Different subregions of monkey lateral prefrontal cortex respond to abstract sequences and their components

Abstract

Sequential information permeates our daily lives, such as when listening to music. These sequences are potentially abstract in that they do not depend on the exact identity of the stimuli (pitch of the notes), but on the rule that they follow (interval between them). Previously, we showed that a subregion of monkey lateral prefrontal cortex (LPFC), area 46, responds to abstract visual sequences in a manner that parallels human responses. However, area 46 has several mapped subregions and abstract sequences require of multiple stimulus features (such as stimulus and time), leaving open questions as to the specificity of responses in the LPFC. To determine the anatomical and functional specificity of abstract visual sequence responses within area 46 subregions, we used awake functional magnetic resonance imaging in three male macaque monkeys during two no-report visual tasks. One task presented images in an abstract visual sequence; the other used the same timing properties and image variation, but no sequential information. We found, using subdivisions from a multimodal parcellation of area 46, that responses to abstract visual sequences were unique to the posterior fundus of area 46, which did not respond to changes in timing or image alone. In contrast, posterior shoulder regions of area 46 showed selectivity to more concrete stimulus changes (i.e., timing and image). These results align with organizational hierarchies observed in monkeys and humans, and suggest that interactions between adjacent LPFC subregions is key scaffolding for complex daily behaviors.

Monkey lateral prefrontal cortex subregions differentiate between perceptual exposure to visual stimuli

“…Each run contained four blocks interleaved with 14 s fixation periods. The two blocks presented in this study were the first and the fourth of these blocks; the middle blocks are presented elsewhere (Yusif Rodriguez et al, 2024). Runs lasted approximately 10 minutes and monkeys typically finished 2-4 runs of this task (along with other tasks) in one scanning session.…”

“…The data analysis and statistical modeling parameters used here are largely the same as those described in (Yusif Rodriguez et al, 2024). All analyses were performed in MATLAB (Mathworks, R2017b) and used SPM 12 (http://www.fil.ion.ucl.ac.uk/spm).…”

“…In the Grouped task, regressors of interest were constructed as previously described in (Yusif Rodriguez et al, 2024) (No Sequence task) and briefly described here. The first image in each group of four images was modeled as an instantaneous onset.…”

“…A visual sequence consists of a series of images appearing in a given order and can be thought of as one category of serially presented information. We have found that deviations from a known sequence elicit activity in p46f (Yusif Rodriguez et al, 2023Rodriguez et al, , 2024. However, it is unknown whether a similar response may be evoked by infrequently presented stimuli outside of a sequential context.…”

“…Specific subregions within LPFC may contribute uniquely to these perceptual exposure responses. One such subregion is the posterior fundus of area 46 (p46f) (Rapan et al, 2023), which we have previously identified as tracking visual sequences (Yusif Rodriguez et al, 2023Rodriguez et al, , 2024. A visual sequence consists of a series of images appearing in a given order and can be thought of as one category of serially presented information.…”