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Differential engagement of brain regions within a 'core' network during scene construction.

ABSTRACT: Reliving past events and imagining potential future events engages a well-established "core" network of brain areas. How the brain constructs, or reconstructs, these experiences or scenes has been debated extensively in the literature, but remains poorly understood. Here we designed a novel task to investigate this (re)constructive process by directly exploring how naturalistic scenes are built up from their individual elements. We "slowed-down" the construction process through the use of auditorily presented phrases describing single scene elements in a serial manner. Participants were required to integrate these elements (ranging from three to six in number) together in their imagination to form a naturalistic scene. We identified three distinct sub-networks of brain areas, each with different fMRI BOLD response profiles, favouring specific points in the scene construction process. Areas including the hippocampus and retrosplenial cortex had a biphasic profile, activating when a single scene element was imagined and when 3 elements were combined together; regions including the intra-parietal sulcus and angular gyrus steadily increased activity from 1 to 3 elements; while activity in areas such as lateral prefrontal cortex was observed from the second element onwards. Activity in these sub-networks did not increase further when integrating more than three elements. Participants confirmed that three elements were sufficient to construct a coherent and vivid scene, and once this was achieved, the addition of further elements only involved maintenance or small changes to that established scene. This task offers a potentially useful tool for breaking down scene construction, a process that may be key to a range of cognitive functions such as episodic memory, future thinking and navigation.

SUBMITTER: Summerfield JJ

PROVIDER: S-EPMC2850391 | biostudies-literature | 2010 Apr

REPOSITORIES: biostudies-literature

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Differential engagement of brain regions within a 'core' network during scene construction.

Summerfield Jennifer J JJ Hassabis Demis D Maguire Eleanor A EA

Neuropsychologia 20100202 5

Reliving past events and imagining potential future events engages a well-established "core" network of brain areas. How the brain constructs, or reconstructs, these experiences or scenes has been debated extensively in the literature, but remains poorly understood. Here we designed a novel task to investigate this (re)constructive process by directly exploring how naturalistic scenes are built up from their individual elements. We "slowed-down" the construction process through the use of audito ...[more]

PMID: 20132831

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Project description:Human retrosplenial complex (RSC), located in medial parietal cortex, has been implicated in numerous cognitive functions, including scene perception, spatial navigation, and autobiographical memory retrieval. Recently, a posterior-anterior distinction within RSC was proposed, such that posterior aspects process scene-related visual information (constituting a medial place area [MPA]), whereas anterior aspects process information that is vividly retrieved from memory, thereby supporting remembering and potentially navigation. Here, we tested this proposed distinction in a single group of participants (both male and female) using fMRI with both perceptual and mnemonic tasks. After completing a resting-state scan, participants performed a task that required constructing scenes from memory and completed a scene selectivity localizer task. We tested directly perceptual and mnemonic responses in MPA and an anterior, connectivity-defined region (CON), which showed strong functional connectivity with anterior parahippocampal place area. A double dissociation was observed, such that CON was more strongly activated during scene construction than was MPA, whereas MPA was more perceptually responsive than CON. Further, peak responses from the scene construction task were anterior to perceptual peaks in all but 1 participant and hemisphere. Finally, through analyses of the posterior-anterior response profiles, we identify the fundus of the parieto-occipital sulcus as a potential location for the crossover from perceptual to mnemonic representations and highlight a potential left-hemisphere advantage for mnemonic representations. Collectively, our results support a distinction between posterior and anterior aspects of the RSC, suggesting that more specific functional-anatomic terms should be used in its place in future work.SIGNIFICANCE STATEMENT The retrosplenial complex (RSC) has been implicated in vision, spatial cognition, and memory. We previously speculated on a potential posterior-anterior distinction within RSC for scene perception and memory-based scene construction/navigation. Here, we tested this distinction through a combination of resting-state, perceptual, and mnemonic task data. Consistent with our predictions, we demonstrate that perceptual responses peak consistently posterior of those elicited by memory-based scene construction within the broader RSC. Further, we highlight (1) the fundus of the parieto-occipital sulcus as a landmark for the transition between these representations, (2) the anterior bank of parieto-occipital sulcus as the point of maximal separation between these representations, and (3) identify a potential hemispheric asymmetry in mnemonic representations. These data support functional dissociations within RSC.

Project description:Introduction Post-traumatic stress disorder (PTSD) is associated with hippocampal system structural and functional impairments. Neurobiological models of PTSD posit that contextual memory for traumatic events is impaired due to hippocampal system dysfunction whilst memory of sensory details is enhanced due to amygdalar impact on sensory cortices. If hippocampal system dysfunction is a core feature of PTSD, then non-traumatic hippocampal-dependent cognitive functions such as scene construction, spatial processing, and memory should also be impaired in individuals with PTSD. Methods Forty-six trauma survivors, half diagnosed with PTSD, performed two tasks that involved spatial processing. The first was a scene construction task which requires conjuring-up spatially coherent multimodal scenarios, completed by all participants. Twenty-six participants (PTSD: n = 13) also completed a navigation task in a virtual environment, and underwent structural T1, T2 and diffusion-tensor MRI to quantify gray and white matter integrity. We examined the relationship between spatial processing, neural integrity, and symptom severity in a multiple factor analysis. Results Overall, patients with PTSD showed impaired performance in both tasks compared to controls. Scenes imagined by patients were less vivid, less detailed, and generated less sense of presence; importantly they had disproportionally reduced spatial coherence between details. Patients also made more errors during virtual navigation. Two components of the multiple factor analysis captured group differences. The first component explained 25% of the shared variance: participants that constructed less spatially coherent scenes also made more navigation errors and had reduced white matter integrity to long association tracts and tracts connecting the hippocampus, thalamus, and cingulate. The second component explained 20% of the variance: participants who generated fewer scene details, with less spatial coherence between them, had smaller hippocampal, parahippocampal and isthmus cingulate volumes. These participants also had increased white matter integrity to the right hippocampal cingulum bundle. Conclusion Our results suggest that patients with PTSD are impaired at imagining even neutral spatially coherent scenes and navigating through a complex spatial environment. Patients that showed reduced spatial processing more broadly had reduced hippocampal systems volumes and abnormal white matter integrity to tracts implicated in multisensory integration.

Project description:Objective: Seek the differentially expressed mRNAs and long non-coding RNAs (LncRNAs) to construct the modulated network and seek for the hub LncRNAs during the process of human immunodeficiency virus (HIV) transcription. Method: Blood samples from HIV-infections were collected. They were divided into transcription active group and relatively inactive group based on the quantitative detection results of total HIV DNA and cell-association RNA (CA-RNA) from peripheral blood mononuclear cells (PBMCs). Individuals within each group were matched by age and genders. Microarray chips detection technology were utilized to detect and find the differentially expressed LncRNAs and mRNAs by statistical method of paired T test, then underwent some bioinformatics analysis. Result: 1240 differentially expressed genes (include 689 LncRNAs and 551 mRNAs) were found. Gene ontology analysis showed the differentially expressed mRNAs mainly enriched in positive or negative gene expression, immune cell formation or epigenetic regulation in the biological process; nucleosome, nucleolus, cytoplasm, nuclear chromatin in the cell component; RNA polymerase II regulatory region sequence-specific DNA binding, DNA, histone, and nucleic acid binding, transcription factor activity in molecular function. Pathway analysis showed the differentially expressed mRNAs enriched in the biological pathways such as systemic lupus erythematosus, alcoholism, cytokine-cytokine receptor interaction, RNA transport, mRNA surveillance pathway, Pathways in cancer, etc. Cis and trans analysis to the differentially expressed LncRNAs searching its targeted genes and then made intersection for the differentially expressed mRNAs, then constructed the modulated network between LncRNAs and mRNAs. Based on this modulated network, four hub transcripts were excavated and validated by quantitative real-time PCR to confirm the veracity of microarray analysis findings. Two hub transcripts of lnc-CCNYL1-1:2 and ZNF793 were found directly interacted in the modulated network and their level of expression transformed parallelly. Conclusion: Quantitative detection results of cellular levels of total HIV DNA and RNA can distinguish whether HIV is in the state of active transcription. During process of HIV transcription, the differentially expressed LncRNAs involve the biological process of gene expression regulation, the hub genes excavated form the modulated network may become the potential candidate targets for HIV antiviral treatment.

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Differential engagement of brain regions within a 'core' network during scene construction.

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Differential engagement of brain regions within a 'core' network during scene construction.

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