Summary: SUPPORTING ONLINE MATERIAL
Parallel and Serial Neural Mechanisms for Visual Search in Macaque Area V4
Narcisse P. Bichot, Andrew F. Rossi, Robert Desimone
Materials and Methods
Two macaque monkeys were used, and all procedures were in accordance with NIH guidelines. Monkeys
were implanted with a post for holding the head, with a scleral search coil for monitoring eye position,
and with a recording chamber over area V4.
Stimuli. In the feature search tasks (see below), the stimuli were combinations of one of eight colors and
one of eight shapes, subtended approximately 1.1 degrees of visual angle (dva), and were matched for
number of pixels. The colors were matched for luminance (~12.5 cd/m2
) and were red (CIE, x = .625, y =
.345), orange (x = .596, y = .368), yellow-green (x = .488, y = .451), green (x = .293, y = .590), cyan (x =
.205, y = .277), blue (x = .165, y = .089), purple (x = .242, y = .121), and magenta (x = .427, y = .229).
Stimuli were presented on a dark background (<0.1 cd/m2
). Gray was never used as a target stimulus
color as it was reserved for the shape cue. The eight shapes were chosen from a set of twenty shapes
based on the response properties of each neuron, determined in exploratory trials. A square was never
used as a target shape as it was reserved for the color cue. In the conjunction search task (see below), the
stimuli were combinations of two colors and two shapes.
Behavioral Tasks. Monkeys were trained to search for a target stimulus embedded among irrelevant,