Fig. 4: Prototype synthesis experiments.

a Firing rate trajectory during a successful vlPFC prototype experiment. The black trace shows the mean firing rate for synthetic images, while the green trace shows the mean firing rate for natural images (mean ± SEM). b Stimuli presented during the experiment in (a). Representative firing rate trajectory toward synthetic images produced by the closed-loop generator (top row) against  fixed reference photographs (bottom row). c Population figure of the mean change in firing rate to natural images (x-axis) against synthetic images (y-axis), per experiment. Red markers mark prototype experiments targeting V4 sites, while blue markers denote vlPFC sites (dark blue=Monkey C; light blue=Monkey D). Marker shape represents unit type: triangles for single-units (SU), squares for distinct multiunits (MU), and circles for whole-site hash. Large markers indicating successful experiments. Each point shows a standard error of the mean change, computed via bootstrap (N = 77 total experiments, see Supplemental Tables 3 and 4). d Segmentation masking of a prototype. e Final prototypes from a vlPFC multiunit isolated for over seven months (top) with their respective segmentation masks (bottom). f Within-site prototype similarity (“stability”) across the population of successful vlPFC prototypes. For a given site, distances between all prototype masks were computed in correlation space, with shorter distances signaling higher correlation between masks. Colors differentiate individual vlPFC sites across both subjects, with the multiunit from (e) in purple. Distances between prototype masks from each vlPFC site (e.g., between site 1 prototypes from sessions 1 through 3) were compared against, 1) prototypes from all other vlPFC sites (e.g., distances between site 1/session 1 and all other non-site 1 prototypes generated by vlPFC sites), 2) prototypes from V4 sites (e.g., site 1/session 1 and all prototypes generated by V4 sites), and 3) shuffled versions of successful prototypes from the targeted vlPFC site (e.g., site 1/session 1 prototype and the same prototype randomly permuted pixelwise). Median distances denoted by large black markers. Triple asterisks denote statistical significance at p < 0.001 by way of randomization test. g Prototypes plotted as a function of signal type. Source data are provided as a Source Data file.