Distributed network flows generate localized category selectivity in human visual cortex
Fig 10
Activity flows directly from V1 are sufficient to generate visual category selectivity.
(A) Theoretical schematic of stimulus-driven activity flow processes generating visual category selectivity (as in Fig 1B). Given prior literature, mapped activity flow processes (gray arrow) have a refined inference: from V1 to later visual regions, we inferred that activity flow processes were primarily stimulus driven. This contrasts with the prior whole-cortex models, which also included top-down and likely recurrent influences. (B) Activity flow mapping procedure for the stimulus-driven model, conducted at the vertex level. V1 sources were used to map targets across VIS. Note that the usage of “step 1” serves as a prelude to later steps tested in an extended visual system model (Fig 11). (C) The null connectivity fingerprint (rsFC) model used for control analyses. The top depicts the true VIS network, and the bottom depicts pseudo-random (edge degree and strength preserved) network architectures over 100 permutations. For visualization purposes, networks are shown at the region level, but analyses were conducted at the vertex level. (D) Actual (coral) and mapped (purple) visual category selectivity exhibited by the right EBA/FBA, FFA/pSTS, PPA/RSC, and LOC (left to right). Category selectivity exhibited by V1 (for each respective image category) is shown to demonstrate that activation patterns in V1 alone do not account for mapped visual category selectivities (V1 selectivity scores were all nonsignificant; see main text for statistics). Most importantly, these results demonstrate that the activity flow mapping process increased the category selectivity of every functional complex relative to V1 activity patterns, despite source activity originating solely from V1. Category selectivity generated by V1-initialized activity flow processes were significant in each functional complex (see main text for statistics). Significant t-statistics are indicated with an asterisk (p<0.00001; see Methods); see Figs 5–8 for significance of actual category selectivity of functional complexes.