Kagan, Igor

[["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","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.artnumber","e1000444"],["dc.bibliographiccitation.issue","8"],["dc.bibliographiccitation.journal","PLoS Biology"],["dc.bibliographiccitation.volume","8"],["dc.contributor.author","Iyer, Asha"],["dc.contributor.author","Lindner, Axel"],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Andersen, Richard A."],["dc.contributor.editor","Ungerleider, Leslie"],["dc.date.accessioned","2017-09-07T11:47:53Z"],["dc.date.available","2017-09-07T11:47:53Z"],["dc.date.issued","2010"],["dc.description.abstract","For optimal response selection, the consequences associated with behavioral success or failure must be appraised. To determine how monetary consequences influence the neural representations of motor preparation, human brain activity was scanned with fMRI while subjects performed a complex spatial visuomotor task. At the beginning of each trial, reward context cues indicated the potential gain and loss imposed for correct or incorrect trial completion. FMRI-activity in canonical reward structures reflected the expected value related to the context. In contrast, motor preparatory activity in posterior parietal and premotor cortex peaked in high “absolute value” (high gain or loss) conditions: being highest for large gains in subjects who believed they performed well while being highest for large losses in those who believed they performed poorly. These results suggest that the neural activity preceding goal-directed actions incorporates the absolute value of that action, predicated upon subjective, rather than objective, estimates of one's performance."],["dc.identifier.doi","10.1371/journal.pbio.1000444"],["dc.identifier.gro","3150753"],["dc.identifier.pmid","20689802"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7544"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.relation.issn","1545-7885"],["dc.title","Motor Preparatory Activity in Posterior Parietal Cortex is Modulated by Subjective Absolute Value"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Scientific Reports"],["dc.bibliographiccitation.volume","8"],["dc.contributor.author","Christopoulos, Vassilios N."],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Andersen, Richard A."],["dc.date.accessioned","2021-06-01T10:50:41Z"],["dc.date.available","2021-06-01T10:50:41Z"],["dc.date.issued","2018"],["dc.identifier.doi","10.1038/s41598-018-26366-9"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/86748"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-425"],["dc.relation.eissn","2045-2322"],["dc.title","Lateral intraparietal area (LIP) is largely effector-specific in free-choice decisions"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","11715"],["dc.bibliographiccitation.issue","35"],["dc.bibliographiccitation.journal","The Journal of neuroscience"],["dc.bibliographiccitation.lastpage","11725"],["dc.bibliographiccitation.volume","30"],["dc.contributor.author","Lindner, Axel"],["dc.contributor.author","Iyer, Asha"],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Andersen, Richard A."],["dc.date.accessioned","2017-09-07T11:47:55Z"],["dc.date.available","2017-09-07T11:47:55Z"],["dc.date.issued","2010"],["dc.description.abstract","In this time-resolved functional magnetic resonance imaging (fMRI) study, we aimed to trace the neuronal correlates of covert planning processes that precede visually guided motor behavior. Specifically, we asked whether human posterior parietal cortex has prospective planning activity that can be distinguished from activity related to retrospective visual memory and attention. Although various electrophysiological studies in monkeys have demonstrated such motor planning at the level of parietal neurons, comparatively little support is provided by recent human imaging experiments. Rather, a majority of experiments highlights a role of human posterior parietal cortex in visual working memory and attention. We thus sought to establish a clear separation of visual memory and attention from processes related to the planning of goal-directed motor behaviors. To this end, we compared delayed-response tasks with identical mnemonic and attentional demands but varying degrees of motor planning. Subjects memorized multiple target locations, and in a random subset of trials targets additionally instructed (1) desired goals or (2) undesired goals for upcoming finger reaches. Compared with the memory/attention-only conditions, both latter situations led to a specific increase of preparatory fMRI activity in posterior parietal and dorsal premotor cortex. Thus, posterior parietal cortex has prospective plans for upcoming behaviors while considering both types of targets relevant for action: those to be acquired and those to be avoided."],["dc.identifier.doi","10.1523/jneurosci.2849-09.2010"],["dc.identifier.gro","3150750"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7540"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.relation.issn","0270-6474"],["dc.title","Human Posterior Parietal Cortex Plans Where to Reach and What to Avoid"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","8274"],["dc.bibliographiccitation.issue","21"],["dc.bibliographiccitation.journal","Proceedings of the National Academy of Sciences"],["dc.bibliographiccitation.lastpage","8279"],["dc.bibliographiccitation.volume","109"],["dc.contributor.author","Wilke, Melanie"],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Andersen, Richard A."],["dc.date.accessioned","2017-09-07T11:43:46Z"],["dc.date.available","2017-09-07T11:43:46Z"],["dc.date.issued","2012"],["dc.description.abstract","Impairments of spatial awareness and decision making occur frequently as a consequence of parietal lesions. Here we used event-related functional MRI (fMRI) in monkeys to investigate rapid reorganization of spatial networks during reversible pharmacological inactivation of the lateral intraparietal area (LIP), which plays a role in the selection of eye movement targets. We measured fMRI activity in control and inactivation sessions while monkeys performed memory saccades to either instructed or autonomously chosen spatial locations. Inactivation caused a reduction of contralesional choices. Inactivation effects on fMRI activity were anatomically and functionally specific and mainly consisted of: (i) activity reduction in the upper bank of the superior temporal sulcus (temporal parietal occipital area) for single contralesional targets, especially in the inactivated hemisphere; and (ii) activity increase accompanying contralesional choices between bilateral targets in several frontal and parieto-temporal areas in both hemispheres. There was no overactivation for ipsilesional targets or choices in the intact hemisphere. Task-specific effects of LIP inactivation on blood oxygen level-dependent activity in the temporal parietal occipital area underline the importance of the superior temporal sulcus for spatial processing. Furthermore, our results agree only partially with the influential interhemispheric competition model of spatial neglect and suggest an additional component of interhemispheric cooperation in the compensation of neglect deficits."],["dc.identifier.doi","10.1073/pnas.1204789109"],["dc.identifier.gro","3151627"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/8441"],["dc.language.iso","en"],["dc.notes.status","public"],["dc.notes.submitter","chake"],["dc.relation.issn","0027-8424"],["dc.title","Functional imaging reveals rapid reorganization of cortical activity after parietal inactivation in monkeys"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","S60"],["dc.bibliographiccitation.journal","Neuroscience Research"],["dc.bibliographiccitation.lastpage","S60"],["dc.bibliographiccitation.volume","65"],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Wilke, Melanie"],["dc.contributor.author","Andersen, Richard A."],["dc.date.accessioned","2018-02-08T12:37:29Z"],["dc.date.available","2018-02-08T12:37:29Z"],["dc.date.issued","2009"],["dc.identifier.doi","10.1016/j.neures.2009.09.164"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/12065"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.relation.issn","0168-0102"],["dc.title","BOLD fMRI dynamics in monkeys reflects spatial decisions in free-choice and reward context tasks"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","11719"],["dc.bibliographiccitation.issue","33"],["dc.bibliographiccitation.journal","The Journal of Neuroscience"],["dc.bibliographiccitation.lastpage","11728"],["dc.bibliographiccitation.volume","35"],["dc.contributor.author","Christopoulos, Vassilios N."],["dc.contributor.author","Bonaiuto, James"],["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Andersen, Richard A."],["dc.date.accessioned","2021-06-01T10:48:22Z"],["dc.date.available","2021-06-01T10:48:22Z"],["dc.date.issued","2015"],["dc.description.abstract","The posterior parietal cortex (PPC) has traditionally been considered important for awareness, spatial perception, and attention. However, recent findings provide evidence that the PPC also encodes information important for making decisions. These findings have initiated a running argument of whether the PPC is critically involved in decision making. To examine this issue, we reversibly inactivated the parietal reach region (PRR), the area of the PPC that is specialized for reaching movements, while two monkeys performed a memory-guided reaching or saccade task. The task included choices between two equally rewarded targets presented simultaneously in opposite visual fields. Free-choice trials were interleaved with instructed trials, in which a single cue presented in the peripheral visual field defined the reach and saccade target unequivocally. We found that PRR inactivation led to a strong reduction of contralesional choices, but only for reaches. On the other hand, saccade choices were not affected by PRR inactivation. Importantly, reaching and saccade movements to single instructed targets remained largely intact. These results cannot be explained as an effector-nonspecific deficit in spatial attention or awareness, since the temporary “lesion” had an impact only on reach choices. Hence, the PPR is a part of a network for reach decisions and not just reach planning."],["dc.identifier.doi","10.1523/JNEUROSCI.1068-15.2015"],["dc.identifier.gro","3150752"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/85913"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-425"],["dc.notes.status","zu prüfen"],["dc.relation.eissn","1529-2401"],["dc.relation.issn","0270-6474"],["dc.title","Inactivation of Parietal Reach Region Affects Reaching But Not Saccade Choices in Internally Guided Decisions"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.contributor.author","Kagan, Igor"],["dc.contributor.author","Wilke, Melanie"],["dc.contributor.author","Andersen, Richard A."],["dc.date.accessioned","2018-02-08T10:22:17Z"],["dc.date.available","2018-02-08T10:22:17Z"],["dc.date.issued","2014"],["dc.description.abstract","A method and system of compensating for a damaged brain node is disclosed. The damaged node is determined by techniques such as fMRI or neural recording. A healthy node that can compensate for the function of the damaged node is determined. A stimulating electrode is placed on at least one functioning node to bypass the activity from the damaged node to compensate for a missing node. The functioning node is then stimulated to compensate for the damaged node."],["dc.identifier.patent","US8831733B2"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/12055"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.title","Brain repair using electrical stimulation of healthy nodes"],["dc.type","patent"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]