The neural representation of abstract visual sequences

Yusif Rodriguez, Nadira del Rosario

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Year:: 2023
Contributor:: Yusif Rodriguez, Nadira del Rosario (creator); Desrochers, Theresa (Advisor); Sheinberg, David (Reader); Shenhav, Amitai (Reader); Vanduffel, Wim (Reader); Brown University. Department of Neuroscience (sponsor)
Genre:: theses
Subject:: Cognitive neuroscience; fmri; Rhesus monkey
Extent:: 7, 148 p.

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Abstract:: Everyday tasks often require to be completed following a specific set of steps or sequentially. Oftentimes, these sequential tasks are abstract, meaning that they are not defined by their specific contents, but instead by the higher order rule which can be used to describe them. As an example, consider taking a daily commute. When taking a bus, you may track a familiar sequence of buildings (three houses, then a library). Additionally, variables like timing and rule could affect sequential monitoring such as when a delay occurs, or when there is a route deviation. Despite its ubiquity, little is known about the neural underpinnings of this tracking process also known as sequential monitoring nor how specific task variables can influence relevant neural responses. Previous work in both human and non-human primates has identified brain areas involved in sequential tasks. In humans, the rostrolateral prefrontal cortex (RLPFC) exhibits a specific pattern of increasing neural activity (i.e., “ramping”) during abstract sequences. Work in non-human primates has identified the dorsolateral prefrontal cortex (DLPFC) as a key area for the representation of sequential information. Furthermore, the monkey DLPFC contains a sub-region, area 46, with homologous functional connectivity to human RLPFC. However, much of this work has yet to directly test the representation of abstract sequences. The work presented in this thesis aims to test the following predictions: First, that the nonhuman primate DLPFC may represent abstract sequence information with parallel dynamics to those found in humans. Second, that these dynamics may be modulated by different sequential characteristics such as abstract sequential rule or structured timing. To investigate these predictions, we conducted functional magnetic resonance imaging (fMRI) in awake monkeys. When monkeys performed no-report abstract sequence viewing, we found that left and right area 46 responded to abstract sequential changes. Interestingly, responses to rule and number changes overlapped in right area 46 and left area 46 exhibited responses to abstract sequence rules with changes in ramping activation, similar to that observed in humans. To further test what specific characteristics of sequences modulated the response observed in area 46, animals did variations of the no-response task which contained either only abstract rule, only structured timing or neither. Our findings suggest that abstract rule and structured timing in combination elicit ramping neural dynamics in area 46. Together, these results indicate that monkey DLPFC monitors abstract visual sequential information. Additionally, these ramping dynamics are elicited by characteristics such as abstract rule and structured timing. More generally, these results show that abstract sequences are represented in functionally homologous regions across monkeys and humans.
Notes:: Thesis (Ph. D.)--Brown University, 2023

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Citation

Yusif Rodriguez, Nadira del Rosario, "The neural representation of abstract visual sequences" (2023). Neuroscience Theses and Dissertations. Brown Digital Repository. Brown University Library. https://repository.library.brown.edu/studio/item/bdr:uruqywsh/

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Neuroscience Theses and Dissertations

Theses and Dissertations for the Neuroscience department.
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