scholarly journals Characterization of the hemodynamic response of the hippocampal and parahippocampal regions using FMRI

2021 ◽  
Author(s):  
Priyanka Mehta
Keyword(s):  
Spatial Memory ◽  
Medial Temporal Lobe ◽  
Dominant Role ◽  
Memory Task ◽  
Hemodynamic Response ◽  
Hemodynamic Responses ◽  
Memory Processing ◽  
Time To Peak ◽  
Hemodynamic Characteristics ◽  
The Right

Previous neuroimaging studies have suggested a dominant role of the right medial temporal lobe (MTL) structures- the hippocampal and parahippocampal regions in spatial memory processing. However, the underlying physiological hemodynamic response functions (HRF) of the MTL substructures remain undefined. Given the neuroanatomical differences between these substructures, it is posited that their hemodynamic characteristics are distinct. In this study, the hemodynamic responses of the MTL substructures are investigated using an optimization algorithm that penalizes the curvature (i.e. second derivative) of HRF. The time-to-peak characteristic of the hemodynamic responses revealed that the right CA3 and DG subfields of the hippocampus are significantly more active than the right CA1 subfield during a specific spatial memory task. Further, the hemodynamic responses of the entorhinal, perirhinal and parahippocampal cortices are presented. Together, these findings may help advance our understanding of neurodegenerative diseases like epilepsy and Alzheimer’s disease that are strongly associated to hippocampal dysfunction.

scholarly journals Characterization of the hemodynamic response of the hippocampal and parahippocampal regions using FMRI

2021 ◽  
Author(s):  
Priyanka Mehta
Keyword(s):  
Spatial Memory ◽  
Medial Temporal Lobe ◽  
Dominant Role ◽  
Memory Task ◽  
Hemodynamic Response ◽  
Hemodynamic Responses ◽  
Memory Processing ◽  
Time To Peak ◽  
Hemodynamic Characteristics ◽  
The Right

Previous neuroimaging studies have suggested a dominant role of the right medial temporal lobe (MTL) structures- the hippocampal and parahippocampal regions in spatial memory processing. However, the underlying physiological hemodynamic response functions (HRF) of the MTL substructures remain undefined. Given the neuroanatomical differences between these substructures, it is posited that their hemodynamic characteristics are distinct. In this study, the hemodynamic responses of the MTL substructures are investigated using an optimization algorithm that penalizes the curvature (i.e. second derivative) of HRF. The time-to-peak characteristic of the hemodynamic responses revealed that the right CA3 and DG subfields of the hippocampus are significantly more active than the right CA1 subfield during a specific spatial memory task. Further, the hemodynamic responses of the entorhinal, perirhinal and parahippocampal cortices are presented. Together, these findings may help advance our understanding of neurodegenerative diseases like epilepsy and Alzheimer’s disease that are strongly associated to hippocampal dysfunction.

scholarly journals Allocentric Spatial Memory Performance in a Virtual Reality-Based Task is Conditioned by Visuospatial Working Memory Capacity

2020 ◽  
Vol 10 (8) ◽  
pp. 552
Author(s):  
Joaquín Castillo Escamilla ◽  
José Javier Fernández Castro ◽  
Shishir Baliyan ◽  
Juan José Ortells-Pareja ◽  
Juan José Ortells Rodríguez ◽  
...  
Keyword(s):  
Working Memory ◽  
Virtual Reality ◽  
Spatial Memory ◽  
Medial Temporal Lobe ◽  
Memory Performance ◽  
Working Memory Capacity ◽  
Memory Task ◽  
Memory Capacity ◽  
Spatial Task ◽  
Analysis Of Covariance

Traditionally, the medial temporal lobe has been considered a key brain region for spatial memory. Nevertheless, executive functions, such as working memory, also play an important role in complex behaviors, such as spatial navigation. Thus, the main goal of this study is to clarify the relationship between working memory capacity and spatial memory performance. Spatial memory was assessed using a virtual reality-based procedure, the Boxes Room task, and the visual working memory with the computer-based Change Localization Task. One hundred and twenty-three (n = 123) participants took part in this study. Analysis of Covariance (ANCOVA) revealed a statistically significant relationship between working memory capacity and spatial abilities. Thereafter, two subgroups n = 60, were formed according to their performance in the working memory task (1st and 4th quartiles, n = 30 each). Results demonstrate that participants with high working memory capacity committed fewer mistakes in the spatial task compared to the low working memory capacity group. Both groups improved their performance through repeated trials of the spatial task, thus showing that they could learn spatial layouts independent of their working memory capacity. In conclusion, these findings support that spatial memory performance is directly related to working memory skills. This could be relevant for spatial memory assessment in brain lesioned patients.

Primate Rhinal Cortex Participates in Both Visual Recognition and Working Memory Tasks: Functional Mapping With 2-DG

2001 ◽  
Vol 85 (6) ◽  
pp. 2590-2601 ◽  
Author(s):  
Lila Davachi ◽  
Patricia S. Goldman-Rakic
Keyword(s):  
Working Memory ◽  
Recognition Memory ◽  
Visual Memory ◽  
Medial Temporal Lobe ◽  
Visual Recognition ◽  
Memory Task ◽  
Perirhinal Cortex ◽  
Delayed Response ◽  
Memory Processing ◽  
Rhinal Cortex

The rhinal cortex in the medial temporal lobe has been implicated in object recognition memory tasks and indeed is considered to be the critical node in a visual memory network. Previous studies using the 2-deoxyglucose method have shown that thalamic and hippocampal structures thought to be involved in visual recognition memory are also engaged by spatial and object working memory tasks in the nonhuman primate. Networks engaged in memory processing can be recognized by analysis of patterns of activation accompanying performance of specifically designed tasks. In the present study, we compared metabolic activation of the entorhinal and perirhinal cortex during the performance of three working memory tasks [delayed response (DR), delayed alternation (DA), and delayed object alternation (DOA)] to that induced by a standard recognition memory task [delayed match-to-sample (DMS)] and a sensorimotor control task in rhesus monkeys. A region-of-interest analysis revealed elevated local cerebral glucose utilization in the perirhinal cortex in animals performing the DA, DOA, and DMS tasks, and animals performing the DMS task were distinct in showing a strong focus of activation in the lateral perirhinal cortex. No significant differences were evident between groups performing memory and control tasks in the entorhinal cortex. These findings suggest that the perirhinal cortex may play a much broader role in memory processing than has been previously thought, encompassing explicit working memory as well as recognition memory.

scholarly journals Individual differences in theta-band oscillations in a spatial memory network revealed by electroencephalography predict rapid place learning

2021 ◽  
Vol 5 ◽  
pp. 239821282110027
Author(s):  
Markus Bauer ◽  
Matthew G. Buckley ◽  
Tobias Bast
Keyword(s):  
Individual Differences ◽  
Spatial Memory ◽  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Place Learning ◽  
Theta Band ◽  
Delayed Matching ◽  
Place Task ◽  
The Right ◽  
Encoding And Retrieval

Spatial memory has been closely related to the medial temporal lobe and theta oscillations are thought to play a key role. However, it remains difficult to investigate medial temporal lobe activation related to spatial memory with non-invasive electrophysiological methods in humans. Here, we combined the virtual delayed-matching-to-place task, reverse-translated from the watermaze delayed-matching-to-place task in rats, with high-density electroencephalography recordings. Healthy young volunteers performed this computerised task in a virtual circular arena, which contained a hidden target whose location moved to a new place every four trials, allowing the assessment of rapid memory formation. Using behavioural measures as predictor variables for source reconstructed frequency-specific electroencephalography power, we found that inter-individual differences in ‘search preference’ during ‘probe trials’, a measure of one-trial place learning known from rodent studies to be particularly hippocampus-dependent, correlated predominantly with distinct theta-band oscillations (approximately 7 Hz), particularly in the right temporal lobe, the right striatum and inferior occipital cortex or cerebellum. This pattern was found during both encoding and retrieval/expression, but not in control analyses and could not be explained by motor confounds. Alpha-activity in sensorimotor and parietal cortex contralateral to the hand used for navigation also correlated (inversely) with search preference. This latter finding likely reflects movement-related factors associated with task performance, as well as a frequency difference in (ongoing) alpha-rhythm for high-performers versus low-performers that may contribute to these results indirectly. Relating inter-individual differences in ongoing brain activity to behaviour in a continuous rapid place-learning task that is suitable for a variety of populations, we could demonstrate that memory-related theta-band activity in temporal lobe can be measured with electroencephalography recordings. This approach holds great potential for further studies investigating the interactions within this network during encoding and retrieval, as well as neuromodulatory impacts and age-related changes.

scholarly journals Sour taste increases swallowing and prolongs hemodynamic responses in the cortical swallowing network

2016 ◽  
Vol 116 (5) ◽  
pp. 2033-2042 ◽  
Author(s):  
Rachel W. Mulheren ◽  
Erin Kamarunas ◽  
Christy L. Ludlow
Keyword(s):  
Near Infrared ◽  
Motion Artifact ◽  
Hemodynamic Response ◽  
Salivary Flow ◽  
Cortical Activation ◽  
Hemodynamic Responses ◽  
Functional Near Infrared Spectroscopy ◽  
Sour Taste ◽  
Slow Infusion ◽  
The Right

Sour stimuli have been shown to upregulate swallowing in patients and in healthy volunteers. However, such changes may be dependent on taste-induced increases in salivary flow. Other mechanisms include genetic taster status (Bartoshuk LM, Duffy VB, Green BG, Hoffman HJ, Ko CW, Lucchina LA, Weiffenbach JM. Physiol Behav 82: 109–114, 2004) and differences between sour and other tastes. We investigated the effects of taste on swallowing frequency and cortical activation in the swallowing network and whether taster status affected responses. Three-milliliter boluses of sour, sour with slow infusion, sweet, water, and water with infusion were compared on swallowing frequency and hemodynamic responses. The sour conditions increased swallowing frequency, whereas sweet and water did not. Changes in cortical oxygenated hemoglobin (hemodynamic responses) measured by functional near-infrared spectroscopy were averaged over 30 trials for each condition per participant in the right and left motor cortex, S1 and supplementary motor area for 30 s following bolus onset. Motion artifact in the hemodynamic response occurred 0–2 s after bolus onset, when the majority of swallows occurred. The peak hemodynamic response 2–7 s after bolus onset did not differ by taste, hemisphere, or cortical location. The mean hemodynamic response 17–22 s after bolus onset was highest in the motor regions of both hemispheres, and greater in the sour and infusion condition than in the water condition. Genetic taster status did not alter changes in swallowing frequency or hemodynamic response. As sour taste significantly increased swallowing and cortical activation equally with and without slow infusion, increases in the cortical swallowing were due to sour taste.

scholarly journals Impaired theta phase coupling underlies frontotemporal dysconnectivity in schizophrenia

Brain ◽  
2020 ◽  
Vol 143 (4) ◽  
pp. 1261-1277 ◽  
Author(s):  
Rick A Adams ◽  
Daniel Bush ◽  
Fanfan Zheng ◽  
Sofie S Meyer ◽  
Raphael Kaplan ◽  
...  
Keyword(s):  
Spatial Memory ◽  
Medial Temporal Lobe ◽  
Memory Task ◽  
Phase Coupling ◽  
Spatial Memory Task ◽  
Theta Power ◽  
Control Subjects ◽  
Memory Integration ◽  
Theta Phase ◽  
Better Than

Abstract Frontotemporal dysconnectivity is a key pathology in schizophrenia. The specific nature of this dysconnectivity is unknown, but animal models imply dysfunctional theta phase coupling between hippocampus and medial prefrontal cortex (mPFC). We tested this hypothesis by examining neural dynamics in 18 participants with a schizophrenia diagnosis, both medicated and unmedicated; and 26 age, sex and IQ matched control subjects. All participants completed two tasks known to elicit hippocampal-prefrontal theta coupling: a spatial memory task (during magnetoencephalography) and a memory integration task. In addition, an overlapping group of 33 schizophrenia and 29 control subjects underwent PET to measure the availability of GABAARs expressing the α5 subunit (concentrated on hippocampal somatostatin interneurons). We demonstrate—in the spatial memory task, during memory recall—that theta power increases in left medial temporal lobe (mTL) are impaired in schizophrenia, as is theta phase coupling between mPFC and mTL. Importantly, the latter cannot be explained by theta power changes, head movement, antipsychotics, cannabis use, or IQ, and is not found in other frequency bands. Moreover, mPFC-mTL theta coupling correlated strongly with performance in controls, but not in subjects with schizophrenia, who were mildly impaired at the spatial memory task and no better than chance on the memory integration task. Finally, mTL regions showing reduced phase coupling in schizophrenia magnetoencephalography participants overlapped substantially with areas of diminished α5-GABAAR availability in the wider schizophrenia PET sample. These results indicate that mPFC-mTL dysconnectivity in schizophrenia is due to a loss of theta phase coupling, and imply α5-GABAARs (and the cells that express them) have a role in this process.

scholarly journals Functional wiring of the human medial temporal lobe

2018 ◽  
Author(s):  
E. A. Solomon ◽  
J. M. Stein ◽  
S. Das ◽  
R. Gorniak ◽  
M. R. Sperling ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Episodic Memory ◽  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Memory Task ◽  
Memory Processing ◽  
High Frequencies ◽  
Functional Connections ◽  
Brain Functions ◽  
Encoding And Retrieval

AbstractThe medial temporal lobe (MTL) is a locus of episodic memory in the human brain. It is comprised of cytologically distinct subregions that, in concert, give rise to successful encoding and retrieval of context-dependent memories. However, the functional connections between these subregions are poorly understood. To determine functional connectivity among MTL subregions, we had 126 subjects fitted with indwelling electrodes perform a verbal memory task, and asked how encoding or retrieval correlated with interregional synchronization. Using phase-based measures of connectivity, we found that synchronous theta (4-8 Hz) activity underlies successful episodic memory, whereas high-frequencies exhibit desynchronization. Moreover, theta functional connectivity during encoding aligned with key anatomic connections, including critical links between the entorhinal cortex, dentate gyrus, and CA1 of the hippocampus. Retrieval-associated networks demonstrated enhanced involvement of the subiculum, reflecting a substantial reorganization of the encoding-associated network. We posit that coherent theta activity within the MTL marks periods of successful memory, but distinct patterns of connectivity dissociate key stages of memory processing.Significance StatementThe brain functions through the interaction of its distinct parts, but little is known about how such connectivity dynamics relate to learning and memory. We used a large dataset of 126 human subjects with intracranial electrodes to assess patterns of electrical connectivity within the medial temporal lobe – a key region for memory processing – as they performed a memory task. We discovered that unique networks of time-varying, low-frequency interactions correlate with memory encoding and retrieval, specifically in the theta band. Simultaneously, we observed elevated spectral power at high frequencies in these same regions. The result is a complete map of physiological dynamics within the MTL, highlighting how a reorganization of theta networks support distinct memory operations.

scholarly journals S153. IMPAIRED THETA PHASE-COUPLING BETWEEN HIPPOCAMPUS AND MEDIAL PREFRONTAL CORTEX IN SCHIZOPHRENIA

2020 ◽  
Vol 46 (Supplement_1) ◽  
pp. S94-S94
Author(s):  
Rick Adams ◽  
Daniel Bush ◽  
Fanfan Zheng ◽  
Sofie Meyer ◽  
Raphael Kaplan ◽  
...  
Keyword(s):  
Spatial Memory ◽  
Medial Temporal Lobe ◽  
Spatial Working Memory ◽  
Memory Task ◽  
Phase Coupling ◽  
Spatial Memory Task ◽  
Theta Power ◽  
Positron Emission ◽  
Memory Integration ◽  
Theta Phase

Abstract Background A genetic schizophrenia (Scz) mouse model has impaired hippocampal-prefrontal synchrony during spatial working memory (Sigurdsson et al., 2000, Nature). These Df(16)A(+/-) mice (models of the human 22q11.2 microdeletion) have impaired mPFC phase coupling to hippocampal theta (1–8 Hz) oscillations, which predicts performance. This deficit has never been demonstrated in human Scz subjects, however, and its mechanistic basis is unclear. Methods 18 Scz (8 unmedicated) and 26 age, gender and IQ-matched controls performed a spatial memory task whilst undergoing magnetoencephalography (MEG), and a ‘memory integration’ task dependent on hippocampal function (without MEG). A partly overlapping group of 33 Scz and 29 controls underwent positron emission tomography (PET) to measure the availability of GABAARs expressing the α5 subunit (concentrated on hippocampal somatostatin interneurons). Results We demonstrate – in the spatial memory task, during memory recall – that theta power increases in left medial temporal lobe (mTL) are impaired in Scz, as is theta phase coupling between mPFC and mTL. Importantly, the latter cannot be explained by theta power changes, head movement, antipsychotics, cannabis use, or IQ, and is not found in other frequency bands. Moreover, mPFC-mTL theta coupling correlated strongly with performance in controls, but not in Scz, who were mildly impaired at the spatial memory task and no better than chance on the memory integration task. Use of antipsychotic medication may ameliorate this mPFC-HC theta coupling deficit. Finally, mTL regions showing reduced theta phase coupling in Scz MEG participants overlapped substantially with areas of diminished α5-GABAAR availability in the wider Scz PET sample. Discussion These results indicate that impaired theta phase coupling between hippocampus and mPFC could underlie hippocampal-prefrontal dysconnectivity in schizophrenia, and impairments in the cognitive domains that depend on communication between these areas. They also imply α5-GABAARs (and the cells that express them) have a role in the phase coupling process.

scholarly journals Are visual working memory and episodic memory distinct processes? Insight from stroke patients by lesion-symptom mapping

2021 ◽  
Author(s):  
Selma Lugtmeijer ◽  
◽  
Linda Geerligs ◽  
Frank Erik de Leeuw ◽  
Edward H. F. de Haan ◽  
...  
Keyword(s):  
Working Memory ◽  
Episodic Memory ◽  
Visual Working Memory ◽  
Visual Memory ◽  
Right Hemisphere ◽  
Memory Task ◽  
Stroke Patients ◽  
Lesion Symptom Mapping ◽  
Criterion Setting ◽  
The Right

AbstractWorking memory and episodic memory are two different processes, although the nature of their interrelationship is debated. As these processes are predominantly studied in isolation, it is unclear whether they crucially rely on different neural substrates. To obtain more insight in this, 81 adults with sub-acute ischemic stroke and 29 elderly controls were assessed on a visual working memory task, followed by a surprise subsequent memory test for the same stimuli. Multivariate, atlas- and track-based lesion-symptom mapping (LSM) analyses were performed to identify anatomical correlates of visual memory. Behavioral results gave moderate evidence for independence between discriminability in working memory and subsequent memory, and strong evidence for a correlation in response bias on the two tasks in stroke patients. LSM analyses suggested there might be independent regions associated with working memory and episodic memory. Lesions in the right arcuate fasciculus were more strongly associated with discriminability in working memory than in subsequent memory, while lesions in the frontal operculum in the right hemisphere were more strongly associated with criterion setting in subsequent memory. These findings support the view that some processes involved in working memory and episodic memory rely on separate mechanisms, while acknowledging that there might also be shared processes.

Task-Irrelevant Sound Corrects Leftward Spatial Bias in Blindfolded Haptic Placement Task

2020 ◽  
Vol 33 (4-5) ◽  
pp. 521-548
Author(s):  
Laura Cacciamani ◽  
Larisa Sheparovich ◽  
Molly Gibbons ◽  
Brooke Crowley ◽  
Kalynn E. Carpenter ◽  
...  
Keyword(s):  
Memory Task ◽  
Spatial Location ◽  
Dominant Hand ◽  
Spatial Bias ◽  
Leftward Bias ◽  
Object Location Memory ◽  
Irrelevant Sound ◽  
Haptic Object ◽  
The Right ◽  
Task Irrelevant

Abstract We often rely on our sense of vision for understanding the spatial location of objects around us. If vision cannot be used, one must rely on other senses, such as hearing and touch, in order to build spatial representations. Previous work has found evidence of a leftward spatial bias in visual and tactile tasks. In this study, we sought evidence of this leftward bias in a non-visual haptic object location memory task and assessed the influence of a task-irrelevant sound. In Experiment 1, blindfolded right-handed sighted participants used their non-dominant hand to haptically locate an object on the table, then used their dominant hand to place the object back in its original location. During placement, participants either heard nothing (no-sound condition) or a task-irrelevant repeating tone to the left, right, or front of the room. The results showed that participants exhibited a leftward placement bias on no-sound trials. On sound trials, this leftward bias was corrected; placements were faster and more accurate (regardless of the direction of the sound). One explanation for the leftward bias could be that participants were overcompensating their reach with the right hand during placement. Experiment 2 tested this explanation by switching the hands used for exploration and placement, but found similar results as Experiment 1. A third Experiment found evidence supporting the explanation that sound corrects the leftward bias by heightening attention. Together, these findings show that sound, even if task-irrelevant and semantically unrelated, can correct one’s tendency to place objects too far to the left.

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