Journal of Neuroscience, Vol 15, 7644-7652, Copyright © 1995 by Society for Neuroscience
Effects of delayed visual information on the rate and amount of prism adaptation in the human
S Kitazawa, T Kohno and T Uka
Neuroscience Section, Electrotechnical Laboratory, Tsukuba, Japan.
Accurate reaching towards a visual target is initially disturbed when the
visual field is displaced by prisms, but recovers with successive trials.
To determine how the improvement depends on the visual error signals
associated with the motor output, the time course of prism adaptation was
studied with delayed visual information on the error. Subjects were trained
to reach rapidly at a target on a tangent screen. Vision was always blocked
during the movement, and allowed again only after the index finger touched
the screen. One experiment consisted of three sets of 30 trials. In the
first set, the subject wore no prisms and vision was allowed without delay.
In the second, the visual field was displaced by prisms, and vision was
available only after a delay period of 0-10,000 msec while the subjects
maintained their final pointing position. Initially, the subject misreached
the target by about the amount of visual displacement (60 mm). Errors
decreased with trials by an amount proportional to the error in the
preceding trial. The rate of decrease of error was generally largest when
the delay was 0 msec, became significantly smaller when the delay was 50
msec, and showed only gradual change with longer delays. In the third set,
the subject wore no prisms and vision was allowed without delay. Initial
misreaching in the direction opposite to the visual displacement,
reflecting the amount of adaptation in the second set, was generally
largest with no delay (median of 46 mm) and significantly smaller with 50
msec and longer delays (17-33 mm).(ABSTRACT TRUNCATED AT 250 WORDS)
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