Questioning the role of sparse coding in the brain

Spanne, Anton; Jörntell, Henrik

doi:10.1016/j.tins.2015.05.005

Cited by 100 publications

(130 citation statements)

References 86 publications

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“…This is sufficient for our theory because granule cells represent heterogeneous combinations of mossy-fiber input relevant to the classification performed by their postsynaptic Purkinje cells, which are unlikely to require all possible input combinations. Some studies have suggested that granule-cell input is more homogeneous (Jörntell and Ekerot, 2006; Bengtsson and Jörntell, 2009) and that granule cells function as noise filters (Ekerot and Jörntell, 2008) or improve generalization (Spanne and Jörntell, 2015). However, even when we impose a corresponding level of similarity of tuning in our cerebellar cortex model, the synaptic degree that maximizes dimension is still small ( K ≤ 4), although the dimension of the resulting representation is reduced (Figure S7).…”

Section: Discussionmentioning

confidence: 99%

Optimal Degrees of Synaptic Connectivity

Litwin-Kumar

Harris

Axel

et al. 2017

Neuron

324

467

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Summary Synaptic connectivity varies widely across neuronal types. Cerebellar granule cells receive five orders of magnitude fewer inputs than the Purkinje cells they innervate, and cerebellum-like circuits including the insect mushroom body also exhibit large divergences in connectivity. In contrast, the number of inputs per neuron in cerebral cortex is more uniform and large. We investigate how the dimension of a representation formed by a population of neurons depends on how many inputs they each receive and what this implies for learning associations. Our theory predicts that the dimensions of the cerebellar granule-cell and Drosophila Kenyon-cell representations are maximized at degrees of synaptic connectivity that match those observed anatomically, showing that sparse connectivity is sometimes superior to dense connectivity. When input synapses are subject to supervised plasticity, however, dense wiring becomes advantageous, suggesting that the type of plasticity exhibited by a set of synapses is a major determinant of connection density.

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Section: Discussionmentioning

confidence: 99%

Optimal Degrees of Synaptic Connectivity

Litwin-Kumar

Harris

Axel

et al. 2017

Neuron

324

467

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“…Although there is a debate on the pattern of convergence of mossy fiber information in individual granule cells, at least for limb controlling areas of the cerebellar cortex mossy fiber information from individual functional pathways is directly transmitted through granule cells and reflected in the output of the Purkinje cells [92, 93]. In this case, there is an unconditional transmission of information through the granule layer from individual functional pathways, which means that the information carried by these pathways can be integrated by the Purkinje cell without being dependent on concomitant input from other mossy fiber systems in contrast to what was assumed in the original Marr-Albus theory of cerebellar information processing [94]. …”

Section: Spinocerebellar Circuitry—consequences For the Organization mentioning

confidence: 99%

Consensus Paper: Towards a Systems-Level View of Cerebellar Function: the Interplay Between Cerebellum, Basal Ganglia, and Cortex

et al. 2016

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Despite increasing evidence suggesting the cerebellum works in concert with the cortex and basal ganglia, the nature of the reciprocal interactions between these three brain regions remains unclear. This consensus paper gathers diverse recent views on a variety of important roles played by the cerebellum within the cerebello-basal ganglia-thalamo-cortical system across a range of motor and cognitive functions. The paper includes theoretical and empirical contributions, which cover the following topics: recent evidence supporting the dynamical interplay between cerebellum, basal ganglia, and cortical areas in humans and other animals; theoretical neuroscience perspectives and empirical evidence on the reciprocal influences between cerebellum, basal ganglia, and cortex in learning and control processes; and data suggesting possible roles of the cerebellum in basal ganglia movement disorders. Although starting from different backgrounds and dealing with different topics, all the contributors agree that viewing the cerebellum, basal ganglia, and cortex as an integrated system enables us to understand the function of these areas in radically different ways. In addition, there is unanimous consensus between the authors that future experimental and computational work is needed to understand the function of cerebellar-basal ganglia circuitry in both motor and non-motor functions. The paper reports the most advanced perspectives on the role of the cerebellum within the cerebello-basal ganglia-thalamo-cortical system and illustrates other elements of consensus as well as disagreements and open questions in the field.

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“…Within the primate prefrontal cortex, the representation of particular spatial locations within spatial working memory depends on the selective activation of particular layer 3 neurons and their associated microcolumns as well as the interneuron-mediated inhibition of neighboring neurons and microcolumns representing competing locations (87, 88). The restriction of activity to a small minority of potential neurons is called sparse coding (89) and its integrity depends on inhibition (90). The interneurons mediating the spatial dispersion of pyramidal neuron activitation are specific to cell type and layer.…”

Section: Deficits In Spatial Tuning Of Cortical Activity and Impairmementioning

confidence: 99%

Impaired Tuning of Neural Ensembles and the Pathophysiology of Schizophrenia: A Translational and Computational Neuroscience Perspective

Krystal

Antičević

Yang

et al. 2017

Biological Psychiatry

168

129

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The functional optimization of neural ensembles is central to human higher cognitive functions. When the functions through which neural activity is tuned fail to develop or break down, symptoms and cognitive impairments arise. This review will consider ways that disturbances in the balance of excitation and inhibition might develop and be expressed in cortical networks in association with schizophrenia. This presentation will be framed within a developmental perspective that begins with disturbances in glutamate synaptic development in utero. It will consider developmental correlates and consequences including compensatory mechanisms that increase intrinsic excitability or reduce inhibitory tone. It will also consider the possibility that these homeostatic increases in excitability have potential negative functional and structural consequences. These negative functional consequences of disinhibition may include reduced working memory-related cortical activity associated with the downslope of the “inverted-U” input-output curve, impaired spatial tuning of neural activity and impaired sparse coding of information, deficits in the temporal tuning of neural activity and its implication for neural codes, and conclude by considering the functional significance of noisy activity for neural network function. This presentation will draw on computational neuroscience and pharmacologic and genetic studies in animals and humans, particularly those involving NMDA glutamate receptor antagonists, to illustrate principles of network regulation that give rise to features of neural dysfunction associated with schizophrenia. While this presentation focuses on schizophrenia, the general principles outlined in this review may have broad implications for considering disturbances in the regulation of neural ensembles in psychiatric disorders.

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Questioning the role of sparse coding in the brain

Cited by 100 publications

References 86 publications

Optimal Degrees of Synaptic Connectivity

Optimal Degrees of Synaptic Connectivity

Consensus Paper: Towards a Systems-Level View of Cerebellar Function: the Interplay Between Cerebellum, Basal Ganglia, and Cortex

Impaired Tuning of Neural Ensembles and the Pathophysiology of Schizophrenia: A Translational and Computational Neuroscience Perspective

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