What Role Does "Elongation" Play in "Tool-Specific" Activation and Connectivity in the Dorsal and Ventral Visual Streams?

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Visual Perception

Background:

• Images of tools activate a left-lateralized network, including ventral and dorsal streams.
• Tool-selective responses may reflect sensitivity to elongation rather than "toolness" alone.

Purpose of the Study:

• To investigate the role of elongation versus "toolness" in driving tool-specific activation and connectivity.
• To disentangle the contributions of shape and function in the tool network.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to study brain responses.
• Psychophysiological interaction (PPI) analysis examined connectivity.
• Dynamic causal modeling (DCM) assessed directed connectivity between brain regions.

Main Results:

• Some "tool-selective" areas coded "toolness" and elongation independently, while others showed co-coding.
• "Toolness", not elongation, modulated connectivity between ventral and dorsal streams.
• Viewing tools increased ventral-to-dorsal stream connectivity; elongated tools uniquely increased reciprocal connectivity.

Conclusions:

• "Toolness" and elongation differentially affect activation and connectivity within the tool network.
• Findings help resolve debates on the relative contribution of "toolness" versus elongation in dorsal-stream areas.