Abstract
The modulatory effects of selective visual attention on the input from the human amblyopic eye are substantially reduced in the primary visual cortex (V1) (Hou et al., 2016). Here, we provided electrophysiological evidence that training with high-attention demand tasks in adult amblyopes enhanced attentional modulation in V1 and intraparietal sulcus (IPS). We designed a dichoptic “feature counting” perceptual learning paradigm (Üner et al., 2017), which requires rapid searching and counting the vertical Gabors presented in the trained eye (90% of trials in the amblyopic eye, 10% in the fellow eye) while simultaneously being presented with distractors (horizontal Gabors) in the untrained eye. The training was about two visits per week and two hours per visit for two months. Before and after training, attentional modulation in V1 and IPS was measured using source-imaged SSVEP, and the stimuli were essentially identical to those used in Hou et al (2016). Two gratings (flickering at 12.5 and 16.67 Hz) were displayed with centers 7 deg to the left and right of a fixation point in the middle of the screen, and viewed monocularly with the non-viewing eye covered. A cue indicated that the observer should attend to left or right to detect a brief contrast increment on the cued grating. We compared the signal-to-noise ratio before and after training at the first harmonic of the driving frequencies. Our data show with the amblyopic eye, the modulation of the evoked response due to attention was enhanced in both V1 and IPS. In the fellow eye, modulation enhancement was observed in IPS, but not in V1. Visual acuity (VA) and counting performance (CP) were improved in both eyes with a higher percentage of improvement in the amblyopic eye. However, neither VA nor CP improvement was correlated to enhanced attentional modulation in V1 and IPS.