001, cluster threshold > 10 mm3). Along the ventral surface of the brain, a bilateral region of the parahippocampal gyrus was significantly more active to big than to small objects (henceforth labeled as “Big-PHC”), while a left-lateralized region in the occipitotemporal
sulcus extending into the inferior temporal gyrus was more active to small relative to big objects (henceforth “Small-OTS”). Along the lateral surface, a more posterior small-preference region was find more observed (“Small-LO” for lateral occipital), with a big-preference region in the right transverse occipital sulcus (“Big-TOS”; Figure 3). These regions of interest were also observed reliably in single subjects (Figures 3B and 3C), even with only one run of <10 min of scanning. A left Small-OTS region was present in 9 of 12 participants (bilateral in 1), a left Small-LO region was present in all 12 participants (bilateral in half the participants), and a Big-PHC region was present in 10 of 12
participants (bilateral in all participants). The Big-TOS region was less reliably observed OSI-744 clinical trial at the single-subject level with a more variable position across subjects, and it was thus not included for further analysis. These results show that big/small object selectivity is more reliable in the left hemisphere, particularly for the Small-OTS and Small-LO regions; an asymmetry opposite that of face-selective regions which show stronger representation in the right hemisphere (Kanwisher et al., 1997). Comparing these ROIs with the size-preference analysis, it is clear that these regions are not discrete regions of selectivity among a heterogeneous mix of big and small object preferences in the surrounding cortex. Instead, these regions-of-interest reflect the peaks of significant differential activity in an otherwise large-scale organization of big and small object preferences across this cortex. From these data, we do not
mean to imply that these entire sections of cortex are devoted solely to representing big objects or small objects. Rather, whatever underlying code is being used to represent object information across this cortex, big and small objects differ strongly in some regions, and the transitions between these regions are more smooth than modular. In Experiment 1a, observers were presented with one run of big and small objects. Adenosine In order to estimate the effect size within these regions, 8 new participants were shown two runs of big and small objects in Experiment 1b. Regions of interest were estimated from the first run for each subject and the magnitude of activation to big and small objects was computed in these regions using data from the second run. All 8 participants showed a Small-OTS region on the left (bilateral in 3) and a Small-LO region (bilateral in all 8), and 7 of 8 showed a Big-PHC region on the left (bilateral in 6 of 8). These regions showed differential responses that were 1.5 to 1.