What is new in perceptual learning?

An investigation of far and near transfer in a gamified visual learning paradigm

After training, visual perceptual learning improvements are mostly constrained to the trained stimulus feature and retinal location. The aim of this study is to construct an integrated paradigm where the visual learning happens in a more natural context and in parallel for multiple stimulus types, and to test the generalization of learning-related improvements towards untrained features, locations, and more general cognitive domains. Half the subjects were trained with a gamified perceptual learning paradigm for ten hours, which consisted of an orientation discrimination task and a novel object categorization task embedded in a three-dimensional maze. A second group of subjects, an active control group, played ten hours of Candy Crush Saga. Before and after training, all subjects completed a 'near transfer' orientation discrimination and novel object categorization task, as well as a set of 'far transfer' general cognitive and attentional tasks. During the perceptual learning tasks, two different stimulus features and two retinal location pairs were assessed in each task. For the experimental group, one stimulus feature and retinal location pair was trained, whilst the other one remained untrained. Both features and location pairs were untrained in the control group. Far transfer did occur in some domains across all subjects irrespective of the training regimen (i.e. executive functioning, mental rotation performance, and multitask performance and speed). Near transfer was present in both groups, however only more pronounced for one particular task in the experimental group, namely novel object categorization. To conclude, all but one near transfer task did not generalize more than the control group.

Bottom-up and top-down factors of motion direction learning transfer

Perceptual learning of motion discrimination has long been believed to be motion direction specific. However, recent studies using a double-training paradigm, in which the to-be-transferred condition was experienced through practicing an irrelevant task, found that perceptual learning in various visual tasks, including motion direction discrimination, can transfer completely to new conditions. This transfer occurred when the transfer stimulus was subconsciously presented, or when top-down attention was allocated to the transfer stimulus (which was absent). In the current study, observers were exposed subconsciously, or directed top-down attention, to the transfer motion direction, either simultaneously or successively with training. Data showed that motion direction learning transferred to the transfer direction, and suggest that motion direction learning specificity may result from under-activations of untrained visual neurons due to insufficient bottom-up stimulation and/or lack of top-down attention during training. These results shed new light on the neural mechanisms underlying motion perceptual learning and provide a constraint for models of motion perceptual learning.

Segregation of Spontaneous and Training Induced Recovery from Visual Field Defects in Subacute Stroke Patients

Whether rehabilitation after stroke profits from an early start is difficult to establish as the contributions of spontaneous recovery and treatment are difficult to tease apart. Here, we use a novel training design to dissociate these components for visual rehabilitation of subacute stroke patients with visual field defects such as hemianopia. Visual discrimination training was started within 6 weeks after stroke in 17 patients. Spontaneous and training-induced recoveries were distinguished by training one-half of the defect for 8 weeks, while monitoring spontaneous recovery in the other (control) half of the defect. Next, trained and control regions were swapped, and training continued for another 8 weeks. The same paradigm was also applied to seven chronic patients for whom spontaneous recovery can be excluded and changes in the control half of the defect point to a spillover effect of training. In both groups, field stability was assessed during a no-intervention period. Defect reduction was significantly greater in the trained part of the defect than in the simultaneously untrained part of the defect irrespective of training onset (p = 0.001). In subacute patients, training contributed about twice as much to their defect reduction as the spontaneous recovery. Goal Attainment Scores were significantly and positively correlated with the total defect reduction (p = 0.01), percentage increase reading speed was significantly and positively correlated with the defect reduction induced by training (epoch 1: p = 0.0044; epoch 2: p = 0.023). Visual training adds significantly to the spontaneous recovery of visual field defects, both during training in the early and the chronic stroke phase. However, field recovery as a result of training in this subacute phase was as large as in the chronic phase. This suggests that patients benefited primarily of early onset training by gaining access to a larger visual field sooner.