# Show Reference: "Mechanisms of visual attention in the human cortex"

Mechanisms of visual attention in the human cortex. Annual Review of Neuroscience, Vol. 23, No. 1. (2000), pp. 315-341, doi:10.1146/annurev.neuro.23.1.315 by Sabine Kastner, Leslie G. Ungerleider
@article{kastner-and-ungerleider-2000,
abstract = {A typical scene contains many different objects that, because of the limited processing capacity of the visual system, compete for neural representation. The competition among multiple objects in visual cortex can be biased by both bottom-up sensory-driven mechanisms and top-down influences, such as selective attention. Functional brain imaging studies reveal that, both in the absence and in the presence of visual stimulation, biasing signals due to selective attention can modulate neural activity in visual cortex in several ways. Although the competition among stimuli for representation is ultimately resolved within visual cortex, the source of top-down biasing signals derives from a network of areas in frontal and parietal cortex.},
address = {Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, USA. sabine@ln.nimh.nih.gov},
author = {Kastner, Sabine and Ungerleider, Leslie G.},
citeulike-article-id = {1297894},
doi = {10.1146/annurev.neuro.23.1.315},
issn = {0147-006X},
journal = {Annual Review of Neuroscience},
keywords = {attention, biology, cortex, visual},
number = {1},
pages = {315--341},
pmid = {10845067},
posted-at = {2014-09-26 10:54:11},
priority = {2},
title = {Mechanisms of visual attention in the human cortex.},
url = {http://dx.doi.org/10.1146/annurev.neuro.23.1.315},
volume = {23},
year = {2000}
}



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Search targets which share few features with mutually similar distractors surrounding them are said to `pop out': it seems to require hardly any effort to identify them and search for them is very fast.

Search targets that share most features with their surrounding, on the other hand, require much more time time be identified.

Neurons at later stages in the hierarchy of visual processing extract very complex features (like faces).

Spatial attention raises baseline activity in neurons whose RF are where the attention is even without a visual stimulus (in visual cortex).

Unilateral lesions in brain areas associated with attention can lead to visuospatial neglect; the failure to consider anything within a certain region of the visual field. In extreme cases this can mean that patients e.g. only read from one side of a book.

Kastner and Ungerleider propose that the top-down signals which lead to the effects of visual attention originate from brain regions outside the visual cortex.

Regions lesions of which can induce visuospatial neglect include

• the parietal lobe, in particular the inferior part,
• temporo-parietal junction,
• the anterior cingulate cortex,
• basal ganglia,
• thalamus,
• the pulvinar nucleus.

Frontal eye fields (FEF) and intraparietal sulcus (IPS) have been associated with voluntary orienting of visual attention.

The visual cortex is hierarchically organized.

Lateral prefrontal cortex (LPFC) and frontal eye fields (FEF) are frontal cortex regions involved in visual attention and target selection.