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571 results on '"Lawrence, Andrew D."'

1. A role for the fornix in temporal sequence memory

Author

Read, Marie‐Lucie, Umla‐Runge, Katja, Lawrence, Andrew D, Costigan, Alison G, Hsieh, Liang‐Tien, Chamberland, Maxime, Ranganath, Charan, and Graham, Kim S

Subjects
Biological Psychology, Psychology, Biomedical Imaging, Mental health, Neurological, Adult, Humans, Diffusion Tensor Imaging, Fornix, Brain, Hippocampus, Temporal Lobe, Diffusion Magnetic Resonance Imaging, White Matter, diffusion MRI, episodic memory, fornix, hippocampus, sequence, time, Neurosciences, Cognitive Sciences, Neurology & Neurosurgery, Biological psychology, Cognitive and computational psychology
Abstract

Converging evidence from studies of human and nonhuman animals suggests that the hippocampus contributes to sequence learning by using temporal context to bind sequentially occurring items. The fornix is a white matter pathway containing the major input and output pathways of the hippocampus, including projections from medial septum and to diencephalon, striatum, lateral septum and prefrontal cortex. If the fornix meaningfully contributes to hippocampal function, then individual differences in fornix microstructure might predict sequence memory. Here, we tested this prediction by performing tractography in 51 healthy adults who had undertaken a sequence memory task. Microstructure properties of the fornix were compared with those of tracts connecting medial temporal lobe regions but not predominantly the hippocampus: the Parahippocampal Cingulum bundle (PHC) (conveying retrosplenial projections to parahippocampal cortex) and the Inferior Longitudinal Fasciculus (ILF) (conveying occipital projections to perirhinal cortex). Using principal components analysis, we combined Free-Water Elimination Diffusion Tensor Imaging and Neurite Orientation Dispersion and Density Imaging measures obtained from multi-shell diffusion MRI into two informative indices: the first (PC1) capturing axonal packing/myelin and the second (PC2) capturing microstructural complexity. We found a significant correlation between fornix PC2 and implicit reaction-time indices of sequence memory, indicating that greater fornix microstructural complexity is associated with better sequence memory. No such relationship was found with measures from the PHC and ILF. This study highlights the importance of the fornix in aiding memory for objects within a temporal context, potentially reflecting a role in mediating inter-regional communication within an extended hippocampal system.

Published
2023

3. The role of the fornix in human navigational learning

Author

Hodgetts, Carl J, Stefani, Martina, Williams, Angharad N, Kolarik, Branden S, Yonelinas, Andrew P, Ekstrom, Arne D, Lawrence, Andrew D, Zhang, Jiaxiang, and Graham, Kim S

Subjects
Biological Psychology, Psychology, Biomedical Imaging, Clinical Research, Mental Health, Behavioral and Social Science, Mental health, Animals, Diffusion Magnetic Resonance Imaging, Fornix, Brain, Hippocampus, Humans, Memory, Episodic, White Matter, Spatial navigation, Spatial learning, Episodic memory, Diffusion MRI, Neurosciences, Cognitive Sciences, Experimental Psychology, Biological psychology, Cognitive and computational psychology
Abstract

Experiments on rodents have demonstrated that transecting the white matter fibre pathway linking the hippocampus with an array of cortical and subcortical structures - the fornix - impairs flexible navigational learning in the Morris Water Maze (MWM), as well as similar spatial learning tasks. While diffusion magnetic resonance imaging (dMRI) studies in humans have linked inter-individual differences in fornix microstructure to episodic memory abilities, its role in human spatial learning is currently unknown. We used high-angular resolution diffusion MRI combined with constrained spherical deconvolution-based tractography, to ask whether inter-individual differences in fornix microstructure in healthy young adults would be associated with spatial learning in a virtual reality navigation task. To efficiently capture individual learning across trials, we adopted a novel curve fitting approach to estimate a single index of learning rate. We found a statistically significant correlation between learning rate and the microstructure (mean diffusivity) of the fornix, but not that of a comparison tract linking occipital and anterior temporal cortices (the inferior longitudinal fasciculus, ILF). Further, this correlation remained significant when controlling for both hippocampal volume and participant gender. These findings extend previous animal studies by demonstrating the functional relevance of the fornix for human spatial learning in a virtual reality environment, and highlight the importance of a distributed neuroanatomical network, underpinned by key white matter pathways, such as the fornix, in complex spatial behaviour.

Published
2020

21. A role for the fornix in temporal sequence memory.

Author

Read, Marie-Lucie, Read, Marie-Lucie, Umla-Runge, Katja, Lawrence, Andrew D, Costigan, Alison G, Hsieh, Liang-Tien, Chamberland, Maxime, Ranganath, Charan, Graham, Kim S, Read, Marie-Lucie, Read, Marie-Lucie, Umla-Runge, Katja, Lawrence, Andrew D, Costigan, Alison G, Hsieh, Liang-Tien, Chamberland, Maxime, Ranganath, Charan, and Graham, Kim S

Abstract

Converging evidence from studies of human and nonhuman animals suggests that the hippocampus contributes to sequence learning by using temporal context to bind sequentially occurring items. The fornix is a white matter pathway containing the major input and output pathways of the hippocampus, including projections from medial septum and to diencephalon, striatum, lateral septum and prefrontal cortex. If the fornix meaningfully contributes to hippocampal function, then individual differences in fornix microstructure might predict sequence memory. Here, we tested this prediction by performing tractography in 51 healthy adults who had undertaken a sequence memory task. Microstructure properties of the fornix were compared with those of tracts connecting medial temporal lobe regions but not predominantly the hippocampus: the Parahippocampal Cingulum bundle (PHC) (conveying retrosplenial projections to parahippocampal cortex) and the Inferior Longitudinal Fasciculus (ILF) (conveying occipital projections to perirhinal cortex). Using principal components analysis, we combined Free-Water Elimination Diffusion Tensor Imaging and Neurite Orientation Dispersion and Density Imaging measures obtained from multi-shell diffusion MRI into two informative indices: the first (PC1) capturing axonal packing/myelin and the second (PC2) capturing microstructural complexity. We found a significant correlation between fornix PC2 and implicit reaction-time indices of sequence memory, indicating that greater fornix microstructural complexity is associated with better sequence memory. No such relationship was found with measures from the PHC and ILF. This study highlights the importance of the fornix in aiding memory for objects within a temporal context, potentially reflecting a role in mediating inter-regional communication within an extended hippocampal system.

Published
2023

22. Conserved cobalamin acquisition protein 1 is essential for vitamin B12 uptake in both Chlamydomonas and Phaeodactylum

Author

Sayer, Andrew P., Llavero-Pasquina, Marcel, Geisler, Katrin, Holzer, Andre, Bunbury, Freddy, Mendoza-Ochoa, Gonzalo I., Lawrence, Andrew D., Warren, Martin J., Mehrshahi, Payam, Smith, Alison G., Sayer, Andrew P., Llavero-Pasquina, Marcel, Geisler, Katrin, Holzer, Andre, Bunbury, Freddy, Mendoza-Ochoa, Gonzalo I., Lawrence, Andrew D., Warren, Martin J., Mehrshahi, Payam, and Smith, Alison G.

Abstract

Microalgae play an essential role in global net primary productivity and global biogeochemical cycling. Despite their phototrophic lifestyle, over half of algal species depend for growth on acquiring an external supply of the corrinoid vitamin B12 (cobalamin), a micronutrient produced only by a subset of prokaryotic organisms. Previous studies have identified protein components involved in vitamin B12 uptake in bacterial species and humans. However, little is known about its uptake in algae. Here, we demonstrate the essential role of a protein, cobalamin acquisition protein 1 (CBA1), in B12 uptake in Phaeodactylum tricornutum using CRISPR-Cas9 to generate targeted knockouts and in Chlamydomonas reinhardtii by insertional mutagenesis. In both cases, CBA1 knockout lines could not take up exogenous vitamin B12. Complementation of the C. reinhardtii mutants with the wild-type CBA1 gene restored B12 uptake, and regulation of CBA1 expression via a riboswitch element enabled control of the phenotype. When visualised by confocal microscopy, a YFP-fusion with C. reinhardtii CBA1 showed association with membranes. Bioinformatics analysis found that CBA1-like sequences are present in all major eukaryotic phyla. In algal taxa, the majority that encoded CBA1 also had genes for B12-dependent enzymes, suggesting CBA1 plays a conserved role. Our results thus provide insight into the molecular basis of algal B12 acquisition, a process that likely underpins many interactions in aquatic microbial communities.

Published
2023

39. A Role for the Fornix in Temporal Sequence Memory

Author

Read, Marie-Lucie, primary, Umla-Runge, Katja, additional, Lawrence, Andrew D., additional, Costigan, Alison G., additional, Hsieh, Liang-Tien, additional, Chamberland, Maxime, additional, Ranganath, Charan, additional, and Graham, Kim S., additional

Published
2022
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