Correlation of auditory event-related potentials and magnetic resonance spectroscopy measures in mild cognitive impairment

Association between hearing ability and cortical morphology in the elderly: multiparametric mapping, cognitive relevance, and neurobiological underpinnings

BACKGROUND

Hearing impairment is a common condition in the elderly. However, a comprehensive understanding of its neural correlates is still lacking.

METHODS

We recruited 284 elderly adults who underwent structural MRI, magnetic resonance spectroscopy, audiometry, and cognitive assessments. Individual hearing abilities indexed by pure tone average (PTA) were correlated with multiple structural MRI-derived cortical morphological indices. For regions showing significant correlations, mediation analyses were performed to examine their role in the relationship between hearing ability and cognitive function. Finally, the correlation maps between hearing ability and cortical morphology were linked with publicly available connectomic gradient, transcriptomic, and neurotransmitter maps.

FINDINGS

Poorer hearing was related to cortical thickness (CT) reductions in widespread regions and gyrification index (GI) reductions in the right Area 52 and Insular Granular Complex. The GI in the right Area 52 mediated the relationship between hearing ability and executive function. This mediating effect was further modulated by glutamate and N-acetylaspartate levels in the right auditory region. The PTA-CT correlation map followed microstructural connectomic hierarchy, were related to genes involved in certain biological processes (e.g., glutamate metabolic process), cell types (e.g., excitatory neurons and astrocytes), and developmental stages (i.e., childhood to young adulthood), and covaried with dopamine receptor 1, dopamine transporter, and fluorodopa. The PTA-GI correlation map was related to 5-hydroxytryptamine receptor 2a.

INTERPRETATION

Poorer hearing is associated with cortical thinning and folding reductions, which may be engaged in the relationship between hearing impairment and cognitive decline in the elderly and have different neurobiological substrates.

FUNDING

See the Acknowledgements section.

Meta-Analysis of Neurochemical Changes Estimated via Magnetic Resonance Spectroscopy in Mild Cognitive Impairment and Alzheimer's Disease

The changes of neurochemicals in mild cognitive impairment (MCI) and Alzheimer's disease (AD) patients has been observed via magnetic resonance spectroscopy in several studies. However, whether it exists the consistent pattern of changes of neurochemicals in the encephalic region during the progression of MCI to AD were still not clear. The study performed meta-analysis to investigate the patterns of neurochemical changes in the encephalic region in the progress of AD. We searched the PubMed, Embase, Cochrane Library, and Web of Science databases, and finally included 63 studies comprising 1,086 MCI patients, 1,256 AD patients, and 1,907 healthy controls. It showed that during the progression from MCI to AD, N-acetyl aspartate (NAA) decreased continuously in the posterior cingulate (PC) (SMD: −0.42 [95% CI: −0.62 to −0.21], z = −3.89, P < 0.05), NAA/Cr (creatine) was consistently reduced in PC (SMD: −0.58 [95% CI: −0.86 to −0.30], z = −4.06, P < 0.05) and hippocampus (SMD: −0.65 [95% CI: −1.11 to −0.12], z = −2.44, P < 0.05), while myo-inositol (mI) (SMD: 0.44 [95% CI: 0.26–0.61], z = 4.97, P < 0.05) and mI/Cr (SMD: 0.43 [95% CI: 0.17–0.68], z = 3.30, P < 0.05) were raised in PC. Furthermore, these results were further verified by a sustained decrease in the NAA/mI of PC (SMD: −0.94 [95% CI: −1.24 to −0.65], z = −6.26, P < 0.05). Therefore, the levels of NAA and mI were associated with the cognitive decline and might be used as potentially biomarkers to predict the possible progression from MCI to AD.

Systematic Review Registration:https://www.crd.york.ac.uk/PROSPERO/, identifier: CRD42020200308.

Event-related brain potential indexes provide evidence for some decline in healthy people with subjective memory complaints during target evaluation and response inhibition processing

In the preclinical stage of the Alzheimer's disease (AD) continuum, subjects report subjective memory complaints (SMCs), although with the absence of any objective decline, and have a higher risk of progressing to dementia than the general population. Early identification of this stage therefore constitutes a major focus of current AD research, to enable early intervention. In this study, healthy adult participants with high and low SMCs (HSMCs and LSMCs) performed a Go/NoGo task during electroencephalogram (EEG) recording. Relative to LSMC participants, HSMC participants performed the task slower (longer reaction times) and showed changes in the event-related potential (ERP) components associated with response preparation (lower readiness potential -RP- amplitude in the Go condition), and also related to response inhibition processes (lower N2-P3 amplitude in the NoGo condition). In addition, HSMC participants showed lower Go-N2 and NoGo-N2 peak-to-baseline amplitudes, however these results seem to be influenced by a negative tendency overlapping stimulus-related waveforms. The declines observed in this study are mostly consistent with those observed in aMCI participants, supporting the notion of the AD continuum regarding SMC state.

Application of the P300 potential in cognitive impairment assessments after transient ischemic attack or minor stroke

Background The aims of this study were to determine the relationships between changes inlatency and amplitude of the P300 event-related potential component and cognitive impairmentsin patients after a transient ischemic attack (TIA) or a minor stroke and to assess thesuitability of the P300 for screening for cognitive impairments.Material and Method Sixty-five TIA or minor stroke patients diagnosed at the NeurologyDepartment of Beijing Tiantan Hospital, Capital Medical University from June 2015 toDecember 2016 and 30 healthy people evaluated in the same period were included. Allpatients were examing neuropsychological scales and event-related potentials within7 ± 3 days of onset of the disease. The TIA/minor stroke group was divided into normal cognition group(NC) and cognitive impairment group. The cognitive impairment group was further divided into vascular cognitive impairment with no dementia(VCIND) group and vascular dementia (VD) group to analyze the relationship between P300 latency.Results The P300 latency at each recording electrode was longer in the NC and VCIND groups than healthy control group (P < 0.001), the P300 latency of VCIND group longer than NC group (P < 0.001). When the P300-Fz latency cut-off value was 358.6 ms,the sensitivity for diagnosing cognitive impairment in patients after TIA/minor stroke was 0.875 and the specificity was 0.765.Conclusions The P300 latency delay can be used to detect cognitive impairments in patients after TIA/minor stroke and the P300-Fz latency is more sensitive for diagnosing cognitiveimpairments in TIA/minor stroke patients.

Investigating Auditory Electrophysiological Measures of Participants with Mild Cognitive Impairment and Alzheimer's Disease: A Systematic Review and Meta-Analysis of Event-Related Potential Studies

BACKGROUND

Objectively measuring auditory functions has been proposed as an avenue in differentiating normal age-related cognitive dysfunction from Alzheimer's disease (AD) and its prodromal states. Previous research has suggested auditory event-related potentials (AERPs) to be non-invasive, cost-effective, and efficient biomarkers for the diagnosis of AD.

OBJECTIVE

The objective of this paper is to review the published literature on AERPs measures in older adults diagnosed with AD and those at higher risk of developing AD, i.e., mild cognitive impairment (MCI) and subjective cognitive decline.

METHODS

The search was performed on six major electronic databases (Ovid MEDLINE, OVID EMBASE, PsycINFO, PubMed, Scopus, and CINAHL Plus). Articles identified prior to 7 May 2019 were considered for this review. A random effects meta-analysis and analysis of between study heterogeneity was conducted using the Comprehensive Meta-Analysis software.

RESULTS

The search identified 1,076 articles; 74 articles met the full inclusion criteria and were included in the systematic review, and 47 articles were included into the analyses. Pooled analysis suggests that AD participants can be differentiated from controls due to significant delays in ABR, N100, P200, N200, and P300 latencies. P300 amplitude was significantly smaller in AD participants compared to controls. P300 latencies differed significantly between MCI participants and controls based on the pooled analysis.

CONCLUSION

The findings of this review indicate that some AERPs may be valuable biomarkers of AD. In conjunction with currently available clinical and neuropsychological assessments, AERPs can aid in screening and diagnosis of prodromal AD.

Cognitive Event-Related Potential Responses Differentiate Older Adults with and without Probable Mild Cognitive Impairment

Background: Older adults rarely seek cognitive assessment, but often visit other healthcare professionals (e.g., audiologists). Noninvasive clinical measures within the scopes of practice of those professions sensitive to cognitive impairment are needed. Purpose: This study examined the differences of probable mild cognitive impairment (MCI) on latency and mean amplitude of the P3b auditory event-related potential. Method: Fifty-four participants comprised two groups according to cognitive status (cognitively normal older adults [CNOA], n = 25; probable MCI, n = 29). P3b was recorded using an oddball paradigm for speech (/ba/, /da/) and non-speech (1000, 2000 Hz) stimuli. Amplitudes and latencies were compared from six electrodes (FPz, Fz, FCz, Cz, CPz, Pz) between groups across stimulus probability and type. Results: CNOA participants had larger P3b mean amplitudes for deviant stimuli than those with probable MCI. Group effects of latency were isolated to deviant stimuli at FCz only when those with unclear P3bs were included. Findings did not covary with age or education. Overall, CNOAs showed a large P3b oddball effect while those with probable MCI did not. Conclusions: P3b can be used to show electrophysiological differences between older adults with and without probable MCI. These results support the development of educational materials targeting professionals using auditory-evoked potentials.

Value of magnetic resonance spectroscopy in geriatric patients with cognitive impairment

Background

Mild cognitive impairment is a transitional stage prior to dementia, and it is reported in depressed patients. Early diagnosis could predict the reversible etiologies and prevent further deterioration. Proton magnetic resonance spectroscopy has been used for early diagnosis and differential diagnosis of cognitive impairment.

Objective

We aimed to study the difference of hippocampal and frontal white matter metabolites between patients with Alzheimer’s disease, mild cognitive impairment, and cognitive impairment associated with depression, and if those metabolites can differentiate between them.

Subjects and methods

Geriatric patients with cognitive impairment were recruited from neurology and psychiatry clinics. All subjects underwent comprehensive medical evaluations, neuropsychological testing, laboratory tests as well as brain MRI and 1H-MRS studies.

Results

The present study included 85 subjects. Patients with MCI and AD had lower hippocampal NAA and NAA/Cr ratio than patients with depression and normal controls, while, frontal NAA and NAA/Cr ratio were lower in all patient’s subgroups compared to normal control.

Conclusion

Hippocampal NAA and NAA/Cr ratio might help to differentiate between MCI and cognitive impairment associated with depression.

A systematic review of cognitive event-related potentials in mild cognitive impairment and Alzheimer's disease

This systematic review examined whether event-related potentials (ERPs) during higher cognitive processing can detect subtle, early signs of neurodegenerative disease. Original, empirical studies retrieved from PsycINFO and PubMed were reviewed if they analyzed patterns in cognitive ERPs (≥150 ms post-stimulus) differentiating mild cognitive impairment (MCI), Alzheimer's disease (AD), or cognitively intact elders who carry AD risk through the Apolipoprotein-E ε4 allele (ε4+) from healthy older adult controls (HC). The 100 studies meeting inclusion criteria (MCI = 47; AD = 47; ε4+ = 6) analyzed N200, P300, N400, and occasionally, later components. While there was variability across studies, patterns of reduced amplitude and delayed latency were apparent in pathological aging, consistent with AD-related brain atrophy and cognitive impairment. These effects were particularly evident in advanced disease progression (i.e., AD > MCI) and in later ERP components measured during complex tasks. Although ERP studies in intact ε4+ elders are thus far scarce, a similar pattern of delayed latency was notable, along with a contrasting pattern of increased amplitude, consistent with compensatory neural activation. This limited work suggests ERPs might be able to index early neural changes indicative of future cognitive decline in otherwise healthy elders. As ERPs are also accessible and affordable relative to other neuroimaging methods, their addition to cognitive assessment might substantively enhance early identification and characterization of neural dysfunction, allowing opportunity for earlier differential diagnosis and targeting of intervention. To evaluate this possibility there is urgent need for well-powered studies assessing late cognitive ERPs during complex tasks, particularly in healthy elders at risk for cognitive decline.

The importance of age in the search for ERP biomarkers of aMCI

Alzheimer's Disease (AD) has become a major health issue in recent decades, and there is now growing interest in amnestic mild cognitive impairment (aMCI), an intermediate stage between healthy aging and dementia, usually AD. Event-related brain potential (ERP) studies have sometimes failed to detect differences between aMCI and control participants in the Go-P3 (or P3b, related to target classification processes in a variety of tasks) and NoGo-P3 (related to response inhibition processes, mainly in Go/NoGo tasks) ERP components. The aim of the present study was to evaluate whether the age factor, which is not usually taken into account in ERP studies, modulates group differences in these components. With this aim, we divided two groups of volunteer participants, 34 subjects with aMCI (51-87 years) and 31 controls (52-86 years), into two age subgroups: 69 years or less and 70 years or more. We recorded brain activity while the participants performed a distraction-attention auditory-visual (AV) task. Task performance was poorer in the older than in the younger group, and aMCI participants produced fewer correct responses than the matched controls; but no interactions of the age and group factors on performance were found. On the other hand, Go-P3 and NoGo-N2 latencies were longer in aMCI participants than in controls only in the younger subgroup. Thus, the younger aMCI participants categorized the Go stimuli in working memory and processed the NoGo stimuli (which required response inhibition) slower than the corresponding controls. Finally, the combination of the number of hits, Go-P3 latency and NoGo-N2 latency yielded acceptable sensitivity and specificity scores (0.70 and 0.92, respectively) as regards distinguishing aMCI participants aged 69 years or less from the age-matched controls. The findings indicate age should be taken into account in the search for aMCI biomarkers.

Neurocognitive and Behavioral Indexes for Identifying the Amnestic Subtypes of Mild Cognitive Impairment

Early identification of amnestic mild cognitive impairment (aMCI) subtypes is important for early diagnosis and prognosis of Alzheimer’s disease. Healthy, single-domain (sdaMCI) and multiple-domain aMCI (mdaMCI) participants performed an auditory-visual distraction-attention task. Event-related brain potentials (ERPs) were recorded while the participants performed the task to evaluate Go/NoGo N2 and P3 ERP components. The results showed the expected behavioral and cognitive decline in mdaMCI participants relative to controls (fewer hits, longer reaction times [RTs], slightly smaller Go-N2 and NoGo-N2 amplitudes), while sdaMCI participants showed some decline (slightly longer RTs, smaller Go- and NoGo-N2 amplitudes) along with some unexpected results (a late positive slow wave, PSW) and good levels of execution. In addition, some of these parameters proved to be useful markers. Thus, the number of hits was the best marker for diagnosing mdaMCI participants (distinguishing them from controls, from sdaMCI participants, and from both groups together), while the PSW amplitude was the best marker for diagnosing sdaMCI participants (distinguishing them from controls, and from control & mdaMCI participants).

Neuromagnetic evidence for hippocampal modulation of auditory processing

The hippocampus is well known to be involved in memory, as well as in perceptual processing. To date, the electrophysiological process by which unilateral hippocampal lesions, such as hippocampal sclerosis (HS), modulate the auditory processing remains unknown. Auditory-evoked magnetic fields (AEFs) are valuable for evaluating auditory functions, because M100, a major component of AEFs, originates from auditory areas. Therefore, AEFs of mesial temporal lobe epilepsy (mTLE, n=17) with unilateral HS were compared with those of healthy (HC, n=17) and disease controls (n=9), thereby determining whether AEFs were indicative of hippocampal influences on the auditory processing. Monaural tone-burst stimuli were presented for each side, followed by analysis of M100 and a previously less characterized exogenous component (M400: 300-500ms). The frequency of acceptable M100 dipoles was significantly decreased in the HS side. Beam-forming-based source localization analysis also showed decreased activity of the auditory area, which corresponded to the inadequately estimated dipoles. M400 was found to be related to the medial temporal structure on the HS side. Volumetric analysis was also performed, focusing on the auditory-related areas (planum temporale, Heschl's gyrus, and superior temporal gyrus), as well as the hippocampus. M100 amplitudes positively correlated with hippocampal and planum temporale volumes in the HC group, whereas they negatively correlated with Heschl's gyrus volume in the mTLE group. Interestingly, significantly enhanced M400 component was observed in the HS side of the mTLE patients. In addition, the M400 component positively correlated with Heschl's gyrus volume and tended to positively correlate with disease duration. M400 was markedly diminished after hippocampal resection. Although volumetric analysis showed decreased hippocampal volume in the HS side, the planum temporale and Heschl's gyrus, the two major sources of M100, were preserved. These results suggested that HS significantly influenced AEFs. Therefore, we concluded that the hippocampus modulates auditory processing differently under normal conditions and in HS.

Using event-related potential P300 as an electrophysiological marker for differential diagnosis and to predict the progression of mild cognitive impairment: a meta-analysis

P300 event-related potential component may sensitively predict mild cognitive impairment (MCI) progression. Here, pooled effect size estimates of P300 amplitude and latency were computed at midline electrodes among controls, MCI patients, and Alzheimer's disease (AD) patients. Baseline data were compared to one-year follow-up data. MCI patients showed decreased P300 amplitude and prolonged latency compared to controls. Pooled standardized mean differences (SMDs) were -0.67 (95 % CI -1.12 to -0.23, P = 0.003) and 0.90 (95 % CI 0.66-1.14, P < 0.00001), respectively. P300 latency decreased in MCI compared to AD patients where the pooled SMD was -0.52 (95 % CI -0.85 to -0.18, P = 0.003). Amplitude and latency differed between MCI baseline and follow-up. Pooled SMDs were 0.47 (95 % CI 0.29 to -0.65, P < 0.00001) and -0.52 (95 % CI -0.71 to -0.34, P < 0.00001), respectively. Group differences in MCI P300 latency existed compared to control and AD patients. P300 latency may therefore be a sensitive indicator for early cognitive decline or disease progression in MCI patients and identifying elderly patient progression to MCI and/or AD.

Mismatch negativity (MMN) amplitude as a biomarker of sensory memory deficit in amnestic mild cognitive impairment

It has been suggested that changes in some event-related potential (ERP) parameters associated with controlled processing of stimuli could be used as biomarkers of amnestic mild cognitive impairment (aMCI). However, data regarding the suitability of ERP components associated with automatic and involuntary processing of stimuli for this purpose are not conclusive. In the present study, we studied the Mismatch Negativity (MMN) component, a correlate of the automatic detection of changes in the acoustic environment, in healthy adults and adults with aMCI (age range: 50-87 years). An auditory-visual attention-distraction task, in two evaluations separated by an interval of between 18 and 24 months, was used. In both evaluations, the MMN amplitude was significantly smaller in the aMCI adults than in the control adults. In the first evaluation, such differences were observed for the subgroup of adults between 50 and 64 years of age, but not for the subgroup of 65 years and over. In the aMCI adults, the MMN amplitude was significantly smaller in the second evaluation than in the first evaluation, but no significant changes were observed in the control adult group. The MMN amplitude was found to be a sensitive and specific biomarker of aMCI, in both the first and second evaluation.

Magnetic resonance spectroscopy in mild cognitive impairment: systematic review and meta-analysis

Research using proton magnetic resonance spectroscopy (MRS) can potentially elucidate metabolite changes representing early degeneration in Mild Cognitive Impairment (MCI), an early stage of dementia. We integrated the published literature using meta-analysis to identify patterns of metabolite changes in MCI. 29 MRS studies (with a total of 607 MCI patients and 862 healthy controls) were classified according to brain regions. Hedges' g was used as effect size in a random effects model. N-Acetyl Aspartate (NAA) measures were consistently reduced in posterior cingulate (PC), hippocampus, and the paratrigonal white matter (PWM). Creatine (Cr) concentration was reduced in the hippocampus and PWM. Choline (Cho) concentration was reduced in the hippocampus while Cho/Cr ratio was raised in the PC. Myo-inositol (mI) concentration was raised in the PC and mI/Cr ratio was raised in the hippocampus. NAA/mI ratio was reduced in the PC. NAA may be the most reliable marker of brain dysfunction in MCI though mI, Cho, and Cr may also contribute towards this.

Metabolic changes in the auditory cortex in presbycusis demonstrated by MR spectroscopy

In humans, aging is accompanied by the deterioration of the hearing function--presbycusis. The major etiology for presbycusis is the loss of hair cells in the inner ear; less well known are changes in the central auditory system. Therefore, we used 1H magnetic resonance spectroscopy at 3T tomograph to examine metabolite levels in the auditory cortex of three groups of subjects: young healthy subjects less than 30 years old and subjects older than 65 years either with mild presbycusis corresponding to their age or with expressed presbycusis. Hearing function in all subjects was examined by pure tone audiometry (125-16,000 Hz). Significant differences were found in the concentrations of glutamate and N-acetylaspartate, with lower levels in aged subjects. Lactate was particularly increased in subjects with expressed presbycusis. Significant differences were not found in other metabolites, including GABA, between young and elderly subjects. The results demonstrate that the age-related changes of the inner ear are accompanied by a decrease in the excitatory neurotransmitter glutamate as well as a lactate increase in the auditory cortex that is more expressed in elderly subjects with large hearing threshold shifts.

Citric acid reduces the decline in P300 amplitude induced by acute alcohol consumption in healthy adults

Event-related potential (ERP) is a reliable neuroelectric measure of brain activity that helps to confirm the assessment of mental status and cognitive impairment. Many studies have reported that alcoholics show a significantly lower ERP P300 amplitude than the norm. In the present study, ERP P300 waves were measured to evaluate the effect of citric acid on cognitive function during excessive alcohol consumption in healthy adults. Five volunteers were selected through clinical interview, physical examination, and psychiatric assessment for participation in this study. In a double-blind placebo-controlled before-after design, each subject was treated with 5 ml/kg body weight alcohol, 5 ml/kg body weight alcohol and 1 mg citric acid, or a placebo on three separate occasions, one week apart. ERP P300, blood biochemical indicators, blood alcohol concentrations (BACs) and acetaldehyde concentrations were assessed. Repeated measure analysis of variance (ANOVA) with a within-subjects factor was used to evaluate differences in blood biochemical indicators, BACs, blood acetaldehyde concentrations, and ERP P300 in the three sessions of assessments. Several blood biochemical indicators showed significant differences between treatments, including the levels of cholinesterase (CHE), total bile acid (TBA), triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), and glycylproline dipeptidyl aminopeptidase (GPDA). BACs after consumption of alcohol alone or citric acid with alcohol were significantly higher compared to those after placebo treatment (P<0.05). There were no significant differences in blood acetaldehyde concentrations between the treatments. The P300 amplitudes on the frontal (Fz), central (Cz), and parietal (Pz) regions of the scalp after consumption of alcohol were significantly lower than those after consumption of the placebo or citric acid with alcohol (P<0.05), while there were no significant differences between the latter two treatments. The results of this study suggest that citric acid could reduce the decline in ERP P300 amplitude and cognitive ability induced by acute alcohol consumption. It may also affect some blood biochemical indicators, but the specific mechanisms need further research.

Brain activation disturbance for target detection in patients with mild cognitive impairment: an fMRI study

Functional brain imaging in mild cognitive impairment (MCI) reveals differences in activation of task-relevant brain areas between patients and age-matched healthy controls. However, some studies reported hyperactivation and others hypoactivation in MCI compared with controls. The inconsistencies may be explained by compensatory mechanisms due to high complexity of the applied tasks. The oddball task is a simple paradigm that is known to activate a widespread network in the brain, involving attentional and monitoring mechanisms. In the present study, we examined amnestic or amnestic multidomain MCI patients (n = 12) and healthy controls (n = 13) in an auditory oddball task. Participants had to respond to infrequent targets and inhibit response to infrequent novel-nontarget stimuli. Lower stimulus related activation was found in MCI patients compared with healthy controls in parts of the middle temporal gyrus, the temporal pole, regions along the superior temporal sulcus, in the left cuneus, the left supramarginal gyrus, the anterior cingulated cortex and in the left inferior and middle frontal gyrus. Activation for oddball stimuli is assumed to reflect an automatic reflexive engagement of many brain regions in response to potentially important changes in the environment as well as cognitive control to monitor responses. The mechanisms of attention and cognitive control may be severely impaired in MCI and thus, underlie the cognitive deficits of this clinical group.