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Dongho Kim, Aaron Seitz, Takeo Watanabe; Effect of reward on perceptual learning. Journal of Vision 2007;7(9):85. doi: 10.1167/7.9.85.
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© ARVO (1962-2015); The Authors (2016-present)
It has been proposed that visual cortical processing is improved for stimuli that are consistently paired with reinforcement, which might be a mechanism underlying perceptual learning (Seitz and Watanabe, Nature, 2003; TICS, 2005). To test this, we examined whether paring stimuli with a liquid reward (in humans) results in a sensitivity improvement to that stimulus. Using a classical conditioning paradigm, we presented every 500 msecs a different sinusoidal noise background that filled the display. At random intervals, a sinusoidal grating that was spatially masked by sinusoidal noise (20% signal; 2 c/deg; 2 deg diameter) and was presented for 500 msecs, superimposed on the noise background. For each subject, one of 112.5 deg or 22.5 deg grating was paired liquid-delivery (C+) and the other orientations was presented without reward (C-). Subjects were asked to restrain from eating or drinking for five hours previous to each experimental session. The liquid reward was provided 400 msecs after presentation of the grating pattern and thus partially overlapped with the grating presentation. Pre and post test was done before and after training to see the learning effect. In the tests, performance was evaluated for the C+ and C- orientations (112.5 deg or 22.5 deg). After the training significant sensitivity improvement occurred in low signal level (55.8% vs. 75.9% in 5% signal) in paired orientation with the reward, however no significant improvement in unpaired orientation (51.3% vs. 53.1% in 5% signal). The pre and post test result of D-prime (0.18 vs. 0.79) and beta (0.97 vs. 0.69) in paired orientation also showed that our result is not a response bias but perceptual learning. These results support the proposal that stimulus reinforcement pairing enhances visual cortical responses selectively for the paired stimulus in human.
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