Learning of the same task subserved by substantially different mechanisms between patients with body dysmorphic disorder and healthy individuals.

It has remained unclear whether individuals with psychiatric disorders involving altered visual processing employ similar neuronal mechanisms during perceptual learning of a visual task. We investigated this question by training patients with body dysmorphic disorder, a psychiatric disorder characterized by distressing or impairing preoccupation with nonexistent or slight defects in one's physical appearance, and healthy controls on a visual detection task for human faces with low spatial frequency components. Brain activation during task performance was measured with functional magnetic resonance imaging before the beginning and after the end of behavioral training. Both groups of participants improved performance on the trained task to a similar extent. However, neuronal changes in the fusiform face area were substantially different between groups such that activation for low spatial frequency faces in the right fusiform face area increased after training in body dysmorphic disorder patients but decreased in controls. Moreover, functional connectivity between left and right fusiform face area decreased after training in patients but increased in controls. Our results indicate that neuronal mechanisms involved in perceptual learning of a face detection task differ fundamentally between body dysmorphic disorder patients and controls. Such different neuronal mechanisms in body dysmorphic disorder patients might reflect the brain's adaptations to altered functions imposed by the psychiatric disorder.

Geometric-relationship specific transfer in visual perceptual learning.

Visual perceptual learning (VPL) is defined as long-term improvement on a visual task as a result of visual experience. In many cases, the improvement is highly specific to the location where the target is presented, which refers to location specificity. In the current study, we investigated the effect of a geometrical relationship between the trained location and an untrained location on transfer of VPL. We found that significant transfer occurs either diagonally or along a line passing the fixation point. This indicates that whether location specificity or location transfer occurs at least partially depends on the geometrical relationship between trained location and an untrained location.

Learning of the same task subserved by substantially different mechanisms between patients with Body Dysmorphic Disorder and healthy individuals.

It is generally believed that learning of a perceptual task involving low-level neuronal mechanisms is similar between individuals. However, it is unclear whether this assumption also applies to individuals with psychiatric disorders that are known to have altered brain activation during visual processing. We investigated this question in patients with body dysmorphic disorder (BDD), a psychiatric disorder characterized by distressing or impairing preoccupation with nonexistent or slight defects in one's physical appearance, and in healthy controls. Participants completed six training sessions on separate days on a visual detection task for human faces with low spatial frequency (LSF) components. Brain activation during task performance was measured with functional magnetic resonance imaging (fMRI) on separate days prior to and after training. The behavioral results showed that both groups of participants improved on the visual detection task to a similar extent through training. Despite this similarity in behavioral improvement, neuronal changes in the Fusiform Face Area (FFA), a core cortical region involved in face processing, with training were substantially different between groups. First, activation in the right FFA for LSF faces relative to High Spatial Frequency (HSF) faces that were used as an untrained control increased after training in BDD patients but decreased in controls. Second, resting state functional connectivity between left and right FFAs decreased after training in BDD patients but increased in controls. Contrary to the assumption that learning of a perceptual task is subserved by the same neuronal mechanisms across individuals, our results indicate that the neuronal mechanisms involved in learning of a face detection task differ fundamentally between patients with BDD and healthy individuals. The involvement of different neuronal mechanisms for learning of even simple perceptual tasks in patients with BDD might reflect the brain's adaptations to altered functions imposed by the psychiatric disorder.

Category-Induced Transfer of Visual Perceptual Learning.

Visual perceptual learning (VPL) refers to a long-term enhancement of visual task performance as a result of visual experience [1-6]. VPL is generally specific for the trained visual feature, meaning that training on a feature leads to performance enhancement only on the feature and those in its close vicinity. In the meantime, visual perception is often categorical [7-10]. This may partially be because the ecological importance of a stimulus is usually determined by the category to which the stimulus belongs (e.g., snake, lightning, and fish) [11]. Thus, it would be advantageous to an observer if encountering or working on a feature from a category increases sensitivity to features under the same category. However, studies of VPL have used uncategorized features. Here, we found a category-induced transfer of VPL, where VPL of an orientation transferred to untrained orientations within the same category as the trained orientation, but not orientations from the different category. Furthermore, we found that, although category learning transferred to other locations in the visual field, the category-induced transfer of VPL occurred only when visual stimuli for the category learning and those for VPL training were presented at the same location. These results altogether suggest that feature specificity in VPL is greatly influenced by cognitive processing, such as categorization in a top-down fashion. In an environment where features are categorically organized, VPL may be more generalized across features under the same category. Such generalization implies that VPL is of more ecological significance than has been thought.

Neural correlates of face gender discrimination learning.

Using combined psychophysics and event-related potentials (ERPs), we investigated the effect of perceptual learning on face gender discrimination and probe the neural correlates of the learning effect. Human subjects were trained to perform a gender discrimination task with male or female faces. Before and after training, they were tested with the trained faces and other faces with the same and opposite genders. ERPs responding to these faces were recorded. Psychophysical results showed that training significantly improved subjects' discrimination performance and the improvement was specific to the trained gender, as well as to the trained identities. The training effect indicates that learning occurs at two levels-the category level (gender) and the exemplar level (identity). ERP analyses showed that the gender and identity learning was associated with the N170 latency reduction at the left occipital-temporal area and the N170 amplitude reduction at the right occipital-temporal area, respectively. These findings provide evidence for the facilitation model and the sharpening model on neuronal plasticity from visual experience, suggesting a faster processing speed and a sparser representation of face induced by perceptual learning.