The role of the dorsal visual processing stream in tool identification

Abstract

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.

Figure 1. Experimental Design

For experiments 1a, 1b, and 2a, we used CFS to suppress the primes. In CFS a static image competes with a dynamic image, with the latter reliably suppressing the former for a prolonged time. To induce CFS we presented a low-luminance, low-contrast version of the prime stimuli to the participant's non-dominant eye, and a dynamic high-contrast random noise pattern that would change every 100 ms on the dominant eye (the high luminance of images in the figure is for visualization purposes). Red/green anaglyph glasses were worn by the participants to allow for dioptic presentation of the images. For experiment 2b, we used BM to suppress the primes. (A) Procedure employed for CFS in experiments 1a, 1b, and 2a. (B) Procedure employed for BM in experiment 2b.

Figure 2. Behavioral priming effects

Average priming effects are plotted as a function of the experimental conditions.* for p < 0.05; ** for p < 0.001. Error bars represent SEM for priming effects across subjects. (A) Results for experiments 1a and 1b; (B) Results for experiments 2a and 2b.

Figure 2. Behavioral priming effects

Average priming effects are plotted as a function of the experimental conditions.* for p < 0.05; ** for p < 0.001. Error bars represent SEM for priming effects across subjects. (A) Results for experiments 1a and 1b; (B) Results for experiments 2a and 2b.