Orientation column

About: Orientation column is a research topic. Over the lifetime, 1142 publications have been published within this topic receiving 130169 citations.

Synaptology of the Visual Cortex

Abstract: The comparative anatomy of visual cortical projections and of the subdivision of the visual region into three main cortical areas 17, 18 and 19 has been discussed in detail in Chapter 19 and cytoarchitectonics — based on Nissl pictures — are mentioned in Chapter 21. This review will be, therefore, mainly concerned with Golgi architectonics and the results of degeneration and electron microscope (EM) analysis of the synaptic relations.

Orientation Selectivity in Pinwheel Centers in Cat Striate Cortex

Abstract: In primary visual cortex of higher mammals neurons are grouped according to their orientation preference, forming "pinwheels" around "orientation centers." Although the general structure of orientation maps is largely resolved, the microscopic arrangement of neuronal response properties in the orientation centers has remained elusive. The tetrode technique, enabling multiple single-unit recordings, in combination with intrinsic signal imaging was used to reveal the fine-grain structure of orientation maps in these locations. The results show that orientation centers represent locations where orientation columns converge containing normal, sharply tuned neurons of different orientation preference lying in close proximity.

The Functional Organization of Local Circuits in Visual Cortex: Insights from the Study of Tree Shrew Striate Cortex

Abstract: We have used a combination of anatomical and physiological techniques to explore the functional organization of vertical and horizontal connections in tree shrew striate cortex. Our studies of vertical connections reveal a remarkable specificity in the laminar arrangement of the projections from layer IV to layer III that establishes three parallel intracortical pathways. The pathways that emerge from layer IV are not simple continuations of parallel thalamocortical pathways. Layer IV and its connections with layer II/III restructure the inputs from the LGN, combining the activity from ON and OFF channels and from the left and right eye and transmit the products of this synthesis to separate strata within the overlying layers. In addition, studies of two other prominent vertical connection pathways, the projections from layer VI to layer IV and from layer II/III to layer V suggest that the parallel nature of these systems is perpetuated throughout the cortical depth. Our studies of horizontal connections have revealed a systematic relationship between a neuron's orientation preference and the distribution of its axon arbor across the cortical map of visual space. Horizontal connections in layer II/III extend for greater distances and give rise to a greater number of terminals along an axis of the visual field map that corresponds to the neuron's preferred orientation. These findings suggest that the contribution of horizontal inputs to the response properties of layer II/III neurons is likely to be greater in regions of visual space that lie along the axis of preferred orientation (endzones) than along the orthogonal axis (side zones). Topographically aligned horizontal connections may contribute to the orientation preference of layer II/III neurons and could account for the axial specificity of some receptive field surround effects. Together, these results emphasize that specificity in the spatial arrangement of local circuit axon arbors plays an important role in shaping the response properties of neurons in visual cortex.

Gateways of Ventral and Dorsal Streams in Mouse Visual Cortex

Abstract: It is widely held that the spatial processing functions underlying rodent navigation are similar to those encoding human episodic memory (Doeller et al., 2010). Spatial and nonspatial information are provided by all senses including vision. It has been suggested that visual inputs are fed to the navigational network in cortex and hippocampus through dorsal and ventral intracortical streams (Whitlock et al., 2008), but this has not been shown directly in rodents. We have used cytoarchitectonic and chemoarchitectonic markers, topographic mapping of receptive fields, and pathway tracing to determine in mouse visual cortex whether the lateromedial field (LM) and the anterolateral field (AL), which are the principal targets of primary visual cortex (V1) (Wang and Burkhalter, 2007) specialized for processing nonspatial and spatial visual information (Gao et al., 2006), are distinct areas with diverse connections. We have found that the LM/AL border coincides with a change in type 2 muscarinic acetylcholine receptor expression in layer 4 and with the representation of the lower visual field periphery. Our quantitative analyses also show that LM strongly projects to temporal cortex as well as the lateral entorhinal cortex, which has weak spatial selectivity (Hargreaves et al., 2005). In contrast, AL has stronger connections with posterior parietal cortex, motor cortex, and the spatially selective medial entorhinal cortex (Haftig et al., 2005). These results support the notion that LM and AL are architecturally, topographically, and connectionally distinct areas of extrastriate visual cortex and that they are gateways for ventral and dorsal streams.