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Caitlin Hilverman, Susan Wagner Cook, Melissa C Duff
Co-speech hand gesture facilitates learning and memory, yet the cognitive and neural mechanisms supporting this remain unclear. One possibility is that motor information in gesture may engage procedural memory representations. Alternatively, iconic information from gesture may contribute to declarative memory representations mediated by the hippocampus. To investigate these alternatives, we examined gesture's effects on word learning in patients with hippocampal damage and declarative memory impairment, with intact procedural memory, and in healthy and in brain-damaged comparison groups...
March 5, 2018: Hippocampus
Jangjin Kim, Leyre Castro, Edward A Wasserman, John H Freeman
The hippocampus may play a role in categorization because of the need to differentiate stimulus categories (pattern separation) and to recognize category membership of stimuli from partial information (pattern completion). We hypothesized that the hippocampus would be more crucial for categorization of low-density (few relevant features) stimuli-due to the higher demand on pattern separation and pattern completion-than for categorization of high-density (many relevant features) stimuli. Using a touchscreen apparatus, rats were trained to categorize multiple abstract stimuli into two different categories...
February 23, 2018: Hippocampus
A Kilias, U Häussler, K Heining, U P Froriep, C A Haas, U Egert
Mesial temporal lobe epilepsy is characterized by focal, recurrent spontaneous seizures, sclerosis and granule cell dispersion in the hippocampal formation. Changes in theta rhythm properties have been correlated with the severity of hippocampal restructuring and were suggested as a cause of memory deficits accompanying epilepsy. For severe sclerosis, it has even been questioned whether theta band oscillations persists. We asked how theta oscillations change with graded restructuring along the longitudinal hippocampal axis and whether these changes correlate with the overall severity of temporal lobe epilepsy...
February 23, 2018: Hippocampus
Tian Li, Juan-Juan Jiao, Christian Hölscher, Mei-Na Wu, Jun Zhang, Jia-Qing Tong, Xue-Fan Dong, Xue-Song Qu, Yue Cao, Hong-Yan Cai, Qiang Su, Jin-Shun Qi
Type 2 diabetes mellitus (T2DM) is an important risk factor for Alzheimer's disease (AD). Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) have been identified to be effective in T2DM treatment and neuroprotection. In the present study, we further explored the effects of a novel unimolecular GLP-1/GIP/Gcg triagonist on the cognitive behavior and cerebral pathology in the 7-month-old triple transgenic mouse model of AD (3xTg-AD), and investigated its possible electrophysiological and molecular mechanisms...
February 23, 2018: Hippocampus
Manindra Nath Tiwari, Sandesh Mohan, Yoav Biala, Yoel Yaari
In many types of CNS neurons, repetitive spiking produces a slow afterhyperpolarization (sAHP), providing sustained, intrinsically generated negative feedback to neuronal excitation. Changes in the sAHP have been implicated in learning behaviors, in cognitive decline in aging, and in epileptogenesis. Despite its importance in brain function, the mechanisms generating the sAHP are still controversial. Here we have addressed the roles of M-type K+ current (IM ), Ca2+ -gated K+ currents (ICa(K) 's) and Na+ /K+ -ATPases (NKAs) current to sAHP generation in adult rat CA1 pyramidal cells maintained at near-physiological temperature (35°C)...
February 12, 2018: Hippocampus
Charlotte M Ermine, Jordan L Wright, Stefano Frausin, Jessica A Kauhausen, Clare L Parish, Davor Stanic, Lachlan H Thompson
Key pathological features of Parkinson's Disease (PD) include the progressive degeneration of midbrain dopaminergic (DA) neurons and hindbrain noradrenergic (NA) neurons. The loss of dopaminergic neurons has been extensively studied and is the main cause of motor dysfunction. Importantly, however, there are a range of 'non-movement' related features of PD including cognitive dysfunction, sleep disturbances and mood disorders. The origins for these non-motor symptoms are less clear, but a possible substrate for cognitive decline may be reduced adult-hippocampal neurogenesis, which is reported to be impaired in PD...
February 12, 2018: Hippocampus
Thu-Huong Hoang, Verena Aliane, Denise Manahan-Vaughan
The specific roles of hippocampal subfields in spatial information processing and encoding are, as yet, unclear. The parallel map theory postulates that whereas the CA1 processes discrete environmental features (positional cues used to generate a 'sketch map'), the dentate gyrus (DG) processes large navigation-relevant landmarks (directional cues used to generate a 'bearing map'). Additionally, the two-streams hypothesis suggests that hippocampal subfields engage in differentiated processing of information from the 'where' and the 'what' streams...
February 2, 2018: Hippocampus
Melissa J Alldred, Helen M Chao, Sang Han Lee, Judah Beilin, Brian E Powers, Eva Petkova, Barbara J Strupp, Stephen D Ginsberg
Although there are changes in gene expression and alterations in neuronal density and afferent inputs in the forebrain of trisomic mouse models of Down syndrome (DS) and Alzheimer's disease (AD), there is a lack of systematic assessments of gene expression and encoded proteins within individual vulnerable cell populations, precluding translational investigations at the molecular and cellular level. Further, no effective treatment exists to combat intellectual disability and basal forebrain cholinergic neurodegeneration seen in DS...
February 2, 2018: Hippocampus
Tatiana D Viena, Stephanie B Linley, Robert P Vertes
The hippocampal formation (HF) and medial prefrontal cortex (mPFC) play critical roles in spatial working memory (SWM). The nucleus reuniens (RE) of the ventral midline thalamus is an important anatomical link between the HF and mPFC, and as such is crucially involved SWM functions that recruit both structures. Little is known, however, regarding the role of RE in other behaviors mediated by this circuit. In the present study, we examined the role of RE in spatial working memory and executive functioning following reversible inactivation of RE with either muscimol or procaine...
January 22, 2018: Hippocampus
Janske G P Willems, Wytse J Wadman, Natalie L M Cappaert
The perirhinal (PER) and lateral entorhinal (LEC) cortex form an anatomical link between the neocortex and the hippocampus. However, neocortical activity is transmitted through the PER and LEC to the hippocampus with a low probability, suggesting the involvement of the inhibitory network. This study explored the role of interneuron mediated inhibition, activated by electrical stimulation in the agranular insular cortex (AiP), in the deep layers of the PER and LEC. Activated synaptic input by AiP stimulation rarely evoked action potentials in the PER-LEC deep layer excitatory principal neurons, most probably because the evoked synaptic response consisted of a small excitatory and large inhibitory conductance...
January 17, 2018: Hippocampus
Signy Sheldon, Brian Levine
The medial temporal lobes (MTL), and more specifically the hippocampus, are critical for forming mental representations of past experiences-autobiographical memories-and for forming other "nonexperienced" types of mental representations, such as imagined scenarios. How the MTL coordinate with other brain areas to create these different types of representations is not well understood. To address this issue, we performed a task-based functional connectivity analysis on a previously published dataset in which fMRI data were collected as participants created different types of mental representations under three conditions...
January 17, 2018: Hippocampus
Leah N Hitchcock, K Matthew Lattal
A key aspect of substance abuse is that drug taking often occurs in a specific context. As a consequence, exposure to drug-associated contexts can trigger cravings and relapse, even after long periods of abstinence. Although many studies have demonstrated that the hippocampus is critical for developing and retrieving contextual and spatial memories, comparatively little is known about the role of the hippocampus in acquiring and inhibiting memories involving contexts and drugs of abuse. We examined the effects of hippocampal inactivation on expression of cocaine-induced conditioned place preference (CPP) after initial acquisition or extinction of CPP in C57BL/6 mice...
January 17, 2018: Hippocampus
Emily Rogalski, Tamar Gefen, Qinwen Mao, Maureen Connelly, Sandra Weintraub, Changiz Geula, Eileen H Bigio, M-Marsel Mesulam
On average, memory capacity is significantly higher in populations of 50-60 year olds than in populations of 80 year olds. We define SuperAgers as individuals 80 or older whose episodic memory capacity is at least as good as that of cognitively average individuals in their 50s and 60s. SuperAgers therefore have memory capacity that is superior for age. Previous work showed that SuperAgers have greater cortical volumes and greater resistance to age-related cortical atrophy than 'cognitively average' individuals of the same age...
January 17, 2018: Hippocampus
Chelsea M Stillman, Fatma Uyar, Haiqing Huang, George A Grove, Jennifer C Watt, Mariegold E Wollam, Kirk I Erickson
Consistent associations have been found between higher cardiorespiratory fitness (CRF) and indices of enhanced brain health and function, including behavioral measures of cognition as well as neuroimaging indicators such as regional brain volume. Several studies have reported that higher CRF levels are associated with a larger hippocampus, yet associations between volume and memory or functional connectivity metrics with the hippocampus remain poorly understood. Using a multi-modal framework, we hierarchically examine the association between CRF and hippocampal volume and resting state functional connectivity (rsFC) in younger adults (ages 22-38), as well as the relationship between these imaging markers and memory function...
January 17, 2018: Hippocampus
Boris Mlinar, Renato Corradetti
The hippocampus is functionally differentiated along its longitudinal axis, with the dorsal and ventral segments preferentially involved in cognitive and emotional processing, respectively. Serotonergic modulation of hippocampal function has been extensively studied, but its relation to the dorsoventral axis has remained largely unknown. To examine the modulation of hippocampal output along the dorsoventral axis by endogenous serotonin (5-HT) we compared the effect of the 5-HT/noradrenaline (NA)-releaser, 3,4-methylenedioxymethamphetamine (MDMA), in transversal slices encompassing the entire rat hippocampus...
December 20, 2017: Hippocampus
Brad E Pfeiffer
One of the most striking features of the hippocampal network is its ability to self-generate neuronal sequences representing temporally compressed, spatially coherent paths. These brief events, often termed "replay" in the scientific literature, are largely confined to non-exploratory states such as sleep or quiet rest. Early studies examining the content of replay noted a strong correlation between the encoded spatial information and the animal's prior behavior; thus, replay was initially hypothesized to play a role in memory formation and/or systems-level consolidation via "off-line" reactivation of previous experiences...
December 20, 2017: Hippocampus
Daniela J Palombo, Agnes Bacopulos, Robert S C Amaral, Rosanna K Olsen, Rebecca M Todd, Adam K Anderson, Brian Levine
Striking individual differences exist in the human capacity to recollect past events, yet, little is known about the neural correlates of such individual differences. Studies investigating hippocampal volume in relation to individual differences in laboratory measures of episodic memory in young adults suggest that whole hippocampal volume is unrelated (or even negatively associated) with episodic memory. However, anatomical and functional specialization across hippocampal subregions suggests that individual differences in episodic memory may be linked to particular hippocampal subregions, as opposed to whole hippocampal volume...
February 2018: Hippocampus
Valentyna Dubovyk, Denise Manahan-Vaughan
The dorsoventral axis of the hippocampus exhibits functional differentiations with regard to (spatial Vs emotional) learning and information retention (rapid encoding Vs long-term storage), as well as its sensitivity to neuromodulation and information received from extrahippocampal structures. The mechanisms that underlie these differentiations remain unclear. Here, we explored neurotransmitter receptor expression along the dorsoventral hippocampal axis and compared hippocampal synaptic plasticity in the CA1 region of the dorsal (DH), intermediate (IH) and ventral hippocampi (VH)...
February 2018: Hippocampus
Kristin Nordin, Jonas Persson, Eva Stening, Agneta Herlitz, Elna-Marie Larsson, Hedvig Söderlund
The hippocampus (HC) interacts with distributed brain regions to support memory and shows significant volume reductions in aging, but little is known about age effects on hippocampal whole-brain structural covariance. It is also unclear whether the anterior and posterior HC show similar or distinct patterns of whole-brain covariance and to what extent these are related to memory functions organized along the hippocampal longitudinal axis. Using the multivariate approach partial least squares, we assessed structural whole-brain covariance of the HC in addition to regional volume, in young, middle-aged and older adults (n = 221), and assessed associations with episodic and spatial memory...
February 2018: Hippocampus
Brook A L Perry, Stephanie A Mercer, Sophie C Barnett, Jungah Lee, John C Dalrymple-Alford
The anterior thalamic nuclei (ATN), mammillary bodies and their interconnecting fiber tract, the mammillothalamic tract (MTT), are important components of an extended hippocampal circuit for episodic memory. In humans, damage to the MTT or ATN in many disorders is associated with severe anterograde amnesia and it is assumed that their influence on memory is functionally equivalent. The relative influence of these two structures on memory has not, however, been assessed explicitly. Here, a direct comparison found that only ATN lesions impaired spatial reference memory in rats...
February 2018: Hippocampus
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