Is medial temporal lobe activation specific for encoding long-term memories?

Campo, Pablo; Maestú, Fernando; Alonso, Tomás Ortiz; Capilla, Almudena; Fernández, Santiago; Fernández, Alberto

doi:10.1016/j.neuroimage.2004.07.074

Cited by 22 publications

(16 citation statements)

References 62 publications

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“…Participants were right handed according to the Edinburgh Handedness Inventory (Oldfield 1971), and Spanish was their primary language. All participants signed a consent form detailing the procedures of the study in accordance with the Declaration of Helsinki (1991).…”

Section: Methodsmentioning

confidence: 99%

“…Human neuroimaging studies have reported activation of MTL during working memory (WM) tasks that engage informational encoding (Campo et al 2005; Karlsgodt et al 2005; Mainy et al 2007), maintenance of information (Ranganath and D'Esposito 2001; Axmacher et al 2007), and retrieval (Cabeza et al 2002; Schon et al 2009). Also supporting this view, neuropsychological and neuroimaging studies have revealed impaired performance and abnormalities in MTL activity during WM tasks in patients with MTL damage with various causes (Owen et al 1996; Krauss et al 1997; Abrahams et al 1999; Grady et al 2001; Lancelot et al 2003; Lee et al 2006; Olson et al 2006; Piekema et al 2007; Ezzyat and Olson 2008; Wagner et al 2009).…”

Section: Introductionmentioning

confidence: 99%

“…Accordingly, the goal of the current study was to investigate the conjoint function of MTL and other functionally related brain regions involved in verbal WM as a large-scale network (Bressler and Menon 2010). We obtained whole-head magnetoencephalographic (MEG) recordings during a verbal WM task, which was designed to ensure that participants encoded words semantically (Campo et al 2005, 2009), as prior neuroimaging investigations have demonstrated that depth processing modulates MTL activity (Kapur et al 1994; Lepage et al 2000). …”

Section: Introductionmentioning

confidence: 99%

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Remote Effects of Hippocampal Sclerosis on Effective Connectivity during Working Memory Encoding: A Case of Connectional Diaschisis?

et al. 2011

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Accumulating evidence suggests a role for the medial temporal lobe (MTL) in working memory (WM). However, little is known concerning its functional interactions with other cortical regions in the distributed neural network subserving WM. To reveal these, we availed of subjects with MTL damage and characterized changes in effective connectivity while subjects engaged in WM task. Specifically, we compared dynamic causal models, extracted from magnetoencephalographic recordings during verbal WM encoding, in temporal lobe epilepsy patients (with left hippocampal sclerosis) and controls. Bayesian model comparison indicated that the best model (across subjects) evidenced bilateral, forward, and backward connections, coupling inferior temporal cortex (ITC), inferior frontal cortex (IFC), and MTL. MTL damage weakened backward connections from left MTL to left ITC, a decrease accompanied by strengthening of (bidirectional) connections between IFC and MTL in the contralesional hemisphere. These findings provide novel evidence concerning functional interactions between nodes of this fundamental cognitive network and sheds light on how these interactions are modified as a result of focal damage to MTL. The findings highlight that a reduced (top-down) influence of the MTL on ipsilateral language regions is accompanied by enhanced reciprocal coupling in the undamaged hemisphere providing a first demonstration of “connectional diaschisis.”

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Remote Effects of Hippocampal Sclerosis on Effective Connectivity during Working Memory Encoding: A Case of Connectional Diaschisis?

et al. 2011

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“…Findings from these investigations have delineated a remarkable consistent group of areas that contribute to WM processes, this is, prefrontal cortex (PFC) (Goldman-Rakic, 1995; Braver et al, 1997; Rypma and D'Esposito, 1999; D'Esposito et al, 2000), neocortical associative areas (Druzgal and D'Esposito, 2001; Postle et al, 2003; Fiebach et al, 2007), and more recently the medial temporal lobes (MTL) (Abrahams et al, 1999; Campo et al, 2005a,b, 2009; Carrozzo et al, 2005; Karlsgodt et al, 2005; Nichols et al, 2006; Olson et al, 2006; Petersson et al, 2006; Axmacher et al, 2007, 2008a; Braun et al, 2008; Cashdollar et al, 2009; Olsen et al, 2009; Schon et al, 2009; Wagner et al, 2009; Öztekin et al, 2010; Toepper et al, 2010; van Vugt et al, 2010; Faraco et al, 2011; Lee and Rudebeck, 2011). Although the involvement of MTL in WM is matter of debate (Talmi et al, 2005; Zarahn et al, 2005; Shrager et al, 2008; Tudesco Ide et al, 2010; Jeneson et al, 2011), it has called for a re-evaluation of the prevailing conception considering that MTL is exclusively dedicated to long-term memory (LTM).…”

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confidence: 99%

Neocortical-hippocampal dynamics of working memory in healthy and diseased brain states based on functional connectivity

Poch¹,

Campo²

2012

Front. Hum. Neurosci.

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Working memory (WM) is the ability to transiently maintain and manipulate internal representations beyond its external availability to the senses. This process is thought to support high level cognitive abilities and been shown to be strongly predictive of individual intelligence and reasoning abilities. While early models of WM have relied on a modular perspective of brain functioning, more recent evidence suggests that cognitive functions emerge from the interactions of multiple brain regions to generate large-scale networks. Here we will review the current research on functional connectivity of WM processes to highlight the critical role played by neural interactions in healthy and pathological brain states. Recent findings demonstrate that WM abilities are not determined solely by local brain activity, but also rely on the functional coupling of neocortical-hippocampal regions to support WM processes. Although the hippocampus has long been held to be important for long-term declarative memory, recent evidence suggests that the hippocampus may also be necessary to coordinate disparate cortical regions supporting the periodic reactivation of internal representations in WM. Furthermore, recent brain imaging studies using connectivity measures, have shown that changes in cortico-limbic interactions can be useful to characterize WM impairments observed in different neuropathological conditions. Recent advances in electrophysiological and neuroimaging techniques to model network activity has led to important insights into how neocortical and hippocampal regions support WM processes and how disruptions along this network can lead to the memory impairments commonly reported in many neuropathological populations.

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“…A number of studies have demonstrated that the medial temporal lobe (MTL) region is crucial for episodic memory function and related working memory functions (Campo et al, 2005;Habeck et al, 2005;Hannula and Ranganath, 2008;Hayes et al, 2004;Piekema et al, 2006;Ranganath et al, 2004;Yonelinas et al, 2007). In the MTL, distinct subregions have been shown to make different contributions to object and spatial memory processes (Pihlajamäki et al, 2003(Pihlajamäki et al, , 2004(Pihlajamäki et al, , 2005, in the binding of object and spatial information (Mitchell et al, 2000), in encoding and retrieval (de Zubicaray et al, 2001;Kirwan and Stark, 2004;Tsukiura et al, 2005), as well as in familiarity and recognition judgments (Daselaar et al, 2006;Gonsalves et al, 2005;Henson, 2005;Henson et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Healthy aging attenuates task-related specialization in the human medial temporal lobe

Ramsøy

Liptrot

Skimminge

et al. 2012

Neurobiology of Aging

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Recent research on aging has established important links between the neurobiology of normal aging and age-related decline in episodic memory, yet the exact nature of this relationship is still unknown. Functional neuroimaging of regions such as the medial temporal lobe (MTL) have produced conflicting findings. Using functional magnetic resonance imaging (fMRI), we have recently shown that young healthy individuals show a stronger activation of the MTL during encoding of objects as compared with encoding of positions. Using the same encoding task, the present study addressed the question whether this greater MTL activation during encoding of objects varies with age. Fifty-four healthy individuals aged between 18 and 81 years underwent functional magnetic resonance imaging while they encoded and subsequently made new-old judgments on objects and positions. Region of interest (ROI) analysis of task related changes in the blood oxygen level-dependent (BOLD) signal was performed in native space after correction for gender effects and individual differences in cerebral blood flow. The hippocampus, amygdala, and parahippocampal, perirhinal, entorhinal, and temporopolar cortices of right and left hemisphere were defined as ROIs. Aging had an adverse effect on memory performance that was similar for memorizing objects or positions. In left and right MTL, relatively greater activation for object stimuli was attenuated in older individuals. Age-related attenuation in content specificity was most prominent in the recognition stage. During recognition, the larger response to objects gradually decreased with age in all ROIs apart from left temporopolar and entorhinal cortex. An age-related attenuation was also present during encoding, but only in right parahippocampus and amygdala. Our results suggest that memory-related processing in the MTL becomes gradually less sensitive to content during normal aging.

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Is medial temporal lobe activation specific for encoding long-term memories?

Cited by 22 publications

References 62 publications

Remote Effects of Hippocampal Sclerosis on Effective Connectivity during Working Memory Encoding: A Case of Connectional Diaschisis?

Remote Effects of Hippocampal Sclerosis on Effective Connectivity during Working Memory Encoding: A Case of Connectional Diaschisis?

Neocortical-hippocampal dynamics of working memory in healthy and diseased brain states based on functional connectivity

Healthy aging attenuates task-related specialization in the human medial temporal lobe

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