Ciba Foundation Symposium 184 - Higher-Order Processing in the Visual System

1994 ◽  
Keyword(s):  
Visual System ◽  
Higher Order ◽  
Ciba Foundation Symposium ◽  
Order Processing

Perceptual Grouping of Dots in Noise

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 160-160
Author(s):  
S P Tripathy ◽  
A J Mussap ◽  
H B Barlow
Keyword(s):  
Visual System ◽  
Perceptual Grouping ◽  
Higher Order ◽  
Line Detection ◽  
Order Processing ◽  
Correct Performance ◽  
Single Mechanism ◽  
Series Of Experiments

Observers were asked to report the orientation of alignment (horizontal vs vertical) of a group of target dots embedded in randomly placed noise dots. For this perceptual grouping task, sensitivity (the number of noise dots giving 75% correct performance) was measured as a function of the number of target dots. We report surprising tolerance to positional jitter of target dots, with far less tolerance exhibited to alignment jitter than separation jitter. In this respect, perceptual grouping in our task resembles line detection. In a further series of experiments the target was produced by positional shifts of an appropriate number of noise dots, rather than by addition of target dots to the noise dots (this procedure minimised density cues). The improvement in sensitivity with increasing number of target dots was found to be linear (when plotted on log — log axes) with a slope of 0.5, as opposed to bilinear [cf B Moulden, 1994, in Higher-Order Processing in the Visual System Eds G R Bock, J A Goode (Chichester: John Wiley) pp 170 – 192]. This linearity suggests that, over the range of target dot numbers tested, a single mechanism may be sufficient to explain performance.

The novel guanylyl cyclase MsGC-I is strongly expressed in higher-order neuropils in the brain of Manduca sexta

2001 ◽  
Vol 204 (2) ◽  
pp. 305-314 ◽  
Author(s):  
A. Nighorn ◽  
P.J. Simpson ◽  
D.B. Morton
Keyword(s):  
Nervous System ◽  
Manduca Sexta ◽  
Guanylyl Cyclase ◽  
Higher Order ◽  
Adult Brain ◽  
Central Complex ◽  
Amino Acid Residues ◽  
Order Processing ◽  
Guanylyl Cyclases ◽  
The Brain

Guanylyl cyclases are usually characterized as being either soluble (sGCs) or receptor (rGCs). We have recently cloned a novel guanylyl cyclase, MsGC-I, from the developing nervous system of the hawkmoth Manduca sexta that cannot be classified as either an sGC or an rGC. MsGC-I shows highest sequence identity with receptor guanylyl cyclases throughout its catalytic and dimerization domains, but does not contain the ligand-binding, transmembrane or kinase-like domains characteristic of receptor guanylyl cyclases. In addition, MsGC-I contains a C-terminal extension of 149 amino acid residues. In this paper, we report the expression of MsGC-I in the adult. Northern blots show that it is expressed preferentially in the nervous system, with high levels in the pharate adult brain and antennae. In the antennae, immunohistochemical analyses show that it is expressed in the cell bodies and dendrites, but not axons, of olfactory receptor neurons. In the brain, it is expressed in a variety of sensory neuropils including the antennal and optic lobes. It is also expressed in structures involved in higher-order processing including the mushroom bodies and central complex. This complicated expression pattern suggests that this novel guanylyl cyclase plays an important role in mediating cyclic GMP levels in the nervous system of Manduca sexta.

Recalibration of Visual Stability Mechanism Occurs in a Higher-Order Visual System

2006 ◽  
Vol 13 (2) ◽  
pp. 111-118
Author(s):  
Kunimitsu Takahara ◽  
Katsunori Okajima ◽  
Masanori Takase
Keyword(s):  
Visual System ◽  
Higher Order ◽  
Visual Stability

Higher Order Visual Processing in Macaque Extrastriate Cortex

2008 ◽  
Vol 88 (1) ◽  
pp. 59-89 ◽  
Author(s):  
Guy A. Orban
Keyword(s):  
Visual Processing ◽  
Higher Order ◽  
Visual Signals ◽  
Extrastriate Cortex ◽  
Temporal Area ◽  
Order Processing ◽  
Neuronal Populations ◽  
Medial Superior Temporal ◽  
Extrastriate Areas ◽  
Putative Mechanism

The extrastriate cortex of primates encompasses a substantial portion of the cerebral cortex and is devoted to the higher order processing of visual signals and their dispatch to other parts of the brain. A first step towards the understanding of the function of this cortical tissue is a description of the selectivities of the various neuronal populations for higher order aspects of the image. These selectivities present in the various extrastriate areas support many diverse representations of the scene before the subject. The list of the known selectivities includes that for pattern direction and speed gradients in middle temporal/V5 area; for heading in medial superior temporal visual area, dorsal part; for orientation of nonluminance contours in V2 and V4; for curved boundary fragments in V4 and shape parts in infero-temporal area (IT); and for curvature and orientation in depth from disparity in IT and CIP. The most common putative mechanism for generating such emergent selectivity is the pattern of excitatory and inhibitory linear inputs from the afferent area combined with nonlinear mechanisms in the afferent and receiving area.

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