How Visual Expertise Changes Representational Geometry: A Behavioral and Neural Perspective.

Many people develop expertise in specific domains of interest, such as chess, microbiology, radiology, and, the case in point in our study: ornithology. It is poorly understood to what extent such expertise alters brain function. Previous neuroimaging studies of expertise have typically focused upon the category level, for example, selectivity for birds versus nonbird stimuli. We present a multivariate fMRI study focusing upon the representational similarity among objects of expertise at the subordinate level. We compare the neural representational spaces of experts and novices to behavioral judgments. At the behavioral level, ornithologists (n = 20) have more fine-grained and task-dependent representations of item similarity that are more consistent among experts compared to control participants. At the neural level, the neural patterns of item similarity are more distinct and consistent in experts than in novices, which is in line with the behavioral results. In addition, these neural patterns in experts show stronger correlations with behavior compared to novices. These findings were prominent in frontal regions, and some effects were also found in occipitotemporal regions. This study illustrates the potential of an analysis of representational geometry to understand to what extent expertise changes neural information processing.

Domain-general and domain-specific neural changes underlying visual expertise.

Visual expertise induces changes in neural processing for many different domains of expertise. However, it is unclear how expertise effects for different domains of expertise are related. In the present fMRI study, we combine large-scale univariate and multi-voxel analyses to contrast the expertise-related neural changes associated with two different domains of expertise, bird expertise (ornithology) and mineral expertise (mineralogy). Results indicated distributed expertise-related neural changes, with effects for both domains of expertise in high-level visual cortex and effects for bird expertise even extending to low-level visual regions and the frontal lobe. Importantly, a multivariate generalization analysis showed that effects in high-level visual cortex were specific to the domain of expertise. In contrast, the neural changes in the frontal lobe relating to expertise showed significant generalization, signaling the presence of domain-independent expertise effects. In conclusion, expertise is related to a combination of domain-specific and domain-general changes in neural processing.

Generalization of Respiratory Symptom Triggers.

Behavioral management of asthma and other chronic conditions depends upon the accurate identification of environmental factors that trigger symptom onset. In this study, we developed a lab-based conditioning method to study category-based acquisition and generalization of respiratory symptom triggers. During trigger acquisition, unique exemplars of two different categories were shown to a sample of healthy participants (n=48). CS+ exemplars were paired with CO2 inhalation on 50% of trials, while CS- exemplars were always paired with room air. Trigger categories differed in their conceptual similarity. In a generalization task, participants rated symptom expectancy for a set of triggers that included previously seen exemplars, novel exemplars, and exemplars from novel categories. Results show that participants acquired differential symptom expectancies based on category information, which generalized to novel CS+ exemplars and novel categories that shared similarity with the CS+ category. Greater similarity between CS+ and CS- categories increased differential effects for both old and novel exemplars of CS+ and CS- categories, and increased the proportion of novel CS+ exemplars that were remembered as being seen during acquisition. These findings suggest that a more narrowly defined contrast between triggers and nontriggers promotes category-based inference and could help to reduce uncertainty about potential triggers.

The Search for the Face of the Visual Homunculus.

The functional organization within face-sensitive regions in the brain is largely unknown. A new fMRI study provided evidence that a face-selective region contains neighboring patches of cortex that encode physically neighboring face features. We suggest that multiple mechanisms should be considered for a full understanding of the functional maps in face-selective cortex.