Abstract
Context affects the salience and visibility of image elements in visual scenes. Collinear flankers can enhance or decrease the perceptual and neuronal sensitivity to flanked stimuli. These effects are mediated through lateral interactions between neurons in the primary visual cortex (area V1), in conjunction with feedback from higher visual areas. The strength of lateral interactions is affected by cholinergic neuromodulation. Blockade of muscarinic receptors should increase the strength of lateral intracortical interactions, while nicotinic blockade should reduce thalamocortical feed-forward drive. Here we test this proposal through local iontophoretic application of the muscarinic receptor antagonist scopolamine and the nicotinic receptor antagonist mecamylamine, while recording single cells in parafoveal representations in awake fixating macaque V1. Collinear flankers generally reduced neuronal contrast sensitivity. Muscarinic and nicotinic receptor blockade equally reduced neuronal contrast sensitivity. Contrary to our hypothesis, flanker interactions were not systematically affected by either receptor blockade.
Highlights
Context affects the salience and visibility of image elements in visual scenes
We recorded the effect of flankers on firing rates when mecamylamine was not applied (10 trials, box 1)
There was a mild trend towards an interaction between flankers and drug (flankers*drug; F(3,1444) = 2.3, p = 0.078), and there was an interaction between flankers and contrast (flanker*contrast; F(21,1444) = 15.45, p < 0.001)
Summary
Context affects the salience and visibility of image elements in visual scenes. Collinear flankers can enhance or decrease the perceptual and neuronal sensitivity to flanked stimuli. Flanker induced inhibition has been reported for larger wavelength (distance) in macaque parafoveal locations[11] These contextual effects have been argued to arise from lateral neuronal interactions in striate cortex[12,13,14,15], but from feedback connections from higher areas[14,15,16,17,18,19]. We hypothesized that muscarinic blockade, increasing lateral and feedback interactions, will facilitate flanker-induced effects while reducing neuronal activity and contrast s ensitivity[37,38,39]. While nicotinic blockade reduced overall neuronal gain it had no systematic effect on flanker induced alterations to contrast sensitivity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
