Gail, Alexander

[["dc.bibliographiccitation.firstpage","519"],["dc.bibliographiccitation.issue","3-5"],["dc.bibliographiccitation.journal","Visual Cognition"],["dc.bibliographiccitation.lastpage","530"],["dc.bibliographiccitation.volume","8"],["dc.contributor.author","Eckhorn, Reinhard"],["dc.contributor.author","Bruns, Andreas"],["dc.contributor.author","Saam, Mirko"],["dc.contributor.author","Gail, Alexander"],["dc.contributor.author","Gabriel, Andreas"],["dc.contributor.author","Brinksmeyer, Hans Jörg"],["dc.date.accessioned","2017-09-07T11:47:50Z"],["dc.date.available","2017-09-07T11:47:50Z"],["dc.date.issued","2002"],["dc.description.abstract","We summarize recent studies of our group from the primary visual cortex V1 of behaving monkeys referring to the hypothesis of spatial feature binding by γ-synchronization (30-90 Hz). In agreement with this hypothesis the data demonstrates decoupling of γ-activities among neural groups representing figure and ground. As γ-synchronization in V1 is restricted to cortical ranges of few millimeters, feature binding may equivalently be restricted in visual space. Closer inspection shows that the restriction in synchrony is due to far-reaching travelling γ-waves with changing phase coupling. Based on this observation we extend the initial binding-by-synchronization hypothesis and suggest object continuity to be coded by phase continuity. It is further argued that the spatial phase changes of the V1 γ-waves in general will also limit lateral phase coupling to higher levels of processing. Instead of phase-locked γ-coupling, corticocortical cooperation among γ-processes may be mediated by mutual amplitude modulations that are more reliable than phase synchrony over larger distances. The relevance of this concept of corticocortical binding is demonstrated with subdural recordings from human subjects performing cognitive tasks. The experimental results are discussed on the basis of network models with spiking neurons."],["dc.identifier.doi","10.1080/13506280143000098"],["dc.identifier.gro","3150728"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7516"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.relation.issn","1350-6285"],["dc.title","Flexible cortical gamma-band correlations suggest neural principles of visual processing"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","840"],["dc.bibliographiccitation.issue","9"],["dc.bibliographiccitation.journal","Cerebral Cortex"],["dc.bibliographiccitation.lastpage","850"],["dc.bibliographiccitation.volume","10"],["dc.contributor.author","Gail, Alexander"],["dc.contributor.author","Brinksmeyer, Hans Jörg"],["dc.contributor.author","Eckhorn, Reinhard"],["dc.date.accessioned","2017-09-07T11:47:47Z"],["dc.date.available","2017-09-07T11:47:47Z"],["dc.date.issued","2002"],["dc.description.abstract","Previous work on figure–ground coding in monkey V1 revealed enhanced spike rates within an object's surface representation, synchronization of gamma oscillations (γ = 35–90 Hz) in object and background regions, but no decrease in signal correlation across the representation of a contour. The latter observation seems to contradict previous statements on the role of γ-synchronization for scene segmentation. We re-examine these findings by analyzing different coupling measures and frequency ranges of population activities potentially contributing to figure–ground segregation. Multiple unit activity (MUA) and local field potentials (LFPs) were recorded by parallel μ-electrodes in monkey V1 during stimulation by a grating in which an object was defined by a shifted rectangle. In contradiction to the conclusions in previous work, we find strong decoupling of population activity between figure and ground representations compared to the situation in which the object is absent. In particular, coherence of lateγ-LFPs is strongly reduced, while reduction is absent during the early epochs of high-amplitude transients for LFP- and MUA-coherence at all frequencies, and at low frequencies also in the subsequent epochs. Our results of decoupling in late LFP γ-components among figure and ground representations suggest that these signals may support figure–ground segregation."],["dc.identifier.doi","10.1093/cercor/10.9.840"],["dc.identifier.gro","3150717"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7504"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.relation.issn","1460-2199"],["dc.title","Contour Decouples Gamma Activity Across Texture Representation in Monkey Striate Cortex"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1039"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","IEEE Transactions on Neural Networks"],["dc.bibliographiccitation.lastpage","1052"],["dc.bibliographiccitation.volume","15"],["dc.contributor.author","Eckhorn, Reinhard"],["dc.contributor.author","Gail, Alexander"],["dc.contributor.author","Bruns, Andreas"],["dc.contributor.author","Gabriel, A."],["dc.contributor.author","Al-Shaikhli, Basim"],["dc.contributor.author","Saam, Mirko"],["dc.date.accessioned","2017-09-07T11:47:46Z"],["dc.date.available","2017-09-07T11:47:46Z"],["dc.date.issued","2004"],["dc.identifier.doi","10.1109/tnn.2004.833130"],["dc.identifier.gro","3150722"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7510"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.relation.issn","1045-9227"],["dc.title","Different Types of Signal Coupling in the Visual Cortex Related to Neural Mechanisms of Associative Processing and Perception"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","41"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Journal of Neuroscience Methods"],["dc.bibliographiccitation.lastpage","56"],["dc.bibliographiccitation.volume","126"],["dc.contributor.author","Gail, Alexander"],["dc.contributor.author","Brinksmeyer, Hans Joerg"],["dc.contributor.author","Eckhorn, Reinhard"],["dc.date.accessioned","2017-09-07T11:47:47Z"],["dc.date.available","2017-09-07T11:47:47Z"],["dc.date.issued","2003"],["dc.description.abstract","We developed a modified Wheatstone stereoscope for simultaneous dichoptical and binocular stimulation in awake monkey. We, therefore, extended the conventional two-screen Wheatstone stereoscope to a setup with an additional third screen viewed binocularly via semi-transparent mirrors. With a sparse noise stimulation we mapped classical receptive field (CRF) positions via each screen independently but simultaneously. This was done for multiple recording positions (16 electrodes) at once in primary visual cortex based on multiple unit spike activity (MUA) and local field potentials (LFP), respectively. The technique can be used to (1) quickly and simultaneously determine binocular as well as left and right eye CRFs, including ocular dominance characteristics (net recording time for the given examples: ∼2 min), (2) precisely adjust dichoptical stimulation by evaluating offsets between monocular and binocular CRF positions (average spatial incongruency between binocular and left/right eye stimulation after calibration: ∼0.025° visual angle), and (3) investigate left and right eye interaction in forming binocular CRFs. Due to the precise adjustment of the dichoptical and the simultaneous binocular stimulation investigations on the basis of stereo vision can be done with appropriate eye vergence alignment matching normal binocular viewing conditions in awake animals."],["dc.identifier.doi","10.1016/s0165-0270(03)00067-0"],["dc.identifier.gro","3150718"],["dc.identifier.pmid","12788501"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/7505"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.relation.issn","0165-0270"],["dc.subject","Receptive field mapping; Binocular RFs; Monocular CRFs; Ocular dominance; Monkey V1; Reverse correlation; Stereo vision; Dichoptical stimulation"],["dc.title","Simultaneous mapping of binocular and monocular receptive fields in awake monkeys for calibrating eye alignment in a dichoptical setup"],["dc.type","journal_article"],["dc.type.internalPublication","no"],["dc.type.peerReviewed","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","239"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Acta Neurobiologiae Experimentalis"],["dc.bibliographiccitation.lastpage","252"],["dc.bibliographiccitation.volume","64"],["dc.contributor.author","Eckhorn, Reinhard"],["dc.contributor.author","Gail, Alexander"],["dc.contributor.author","Bruns, Andreas"],["dc.contributor.author","Gabriel, Andreas"],["dc.contributor.author","Al-Shaikhli, Basim"],["dc.contributor.author","Saam, Mirko"],["dc.date.accessioned","2017-11-13T14:42:35Z"],["dc.date.available","2017-11-13T14:42:35Z"],["dc.date.issued","2004"],["dc.description.abstract","This is a review of our work on multiple microelectrode recordings from the visual cortex of monkeys and subdural recordings from humans--related to the potential underlying neural mechanisms. The former hypothesis of object representation by synchronization in visual cortex (or more generally: of flexible associative processing) has been supported by our recent experiments in monkeys. They demonstrated local synchrony among rhythmic or stochastic gamma-activities (30-90 Hz) and perceptual modulation, according to the rules of figure-ground segregation. However, gamma-synchrony in primary visual cortex is restricted to few millimeters, challenging the synchronization hypothesis for larger cortical object representations. We found that the spatial restriction is due to gamma-waves, traveling in random directions across the object representations. It will be argued that phase continuity of these waves can support the coding of object continuity. Based on models with spiking neurons, potentially underlying neural mechanisms are proposed: (i) Fast inhibitory feedback loops can generate locally synchronized gamma-activities; (ii) Hebbian learning of lateral and feed forward connections with distance-dependent delays can explain the stabilization of cortical retinotopy, the limited size of synchronization, the occurrence of gamma-waves, and the larger receptive fields at successive levels; (iii) slow inhibitory feedback can support figure-ground segregation; (iv) temporal dispersion in far projections destroys coherence of fast signals but preserves slow amplitude modulations. In conclusion, it is proposed that the hypothesis of flexible associative processing by gamma-synchronization, including coherent representations of visual objects, has to be extended to more general forms of signal coupling."],["dc.identifier.pmid","15366256"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/9944"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.subject","feature binding; scene segmentation; synchrony; gamma activity"],["dc.title","Neural mechanisms of visual associative processing"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]