scholarly journals Psychophysical evidence for object segregation through endogenous asynchrony

2010 ◽  
Vol 9 (8) ◽  
pp. 928-928
Author(s):  
A. Clarke ◽  
S. Rainville
Keyword(s):  
Object Segregation

scholarly journals Neuronal Correlates of Multiple Top–Down Signals during Covert Tracking of Moving Objects in Macaque Prefrontal Cortex

2012 ◽  
Vol 24 (10) ◽  
pp. 2043-2056 ◽  
Author(s):  
Ayano Matsushima ◽  
Masaki Tanaka
Keyword(s):  
Prefrontal Cortex ◽  
Object Tracking ◽  
Visual Processing ◽  
Moving Objects ◽  
Top Down ◽  
Selective Suppression ◽  
Internal Object ◽  
Object Segregation ◽  
Task Irrelevant ◽  
The Brain

Resistance to distraction is a key component of executive functions and is strongly linked to the prefrontal cortex. Recent evidence suggests that neural mechanisms exist for selective suppression of task-irrelevant information. However, neuronal signals related to selective suppression have not yet been identified, whereas nonselective surround suppression, which results from attentional enhancement for relevant stimuli, has been well documented. This study examined single neuron activities in the lateral PFC when monkeys covertly tracked one of randomly moving objects. Although many neurons responded to the target, we also found a group of neurons that exhibited a selective response to the distractor that was visually identical to the target. Because most neurons were insensitive to an additional distractor that explicitly differed in color from the target, the brain seemed to monitor the distractor only when necessary to maintain internal object segregation. Our results suggest that the lateral PFC might provide at least two top–down signals during covert object tracking: one for enhancement of visual processing for the target and the other for selective suppression of visual processing for the distractor. These signals might work together to discriminate objects, thereby regulating both the sensitivity and specificity of target choice during covert object tracking.

scholarly journals Triggerfish uses chromaticity and lightness for object segregation

2017 ◽  
Vol 4 (12) ◽  
pp. 171440 ◽  
Author(s):  
Laurie Mitchell ◽  
Karen L. Cheney ◽  
Fabio Cortesi ◽  
N. Justin Marshall ◽  
Misha Vorobyev
Keyword(s):  
Visual Perception ◽  
Human Visual Perception ◽  
Chromatic Contrast ◽  
Visual Patterns ◽  
Ishihara Test ◽  
Achromatic Contrast ◽  
Chromatic Cues ◽  
Object Segregation

Humans group components of visual patterns according to their colour, and perceive colours separately from shape. This property of human visual perception is the basis behind the Ishihara test for colour deficiency, where an observer is asked to detect a pattern made up of dots of similar colour with variable lightness against a background of dots made from different colour(s) and lightness. To find out if fish use colour for object segregation in a similar manner to humans, we used stimuli inspired by the Ishihara test. Triggerfish ( Rhinecanthus aculeatus ) were trained to detect a cross constructed from similarly coloured dots against various backgrounds. Fish detected this cross even when it was camouflaged using either achromatic or chromatic noise, but fish relied more on chromatic cues for shape segregation. It remains unknown whether fish may switch to rely primarily on achromatic cues in scenarios where target objects have higher achromatic contrast and lower chromatic contrast. Fish were also able to generalize between stimuli of different colours, suggesting that colour and shape are processed by fish independently.

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