Spatial frequency tuning of perceptual learning and transfer in global motion

Abstract

Perceptual learning is typically highly specific to the stimuli and task used during training. However, recently it has been shown that training on global motion can transfer to untrained tasks, reflecting the generalising properties of mechanisms at this level of processing. We investigated a) if feedback was required for learning when using an equivalent noise global motion coherence task, and b) the transfer across spatial frequency of training on a global motion coherence task, and the transfer of this training to a measure of contrast sensitivity. For our first experiment two groups, with and without feedback, trained for ten days on a broadband global motion coherence task. Results indicated that feedback was a requirement for learning. For the second experiment training consisted of five days of direction discrimination on one of three global motion tasks (broadband, low or high frequency random-dot Gabors), with trial-by-trial auditory feedback. A pre-and post-training assessment was also conducted, consisting of all three types of global motion stimuli (without feedback) and high and low spatial frequency contrast sensitivity. We predicted that if learning and transfer is cortically localised, then transfer would show specificity to the area processing the task (global motion). In this case, we would predict a broad transfer between spatial frequency conditions of global motion only. However, if transfer occurred as a result of backward generalisation, a more selective transfer would occur matching the low-pass broadband tuning of the area processing global motion. Our training paradigm was successful at eliciting improvement in the trained tasks over the five days. However, post-training transfer to trained or untrained tasks was only reported for the low spatial frequency trained group. This group exhibited increased sensitivity to low spatial frequency contrast, and an improvement for the broadband global motion condition. Our findings suggest that the feedback projections from global to local stages of processing play a role in transfer. November 28, 2018 1/51 1 Perceptual learning has attracted much attention as a potential tool to aid 2 recovery of lost visual function for clinical populations [1]. The success of 3 perceptual training in amblyopia [2-4], presbyopia [4] and cortical damage [5-7] 4 has demonstrated sensory plasticity in adulthood. This evidence contradicts the 5 position that sensory development is restricted to a critical period early in 6 life [8, 9] and that the visual system is hard-wired in mature systems [10]. While 7 it has repeatedly been established that training can improve perceptual 8 abilities [11], these benefits tend to be highly specific for both the perceptual 9 features of the stimuli [12-14] and the behavioural task used in training [15]. 10 This specificity severely limits the effectiveness of perceptual learning as a 11 general therapeutic tool. Resolving the conditions under which learning is tied 12 to the features and tasks used in training, and how much it ca...