scholarly journals Gamma phase synchronization during olfactory stimulation as a marker for Alzheimer’s disease

2021 ◽  
Vol 17 (S5) ◽  
Author(s):  
Arshia Afzal ◽  
Mohammad Javad Sedghizadeh ◽  
Hamid Aghajan ◽  
Zahra Vahabi
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Phase Synchronization ◽  
Olfactory Stimulation ◽  
Gamma Phase

ODor-evoked Autobiographical Memory in Alzheimer’s disease?

2021 ◽  
Author(s):  
Mohamad El Haj
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Autobiographical Memory ◽  
Personal Information ◽  
Disease Model ◽  
Olfactory Stimulation ◽  
Autobiographical Memories ◽  
Comprehensive Overview ◽  
Memory Decline ◽  
Stimulation Of

Abstract Objective Because memory decline is the hallmark of Alzheimer’s disease (AD), an important endeavor for both clinicians and researchers is to improve memory performances in AD. This can be pursued by olfactory stimulation of memory in patients with AD and by studying the effects of olfactory stimulation on autobiographical memory (i.e., memory for personal information). The effects of olfactory stimulation on autobiographical memory in patients with mild AD have been reported by recent research. We thus provide the first comprehensive overview of research on odor-evoked autobiographical memory in AD. We also establish the basis for solid theoretical analysis concerning the memory improvement reported by research on odor-evoked autobiographical memory in AD. Method We examined literature on odor-evoked autobiographical memories in AD and propose the “OdAMA” (Odor-evoked Autobiographical Memory in Alzheimer’s disease) model. Results and discussion According to OdAMA model, odor exposure activates involuntary access to specific autobiographical memories, which promotes enhanced experience subjective of retrieval in patients with AD and improves their ability to construct not only recent and remote events but also future ones. The OdAMA model could serve as a guide for researchers and clinicians interested in odor-evoked autobiographical memory in AD.

scholarly journals Olfactory response as a marker for Alzheimer’s disease: Evidence from perceptual and frontal lobe oscillation coherence deficit

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0243535
Author(s):  
Mohammad Javad Sedghizadeh ◽  
Hadi Hojjati ◽  
Kiana Ezzatdoost ◽  
Hamid Aghajan ◽  
Zahra Vahabi ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Frontal Cortex ◽  
High Frequency ◽  
Medial Temporal Lobe ◽  
Spatial Coherence ◽  
Olfactory Stimulation ◽  
Olfactory Perception ◽  
Potential Biomarker ◽  
The Brain

High-frequency oscillations of the frontal cortex are involved in functions of the brain that fuse processed data from different sensory modules or bind them with elements stored in the memory. These oscillations also provide inhibitory connections to neural circuits that perform lower-level processes. Deficit in the performance of these oscillations has been examined as a marker for Alzheimer’s disease (AD). Additionally, the neurodegenerative processes associated with AD, such as the deposition of amyloid-beta plaques, do not occur in a spatially homogeneous fashion and progress more prominently in the medial temporal lobe in the early stages of the disease. This region of the brain contains neural circuitry involved in olfactory perception. Several studies have suggested that olfactory deficit can be used as a marker for early diagnosis of AD. A quantitative assessment of the performance of the olfactory system can hence serve as a potential biomarker for Alzheimer’s disease, offering a relatively convenient and inexpensive diagnosis method. This study examines the decline in the perception of olfactory stimuli and the deficit in the performance of high-frequency frontal oscillations in response to olfactory stimulation as markers for AD. Two measurement modalities are employed for assessing the olfactory performance: 1) An interactive smell identification test is used to sample the response to a sizable variety of odorants, and 2) Electroencephalography data are collected in an olfactory perception task with a pair of selected odorants in order to assess the connectivity of frontal cortex regions. Statistical analysis methods are used to assess the significance of selected features extracted from the recorded modalities as Alzheimer’s biomarkers. Olfactory decline regressed to age in both healthy and mild AD groups are evaluated, and single- and multi-modal classifiers are also developed. The novel aspects of this study include: 1) Combining EEG response to olfactory stimulation with behavioral assessment of olfactory perception as a marker of AD, 2) Identification of odorants most significantly affected in mild AD patients, 3) Identification of odorants which are still adequately perceived by mild AD patients, 4) Analysis of the decline in the spatial coherence of different oscillatory bands in response to olfactory stimulation, and 5) Being the first study to quantitatively assess the performance of olfactory decline due to aging and AD in the Iranian population.

Effects of olfactory stimulation on autobiographical memory in Alzheimer's disease

2018 ◽  
Vol 16 (3) ◽  
pp. 311-320 ◽  
Author(s):  
Ophélie Glachet ◽  
Marie-Charlotte Gandolphe ◽  
Karim Gallouj ◽  
Pascal Antoine ◽  
Mohamad El Haj
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Autobiographical Memory ◽  
Olfactory Stimulation

Topography of EEG multivariate phase synchronization in early Alzheimer's disease

2010 ◽  
Vol 31 (7) ◽  
pp. 1132-1144 ◽  
Author(s):  
Maria G. Knyazeva ◽  
Mahdi Jalili ◽  
Andrea Brioschi ◽  
Isabelle Bourquin ◽  
Eleonora Fornari ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Phase Synchronization ◽  
Early Alzheimer’S Disease

scholarly journals Olfactory Response as a Marker for Alzheimer's Disease: Evidence from Perceptual and Frontal Oscillation Coherence Deficit

2019 ◽  
Author(s):  
Mohammad Javad Sedghizadeh ◽  
Hadi Hojjati ◽  
Kiana Ezzatdoost ◽  
Hamid Aghajan ◽  
Zahra Vahabi ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Frontal Cortex ◽  
High Frequency ◽  
Medial Temporal Lobe ◽  
Spatial Coherence ◽  
Olfactory Stimulation ◽  
Olfactory Perception ◽  
Potential Biomarker ◽  
The Brain

High-frequency oscillations of the frontal cortex are involved in functions of the brain that fuse processed data from different sensory modules or bind them with elements stored in the memory. These oscillations also provide inhibitory connections to neural circuits that perform lower-level processes. Deficit in the performance of these oscillations has been examined as a marker for Alzheimer's disease (AD). Additionally, the neurodegenerative processes associated with AD, such as the deposition of amyloid-beta plaques, do not occur in a spatially homogeneous fashion and progress more prominently in the medial temporal lobe in the early stages of the disease. This region of the brain contains neural circuitry involved in olfactory perception. Several studies have suggested that olfactory deficit can be used as a marker for early diagnosis of AD. A quantitative assessment of the performance of the olfactory system can hence serve as a potential biomarker for Alzheimer's disease, offering a relatively convenient and inexpensive diagnosis method. This study examines the decline in the perception of olfactory stimuli and the deficit in the performance of high-frequency frontal oscillations in response to olfactory stimulation as markers for AD. Two measurement modalities are employed for assessing the olfactory performance: 1) An interactive smell identification test is used to sample the response to a sizable variety of odorants, and 2) Electrophysiological data are collected in an olfactory perception task with a pair of selected odorants in order to assess the connectivity of frontal cortex regions. Statistical analysis methods are used to assess the significance of selected features extracted from the recorded modalities as Alzheimer's biomarkers. Olfactory decline regressed to age in both healthy and Mild AD groups are evaluated, and single- and multi-modal classifiers are also developed. The novel aspects of this study include: 1) Combining EEG response to olfactory stimulation with behavioral assessment of olfactory perception as a marker of AD, 2) Identification of odorants most significantly affected in Mild AD patients, 3) Identification of odorants which are still adequately perceived by Mild AD patients, 4) Analysis of the decline in the spatial coherence of different oscillatory bands in response to olfactory stimulation, and 5) Being the first study to quantitatively assess the performance of olfactory decline due to aging and AD in the Iranian population.

Functional Connectivity Alterations Based on the Weighted Phase Lag Index: An Exploratory Electroencephalography Study on Alzheimer’s Disease

2021 ◽  
Vol 18 ◽  
Author(s):  
Yi Yan ◽  
Aonan Zhao ◽  
Yinghui Qiu ◽  
Yanfei Ding ◽  
Ying Wang ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Functional Connectivity ◽  
Phase Synchronization ◽  
Significant Negative Correlation ◽  
Phase Lag ◽  
Connection Strength ◽  
Theta Band ◽  
Delta Band ◽  
Weighted Phase Lag Index

Objectives: Numerous electroencephalography (EEG) studies focus on the alteration of electrical activity in patients with Alzheimer’s Disease (AD), but there are no consistent results es- pecially regarding functional connectivity. We supposed that the weighted Phase Lag Index (w- PLI), as phase-based measures of functional connectivity, may be used as an auxiliary diagnostic method for AD. Methods: We enrolled 30 patients with AD, 30 patients with Mild Cognitive Impairment (MCI), and 30 Healthy Controls (HC). EEGs were recorded in all participants at baseline during relaxed wakefulness. Following EEG preprocessing, Power Spectral Density (PSD) and wPLI parameters were determined to further analyze whether they were correlated to cognitive scores. Results: In the patients with AD, the increased PSD in theta band was presented compared with MCI and HC groups, which was associated with disturbances of the directional, computational, and delayed memory capacity. Furthermore, the wPLI revealed a distinctly lower connection strength between frontal and distant areas in the delta band and a higher connection strength of the central and temporo-occipital region in the theta band for AD patients. Moreover,we found a significant negative correlation between theta functional connectivity and cognitive scores. Conclusions: Increased theta PSD and decreased delta wPLI may be one of the earliest changes in AD and associated with disease severity. The parameter wPLI is a novel measurement of phase synchronization and has potentials in understanding underlying functional connectivity and aiding in the diagnostics of AD.

Cognitive control constrains memory attributions

2019 ◽  
Vol 42 ◽  
Author(s):  
Colleen M. Kelley ◽  
Larry L. Jacoby
Keyword(s):  
Alzheimer’S Disease ◽  
Older Adults ◽  
Alzheimer's Disease ◽  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Cognitive Control

Abstract Cognitive control constrains retrieval processing and so restricts what comes to mind as input to the attribution system. We review evidence that older adults, patients with Alzheimer's disease, and people with traumatic brain injury exert less cognitive control during retrieval, and so are susceptible to memory misattributions in the form of dramatic levels of false remembering.

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