| 1. |
- Bengtsson, Fredrik, et al.
(författare)
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Cross-correlations between pairs of neurons in cerebellar cortex in vivo.
- 2013
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Ingår i: Neural Networks. - : Elsevier BV. - 1879-2782 .- 0893-6080. ; 47:Dec.,06, s. 88-94
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Tidskriftsartikel (refereegranskat)abstract
- In the present paper we apply a new neurophysiological technique to make single-electrode, dual loose-patch recordings from pairs of neuronal elements in the cerebellar cortex in vivo. The analyzed cell pairs consisted of an inhibitory molecular layer interneuron and a Purkinje cell (PC) or a Golgi cell and a granule cell, respectively. To detect the magnitude of the unitary inhibitory synaptic inputs we used histograms of the spike activity of the target cell, triggered by the spikes of the inhibitory cell. Using this analysis, we found that single interneurons had no detectable effect on PC firing, which could be explained by an expected very low synaptic weight of individual interneuron-PC connections. However, interneurons did have a weak delaying effect on the overall series of interspike intervals of PCs. Due to the very high number of inhibitory synapses on each PC, a concerted activation of the interneurons could still achieve potent PC inhibition as previously shown. In contrast, in the histograms of the Golgi cell-granule cell pairs, we found a weak inhibitory effect on the granule cell but only at the time period defined as the temporal domain of the slow IPSP previously described for this connection. Surprisingly, the average granule cell firing frequency sampled at one second was strongly modulated with a negative correlation to the overall firing level of the Golgi cell when the latter was modified through current injection via the patch pipette. These findings are compatible with that tonic inhibition is the dominant form of Golgi cell-granule cell inhibition in the adult cerebellum in vivo.
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| 2. |
- Foulsham, Tom, et al.
(författare)
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Modeling eye movements in visual agnosia with a saliency map approach: Bottom–up guidance or top–down strategy?
- 2011
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Ingår i: Neural Networks. - : Elsevier BV. - 1879-2782 .- 0893-6080. ; 24:6, s. 665-677
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Tidskriftsartikel (refereegranskat)abstract
- Two recent papers (Foulsham, Barton, Kingstone, Dewhurst, & Underwood, 2009; Mannan, Kennard, & Husain, 2009) report that neuropsychological patients with a profound object recognition problem (visual agnosic subjects) show differences from healthy observers in the way their eye movements are controlled when looking at images. The interpretation of these papers is that eye movements can be modeled as the selection of points on a saliency map, and that agnosic subjects show an increased reliance on visual saliency, i.e., brightness and contrast in low-level stimulus features. Here we review this approach and present new data from our own experiments with an agnosic patient that quantifies the relationship between saliency and fixation location. In addition, we consider whether the perceptual difficulties of individual patients might be modeled by selectively weighting the different features involved in a saliency map. Our data indicate that saliency is not always a good predictor of fixation in agnosia: even for our agnosic subject, as for normal observers, the saliency–fixation relationship varied as a function of the task. This means that top–down processes still have a significant effect on the earliest stages of scanning in the setting of visual agnosia, indicating severe limitations for the saliency map model. Top–down, active strategies – which are the hallmark of our human visual system – play a vital role in eye movement control, whether we know what we are looking at or not.
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| 3. |
- Hesslow, Germund, et al.
(författare)
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Classical conditioning of motor responses: What is the learning mechanism?
- 2013
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Ingår i: Neural Networks. - : Elsevier BV. - 1879-2782 .- 0893-6080. ; 47:Mar,28, s. 81-87
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Tidskriftsartikel (refereegranskat)abstract
- According to a widely held assumption, the main mechanism underlying motor learning in the cerebellum, such as eyeblink conditioning, is long-term depression (LTD) of parallel fibre to Purkinje cell synapses. Here we review some recent physiological evidence from Purkinje cell recordings during conditioning with implications for models of conditioning. We argue that these data pose four major challenges to the LTD hypothesis of conditioning. (i) LTD cannot account for the pause in Purkinje cell firing that is believed to drive the conditioned blink. (ii) The temporal conditions conducive to LTD do not match those for eyeblink conditioning. (iii) LTD cannot readily account for the adaptive timing of the conditioned response. (iv) The data suggest that parallel fibre to Purkinje cell synapses are not depressed after learning a Purkinje cell CR. Models based on metabotropic glutamate receptors are also discussed and found to be incompatible with the recording data.
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| 4. |
- Jaeger, Dieter, et al.
(författare)
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Computation in the Cerebellum
- 2013
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Ingår i: Neural Networks. - : Elsevier BV. - 1879-2782 .- 0893-6080. ; 47, s. 1-2
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Metta, Giorgio, et al.
(författare)
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The iCub humanoid robot : An open-systems platform for research in cognitive development
- 2010
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Ingår i: Neural Networks. - : Elsevier BV. - 0893-6080 .- 1879-2782. ; 23:8-9, s. 1125-1134
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Tidskriftsartikel (refereegranskat)abstract
- We describe a humanoid robot platform - the iCub - which was designed to support collaborative research in cognitive development through autonomous exploration and social interaction. The motivation for this effort is the conviction that significantly greater impact can be leveraged by adopting an open systems policy for software and hardware development. This creates the need for a robust humanoid robot that offers rich perceptuo-motor capabilities with many degrees of freedom, a cognitive capacity for learning and development, a software architecture that encourages reuse & easy integration, and a support infrastructure that fosters collaboration and sharing of resources. The iCub satisfies all of these needs in the guise of an open-system platform which is freely available and which has attracted a growing community of users and developers. To date, twenty iCubs each comprising approximately 5000 mechanical and electrical parts have been delivered to several research labs in Europe and to one in the USA.
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| 6. |
- Viejo, Diego, et al.
(författare)
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Using GNG to improve 3D features extractio - Application to 6DoF Egomotion
- 2012
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Ingår i: Neural Networks. - : Elsevier BV. - 1879-2782 .- 0893-6080. ; 32, s. 138-146
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedSeveral recent works deal with 3D data in mobile robotic problems, e.g. mapping or egomotion. Data comes from any kind of sensor such as stereo vision systems, time of flight cameras or 3D lasers, providing a huge amount of unorganized 3D data. In this paper, we describe an efficient method to build complete 3D models from a Growing Neural Gas (GNG). The GNG is applied to the 3D raw data and it reduces both the subjacent error and the number of points, keeping the topology of the 3D data. The GNG output is then used in a 3D feature extraction method. We have performed a deep study in which we quantitatively show that the use of GNG improves the 3D feature extraction method. We also show that our method can be applied to any kind of 3D data. The 3D features obtained are used as input in an Iterative Closest Point (ICP)-like method to compute the 6DoF movement performed by a mobile robot. A comparison with standard ICP is performed, showing that the use of GNG improves the results. Final results of 3D mapping from the egomotion calculated are also shown. (C) 2012 Elsevier Ltd. All rights reserved.
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| 7. |
- Zhdanov, Vladimir, 1952
(författare)
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Neural networks including microRNAs
- 2012
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Ingår i: Neural Networks. - : Elsevier BV. - 1879-2782 .- 0893-6080. ; 25, s. 200-204
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Zhdanov, Vladimir, 1952
(författare)
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Three generic bistable scenarios of the interplay of voltage pulses and gene expression in neurons
- 2013
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Ingår i: Neural Networks. - : Elsevier BV. - 1879-2782 .- 0893-6080. ; 44, s. 51-63
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Tidskriftsartikel (refereegranskat)abstract
- The long-term changes of the neuron function are often related to the interplay of the membrane voltage pulses and gene expression. In the present work, this phenomenon is modeled by combining the standard stochastic integrate-and-fire neuron model with generic kinetic models describing gene expression. The three scenarios under consideration include, respectively, the voltage-related regulation of (i) gene transcription into mRNA, (ii) gene transcription into miRNA, and (iii) proteasome formation. Typical transient and steady-state kinetics are shown. The latter kinetics exhibit a unique steady state, bistability, or oscillations. The conditions of realization of these regimes are investigated numerically. The transient and oscillatory kinetics are predicted on the time scale of about one hour or longer. The implications of these results for interpretation of synaptic plasticity and learning and long-term memory are briefly discussed.
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