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Succesive Task Steps Elicit Orthogonal Activity Patterns in Widespread Brain Regions

Poster Session B - Sunday, March 8, 2026, 8:00 – 10:00 am PDT, Fairview/Kitsilano Ballroom

İrem Giray^1,3,4 (), Gülsüm Özge Şengil², Ausaf A. Farooqui^1,3,4; ¹Bilkent University, ²Goldsmiths University of London, ³Aysel Sabuncu Brain Research Center, ⁴National Magnetic Resonance Research Center

Our goals require a sequence of steps for their completion. This sequential organisation is a key principle of cognition. While existing research has explored the initiation and termination of tasks, the relation between their sequential steps remains underexplored. Primate neurophysiology has suggested that neural population activity-patterns in the fronto-parietal cortices dynamically evolve across extended tasks, going through a series of states such that successive steps elicit orthogonal or uncorrelated patterns of activity (Sigala et al., 2008; Kadohisa et al., 2020). These observations come from task steps with distinct demands and have been explained as the same population of neurons doing different cognitive operations required across the successive steps. Here, we investigated whether orthogonal coding of successive steps is a general feature of cognition and occurs in other neural regions, and during any sequential task – even when successive steps do not require different cognitive operations – and if this occurs for steps that are not proximate in time but are construed by participants as being successive. Participants (N = 33) executed a 3-back task consisting of 9-trial episodes. They covertly detected ‘targets’ (i.e., matches) across fMRI runs. The maximum number of targets within episodes was three. We found that activity-patterns generated by successive steps were less correlated with each other compared to those generated by non-successive steps. Further, successive targets, although they never occurred consecutively, also showed decreased correlation in their activity-patterns. Crucially, these were seen not just in the control-related fronto-parietal regions but were seen in most brain regions.

Topic Area: EXECUTIVE PROCESSES: Working memory