The scheme of paradigm and stimuli used in the present study.

<p>Two Structure-From-Motion stimuli were used in the present study, sphere and cylinder. The SFM stimuli displayed as the prime stimuli were unambiguous and only with dots from the projection of the surfaces (cylinder or sphere), while the SFM stimuli displayed as the target stimuli were ambiguous and with a high percentage of noise dots. There are three priming conditions used in the present study, congruent (when the prime and target SFM stimuli defined same object), incongruent (when the prime and target SFM defined different object), and control (when the prime stimuli were random dots). For prime stimuli, the dots in the front were larger (3:1) and brighter (4:1) than the dots in the back. For the target stimuli, all dots had the same size and luminance as the dots in the back of prime stimuli. It might be worth to note that during the experiment, there was no drawing of objects as shown here (for illustration purpose).</p

Experiment 2A.

<p>Mean accuracy of the shape judgment about the target SFM stimuli from eleven participants in the Experiment 2A. The data for the control condition was only recorded when ISI was two thousand milliseconds. Again, perceptual priming was found as indicated by the highest accuracy under congruent condition, and such priming effect became smaller with longer ISI (ISI = 4000 milliseconds), but still significant. Error bars show standard error of mean (SEM).</p

Experiment 1.

<p>Mean accuracy of the shape judgment about the target SFM stimuli from fourteen participants in Experiment 1. The data showed that participants could perceive the object of the target Structure-From-Motion (SFM) stimuli more accurately under congruent condition than the other two conditions (control and incongruent), while ISI did not affect their performance significantly. Thus, the shape perception of SFM stimulus can be primed by previous exposure to a SFM that defined the same shape. Error bars show standard error of mean (SEM).</p

Experiment 3A and 3B.

<p>Mean accuracy of the shape judgment about the target SFM stimuli from nine participants in the Experiment 3A and 3B. The data indicated that when preceded by a static shape or a semantic word, there was no priming effect with a prime defining the same shape, but a prime defining the opposite shape had a strong negative impact on the accuracy, suggesting a strong response-bias due to a top-down modulation. Error bars show standard error of mean (SEM).</p

Experiment 2B.

<p>Mean accuracy of the shape judgment about the target SFM stimuli from nine participants in the Experiment 2B. This data not only found the priming effect again, but also show such priming effect started to decay after two seconds, and such decay was small and smooth. Error bars show standard error of mean (SEM).</p

Overlap in behavioral improvement related activity with target feedback activity that is greater for the active stim group over the sham group.

<p>Overlap in significant voxels for the two analyses (Improvement Related Activity and Target Feedback Activity) are rendered on the surface of the cortex and are present in the pre- and post-central gyrus.</p

Target feedback incorrect trials relative to target feedback correct trials (Stim—Sham).

<p>Target feedback incorrect trials relative to target feedback correct trials (Stim—Sham).</p

Behavioral improvement related activity post- relative to pre-training (Visual search—Baseline control) greater for the active stim group over the sham group.

<p>A. Clusters of differential activity included: right pre- and post-central gyrus, left superior and middle temporal gyrus, as well as right Heshyl’s gyrus and superior temporal gyrus. The results are corrected for multiple comparisons at the cluster level (p < 0.05) using Monte-Carlo simulation (corrected cluster extent threshold greater than 781 contiguous voxels over uncorrected significance threshold of p < 0.005). The white arrow indicates the location of the peak-voxel for the corresponding contrast. B. The linear relationship between behavioral improvement in performance (percent correct change) on the visual search task and the corresponding change in brain activity (contrast estimate: post-pre brain activity) post- relative to pre-training. PreCG = Precentral Gyrus.</p

Individual differences in learning correlate with modulation of brain activity induced by transcranial direct current stimulation

<div><p>Transcranial direct current stimulation (tDCS) has been shown to enhance cognitive performance on a variety of tasks. It is hypothesized that tDCS enhances performance by affecting task related cortical excitability changes in networks underlying or connected to the site of stimulation facilitating long term potentiation. However, many recent studies have called into question the reliability and efficacy of tDCS to induce modulatory changes in brain activity. In this study, our goal is to investigate the individual differences in tDCS induced modulatory effects on brain activity related to the degree of enhancement in performance, providing insight into this lack of reliability. In accomplishing this goal, we used functional magnetic resonance imaging (fMRI) concurrently with tDCS stimulation (1 mA, 30 minutes duration) using a visual search task simulating real world conditions. The experiment consisted of three fMRI sessions: pre-training (no performance feedback), training (performance feedback which included response accuracy and target location and either real tDCS or sham stimulation given), and post-training (no performance feedback). The right posterior parietal cortex was selected as the site of anodal tDCS based on its known role in visual search and spatial attention processing. Our results identified a region in the right precentral gyrus, known to be involved with visual spatial attention and orienting, that showed tDCS induced task related changes in cortical excitability that were associated with individual differences in improved performance. This same region showed greater activity during the training session for target feedback of incorrect (target-error feedback) over correct trials for the tDCS stim over sham group indicating greater attention to target features during training feedback when trials were incorrect. These results give important insight into the nature of neural excitability induced by tDCS as it relates to variability in individual differences in improved performance shedding some light the apparent lack of reliability found in tDCS research.</p></div

Behavioral improvement related activity post-training relative to pre-training (Sham—Stim).

<p>Behavioral improvement related activity post-training relative to pre-training (Sham—Stim).</p