TY - JOUR A1 - Ehrenfeld, Stephan A1 - Herbort, Oliver A1 - Butz, Martin V. T1 - Modular neuron-based body estimation: maintaining consistency over different limbs, modalities, and frames of reference JF - Frontiers in Computational Neuroscience N2 - This paper addresses the question of how the brain maintains a probabilistic body state estimate over time from a modeling perspective. The neural Modular Modality Frame (nMMF) model simulates such a body state estimation process by continuously integrating redundant, multimodal body state information sources. The body state estimate itself is distributed over separate, but bidirectionally interacting modules. nMMF compares the incoming sensory and present body state information across the interacting modules and fuses the information sources accordingly. At the same time, nMMF enforces body state estimation consistency across the modules. nMMF is able to detect conflicting sensory information and to consequently decrease the influence of implausible sensor sources on the fly. In contrast to the previously published Modular Modality Frame (MMF) model, nMMF offers a biologically plausible neural implementation based on distributed, probabilistic population codes. Besides its neural plausibility, the neural encoding has the advantage of enabling (a) additional probabilistic information flow across the separate body state estimation modules and (b) the representation of arbitrary probability distributions of a body state. The results show that the neural estimates can detect and decrease the impact of false sensory information, can propagate conflicting information across modules, and can improve overall estimation accuracy due to additional module interactions. Even bodily illusions, such as the rubber hand illusion, can be simulated with nMMF. We conclude with an outlook on the potential of modeling human data and of invoking goal-directed behavioral control. KW - information KW - posterior parietal cortex KW - hand KW - population code KW - conflicting information KW - multimodal interaction KW - probabilistic inference KW - modular body schema KW - sensor fusion KW - multisensory perception KW - fusion KW - representation KW - multisensory processing KW - see KW - implementation KW - perspective KW - multisensory integration KW - population codes Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-122253 VL - 7 IS - 148 ER - TY - JOUR A1 - Borchers, Svenja A1 - Müller, Laura A1 - Synofzik, Matthis A1 - Himmelbach, Marc T1 - Guidelines and quality measures for the diagnosis of optic ataxia JF - Frontiers in Human Neuroscience N2 - Since the first description of a systematic mis-reaching by Balint in 1909, a reasonable number of patients showing a similar phenomenology, later termed optic ataxia (OA), has been described. However, there is surprising inconsistency regarding the behavioral measures that are used to detect OA in experimental and clinical reports, if the respective measures are reported at all. A typical screening method that was presumably used by most researchers and clinicians, reaching for a target object in the peripheral visual space, has never been evaluated. We developed a set of instructions and evaluation criteria for the scoring of a semi-standardized version of this reaching task. We tested 36 healthy participants, a group of 52 acute and chronic stroke patients, and 24 patients suffering from cerebellar ataxia. We found a high interrater reliability and a moderate test-retest reliability comparable to other clinical instruments in the stroke sample. The calculation of cut-off thresholds based on healthy control and cerebellar patient data showed an unexpected high number of false positives in these samples due to individual outliers that made a considerable number of errors in peripheral reaching. This study provides first empirical data from large control and patient groups for a screening procedure that seems to be widely used but rarely explicitly reported and prepares the grounds for its use as a standard tool for the description of patients who are included in single case or group studies addressing optic ataxia similar to the use of neglect, extinction, or apraxia screening tools. KW - systems KW - deficit KW - target KW - damage KW - delay KW - posterior cortical atrophy KW - Balints-Syndrome KW - hand KW - impairments KW - reliability KW - cerebellar atrophy KW - cerebellar ataxia KW - cerebellum KW - parietal lobe KW - optic ataxia KW - beside test Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-122439 SN - 1662-5161 VL - 7 IS - 324 ER -