Perceptual shape sensitivity to upright and inverted faces is reflected in neuronal adaptation

Area of Science:

• Neuroscience
• Cognitive Science
• Perception

Background:

• Previous research demonstrated narrow neuronal tuning to faces, linked to perceptual discrimination.
• It remained unclear if this tuning is face-specific or a general property of object representation.
• The role of physical stimulus changes versus perceptual discrimination in adaptation tuning was also undetermined.

Purpose of the Study:

• To investigate whether neuronal tuning to object discrimination is a general property beyond faces.
• To differentiate the influence of physical stimulus changes versus perceptual discrimination on fMR-adaptation tuning.
• To examine how familiarity and perceptual sensitivity modulate neural tuning in object-selective brain regions.

Main Methods:

• Employed a functional Magnetic Resonance Imaging (fMRI)-adaptation paradigm using face morphing at varying levels.
• Compared upright and inverted faces to manipulate familiarity and perceptual discrimination while controlling low-level features.
• Analyzed adaptation tuning in the fusiform face area (FFA) and other object-selective regions.

Main Results:

• Confirmed a perceptual "inversion effect," showing reduced discrimination for inverted faces.
• Observed that fMR-adaptation tuning in the FFA adjusted to perceptual sensitivity for both upright and inverted faces.
• Identified differential tuning widths in other object-selective areas for the two face categories.

Conclusions:

• Neuronal adaptation tuning in the FFA reflects perceptual sensitivity to object features, not just physical stimulus properties.
• The findings support a model where object discrimination relies on the shape tuning characteristics of individual neurons.
• This suggests that the neural mechanisms for object discrimination are adaptable and linked to perceptual experience.