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Unformatted text preview: time. Solid lines are best-ﬁtting functions based on a model for the
decision using signal detection theory. The best ﬁts suggest that the
internal signals are proportional to motion strength and longer
performance increased with time (overviewing than 200
time. N = 45,511 trials from 32 experiments in two monkeys.
(Reprinted with permission from J. I. Gold and M. N. Shadlen, The
inﬂuence of behavioral context on the representation of a percepSuggests an “evidence accumulator”
tual decision in developing oculomotor commands. J. Neurosci.
23:632–651. © 2003 by the Society for Neuroscience.) msec) Two variants of the dot direction task B Variable Viewing
Duration experimenter controls
viewing time Motion Saccade Response Time monkey controls
viewing time Targets RT A Saccade Motion Targets Fixation Fixation e Tim F 88.1 Two versions of the motion task used to study decision making in monkeys. This task was formerly used to study the
relationship between the properties of neurons in the visual cortex
and the limits of perception (see Parker and Newsome, 1998). The
monkey decides whether the net direction of random-dot motion
is in one of two directions—here, right or left. The ease and difﬁculty of the task can be controlled by varying the percentage of
dots that are moving coherently in one of the two directions. The
remaining dots merely appear and disappear at random locations. The experimenter determines
viewing time Tim e motion, to the left for leftward motion, and so on. The monkey is
also trained to handle stimuli with different directions, speeds, and
locations in the visual ﬁeld. To study sensory processing, the
random-dot stimulus is placed in the receptive ﬁeld of a directionselective neuron. To study decision making, one of the targets that
signals the monkey’s commitment to a particular choice is placed
in a neuron’s response ﬁeld. (A) In the variable-duration version of
the task, the viewing time is a random value drawn from an expo...
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This note was uploaded on 09/08/2013 for the course BBB 217 taught by Professor Nicolerust during the Spring '12 term at UPenn.
- Spring '12