Neural correlates of explicit encoding in the deferred imitation of long visuospatial sequences

Mihovilović, Milena (2025): Neural correlates of explicit encoding in the deferred imitation of long visuospatial sequences. Dissertation, LMU München: Graduate School of Systemic Neurosciences (GSN)

Abstract

The explicit acquisition of a visual sequence requires a variety of fundamental attentional and sensory processing mechanisms without which encoding cannot take place. Previous studies on this topic have often either focused on implicit learning or involved high-context experimental environments (e.g., real-world navigation). In our project, we examined the deferred imitation of long spatial sequences (via ocular reproduction of shifting visual targets) and aimed to identify brain activity concurrent with the encoding stages of explicit sequence learning. To this end, we designed a functional magnetic resonance imaging study (n=34) with both learning and attention-only conditions. This enabled us to better differentiate learning-specific activation from other concurrently active attentional mechanisms. Our sequence learning paradigm, labeled the ‘deferred imitation of long spatial sequences’ (DILSS), consisted of alternating phases of presentation and recall of a 20-target-long visuospatial sequence. Behavioral data from the recall phase was used to determine encoding progress as a function of time during presentation, with this progress taken as a continuous regressor of the blood oxygen level dependent (BOLD) signal. To elicit attention but not learning, we designed a spatial discrimination task where attention was allocated in a temporally analogous manner to presumed encoding in the first experiment, but without any learning component. General linear model analysis using the constructed learning and attention regressors revealed heightened activation during encoding in area V5 bilaterally, bilateral superior parietal lobules, and right superior frontal gyrus, whereas the attention regressor revealed significant activation in areas comprising the dorsal attention network. Regions of interest were constructed based on overlapping activity between the two conditions. Repeated measures analysis of variance resulted in significant main effects for task and region (which were, however, of minor interest) and a significant interaction effect between them. This suggested a dissociation in function for the overlapping regions depending on condition, which, critically, indicates that activation of V5 and the superior parietal lobule during encoding is not merely the result of increased attentional demands, but instead specific to learning. Past literature indeed supports the recruitment of underlying cognitive processes specific to encoding in V5, the superior parietal lobule, and superior frontal gyrus (though this last region did not significantly differ between experimental conditions). Our results therefore both substantiate prior literature and provide a basis for continued investigation.

• Item Type: Theses (Dissertation, LMU Munich)
• Keywords: Sequence learning, memory encoding, visuospatial attention, cognitive neuroscience, fMRI
• Subjects: 500 Natural sciences and mathematics; 500 Natural sciences and mathematics > 570 Life sciences
• Faculties: Graduate School of Systemic Neurosciences (GSN)
• Language: English
• Date of oral examination: 13. May 2025
• 1. Referee: Eggert, Thomas
• Signature of the printed copy: 0001/UMC 31969