Figure-ground organization in the visual cortex: does meaning matter?

Figure-ground organization in the visual cortex is generally assumed to be based partly on general rules, and partly on specific influences of object recognition in higher centers as found in the temporal lobe. To see if shape familiarity influences figure-ground organization we tested border-ownership selective neurons in monkey V1-V2 with silhouettes of human and monkey face profiles and 'nonsense' silhouettes constructed by mirror-reversing the front part of the profile. We found no superiority of face silhouettes compared to nonsense shapes in eliciting border-ownership signals over all. However, in some neurons, border-ownership signals differed strongly between the two categories consistently across many different profile shapes. Surprisingly, this category selectivity appeared as early as 70 ms after stimulus onset, which is earlier than the typical latency of shape selective responses, but compatible with the earliest face selective responses in the inferior temporal lobe. While our results provide no evidence for a delayed top-down influence from object recognition centers, they indicate sophisticated shape categorization mechanisms that are much faster than generally assumed.

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