Person:

Almeida, Jorge

The dorsal visual processing stream subserves object-directed action, whereas the ventral visual processing stream subserves visual object recognition. Little is known about how information computed by dorsal-stream structures influences object recognition. We used continuous flash suppression to functionally separate information computed by the dorsal stream from that computed by the ventral stream. We show that information originating from the dorsal stream influences not only decisions requiring the selection of superordinate category labels, but also decisions that entail the selection of a basic-level object. We further show that information computed by the dorsal stream does not carry specific functional information about objects. Our results indicate that the dorsal stream, in isolation from the ventral stream, is agnostic as to the identity of the objects that it processes. We suggest that structures within the dorsal visual processing stream compute motor-relevant information (e.g., graspability), which influences the identification of manipulable objects, and is not either about the function of the object or function-specific.

Visual object recognition is subserved by ventral temporal and occipital regions of the brain. Regions comprising the dorsal visual pathway have not been considered relevant for object recognition, despite strong categorical biases for tool-related information in those regions. Here, we show that dorsal stream processes influence object categorization. We used two techniques to render prime pictures invisible: continuous flash suppression (CFS), which obliterates input into ventral temporal regions, but leaves dorsal stream processes largely unaffected, and backward masking (BM), which allows suppressed information to reach both ventral and dorsal stream structures. Categorically congruent primes suppressed under CFS facilitate categorization of tools but have no effect on nonmanipulable objects; in contrast, primes rendered invisible through BM facilitate target categorization for both tools and nonmanipulable things. Our findings demonstrate that information computed by the dorsal stream is used in object categorization, but only for a category of manipulable objects.