Soft-competitive versus EM learning in cortical map modeling

1999 ◽  
pp. 120-125
Author(s):  
Francesco Frisone ◽  
Pietro G. Morasso
Keyword(s):  
Cortical Map

A Comprehensive Three-dimensional Cortical Map of Vowel Space

2011 ◽  
Vol 23 (12) ◽  
pp. 3972-3982 ◽  
Author(s):  
Mathias Scharinger ◽  
William J. Idsardi ◽  
Samantha Poe
Keyword(s):  
Basilar Membrane ◽  
Speech Sound ◽  
Three Dimensional ◽  
Sensory Information ◽  
Stimulus Onset ◽  
Acoustic Properties ◽  
Spatial Encoding ◽  
Spatial Gradients ◽  
Vowel Space ◽  
Cortical Map

Mammalian cortex is known to contain various kinds of spatial encoding schemes for sensory information including retinotopic, somatosensory, and tonotopic maps. Tonotopic maps are especially interesting for human speech sound processing because they encode linguistically salient acoustic properties. In this study, we mapped the entire vowel space of a language (Turkish) onto cortical locations by using the magnetic N1 (M100), an auditory-evoked component that peaks approximately 100 msec after auditory stimulus onset. We found that dipole locations could be structured into two distinct maps, one for vowels produced with the tongue positioned toward the front of the mouth (front vowels) and one for vowels produced in the back of the mouth (back vowels). Furthermore, we found spatial gradients in lateral–medial, anterior–posterior, and inferior–superior dimensions that encoded the phonetic, categorical distinctions between all the vowels of Turkish. Statistical model comparisons of the dipole locations suggest that the spatial encoding scheme is not entirely based on acoustic bottom–up information but crucially involves featural–phonetic top–down modulation. Thus, multiple areas of excitation along the unidimensional basilar membrane are mapped into higher dimensional representations in auditory cortex.

Dynamics of cortical map development in the elastic net model

2000 ◽  
Vol 32-33 ◽  
pp. 83-90 ◽  
Author(s):  
Andrei Cimponeriu ◽  
Geoffrey J. Goodhill
Keyword(s):  
Elastic Net ◽  
Cortical Map

scholarly journals Synapse Plasticity in Motor, Sensory, and Limbo-Prefrontal Cortex Areas as Measured by Degrading Axon Terminals in an Environment Model of Gerbils (Meriones unguiculatus)

2009 ◽  
Vol 2009 ◽  
pp. 1-14 ◽  
Author(s):  
Janina Neufeld ◽  
Gertraud Teuchert-Noodt ◽  
Keren Grafen ◽  
York Winter ◽  
A. Veronica Witte
Keyword(s):  
Prefrontal Cortex ◽  
Synaptic Plasticity ◽  
Meriones Unguiculatus ◽  
Secondary Lysosome ◽  
Axon Terminals ◽  
Environment Model ◽  
Naturally Occurring ◽  
Synapse Plasticity ◽  
Map Adaptation ◽  
Cortical Map

Still little is known about naturally occurring synaptogenesis in the adult neocortex and related impacts of epigenetic influences. We therefore investigated (pre)synaptic plasticity in various cortices of adult rodents, visualized by secondary lysosome accumulations (LA) in remodeling axon terminals. Twenty-two male gerbils from either enriched (ER) or impoverished rearing (IR) were used for quantification of silver-stained LA. ER-animals showed rather low LA densities in most primary fields, whereas barrel and secondary/associative cortices exhibited higher densities and layer-specific differences. In IR-animals, these differences were evened out or even inverted. Basic plastic capacities might be linked with remodeling of local intrinsic circuits in the context of cortical map adaptation in both IR- and ER-animals. Frequently described disturbances due to IR in multiple corticocortical and extracortical afferent systems, including the mesocortical dopamine projection, might have led to maladaptations in the plastic capacities of prefronto-limbic areas, as indicated by different LA densities in IR- compared with ER-animals.

Influence of Lateral Connections on the Structure of Cortical Maps

2004 ◽  
Vol 92 (5) ◽  
pp. 2947-2959 ◽  
Author(s):  
Miguel Á. Carreira-Perpiñán ◽  
Geoffrey J. Goodhill
Keyword(s):  
Visual Cortex ◽  
Computational Model ◽  
Primary Visual Cortex ◽  
Short Range ◽  
Ocular Dominance ◽  
Characteristic Structure ◽  
Interaction Function ◽  
Mexican Hat ◽  
Visual Cortical ◽  
Cortical Map

Maps of ocular dominance and orientation in primary visual cortex have a highly characteristic structure. The factors that determine this structure are still largely unknown. In particular, it is unclear how short-range excitatory and inhibitory connections between nearby neurons influence structure both within and between maps. Using a generalized version of a well-known computational model of visual cortical map development, we show that the number of excitatory and inhibitory oscillations in this interaction function critically influences map structure. Specifically, we demonstrate that functions that oscillate more than once do not produce maps closely resembling those seen biologically. This strongly suggests that local lateral connections in visual cortex oscillate only once and have the form of a Mexican hat.

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