Intrinsic connections in tree shrew V1 imply a global to local mapping

Abstract

The local-global map hypothesis states that locally organized response properties--such as orientation preference--result from visuotopically organized local maps of non-retinotopic response properties. In the tree shrew, the lateral extent of horizontal patchy connections is as much as 80-100% of V1 and is consistent with the length summation property. We argue that neural signals can be transmitted across the entire extent of V1 and this allows the formation of maps at the local scale that are visuotopically organized. We describe mechanisms relevant to the formation of local maps and report modeling results showing the same patterns of horizontal connectivity, and relationships to orientation preference, seen in vivo. The structure of the connectivity that emerges in the simulations reveals a 'hub and spoke' organization. Singularities form the centers of local maps, and linear zones and saddle-points arise as smooth border transitions between maps. These findings are used to present the case for the local-global map hypothesis for tree shrew V1.

An outline of functional self-organization in V1: synchrony, STLR and Hebb rules

“…A possible way in which contextual information might be relayed widely in V1 was suggested by Alexander et al (2004) who proposed the idea that V1 is tiled by many ''local maps'', each one of which is a compressed representation of a ''global map''-the whole, or part of, V1 itself-and therefore a representation of the visual field wider than the RF. This notion was further developed in a theoretical account of the self-organization of synapses during development of V1 (Wright et al 2006) which deduced the most stable configuration of synapses to emerge under a Hebbian learning rule, and depended upon theoretical analyses of synchronous oscillation (Wright 1997;Robinson et al 1998;Wright et al 2000;Chapman et al 2002) as an organizing principle.…”

Mapping of contextual modulation in the population response of primary visual cortex

“…1 Optical imaging techniques have since clarified the mapping of orientation preference in the supra-granular layers of V1 (Bonhoeffer and Grinvald 1991;Blasdel 1992), revealing the pervasiveness of orientation pinwheels. To reconcile this result with Hubel and Wiesel's (1977) ice cube model, we have argued that orientation pinwheels are the building blocks in the organization of the orientation preference map (Alexander et al 2004). In the section ''The local-global map hypothesis'', we will further develop this idea, which assumes the presence of functional units of contextual modulation in V1 called local maps.…”

“…From this definition, other features of the orientation preference map naturally follow. Linear zones and saddle points (Blasdel 1992) arise as smooth transitions between orientation pinwheel borders (Alexander et al 2004). In Fig.…”

“…Hubener et al 1997;White et al 2001). The geometry of local maps is described by the localglobal map (LGM) hypothesis of V1 (Alexander et al 1998(Alexander et al , 2004. The key concept of LGM hypothesis is that the mapping of contextual properties is visuotopic.…”

Cortical Specification of a Fast Fourier Transform Supports a Convolution Model of Visual Perception

“…These feedback connections are an obvious substrate for the integration of global signals into V1 (Bullier, 2001). The local-global map hypothesis (Alexander et al, 2004) of V1 posits a non-local influence on the structure of local maps in V1. This hypothesis states that the global visual map in V1 is remapped to the local map scale in V1 in the form of a map of response properties, e.g.…”