Effects of DHEA administration on episodic memory, cortisol and mood in healthy young men: a double-blind, placebo-controlled study

Alhaj, Hamid; Massey, Anna E.; McAllister-Williams, R. Hamish

doi:10.1007/s00213-005-0136-y

Cited by 76 publications

(59 citation statements)

References 78 publications

(83 reference statements)

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“…BSS methods such as AJDC may be a suitable method for counteracting volume conduction effects which lead to the 'poor spatial resolution' of EEG recordings. Whilst source localization of ERP data has provided suggestive evidence of memory-related medial temporal lobe activity, averaged responses across many trials are required to enhance signal-to-noise ratio (Alhaj et al, 2006). BSS techniques combined with source localization provide a useful tool for exploring task-related EEG (eg.…”

Section: Source Localization With Ajdc and Sloretamentioning

confidence: 99%

Brain Oscillatory Activity during Spatial Navigation: Theta and Gamma Activity Link Medial Temporal and Parietal Regions

White

Congedo

Ciorciari

et al. 2012

Journal of Cognitive Neuroscience

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Brain oscillatory correlates of spatial navigation were investigated using blind source separation (BSS) and standardized low resolution electromagnetic tomography (sLORETA) analyses of 62-channel EEG recordings. Twenty-five participants were instructed to navigate to distinct landmark buildings in a previously learned virtual reality town environment. Data from periods of navigation between landmarks were subject to BSS analyses to obtain source components. Two of these cortical sources were found to exhibit significant spectral power differences during navigation with respect to a resting eyes open condition and were subject to source localization using sLORETA. These two sources were localized as a right parietal component with gamma activation and a right medial-temporal-parietal component with activation in theta and gamma bandwidths. The parietal gamma activity was thought to reflect visuospatial processing associated with the task. The medial-temporal-parietal activity was thought to be more specific to the navigational processing, representing the integration of ego-and allo-centric representations of space required for successful navigation, suggesting theta and gamma oscillations may have a role in integrating information from parietal and medialtemporal regions. Theta activity on this medial-temporal-parietal source was positively correlated with more efficient navigation performance. Results are discussed in light of the depth and proposed closed field structure of the hippocampus and potential implications for scalp EEG data. The findings of the present study suggest that appropriate BSS methods are ideally suited to minimizing the effects of volume conduction in non invasive recordings, allowing more accurate exploration of deep brain processes.

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Section: Source Localization With Ajdc and Sloretamentioning

confidence: 99%

Brain Oscillatory Activity during Spatial Navigation: Theta and Gamma Activity Link Medial Temporal and Parietal Regions

White

Congedo

Ciorciari

et al. 2012

Journal of Cognitive Neuroscience

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“…Using LOR-ETA, Alhaj et al [2005] analyzed the sources of the current density corresponding to successful memory retrieval, and reported hippocampal activation. In their study, they used electroencephalograph (EEG) with 29 channels and a spherical head model.…”

Section: Introductionmentioning

confidence: 99%

Cortical network dynamics during source memory retrieval: Current density imaging with individual MRI

Kim

Roh²,

Namgoong³

et al. 2007

Human Brain Mapping

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Abstract:We investigated the neural correlates of source memory retrieval using low-resolution electromagnetic tomography (LORETA) with 64 channels EEG and individual MRI as a realistic head model. Event-related potentials (ERPs) were recorded while 13 healthy subjects performed the source memory task for the voice of the speaker in spoken words. The source correct condition of old words elicited more positive-going potentials than the correct rejection condition of new words at 400-700 ms post-stimulus and the old/new effects also appeared in the right anterior region between 1,000 and 1,200 ms. We conducted source reconstruction at mean latencies of 311, 604, 793, and 1,100 ms and used statistical parametric mapping for the statistical analysis. The results of source analysis suggest that the activation of the right inferior parietal region may reflect retrieval of source information. The source elicited by the difference ERPs between the source correct and source incorrect conditions exhibited dynamic change of current density activation in the overall cortices with time during source memory retrieval. These results indicate that multiple neural systems may underlie the ability to recollect

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“…In addition, 7␣-hydroxyDHEA can be further converted to 7-oxo-DHEA by 11␤-HSD1 (Robinzon et al, 2003), itself widespread in the CNS (Moisan et al, 1990), and 7-oxo-DHEA reverses scopolamine-induced memory impairments in young mice (Shi et al, 2000). Indeed, if 7␣-hydroxylated metabolites are more active than the parent steroid, then this may in part explain why oral DHEA replacement in the elderly has not successfully improved memory (Wolf et al, 1997;Huppert and Van Niekerk, 2001), whereas DHEA administration is effective at improving memory recollection and mood in healthy young subjects (Alhaj et al, 2006), presumably because they maintain greater hippocampal CYP7B activity. It may be that the 7␣-hydroxylated metabolite rather than the parent steroid would be more effective therapy in the elderly.…”

Section: Discussionmentioning

confidence: 99%

Central Administration of a Cytochrome P450-7B Product 7α-Hydroxypregnenolone Improves Spatial Memory Retention in Cognitively Impaired Aged Rats

Yau¹,

Noble²,

Graham³

2006

J. Neurosci.

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Pregnenolone (PREG) and dehydroepiandrosterone (DHEA) have been reported to improve memory in aged rodents. In brain, these neurosteroids are transformed predominantly into 7␣-hydroxylated metabolites by the cytochrome P450-7B1 (CYP7B). The biological role of steroid B-ring hydroxylation is unclear. It has been proposed to generate bioactive derivatives that enhance cognition, immune, and other physiological processes. In support, 7␣-hydroxylated DHEA increases the immune response in mice with greater potency than the parent steroid. Whether the memory-enhancing effects of PREG in rats is mediated via its 7␣-hydroxylated metabolite 7␣-hydroxyPREG is not known. We investigated this by treating memory-impaired aged rats (identified by their spatial memory performances in the Morris water maze task compared with young controls) with 7␣-hydroxyPREG or PREG administered intracerebroventricularly using osmotic minipumps and then tested the rats during week 2 of steroid treatment in the eight-arm radial-arm version of the water maze (RAWM) that allows repeated assessment of learning. CYP7B bioactivity in hippocampal tissue (percentage conversion of [ 14 C]DHEA to [ 14 C]7␣-hydroxyDHEA) was decreased selectively in memory-impaired aged rats compared with both young and memory-intact aged rats. 7␣-hydroxyPREG (100 ng/h) but not PREG (100 ng/h) administration to memory-impaired aged rats for 11 d enhanced spatial memory retention (after a 30 min delay between an exposure trial 1 and test trial 2) in the RAWM. These data provide evidence for a biologically active enzyme product 7␣-hydroxyPREG and suggests that reduced CYP7B function in the hippocampus of memory-impaired aged rats may, in part, be overcome by administration of 7␣-hydroxyPREG.

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Effects of DHEA administration on episodic memory, cortisol and mood in healthy young men: a double-blind, placebo-controlled study

Cited by 76 publications

References 78 publications

Brain Oscillatory Activity during Spatial Navigation: Theta and Gamma Activity Link Medial Temporal and Parietal Regions

Brain Oscillatory Activity during Spatial Navigation: Theta and Gamma Activity Link Medial Temporal and Parietal Regions

Cortical network dynamics during source memory retrieval: Current density imaging with individual MRI

Central Administration of a Cytochrome P450-7B Product 7α-Hydroxypregnenolone Improves Spatial Memory Retention in Cognitively Impaired Aged Rats

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