​Reprezentacije položaja v prostorskem delovnem spominu

Purg, Nina (author), Repovš, Grega (mentor), Anticevic, Alan (comentor)

Uvod: Vzdrževana aktivnost v frontalnih in parietalnih možganskih področjih med prostorskim delovnim spominom bi naj odražala procese aktivnega shranjevanja in vzdrževanja informacij, vendar narava reprezentacij, zabeleženih v tej aktivnosti, ostaja neznana. Namen doktorske disertacije je bil raziskati nevro?ziološke mehanizme prostorskih reprezentacij v delovnem spominu in kako se te reprezentacije spreminjajo glede na zahteve naloge in individualne razlike. Natančneje smo preverili, katera vrsta prostorskih informacij, izražena v različnih koordinatnih sistemih, se odraža v možganski aktivnosti med delovnim spominom. Zanimalo nas je tudi, kakšne strategije uporabljamo za kodiranje in vzdrževanje prostorskih reprezentacij ter kakšna je vloga posameznih možganskih področij v procesih prostorskega delovnega spomina. Metode: V okviru doktorske naloge smo izvedli dve ločeni študiji. V prvi študiji smo združili podatke šestih eksperimentov s skupno 158 udeleženci (78 žensk, 25 ± 6 let). V drugi študiji smo izvedli dva eksperimenta z 31 (20 žensk, 23 ± 5 let) in 44 (23 žensk, 21 ± 2 let) udeleženci. V obeh študijah so udeleženci izvedli nalogo prostorskega delovnega spomina, pri kateri so si morali zapomniti položaj tarčnega dražljaja in po zamiku premakniti prikazan disk s pomočjo igralne palice na položaj zapomnjene tarče, medtem ko smo merili njihovo možgansko aktivnost s fMR slikanjem. V drugi študiji je bila naloga sestavljena iz več pogojev, ki so bili zasnovani z namenom manipulacije med uporabo retrospektivno senzoričnega ali prospektivno motoričnega kodiranja prostorskih reprezentacij. Rezultati: V prvi študiji nismo odkrili nobenih statistično pomembnih povezav med možgansko aktivnostjo in različnimi vedenjskimi merami natančnosti odgovorov, kar bi kazalo na vrsto prostorskih informacij, vkodiranih in vzdrževanih v prostorskem delovnem spominu. Opazili pa smo, da so na vedenjske odzive vplivali različni sistematični učinki, ki bi naj odražali uporabo kategoričnih prostorskih reprezentacij. Rezultati so pokazali, da so posamezniki, ki so se v večji meri zanašali na kategorične reprezentacije, imeli slabšo natančnost preciznih reprezentacij, kar se je odražalo tudi v možganski aktivnosti med nalogo. V drugi študiji je bilo prospektivno motorično kodiranje povezano s povečano aktivnostjo in funkcijsko povezanostjo v somatomotoričnih področjih, medtem ko je bilo retrospektivno senzorično kodiranje povezano s povečano aktivnostjo in funkcijsko povezanostjo v parietalnih in vidnih področjih. Zaključek: Naša spoznanja prispevajo k razumevanju, da lahko uporabljamo različne reprezentacije in strategije za vkodiranje in vzdrževanje prostorskih informacij v delovnem spominu. Poleg tega pa se uporaba različnih strategij med seboj ne izključuje ter je lahko odvisna od zahtev naloge in individualnih razlik.

• Language: Slovenian
• Keywords: prostorski delovni spomin, fMR, vkodiranje, vzdrževanje, reprezentacije, strategije kodiranja
• Work type: Doctoral dissertation
• Organization: MF - Faculty of Medicine
• Year: 2022
• PID: 20.500.12556/RUL-138334
• Publication date in RUL: 16.07.2022

Secondary language

• Language: English
• Title: Representations of position in spatial working memory

Abstract

Introduction: Sustained activity in frontal and parietal brain areas during spatial working memory is thought to reflect active storage and maintenance processes, but the nature of the representations carried by this activity continues to be investigated. The aim of the doctoral thesis was to investigate neural mechanisms of spatial representations in working memory and how these representations change depending on task demands and in relation to individual differences. First, we were interested in which type of positional information, expressed in different coordinate systems, is represented in neural activity during working memory. Second, we were interested in strategies used to encode and maintain spatial representations and the role of individual brain areas in spatial working memory processes. Methods: We conducted two separate studies. In Study I, we combined data from six experiments, including a total of 158 participants (78 women, 25 ± 6 years). In Study II, we conducted two experiments with 31 (20 women, 23 ± 5 years) and 44 (23 women, 21 ± 2 years) participants, respectively. In both studies, participants performed a spatial working memory task, where they were asked to remember the position of a briefly presented target stimulus and, after a delay period, to move a disk using a joystick to the position of the remembered target, while we measured their brain activity using fMRI. In Study II, different task conditions were included, designed to manipulate the use of retrospective sensory or prospective motor coding of spatial representations. Results: In Study I, our results revealed no significant relationships between brain activity and any of the behavioral measures of memory precision, which would indicate the type of positional information encoded and maintained in spatial working memory. However, we observed systematic biases in behavioral performance that are thought to reflect the use of categorical spatial representations. The results showed that participants who strongly relied on categorical representations had poorer fine-grained memory precision, which was reflected also in the brain activity during the task. In Study II, prospective motor coding was associated with increased activity and functional connectivity in somatomotor areas, whereas retrospective sensory coding was related to increased activity and functional connectivity in parietal and visual areas. Conclusion: Our findings contribute to the understanding that multiple representations and strategies can be used to encode and maintain information in working memory. They also suggest that the available strategies are not mutually exclusive and that their use may depend on task demands and individual differences.

• Keywords: spatial working memory, fMRI, encoding, maintenance, representations, coding strategies