Kagan, Igor

[["dc.bibliographiccitation.firstpage","125"],["dc.bibliographiccitation.issue","7"],["dc.bibliographiccitation.journal","Journal of Vision"],["dc.bibliographiccitation.lastpage","125a"],["dc.bibliographiccitation.volume","2"],["dc.contributor.author","Max, D."],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Gur, Moshe"],["dc.date.accessioned","2018-02-08T10:53:58Z"],["dc.date.available","2018-02-08T10:53:58Z"],["dc.date.issued","2010"],["dc.description.abstract","Although it has long been routine to classify neurons in V1 of anesthetized animals into simple and complex categories, it has not been easy to apply the original criteria to alert animals because of the omnipresent eye movements. In our experiments, effects of eye movements were minimized by compensating for them and by data processing. Activating regions (ARs) of 228 cells in parafoveal V1 of alert monkeys were mapped with increment and decrement moving and flashing bars. Most cells had two ARs, one responsive to increments (INC) and one responsive to decrements (DEC). The majority of the cells (78%, “duplex”) had completely or partially overlapping INC and DEC ARs. Simple cells with minimal spatial overlap of INC and DEC ARs comprised 14% of our sample. 114 neurons were also studied with drifting gratings of varied spatial frequencies and window widths. Responses to the stimulus condition generating the maximal harmonic (F0 or F1) and the one generating the maximal relative modulation, RM (F1/F0), were analyzed. Most duplex cells responded with considerable modulation at the stimulus temporal frequency in both the maximal harmonic condition (mean RM 0.60±0.41 to 0.92±0.45) and the maximal RM condition (RM = 0.79±0.43 to 1.12±0.46), with the range dependent on the method of correcting for eye movements. A subset of duplex cells had RM>1, the traditional criterion for identifying simple cells, even though variations in stimulus conditions evoked clearly nonlinear behavior. There was little or no correlation between the degree of overlap of INC and DEC ARs and the value of RM, indicating that neither linearity nor the spatial organization of receptive fields can be predicted reliably from RM values. Our results suggest that nonlinear duplex cells represent the largest neuronal class in primate V1, whereas the linear simple cells are less numerous, more homogeneous, and probably preferentially associated with the magnocellular pathway. Support: NIH R01 EY12243, Technion VPR Funds 130347; 130358."],["dc.identifier.doi","10.1167/2.7.125"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/12059"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.relation.eissn","1534-7362"],["dc.title","Receptive fields and quasi-linear response modulation in V1 of alert macaques"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","557"],["dc.bibliographiccitation.journal","NeuroImage"],["dc.bibliographiccitation.lastpage","569"],["dc.bibliographiccitation.volume","179"],["dc.contributor.author","Hammerschmidt, Wiebke"],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Kulke, Louisa"],["dc.contributor.author","Schacht, Annekathrin"],["dc.date.accessioned","2020-12-10T15:20:29Z"],["dc.date.available","2020-12-10T15:20:29Z"],["dc.date.issued","2018"],["dc.identifier.doi","10.1016/j.neuroimage.2018.06.055"],["dc.identifier.issn","1053-8119"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/72681"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Implicit reward associations impact face processing: Time-resolved evidence from event-related brain potentials and pupil dilations"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","40"],["dc.bibliographiccitation.journal","Cognition"],["dc.bibliographiccitation.lastpage","52"],["dc.bibliographiccitation.volume","176"],["dc.contributor.author","Moreira, Caio M."],["dc.contributor.author","Rollwage, Max"],["dc.contributor.author","Kaduk, Kristin"],["dc.contributor.author","Wilke, Melanie"],["dc.contributor.author","Kagan, Igor"],["dc.date.accessioned","2020-12-10T14:23:11Z"],["dc.date.available","2020-12-10T14:23:11Z"],["dc.date.issued","2018"],["dc.identifier.doi","10.1016/j.cognition.2018.02.026"],["dc.identifier.issn","0010-0277"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/71863"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Post-decision wagering after perceptual judgments reveals bi-directional certainty readouts"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1109"],["dc.bibliographiccitation.issue","14"],["dc.bibliographiccitation.journal","NeuroReport"],["dc.bibliographiccitation.lastpage","1115"],["dc.bibliographiccitation.volume","25"],["dc.contributor.author","Przybyszewski, Andrzej W."],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Snodderly, D. M."],["dc.date.accessioned","2017-09-07T11:47:54Z"],["dc.date.available","2017-09-07T11:47:54Z"],["dc.date.issued","2014"],["dc.description.abstract","Although neuronal responses in behaving monkeys are typically studied while the monkey fixates straight ahead, it is known that eye position modulates responses of visual neurons. The modulation has been found to enhance neuronal responses when the receptive field is placed in the straight-ahead position for neurons receiving input from the peripheral but not the central retina. We studied the effect of eye position on the responses of V1 complex cells receiving input from the central retina (1.1–5.7° eccentricity) while minimizing the effect of fixational eye movements. Contrast response functions were obtained separately with drifting light and dark bars. Data were fit with the Naka–Rushton equation: r(c)=Rmax×cn/(cn+c50n)+s, where r(c) is mean spike rate at contrast c, Rmax is the maximum response, c50 is the contrast that elicits half of Rmax, and s is the spontaneous activity. Contrast sensitivity as measured by c50 was not affected by eye position. For dark bars, there was a statistically significant decline in the normalized Rmax with increasing deviation from straight ahead. Data for bright bars showed a similar trend with a less rapid decline. Our results indicate that neurons representing the central retina show a bias for the straight-ahead position resulting from modulation of the response gain without an accompanying modulation of contrast sensitivity. The modulation is especially obvious for dark stimuli, which might be useful for directing attention to hazardous situations such as dark holes or shadows concealing important objects."],["dc.identifier.doi","10.1097/wnr.0000000000000235"],["dc.identifier.gro","3150749"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7539"],["dc.language.iso","en"],["dc.notes.status","public"],["dc.relation.issn","0959-4965"],["dc.subject","behaving monkey; contrast; eye movements; eye position; primary visual cortex; receptive fields"],["dc.title","Primate area V1: largest response gain for receptive fields in the straight-ahead direction"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","7933"],["dc.bibliographiccitation.issue","17"],["dc.bibliographiccitation.journal","Proceedings of the National Academy of Sciences"],["dc.bibliographiccitation.lastpage","7938"],["dc.bibliographiccitation.volume","107"],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Iyer, Asha"],["dc.contributor.author","Lindner, Axel"],["dc.contributor.author","Andersen, Richard A."],["dc.date.accessioned","2017-09-07T11:47:54Z"],["dc.date.available","2017-09-07T11:47:54Z"],["dc.date.issued","2010"],["dc.description.abstract","Contralateral hemispheric representation of sensory inputs (the right visual hemifield in the left hemisphere and vice versa) is a fundamental feature of primate sensorimotor organization, in particular the visuomotor system. However, many higher-order cognitive functions in humans show an asymmetric hemispheric lateralization—e.g., right brain specialization for spatial processing—necessitating a convergence of information from both hemifields. Electrophysiological studies in monkeys and functional imaging in humans have investigated space and action representations at different stages of visuospatial processing, but the transition from contralateral to unified global spatial encoding and the relationship between these encoding schemes and functional lateralization are not fully understood. Moreover, the integration of data across monkeys and humans and elucidation of interspecies homologies is hindered, because divergent findings may reflect actual species differences or arise from discrepancies in techniques and measured signals (electrophysiology vs. imaging). Here, we directly compared spatial cue and memory representations for action planning in monkeys and humans using event-related functional MRI during a working-memory oculomotor task. In monkeys, cue and memory-delay period activity in the frontal, parietal, and temporal regions was strongly contralateral. In putative human functional homologs, the contralaterality was significantly weaker, and the asymmetry between the hemispheres was stronger. These results suggest an inverse relationship between contralaterality and lateralization and elucidate similarities and differences in human and macaque cortical circuits subserving spatial awareness and oculomotor goal-directed actions."],["dc.identifier.doi","10.1073/pnas.1002825107"],["dc.identifier.gro","3150759"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7549"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.relation.issn","0027-8424"],["dc.title","Space representation for eye movements is more contralateral in monkeys than in humans"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","21"],["dc.bibliographiccitation.issue","9"],["dc.bibliographiccitation.journal","Journal of Vision"],["dc.bibliographiccitation.lastpage","21a"],["dc.bibliographiccitation.volume","3"],["dc.contributor.author","Gur, Moshe"],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Eye, Schepens"],["dc.contributor.author","Snodderly, Max D."],["dc.date.accessioned","2018-02-08T11:07:35Z"],["dc.date.available","2018-02-08T11:07:35Z"],["dc.date.issued","2010"],["dc.description.abstract","Area V1 is known for its neural cell density and intricate histology. Physiological recordings, however, often are not integrated into this complex anatomy. We have previously shown, in alert monkeys, that physiological properties of single cells reflect an alternating arrangement of anatomical layers. Here we report how orientation selectivity is related to the cortical layers and to the cell properties of spontaneous activity, classical receptive field (CRF) size, and spatial organization. Recordings were made from single cells in area V1 of alert monkeys performing a fixation task. The cells' spatial organization was studied with drifting increment and decrement bars while compensating for fixational drift. Orientation selectivity was measured by the orientation tuning curve bandwidth and by circular variance. Orientation selectivity by either measure was clearly correlated with CRF size and spontaneous activity but not with overlap of increment and decrement zones (Simple/Complex) or with relative modulation in response to sinusoidal gratings. The former 3 measures were strongly predicted by the layer of origin such that small CRFs, low spontaneous activity, and a high degree of orientation selectivity were found in the output layers 2/3, 4B and 5 while the reverse was true for the input layers 4A, 4C and 6. We conclude that the conjunction of these physiological measures with their anatomical locations reflect interactions between excitatory and inhibitory mechanisms specific to each lamina. When excitation is stronger than inhibition, large CRFs, high spontaneous activity and a low degree of orientation tuning are found. When inhibition becomes dominant, CRFs shrink, spontaneous activity almost disappears and orientation selectivity is high."],["dc.identifier.doi","10.1167/3.9.21"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/12060"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.relation.eissn","1534-7362"],["dc.title","Orientation selectivity in V1 of alert monkeys"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.journal","Neuroscience Letters"],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Gur, Moshe"],["dc.contributor.author","Snodderly, D.M."],["dc.date.accessioned","2018-02-08T13:22:27Z"],["dc.date.available","2018-02-08T13:22:27Z"],["dc.date.issued","1999"],["dc.description.abstract","In alert monkeys, as in humans, small eye movements- tremor, drift and small saccades- occur during fixation periods. These movements constantly shift retinal image, thusmodifying the stimulus-generated responses. We analyzed the effects of eye movementson responses of simple and duplex (“complex-like”) cells to drifting sinusoidal gratings.Eye positions were recorded from monkeys trained to perform a fixation task. Duringfixation extracellular responses of V1 neurons in parafoveal region and eye positionswere recorded. From the eye position records we identified epochs of fast movements,slow drifts and stable fixation and compared patterns of neuronal firing during thevarious eye movement phases. Neuronal responses were sensitive to both fast and sloweye movements that occurred during grating presentations. In the case when no periodsof eye movements were excluded from the records, averaging across many repetitionsof the grating temporal cycle resulted in smearing of the response time course, althougheach individual sweep produced a modulated response. Eye movements affect neuronalresponses in a way that depends on eye movement trajectory, stimulus parameters andreceptive field properties. In particular, eye movements caused shifts in response phaseand/or duration, produced spurious firing bursts or caused cells to miss a response. Ourresults suggest that fixational eye movements account for variations in neuronalresponses over successive grating presentations and that these movements should beconsidered in analysis of grating-evoked activity"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/12067"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.title","The influence of fixational eye movements on grating-elicited responses of V1 neurons"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1270"],["dc.bibliographiccitation.issue","8"],["dc.bibliographiccitation.journal","Journal of Cognitive Neuroscience"],["dc.bibliographiccitation.lastpage","1283"],["dc.bibliographiccitation.volume","25"],["dc.contributor.author","Wilke, Melanie"],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Andersen, Richard A."],["dc.date.accessioned","2017-09-07T11:43:44Z"],["dc.date.available","2017-09-07T11:43:44Z"],["dc.date.issued","2013"],["dc.description.abstract","The ability to selectively process visual inputs and to decide between multiple movement options in an adaptive manner is critical for survival. Such decisions are known to be influenced by factors such as reward expectation and visual saliency. The dorsal pulvinar connects to a multitude of cortical areas that are involved in visuospatial memory and integrate information about upcoming eye movements with expected reward values. However, it is unclear whether the dorsal pulvinar is critically involved in spatial memory and reward-based oculomotor decision behavior. To examine this, we reversibly inactivated the dorsal portion of the pulvinar while monkeys performed a delayed memory saccade task that included choices between equally or unequally rewarded options. Pulvinar inactivation resulted in a delay of saccade initiation toward memorized contralesional targets but did not affect spatial memory. Furthermore, pulvinar inactivation caused a pronounced choice bias toward the ipsilesional hemifield when the reward value in the two hemifields was equal. However, this choice bias could be alleviated by placing a high reward target into the contralesional hemifield. The bias was less affected by the manipulation of relative visual saliency between the two competing targets. These results suggest that the dorsal pulvinar is involved in determining the behavioral desirability of movement goals while being less critical for spatial memory and reward processing."],["dc.identifier.doi","10.1162/jocn_a_00399"],["dc.identifier.gro","3151624"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/8437"],["dc.notes.status","public"],["dc.notes.submitter","chake"],["dc.relation.issn","0898-929X"],["dc.title","Effects of Pulvinar Inactivation on Spatial Decision-making between Equal and Asymmetric Reward Options"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","204"],["dc.bibliographiccitation.lastpage","219"],["dc.bibliographiccitation.volume","11454"],["dc.contributor.author","Unakafov, Anton M."],["dc.contributor.author","Schultze-Gerlach, Thomas"],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Moeller, Sebastian"],["dc.contributor.author","Gail, Alexander"],["dc.contributor.author","Treue, Stefan"],["dc.contributor.author","Eule, Stephan"],["dc.contributor.author","Wolf, Fred"],["dc.contributor.editor","Kaufmann, P."],["dc.contributor.editor","Castillo, P."],["dc.date.accessioned","2019-07-30T07:45:17Z"],["dc.date.available","2019-07-30T07:45:17Z"],["dc.date.issued","2019"],["dc.description.abstract","A Transparent game is a game-theoretic setting that takes action visibility into account. In each round, depending on the relative timing of their actions, players have a certain probability to see their partner’s choice before making their own decision. This probability is determined by the level of transparency. At the two extremes, a game with zero transparency is equivalent to the classical simultaneous game, and a game with maximal transparency corresponds to a sequential game. Despite the prevalence of intermediate transparency in many everyday interactions such scenarios have not been sufficiently studied. Here we consider a transparent iterated Prisoner’s dilemma (iPD) and use evolutionary simulations to investigate how and why the success of various strategies changes with the level of transparency. We demonstrate that non-zero transparency greatly reduces the set of successful memory-one strategies compared to the simultaneous iPD. For low and moderate transparency the classical “Win - Stay, Lose - Shift” (WSLS) strategy is the only evolutionary successful strategy. For high transparency all strategies are evolutionary unstable in the sense that they can be easily counteracted, and, finally, for maximal transparency a novel “Leader-Follower” strategy outperforms WSLS. Our results provide a partial explanation for the fact that the strategies proposed for the simultaneous iPD are rarely observed in nature, where high levels of transparency are common."],["dc.identifier.doi","10.1007/978-3-030-16692-2_14"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/62176"],["dc.language.iso","en"],["dc.publisher","Springer"],["dc.publisher.place","hm"],["dc.relation.crisseries","Lecture Notes in Computer Science"],["dc.relation.isbn","978-3-030-16691-5"],["dc.relation.isbn","978-3-030-16692-2"],["dc.relation.ispartof","Applications of Evolutionary Computation. Applications of Evolutionary Computation."],["dc.relation.ispartofseries","Lecture Notes in Computer Science;"],["dc.relation.issn","0302-9743"],["dc.relation.issn","1611-3349"],["dc.title","Evolutionary Successful Strategies in a Transparent iterated Prisoner’s Dilemma"],["dc.type","book_chapter"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","123"],["dc.bibliographiccitation.issue","Part A"],["dc.bibliographiccitation.journal","Neuropsychologia"],["dc.bibliographiccitation.lastpage","137"],["dc.bibliographiccitation.volume","79"],["dc.contributor.author","Paschke, Kerstin"],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Wüstenberg, Torsten"],["dc.contributor.author","Bähr, Mathias"],["dc.contributor.author","Wilke, Melanie"],["dc.date.accessioned","2017-09-07T11:47:55Z"],["dc.date.available","2017-09-07T11:47:55Z"],["dc.date.issued","2015"],["dc.description.abstract","Manipulation of the trunk midline has been shown to improve visuospatial performance in patients with unilateral visual neglect. The goal of the present study was to disentangle motor and perceptual components of egocentric midline manipulations and to investigate the contribution of individual hand preference. Two versions of visual temporal order judgment (TOJ) tasks were tested in healthy right- and left-handed subjects while trunk rotation was varied. In the congruent version, subjects were required to execute a saccade to the first of two horizontal stimuli presented with different stimulus onset asynchronies (SOA). In the incongruent version, subjects were required to perform a vertical saccade to a pre-learned color target, thereby dissociating motor response from the perceptual stimulus location. The main findings of this study are a trunk rotation and response direction specific impact on temporal judgments in form of a prior entry bias for right hemifield stimuli during rightward trunk rotation, but only in the congruent task. This trunk rotation-induced spatial bias was most pronounced in left-handed participants but had the same sign in the right-handed group. Results suggest that egocentric midline shifts in healthy subjects induce a spatially-specific motor, but not a perceptual, bias and underline the importance of taking individual differences in functional laterality such as handedness and mode of perceptual report into account when evaluating effects of trunk rotation in either healthy subjects or neurological patients."],["dc.identifier.doi","10.1016/j.neuropsychologia.2015.10.031"],["dc.identifier.gro","3150766"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7555"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.notes.submitter","chake"],["dc.relation.issn","0028-3932"],["dc.title","Trunk rotation affects temporal order judgments with direct saccades: Influence of handedness"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","no"],["dspace.entity.type","Publication"]]