Understanding the concept of a novel tool requires interaction of the dorsal and ventral streams

The left hemisphere tool-use network consists of the dorso-dorsal, ventro-dorsal, and ventral streams, each with distinct computational abilities. In the dual-loop model, the ventral pathway through the extreme capsule is associated with conceptual understanding. We performed a learning experiment with fMRI to investigate how these streams interact when confronted with novel tools. In session one, subjects observed pictures and video sequences in real world action of known and unknown tools and were asked whether they knew the tools and whether they understood their function. In session two, video sequences of unknown tools were presented again, followed again by the question of understanding their function. Different conditions were compared to each other and effective connectivity (EC) in the tool-use network was examined. During concept acquisition of an unknown tool, EC between dorsal and ventral streams was found posterior in fusiform gyrus and anterior in inferior frontal gyrus, with a functional interaction between BA44d and BA45. When previously unknown tools were presented for a second time, EC was prominent only between dorsal stream areas. Understanding the concept of a novel tool requires an interaction of the ventral stream with the dorsal streams. Once the concept is acquired, dorsal stream areas are sufficient.

Automated summary

The left hemisphere tool-use network consists of distinct streams with different computational abilities, and the ventral pathway is associated with conceptual understanding. An fMRI study was conducted to investigate the interaction between these streams when confronted with novel tools. The study found that during concept acquisition of unknown tools, there was an EC between dorsal and ventral streams, while when previously unknown tools were presented again, EC was prominent only between dorsal stream areas. The findings suggest that the ventral stream is involved in understanding the concept of a novel tool, while the dorsal stream areas are sufficient once the concept is acquired.