrangement of object selectivities in visual areas. In the process, the study also points to important caveats regarding the ability of standard fMRI studies to make inferences about neuronal selectivity. Publication Types: Comment Editorial Review PMID: 17678848 [PubMed - indexed for MEDLINE]