[18F]PI-2620 Binding Patterns in Patients with Suspected Alzheimer Disease and Frontotemporal Lobar Degeneration

Tau PET has enabled the visualization of paired helical filaments of 3 or 4 C-terminal repeat tau in Alzheimer disease (AD), but its ability to detect aggregated tau in frontotemporal lobar degeneration (FTLD) spectrum disorders is uncertain. We investigated 2-(2-([18F]fluoro)pyridin-4-yl)-9H-pyrrolo[2,3-b:4,5c']dipyridine ([18F]PI-2620), a newer tracer with ex vivo evidence for binding to FTLD tau, in a convenience sample of patients with suspected FTLD and AD using a static acquisition protocol and parametric SUV ratio (SUVr) images. Methods: We analyzed [18F]PI-2620 PET data from 65 patients with clinical diagnoses associated with AD or FTLD neuropathology; most (60/65) also had amyloid-β (Aβ) PET. Scans were acquired 30-60 min after injection; SUVr maps (reference, inferior cerebellar cortex) were created for the full acquisition and for 10-min truncated sliding windows (30-40, 35-45,…50-60 min). Age- and sex-adjusted z score maps were computed for each patient, relative to 23 Aβ-negative cognitively healthy controls (HC). Mean SUVr in the globus pallidus, substantia nigra, subthalamic nuclei, dentate nuclei, white matter, and temporal gray matter was extracted for the full and truncated windows. Results: Patients with suspected AD neuropathology (Aβ-positive patients with mild cognitive impairment or AD dementia) showed high-intensity temporoparietal cortex-predominant [18F]PI-2620 binding. At the group level, patients with clinical diagnoses associated with FTLD (progressive supranuclear palsy with Richardson syndrome [PSP Richardson syndrome], corticobasal syndrome, and nonfluent-variant primary progressive aphasia) exhibited higher globus pallidus SUVr than did HCs; pallidal retention was highest in the PSP Richardson syndrome group, in whom SUVr was correlated with symptom severity (ρ = 0.53, P = 0.05). At the individual level, only half of PSP Richardson syndrome, corticobasal syndrome, and nonfluent-variant primary progressive aphasia patients had a pallidal SUVr above that of HCs. Temporal SUVr discriminated AD patients from HCs with high accuracy (area under the receiver operating characteristic curve, 0.94 [95% CI, 0.83-1.00]) for all time windows, whereas discrimination between patients with PSP Richardson syndrome and HCs using pallidal SUVr was fair regardless of time window (area under the receiver operating characteristic curve, 0.77 [95% CI, 0.61-0.92] at 30-40 min vs. 0.81 [95% CI, 0.66-0.96] at 50-60 min; P = 0.67). Conclusion: [18F]PI-2620 SUVr shows an intense and consistent signal in AD but lower-intensity, heterogeneous, and rapidly decreasing binding in patients with suspected FTLD. Further work is needed to delineate the substrate of [18F]PI-2620 binding and the usefulness of [18F]PI2620 SUVr quantification outside the AD continuum.

Head-to-head comparison between plasma p-tau217 and flortaucipir-PET in amyloid-positive patients with cognitive impairment

BACKGROUND

Plasma phosphorylated tau (p-tau) has emerged as a promising biomarker for Alzheimer's disease (AD). Studies have reported strong associations between p-tau and tau-PET that are mainly driven by differences between amyloid-positive and amyloid-negative patients. However, the relationship between p-tau and tau-PET is less characterized within cognitively impaired patients with a biomarker-supported diagnosis of AD. We conducted a head-to-head comparison between plasma p-tau217 and tau-PET in patients at the clinical stage of AD and further assessed their relationships with demographic, clinical, and biomarker variables.

METHODS

We retrospectively included 87 amyloid-positive patients diagnosed with MCI or dementia due to AD who underwent structural MRI, amyloid-PET (11C-PIB), tau-PET (18F-flortaucipir, FTP), and blood draw assessments within 1 year (age = 66 ± 10, 48% female). Amyloid-PET was quantified in Centiloids (CL) while cortical tau-PET binding was measured using standardized uptake value ratios (SUVRs) referenced against inferior cerebellar cortex. Plasma p-tau217 concentrations were measured using an electrochemiluminescence-based assay on the Meso Scale Discovery platform. MRI-derived cortical volume was quantified with FreeSurfer. Mini-Mental State Examination (MMSE) scores were available at baseline (n = 85) and follow-up visits (n = 28; 1.5 ± 0.7 years).

RESULTS

Plasma p-tau217 and cortical FTP-SUVR were correlated (r = 0.61, p < .001), especially in temporo-parietal and dorsolateral frontal cortices. Both higher p-tau217 and FTP-SUVR values were associated with younger age, female sex, and lower cortical volume, but not with APOE-ε4 carriership. PIB-PET Centiloids were weakly correlated with FTP-SUVR (r = 0.26, p = 0.02), but not with p-tau217 (r = 0.10, p = 0.36). Regional PET-plasma associations varied with amyloid burden, with p-tau217 being more strongly associated with tau-PET in temporal cortex among patients with moderate amyloid-PET burden, and with tau-PET in primary cortices among patients with high amyloid-PET burden. Higher p-tau217 and FTP-SUVR values were independently associated with lower MMSE scores cross-sectionally, while only baseline FTP-SUVR predicted longitudinal MMSE decline when both biomarkers were included in the same model.

CONCLUSION

Plasma p-tau217 and tau-PET are strongly correlated in amyloid-PET-positive patients with MCI or dementia due to AD, and they exhibited comparable patterns of associations with demographic variables and with markers of downstream neurodegeneration.

Plasma inflammation for predicting phenotypic conversion and clinical progression of autosomal dominant frontotemporal lobar degeneration

BACKGROUND

Measuring systemic inflammatory markers may improve clinical prognosis and help identify targetable pathways for treatment in patients with autosomal dominant forms of frontotemporal lobar degeneration (FTLD).

METHODS

We measured plasma concentrations of IL-6, TNFα and YKL-40 in pathogenic variant carriers (MAPT, C9orf72, GRN) and non-carrier family members enrolled in the ARTFL-LEFFTDS Longitudinal Frontotemporal Lobar Degeneration consortium. We evaluated associations between baseline plasma inflammation and rate of clinical and neuroimaging changes (linear mixed effects models with standardised (z) outcomes). We compared inflammation between asymptomatic carriers who remained clinically normal ('asymptomatic non-converters') and those who became symptomatic ('asymptomatic converters') using area under the curve analyses. Discrimination accuracy was compared with that of plasma neurofilament light chain (NfL).

RESULTS

We studied 394 participants (non-carriers=143, C9orf72=117, GRN=62, MAPT=72). In MAPT, higher TNFα was associated with faster functional decline (B=0.12 (0.02, 0.22), p=0.02) and temporal lobe atrophy. In C9orf72, higher TNFα was associated with faster functional decline (B=0.09 (0.03, 0.16), p=0.006) and cognitive decline (B=-0.16 (-0.22, -0.10), p<0.001), while higher IL-6 was associated with faster functional decline (B=0.12 (0.03, 0.21), p=0.01). TNFα was higher in asymptomatic converters than non-converters (β=0.29 (0.09, 0.48), p=0.004) and improved discriminability compared with plasma NfL alone (ΔR2=0.16, p=0.007; NfL: OR=1.4 (1.03, 1.9), p=0.03; TNFα: OR=7.7 (1.7, 31.7), p=0.007).

CONCLUSIONS

Systemic proinflammatory protein measurement, particularly TNFα, may improve clinical prognosis in autosomal dominant FTLD pathogenic variant carriers who are not yet exhibiting severe impairment. Integrating TNFα with markers of neuronal dysfunction like NfL could optimise detection of impending symptom conversion in asymptomatic pathogenic variant carriers and may help personalise therapeutic approaches.

Evaluation of Plasma Phosphorylated Tau217 for Differentiation Between Alzheimer Disease and Frontotemporal Lobar Degeneration Subtypes Among Patients With Corticobasal Syndrome

Importance

Plasma phosphorylated tau217 (p-tau217), a biomarker of Alzheimer disease (AD), is of special interest in corticobasal syndrome (CBS) because autopsy studies have revealed AD is the driving neuropathology in up to 40% of cases. This differentiates CBS from other 4-repeat tauopathy (4RT)-associated syndromes, such as progressive supranuclear palsy Richardson syndrome (PSP-RS) and nonfluent primary progressive aphasia (nfvPPA), where underlying frontotemporal lobar degeneration (FTLD) is typically the primary neuropathology.

Objective

To validate plasma p-tau217 against positron emission tomography (PET) in 4RT-associated syndromes, especially CBS.

Design, Setting, and Participants

This multicohort study with 6, 12, and 24-month follow-up recruited adult participants between January 2011 and September 2020 from 8 tertiary care centers in the 4RT Neuroimaging Initiative (4RTNI). All participants with CBS (n = 113), PSP-RS (n = 121), and nfvPPA (n = 39) were included; other diagnoses were excluded due to rarity (n = 29). Individuals with PET-confirmed AD (n = 54) and PET-negative cognitively normal control individuals (n = 59) were evaluated at University of California San Francisco. Operators were blinded to the cohort.

Main Outcome and Measures

Plasma p-tau217, measured by Meso Scale Discovery electrochemiluminescence, was validated against amyloid-β (Aβ) and flortaucipir (FTP) PET. Imaging analyses used voxel-based morphometry and bayesian linear mixed-effects modeling. Clinical biomarker associations were evaluated using longitudinal mixed-effect modeling.

Results

Of 386 participants, 199 (52%) were female, and the mean (SD) age was 68 (8) years. Plasma p-tau217 was elevated in patients with CBS with positive Aβ PET results (mean [SD], 0.57 [0.43] pg/mL) or FTP PET (mean [SD], 0.75 [0.30] pg/mL) to concentrations comparable to control individuals with AD (mean [SD], 0.72 [0.37]), whereas PSP-RS and nfvPPA showed no increase relative to control. Within CBS, p-tau217 had excellent diagnostic performance with area under the receiver operating characteristic curve (AUC) for Aβ PET of 0.87 (95% CI, 0.76-0.98; P < .001) and FTP PET of 0.93 (95% CI, 0.83-1.00; P < .001). At baseline, individuals with CBS-AD (n = 12), defined by a PET-validated plasma p-tau217 cutoff 0.25 pg/mL or greater, had increased temporoparietal atrophy at baseline compared to individuals with CBS-FTLD (n = 39), whereas longitudinally, individuals with CBS-FTLD had faster brainstem atrophy rates. Individuals with CBS-FTLD also progressed more rapidly on a modified version of the PSP Rating Scale than those with CBS-AD (mean [SD], 3.5 [0.5] vs 0.8 [0.8] points/year; P = .005).

Conclusions and Relevance

In this cohort study, plasma p-tau217 had excellent diagnostic performance for identifying Aβ or FTP PET positivity within CBS with likely underlying AD pathology. Plasma P-tau217 may be a useful and inexpensive biomarker to select patients for CBS clinical trials.

Retinal imaging demonstrates reduced capillary density in clinically unimpaired APOE ε4 gene carriers

INTRODUCTION

Apolipoprotein E (APOE) ε4, the strongest non-Mendelian genetic risk factor for Alzheimer's disease (AD), has been shown to affect brain capillaries in mice, with potential implications for AD-related neurodegenerative disease. However, human brain capillaries cannot be directly visualized in vivo. We therefore used retinal imaging to test APOE ε4 effects on human central nervous system capillaries.

METHODS

We collected retinal optical coherence tomography angiography, cognitive testing, and brain imaging in research participants and built statistical models to test genotype-phenotype associations.

RESULTS

Our analyses demonstrate lower retinal capillary densities in early disease, in cognitively normal APOE ε4 gene carriers. Furthermore, through regression modeling with a measure of brain perfusion (arterial spin labeling), we provide support for the relevance of these findings to cerebral vasculature.

DISCUSSION

These results suggest that APOE ε4 affects capillary health in humans and that retinal capillary measures could serve as surrogates for brain capillaries, providing an opportunity to study microangiopathic contributions to neurodegenerative disorders directly in humans.

Late-Life Depression Is Associated With Reduced Cortical Amyloid Burden: Findings From the Alzheimer's Disease Neuroimaging Initiative Depression Project

BACKGROUND

We evaluated the role of cortical amyloid deposition as a factor contributing to memory dysfunction and increased risk of dementia associated with late-life depression (LLD).

METHODS

A total of 119 older adult participants with a current diagnosis of major depression (LLD) from the Alzheimer's Disease Neuroimaging Initiative (ADNI) Depression Project study and 119 nondepressed (ND) cognitively unimpaired participants matched on age, sex, and APOE genotype were obtained from the ADNI database.

RESULTS

Thirty-three percent of LLD participants met ADNI criteria for mild cognitive impairment. Compared with ND individuals, the LLD group exhibited less global amyloid beta (Aβ) accumulation (p = .05). The proportion of amyloid positivity in the LLD group was 19.3% compared with 31.1% for the ND participants (p = .02). Among LLD participants, global Aβ was not associated with lifetime number of depressive episodes, lifetime length of depression, length of lifetime selective serotonin reuptake inhibitor use, or lifetime length of untreated depression (p > .21 for all). Global Aβ was associated with worse memory performance (p = .05). Similar results were found in secondary analyses restricting comparisons to the cognitively unimpaired LLD participants as well as when comparing the LLD group with an ND group that included participants with mild cognitive impairment.

CONCLUSIONS

Contrary to expectation, the LLD group showed less Aβ deposition than the ND group and Aβ deposition was not associated with depression history characteristics. Aβ was associated with memory, but this relationship did not differ between LLD and ND. Our results suggest that memory deficits and accelerated cognitive decline reported in previous studies of LLD are not due to greater cortical Aβ accumulation.

The Impact of Amyloid Burden and APOE on Rates of Cognitive Impairment in Late Life Depression

BACKGROUND

Cognitive impairment (CI) is a key feature of late life depression (LLD), but the contribution of underlying neurodegenerative pathology remains unclear.

OBJECTIVE

To evaluate cognitive dysfunction in LLD relative to a sample of nondepressed (ND) older adults with matched levels of memory impairment and amyloid-β (Aβ) burden.

METHODS

Participants included 120 LLD and 240 ND older adults matched on age, education, sex, Mini-Mental State Exam, mild cognitive impairment diagnosis, and PET Aβ burden.

RESULTS

LLD showed higher rates of impairment relative to ND with 54.6% of the LLD sample demonstrating impairment in at least one cognitive domain compared to 42.9% of controls (H = 7.13, p = 0.008). LLD had poorer performance and higher rates of impairment on Rey Auditory Verbal Learning Test learning and memory compared to controls. In the overall sample, Aβ positivity was associated with worse performance on Logical Memory I (p = 0.044), Logical Memory II (p = 0.011), and Trail Making Test -B (p = 0.032), and APOEɛ4 genotype was associated with worse performance on Logical Memory I (p = 0.022); these relationships did not differ between LLD and ND.

CONCLUSION

LLD showed higher rates of CI driven by focal deficits in verbal learning and memory. Alzheimer's disease (AD) biomarkers were associated with worse performance on timed set-shifting and story learning and memory, and these relationships were not impacted by depression status. These findings suggest that AD may account for a portion of previously reported multi-domain CI in LLD and highlight the potential for AD to confound studies of cognition in LLD.

Deformation-based shape analysis of the hippocampus in the semantic variant of primary progressive aphasia and Alzheimer's disease

BACKGROUND

Increasing evidence shows that the semantic variant of primary progressive aphasia (svPPA) is characterized by hippocampal atrophy. However, less is known about disease-related morphological hippocampal changes. The goal of the present study is to conduct a detailed characterization of the impact of svPPA on global hippocampus volume and morphology compared with control subjects and patients with Alzheimer's disease (AD).

METHODS

We measured hippocampal volume and deformation-based shape differences in 22 patients with svPPA compared with 99 patients with AD and 92 controls. Multiple Automatically Generated Templates Brain Segmentation Algorithm (MAGeT-Brain) was used on MRI images obtained at the diagnostic visit.

RESULTS

Comparable left and right hippocampal atrophy were observed in svPPA and AD. Deformation-based shape analysis showed a common pattern of morphological deformation in svPPA and AD compared with controls. More specifically, both svPPA and AD showed inward deformations in the dorsal surface of the hippocampus, from head to tail on the left side, and more limited to the anterior portion of the body in the right hemisphere. These results also pointed out that both diseases are characterized by a lateral displacement of the central part (body) of the hippocampus.

DISCUSSION

Our study provides critical new evidence of hippocampal morphological changes in svPPA, similar to those found in AD. These findings highlight the importance of considering morphological hippocampal changes as part of the anatomical profile of patients with svPPA.

Neuropathological correlates of structural and functional imaging biomarkers in 4-repeat tauopathies

Neurodegenerative dementia syndromes are characterized by spreading of pathological protein deposition along syndrome-specific neural networks. Structural and functional MRI measures can assess the integrity of these networks and have been proposed as biomarkers of disease progression for clinical trials. The relationship between in vivo imaging measures and pathological features, at the single subject level, remains largely unknown. Patient-specific maps of atrophy and seed-based intrinsic connectivity disruption, as compared to normal controls, were obtained for 27 patients subsequently diagnosed with progressive supranuclear palsy (n = 16, seven males, age at death 68.9 ± 6.0 years, imaging-to-pathology interval = 670.2 ± 425.1 days) or corticobasal degeneration (n = 11, two males, age at death 66.7 ± 5.4 years, imaging-to-pathology interval = 696.2 ± 482.2 days). A linear mixed effect model with crossed random effects was used to test regional and single-subject level associations between post-mortem regional measures of neurodegeneration and tau inclusion burden, on the one hand, and regional volume loss and seed-based intrinsic connectivity reduction, on the other. A significant association was found between tau inclusion burden and in vivo volume loss, at the regional level and independent of neurodegeneration severity, in both progressive supranuclear palsy [n = 340 regions; beta 0.036; 95% confidence interval (CI): 0.001, 0.072; P = 0.046] and corticobasal degeneration (n = 215 regions; beta 0.044; 95% CI: 0.009, 0.079; P = 0.013). We also found a significant association between post-mortem neurodegeneration and in vivo volume loss in both progressive supranuclear palsy (n = 340 regions; beta 0.155; 95% CI: 0.061, 0.248; P = 0.001) and corticobasal degeneration (n = 215 regions; beta 0.277; 95% CI: 0.104, 0.450; P = 0.002). We found a significant association between regional neurodegeneration and intrinsic connectivity dysfunction in corticobasal degeneration (n = 215 regions; beta 0.074; 95% CI: 0.005, 0.143; P = 0.035), but no other associations between post-mortem measures of tauopathy and intrinsic connectivity dysfunction reached statistical significance. Our data suggest that in vivo structural imaging measures reflect independent contributions from neurodegeneration and tau burden in progressive supranuclear palsy and corticobasal degeneration. Seed-based measures of intrinsic connectivity dysfunction showed less reliable predictive value when used as in vivo biomarkers of tauopathy. The findings provide important guidance for the use of imaging biomarkers as indirect in vivo assays of microscopic pathology.

Comparison of sporadic and familial behavioral variant frontotemporal dementia (FTD) in a North American cohort

INTRODUCTION

Behavioral variant frontotemporal dementia (bvFTD) may present sporadically or due to an autosomal dominant mutation. Characterization of both forms will improve understanding of the generalizability of assessments and treatments.

METHODS

A total of 135 sporadic (s-bvFTD; mean age 63.3 years; 34% female) and 99 familial (f-bvFTD; mean age 59.9; 48% female) bvFTD participants were identified. f-bvFTD cases included 43 with known or presumed chromosome 9 open reading frame 72 (C9orf72) gene expansions, 28 with known or presumed microtubule-associated protein tau (MAPT) mutations, 14 with known progranulin (GRN) mutations, and 14 with a strong family history of FTD but no identified mutation.

RESULTS

Participants with f-bvFTD were younger and had earlier age at onset. s-bvFTD had higher total Neuropsychiatric Inventory Questionnaire (NPI-Q) scores due to more frequent endorsement of depression and irritability.

DISCUSSION

f-bvFTD and s-bvFTD cases are clinically similar, suggesting the generalizability of novel biomarkers, therapies, and clinical tools developed in either form to the other.

Dopamine receptor D4 (DRD4) polymorphisms with reduced functional potency intensify atrophy in syndrome-specific sites of frontotemporal dementia

OBJECTIVE

We aimed to understand the impact of dopamine receptor D4 (DRD4) polymorphisms on neurodegeneration in patients with dementia. We hypothesized that DRD4dampened-variants with reduced functional potency would be associated with greater atrophy in regions with higher receptor density. Given that DRD4 is concentrated in anterior regions of the limbic and cortical forebrain we anticipated genotype effects in patients with a more rostral pattern of neurodegeneration.

METHODS

337 subjects, including healthy controls, patients with Alzheimer's disease (AD) and frontotemporal dementia (FTD) underwent genotyping, structural MRI, and cognitive/behavioral testing. We conducted whole-brain voxel-based morphometry to examine the relationship between DRD4 genotypes and brain atrophy patterns within and across groups. General linear modeling was used to evaluate relationships between genotype and cognitive/behavioral measures.

RESULTS

DRD4 dampened-variants predicted gray matter atrophy in disease-specific regions of FTD in anterior cingulate, ventromedial prefrontal, orbitofrontal and insular cortices on the right greater than the left. Genotype predicted greater apathy and repetitive motor disturbance in patients with FTD. These results covaried with frontoinsular cortical atrophy. Peak atrophy patterned along regions of neuroanatomic vulnerability in FTD-spectrum disorders. In AD subjects and controls, genotype did not impact gray matter intensity.

CONCLUSIONS

We conclude that DRD4 polymorphisms with reduced functional potency exacerbate neuronal injury in sites of higher receptor density, which intersect with syndrome-specific regions undergoing neurodegeneration in FTD.

Application of quantitative DTI metrics in sporadic CJD

Diffusion Weighted Imaging is extremely important for the diagnosis of probable sporadic Jakob-Creutzfeldt disease, the most common human prion disease. Although visual assessment of DWI MRI is critical diagnostically, a more objective, quantifiable approach might more precisely identify the precise pattern of brain involvement. Furthermore, a quantitative, systematic tracking of MRI changes occurring over time might provide insights regarding the underlying histopathological mechanisms of human prion disease and provide information useful for clinical trials. The purposes of this study were: 1) to describe quantitatively the average cross-sectional pattern of reduced mean diffusivity, fractional anisotropy, atrophy and T1 relaxation in the gray matter (GM) in sporadic Jakob-Creutzfeldt disease, 2) to study changes in mean diffusivity and atrophy over time and 3) to explore their relationship with clinical scales. Twenty-six sporadic Jakob-Creutzfeldt disease and nine control subjects had MRIs on the same scanner; seven sCJD subjects had a second scan after approximately two months. Cortical and subcortical gray matter regions were parcellated with Freesurfer. Average cortical thickness (or subcortical volume), T1-relaxiation and mean diffusivity from co-registered diffusion maps were calculated in each region for each subject. Quantitatively on cross-sectional analysis, certain brain regions were preferentially affected by reduced mean diffusivity (parietal, temporal lobes, posterior cingulate, thalamus and deep nuclei), but with relative sparing of the frontal and occipital lobes. Serial imaging, surprisingly showed that mean diffusivity did not have a linear or unidirectional reduction over time, but tended to decrease initially and then reverse and increase towards normalization. Furthermore, there was a strong correlation between worsening of patient clinical function (based on modified Barthel score) and increasing mean diffusivity.

Trajectories of behavioral disturbance in dementia

Predicting the progression of dementia is a challenge for clinicians yet this information is highly valued by patients' families. An informally observed 4-stage model of dementia can be helpful in educating caregivers and preparing them for what lies ahead. In the behavioral variant of frontotemporal dementia (bvFTD), this model describes the evolution of behavioral disturbances and is characterized by an inflection point between stage 2 (progressively severe behavioral aberration) and stage 3 (increasing apathy and remission of behavior problems). In this study, we sought evidence for this model using a database of serial Neuropsychiatric Inventory (NPI) scores for 45 patients with FTD and 47 patients with Alzheimer's disease (AD). We transformed the NPI scores into a single variable for each participant that represented the yearly rate of change in total NPI score and used this as the dependent variable in a multivariate linear regression. Age at onset of dementia, NPI score at initial visit, and duration of illness at first NPI all contributed significantly to the regression model in the bvFTD group. Participants with an initial NPI acquired before 6 years of disease duration tended to have a more positive rate of change in NPI total score (representing worsening behavioral disturbances) than those with an initial NPI performed after 6 years. None of the aforementioned variables were significantly associated with yearly change in NPI total score in the AD group. These results support a crescendo-decrescendo trajectory of behavioral symptoms in bvFTD but do not suggest that there is a similar pattern in AD, and further longitudinal data collection is necessary.

COMT Val158Met genotype influences neurodegeneration within dopamine-innervated brain structures

OBJECTIVE

We sought to determine whether the Val(158)Met polymorphism in the catechol-O-methyltransferase (COMT) gene influences neurodegeneration within dopamine-innervated brain regions.

METHODS

A total of 252 subjects, including healthy controls and patients with Alzheimer disease, behavioral variant frontotemporal dementia, and semantic dementia, underwent COMT genotyping and structural MRI.

RESULTS

Whole-brain voxel-wise regression analyses revealed that COMT Val(158)Met Val allele dosage, known to produce a dose-dependent decrease in synaptic dopamine (DA) availability, correlated with decreased gray matter in the region of the ventral tegmental area (VTA), ventromedial prefrontal cortex, bilateral dorsal midinsula, left dorsolateral prefrontal cortex, and right ventral striatum. Unexpectedly, patients carrying a Met allele showed greater VTA volumes than age-matched controls. Gray matter intensities within COMT-related brain regions correlated with cognitive and behavioral deficits.

CONCLUSIONS

The results are consistent with the hypothesis that increased synaptic DA catabolism promotes neurodegeneration within DA-innervated brain regions.

Amyloid vs FDG-PET in the differential diagnosis of AD and FTLD

OBJECTIVE

To compare the diagnostic performance of PET with the amyloid ligand Pittsburgh compound B (PiB-PET) to fluorodeoxyglucose (FDG-PET) in discriminating between Alzheimer disease (AD) and frontotemporal lobar degeneration (FTLD).

METHODS

Patients meeting clinical criteria for AD (n = 62) and FTLD (n = 45) underwent PiB and FDG-PET. PiB scans were classified as positive or negative by 2 visual raters blinded to clinical diagnosis, and using a quantitative threshold derived from controls (n = 25). FDG scans were visually rated as consistent with AD or FTLD, and quantitatively classified based on the region of lowest metabolism relative to controls.

RESULTS

PiB visual reads had a higher sensitivity for AD (89.5% average between raters) than FDG visual reads (77.5%) with similar specificity (PiB 83%, FDG 84%). When scans were classified quantitatively, PiB had higher sensitivity (89% vs 73%) while FDG had higher specificity (83% vs 98%). On receiver operating characteristic analysis, areas under the curve for PiB (0.888) and FDG (0.910) were similar. Interrater agreement was higher for PiB (κ = 0.96) than FDG (κ = 0.72), as was agreement between visual and quantitative classification (PiB κ = 0.88-0.92; FDG κ = 0.64-0.68). In patients with known histopathology, overall classification accuracy (2 visual and 1 quantitative classification per patient) was 97% for PiB (n = 12 patients) and 87% for FDG (n = 10).

CONCLUSIONS

PiB and FDG showed similar accuracy in discriminating AD and FTLD. PiB was more sensitive when interpreted qualitatively or quantitatively. FDG was more specific, but only when scans were classified quantitatively. PiB slightly outperformed FDG in patients with known histopathology.

Distinct clinical and metabolic deficits in PCA and AD are not related to amyloid distribution

BACKGROUND/OBJECTIVE

Patients with posterior cortical atrophy (PCA) often have Alzheimer disease (AD) at autopsy, yet are cognitively and anatomically distinct from patients with clinical AD. We sought to compare the distribution of β-amyloid and glucose metabolism in PCA and AD in vivo using Pittsburgh compound B (PiB) and FDG-PET.

METHODS

Patients with PCA (n = 12, age 57.5 ± 7.4, Mini-Mental State Examination [MMSE] 22.2 ± 5.1), AD (n = 14, age 58.8 ± 9.6, MMSE 23.8 ± 6.7), and cognitively normal controls (NC, n = 30, age 73.6 ± 6.4) underwent PiB and FDG-PET. Group differences in PiB distribution volume ratios (DVR, cerebellar reference) and FDG uptake (pons-averaged) were assessed on a voxel-wise basis and by comparing binding in regions of interest (ROIs).

RESULTS

Compared to NC, both patients with AD and patients with PCA showed diffuse PiB uptake throughout frontal, temporoparietal, and occipital cortex (p < 0.0001). There were no regional differences in PiB binding between PCA and AD even after correcting for atrophy. FDG patterns in PCA and AD were distinct: while both groups showed hypometabolism compared to NC in temporoparietal cortex and precuneus/posterior cingulate, patients with PCA further showed hypometabolism in inferior occipitotemporal cortex compared to both NC and patients with AD (p < 0.05). Patients with AD did not show areas of relative hypometabolism compared to PCA.

CONCLUSIONS

Fibrillar amyloid deposition in PCA is diffuse and similar to AD, while glucose hypometabolism extends more posteriorly into occipital cortex. Further studies are needed to determine the mechanisms of selective network degeneration in focal variants of AD.

Fear conditioning in frontotemporal lobar degeneration and Alzheimer's disease

Emotional blunting and abnormal processing of rewards and punishments represent early features of frontotemporal lobar degeneration (FTLD). Better understanding of the physiological underpinnings of these emotional changes can be facilitated by the use of classical psychology approaches. Fear conditioning (FC) is an extensively used paradigm for studying emotional processing that has rarely been applied to the study of dementia. We studied FC in controls (n = 25), Alzheimer's disease (n = 25) and FTLD (n = 25). A neutral stimulus (coloured square on a computer screen) was repeatedly paired with a 1 s burst of 100 db white noise. Change in skin conductance response to the neutral stimulus was used to measure conditioning. Physiological-anatomical correlations were examined using voxel-based morphometry (VBM). Both patient groups showed impaired acquisition of conditioned responses. However, the basis for this deficit appeared to differ between groups. In Alzheimer's disease, impaired FC occurred despite normal electrodermal responses to the aversive stimulus. In contrast, FTLD patients showed reduced skin conductance responses to the aversive stimulus, which contributed significantly to their FC deficit. VBM identified correlations with physiological reactivity in the amygdala, anterior cingulate cortex, orbitofrontal cortex and insula. These data indicate that Alzheimer's disease and FTLD both show abnormalities in emotional learning, but they suggest that in FTLD this is associated with a deficit in basic electrodermal response to aversive stimuli, consistent with the emotional blunting described with this disorder. Deficits in responses to aversive stimuli could contribute to both the behavioural and cognitive features of FTLD and Alzheimer's disease. Further study of FC in humans and animal models of dementia could provide a valuable window into these symptoms.

Distinct MRI atrophy patterns in autopsy-proven Alzheimer's disease and frontotemporal lobar degeneration

To better define the anatomic distinctions between Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD), we retrospectively applied voxel-based morphometry to the earliest magnetic resonance imaging scans of autopsy-proven AD (N = 11), FTLD (N = 18), and controls (N = 40). Compared with controls, AD patients showed gray matter reductions in posterior temporoparietal and occipital cortex; FTLD patients showed atrophy in medial prefrontal and medial temporal cortex, insula, hippocampus, and amygdala; and patients with both disorders showed atrophy in dorsolateral and orbital prefrontal cortex and lateral temporal cortex (P(FWE-corr) < .05). Compared with FTLD, AD patients had decreased gray matter in posterior parietal and occipital cortex, whereas FTLD patients had selective atrophy in anterior cingulate, frontal insula, subcallosal gyrus, and striatum (P < .001, uncorrected). These findings suggest that AD and FTLD are anatomically distinct, with degeneration of a posterior parietal network in AD and degeneration of a paralimbic fronto-insular-striatal network in FTLD.

Patterns of MRI atrophy in tau positive and ubiquitin positive frontotemporal lobar degeneration

We applied optimised voxel based morphometry (VBM) to brain MRIs from autopsy proven cases of tau positive frontotemporal lobar degeneration (FTLD-T, n = 6), ubiquitin and TDP-43 positive/tau negative FTLD (FTLD-U, n = 8) and cognitively normal controls (n = 61). The analysis revealed that FTLD-T and FTLD-U both show atrophy in the frontal cortex and striatum, but striatal atrophy is more severe in FTLD-T. Manual region of interest tracing of caudate and putamen volumes confirmed the VBM findings. These anatomical differences may help distinguish between FTLD spectrum pathological subtypes in vivo.

Emotional reactivity and emotion recognition in frontotemporal lobar degeneration

BACKGROUND

Frontotemporal lobar degeneration (FTLD) is associated with a profound decline in social and emotional behavior; however, current understanding regarding the specific aspects of emotional functioning that are preserved and disrupted is limited.

OBJECTIVE

To assess preservation of function and deficits in two aspects of emotional processing (emotional reactivity and emotion recognition) in FTLD.

METHODS

Twenty-eight FTLD patients were compared with 16 controls in emotional reactivity (self-reported emotional experience, emotional facial behavior, and autonomic nervous system response to film stimuli) and emotion recognition (ability to identify a target emotion of fear, happy, or sad experienced by film characters). Additionally, the neural correlates of emotional reactivity and emotion recognition were investigated.

RESULTS

FTLD patients were comparable to controls in 1) emotional reactivity to the fear, happy, and sad film clips and 2) emotion recognition for the happy film clip. However, FTLD patients were significantly impaired compared with controls in emotion recognition for the fear and sad film clips. Volumetric analyses revealed that deficits in emotion recognition were associated with decreased lobar volumes in the frontal and temporal lobes.

CONCLUSIONS

The socioemotional decline typically seen in frontotemporal lobar degeneration patients may result more from an inability to process certain emotions in other people than from deficits in emotional reactivity.

11C-PIB PET imaging in Alzheimer disease and frontotemporal lobar degeneration

BACKGROUND

The PET tracer (11)C-labeled Pittsburgh Compound-B ((11)C-PIB) specifically binds fibrillar amyloid-beta (Abeta) plaques and can be detected in Alzheimer disease (AD). We hypothesized that PET imaging with (11)C-PIB would discriminate AD from frontotemporal lobar degeneration (FTLD), a non-Abeta dementia.

METHODS

Patients meeting research criteria for AD (n = 7) or FTLD (n = 12) and cognitively normal controls (n = 8) underwent PET imaging with (11)C-PIB (patients and controls) and (18)F-fluorodeoxyglucose ((18)F-FDG) (patients only). (11)C-PIB whole brain and region of interest (ROI) distribution volume ratios (DVR) were calculated using Logan graphical analysis with cerebellum as a reference region. DVR images were visually rated by a blinded investigator as positive or negative for cortical (11)C-PIB, and summed (18)F-FDG images were rated as consistent with AD or FTLD.

RESULTS

All patients with AD (7/7) had positive (11)C-PIB scans by visual inspection, while 8/12 patients with FTLD and 7/8 controls had negative scans. Of the four PIB-positive patients with FTLD, two had (18)F-FDG scans that suggested AD, and two had (18)F-FDG scans suggestive of FTLD. Mean DVRs were higher in AD than in FTLD in whole brain, lateral frontal, precuneus, and lateral temporal cortex (p < 0.05), while DVRs in FTLD did not significantly differ from controls.

CONCLUSIONS

PET imaging with (11)C-labeled Pittsburgh Compound-B ((11)C-PIB) helps discriminate Alzheimer disease (AD) from frontotemporal lobar degeneration (FTLD). Pathologic correlation is needed to determine whether patients with PIB-positive FTLD represent false positives, comorbid FTLD/AD pathology, or AD pathology mimicking an FTLD clinical syndrome.

Behavioral features in semantic dementia vs other forms of progressive aphasias

OBJECTIVE

To compare the behavioral profiles in different variants of primary progressive aphasia (PPA).

METHODS

We classified 67 patients with PPA into three clinical variants: semantic dementia (SEMD), progressive nonfluent aphasia (PNFA), and logopenic progressive aphasia (LPA), and we compared the severity of behavioral dysfunction, as measured by the Neuropsychiatric Inventory, in these groups and patients with frontotemporal dementia (FTD) and Alzheimer disease (AD).

RESULTS

SEMD was associated with significantly more socioemotional behavioral dysfunction than the other two variants of PPA and than AD, specifically more disinhibition, aberrant motor behavior, and eating disorders-behaviors that are typical of FTD. In contrast, PNFA and LPA did not differ from each other or from AD in the type or severity of behavioral dysfunction. Behavioral abnormalities increased in severity with disease duration in SEMD, but this association was not detected in PNFA or LPA.

CONCLUSIONS

Semantic dementia is associated with significantly more behavioral dysfunction than other variants of primary progressive aphasia, specifically behavioral features typical of frontotemporal dementia.

The anatomy of category-specific object naming in neurodegenerative diseases

Neuropsychological studies suggest that knowledge about living and nonliving objects is processed in separate brain regions. However, lesion and functional neuroimaging studies have implicated different areas. To address this issue, we used voxel-based morphometry to correlate accuracy in naming line drawings of living and nonliving objects with gray matter volumes in 152 patients with various neurodegenerative diseases. The results showed a significant positive correlation between gray matter volumes in bilateral temporal cortices and total naming accuracy regardless of category. Naming scores for living stimuli correlated with gray matter volume in the medial portion of the right anterior temporal pole, whereas naming accuracy for familiarity-matched nonliving items correlated with the volume of the left posterior middle temporal gyrus. A previous behavioral study showed that the living stimuli used here also had in common the characteristic that they were defined by shared sensory semantic features, whereas items in the nonliving group were defined by their action-related semantic features. We propose that the anatomical segregation of living and nonliving categories is the result of their defining semantic features and the distinct neural subsystems used to process them.

Hypoperfusion in frontotemporal dementia and Alzheimer disease by arterial spin labeling MRI

OBJECTIVES

To test if arterial spin labeling (ASL) MRI could detect a pattern of hypoperfusion in frontotemporal dementia (FTD) vs cognitively normal (CN) control subjects; to determine the regional difference of perfusion between FTD and Alzheimer disease (AD); and to determine whether hypoperfusion in FTD correlates with cognitive impairment.

METHODS

We included 21 patients with FTD, 24 patients with AD, and 25 CN subjects in this cross-sectional MRI study. All subjects had MRI scans including T1-weighted structural images and ASL-MR images.

RESULTS

ASL-MRI detected a pattern of hypoperfusion in right frontal regions in patients with FTD vs CN subjects, similar to PET and SPECT. FTD had higher perfusion than AD in the parietal regions and posterior cingulate. Frontal hypoperfusion in FTD correlated with deficits in judgment and problem solving. Adding frontal perfusion to gray matter (GM) atrophy significantly improved the classification of FTD from normal aging to 74%, and adding parietal perfusion to GM atrophy significantly improved the classification of FTD from AD to 75%. Combining frontal and parietal lobe perfusion further improved the classification of FTD from AD to 87%.

CONCLUSION

Frontotemporal dementia and Alzheimer disease display different spatial distributions of hypoperfusion on arterial spin labeling MRI. With further development and evaluation, arterial spin labeling MRI could contribute to the differential diagnosis between frontotemporal dementia and Alzheimer disease.

The natural history of temporal variant frontotemporal dementia

BACKGROUND

The temporal variant of frontotemporal dementia (tvFTD) features asymmetric anterior temporal/amygdala degeneration as well as ventromedial frontal, insular, and inferoposterior temporal involvement. Left temporal atrophy has been linked to loss of semantic knowledge, whereas behavioral symptoms dominate the right temporal variant.

OBJECTIVE

To investigate the first symptoms and the timing of subsequent symptoms in patients with left versus right tvFTD.

METHODS

Twenty-six patients with tvFTD were identified. Six had right > left temporal atrophy (right temporal lobe variant [RTLV]) and were matched with six having comparable left > right temporal atrophy (left temporal lobe variant [LTLV]). Clinical records were reviewed to generate individualized symptom chronologies.

RESULTS

In all patients, first symptoms involved semantics (4/6 LTLV, 1/6 RTLV), behavior (4/6 RTLV, 1/6 LTLV), or both (1 LTLV, 1 RTLV). Semantic loss began with anomia, word-finding difficulties, and repetitive speech, whereas the early behavioral syndrome was characterized by emotional distance, irritability, and disruption of physiologic drives (sleep, appetite, libido). After an average of 3 years, patients developed whichever of the two initial syndromes--semantic or behavioral--that they lacked at onset. A third stage, 5 to 7 years from onset, saw the emergence of disinhibition, compulsions, impaired face recognition, altered food preference, and weight gain. Compulsions in LTLV were directed toward visual, nonverbal stimuli, whereas patients with RTLV were drawn to games with words and symbols.

CONCLUSIONS

The temporal variant of frontotemporal dementia follows a characteristic cognitive and behavioral progression that suggests early spread from one anterior temporal lobe to the other. Later symptoms implicate ventromedial frontal, insular, and inferoposterior temporal regions, but their precise anatomic correlates await confirmation.

Behavioral disorders in the frontal and temporal variants of frontotemporal dementia

OBJECTIVE

To compare the behavioral features and to investigate the neuroanatomic correlates of behavioral dysfunction in anatomically defined temporal and frontal variants of frontotemporal dementia (tvFTD and fvFTD).

METHODS

Volumetric measurements of the frontal, anterior temporal, ventromedial frontal cortical (VMFC), and amygdala regions were made in 51 patients with FTD and 20 normal control subjects, as well as 22 patients with Alzheimer disease (AD) who were used as dementia controls. FTD patients were classified as fvFTD or tvFTD based on the relative degree of frontal and anterior temporal volume loss compared with controls. Behavioral symptoms, cerebral volumes, and the relationship between them were examined across groups.

RESULTS

Both variants of FTD showed significant increases in rates of elation, disinhibition, and aberrant motor behavior compared with AD. The fvFTD group also showed more anxiety, apathy, and eating disorders, and tvFTD showed a higher prevalence of sleep disturbances than AD. The only behaviors that differed significantly between fvFTD and tvFTD were apathy, greater in fvFTD, and sleep disorders, more frequent in tvFTD. FvFTD was associated with greater frontal atrophy and tvFTD was associated with more temporal and amygdala atrophy compared with AD, but both groups showed significant atrophy in the VMFC compared with AD, which was not associated with VMFC atrophy. In FTD, the presence of many of the behavioral disorders was associated with decreased volume in right-hemispheric regions.

CONCLUSION

FvFTD and tvFTD show many similarities in behavior, which appear to be associated with damage to right frontal and temporal structures.

Deformation tensor morphometry of semantic dementia with quantitative validation

High-resolution structural MRI scans of 20 subjects diagnosed with semantic dementia were compared against scans of 20 cognitively normal control subjects using whole brain deformation tensor morphometry to study spatially consistent differences in local anatomical size. A fine lattice free-form volume registration algorithm was used to estimate a continuous mapping from a reference MRI to each individual subject MRI. The Jacobian of these transformations at each voxel were used to quantitatively map relative anatomical size in each individual brain. Intensity consistent filtering was applied to the determinant of these Jacobians. A careful validation using manually traced gyral anatomy was carried out and used to select an optimal deformation tensor filter scale at which to examine the anatomical size maps. General linear modeling at each voxel was used to decompose the influence of age and head size from the primary diagnosis. Maps of the T statistic of the diagnosis across the 40 subjects highlighted significant (P < 0.01 Bonferroni corrected) focal tissue contraction effects related to dementia diagnosis in the left temporal pole extending into the hippocampus, occipitotemporal gyrus and parahippocampal gyrus. Some evidence of greater focal contraction in gray over white matter was also apparent. Contraction effects were also seen, but with reduced significance in the right temporal anatomy, focused toward the temporal pole and hippocampal regions. Additional lower significance findings (P < 0.05 permutation corrected) were detected in the left superior frontal gyrus, left orbital gyrus and left parietal lobe.

Focal right inferotemporal atrophy in AD with disproportionate visual constructive impairment

OBJECTIVE

To explore the structural neuroimaging correlates of visual constructive impairment in patients with mild to moderate Alzheimer disease (AD).

BACKGROUND

There is considerable heterogeneity in the non-memory cognitive deficits associated with AD. Structural neuroimaging with MRI is an important diagnostic tool that is gaining acceptance as a surrogate measure of brain pathology in AD treatment trials. Most MRI measurements have focused on medial temporal lobe or global cortical atrophy, which may not reflect some important clinical features of AD.

METHODS

Thirty-two patients with probable AD were stratified into two groups based on their relative performance on a visual constructive task, the copy of a modified Rey-Osterrieth figure (Rey). The two groups did not differ in basic demographic features or in neuropsychological performance, other than on the visual constructive task. MRI measurements of hippocampal volume, cortical gray matter volume, and focal cortical gray matter loss were performed in the patients and a group of 71 age-matched, normal controls.

RESULTS

Both groups showed significant, bilateral hippocampal as well as cortical gray matter volume loss relative to controls. The more spatially impaired AD group (SAD) had more right than left cortical gray matter loss, whereas the opposite was true in the less spatially impaired group (NSAD). The SAD group had significantly less gray matter in the right inferior temporal gyrus relative to the NSAD group. Atrophy of this region was correlated with performance on the Rey task in all patients with AD.

CONCLUSIONS

Right inferotemporal atrophy may serve as a neuroimaging marker of visual constructive impairment in mild to moderate AD. Heterogeneous cortical atrophy is a common feature of AD.

Patterns of brain atrophy in frontotemporal dementia and semantic dementia

OBJECTIVE

To identify and compare the patterns of cerebral atrophy associated with two clinical variants of frontotemporal lobar degeneration (FTLD): frontotemporal dementia (FTD) and semantic dementia (SemD).

METHODS

Twenty patients with FTLD were classified as having FTD (N = 8) or SemD (N = 12) based on current clinical criteria. Both groups showed a similar spectrum of behavioral abnormalities, as indicated by the neuropsychiatric inventory. T1-weighted MRI was obtained for each patient and 20 control subjects. The regions of focal gray matter tissue loss associated with both FTD and SemD, as well as those differing between the two groups were examined using voxel-based morphometry.

RESULTS

Regions of significant atrophy seen in both groups were located in the ventromedial frontal cortex, the posterior orbital frontal regions bilaterally, the insula bilaterally, and the left anterior cingulate cortex. The FTD, but not the SemD, group showed atrophy in the right dorsolateral frontal cortex and the left premotor cortex. The SemD, but not the FTD, group showed tissue loss in the anterior temporal cortex and the amygdala/anterior hippocampal region bilaterally.

CONCLUSIONS

Although FTD and SemD are associated with different overall patterns of brain atrophy, regions of gray matter tissue loss in the orbital frontal, insular, and anterior cingulate regions are present in both groups. The authors suggest that pathology in the areas of atrophy associated with both FTD and SemD may underlie some the behavioral symptoms seen in the two disorders.

Neuroanatomy of the self: evidence from patients with frontotemporal dementia

OBJECTIVE

To evaluate the frequency and types of change in "self" seen in frontotemporal dementia (FTD) and to determine the relative involvement of the nondominant and dominant frontal and temporal brain regions in FTD patients with or without changes in a sense of self using neuropsychology tests and neuroimaging.

BACKGROUND

The self has been defined as "the total, essential, or particular being of a person" involving "the essential qualities distinguishing one person from another." Some suggest that the frontal lobes play a dominant role in maintaining the self. FTD affects anterior frontal and temporal areas and can be associated with a loss of self.

METHODS

Seventy-two consecutive FTD patients were evaluated with neuropsychiatric, neuropsychologic, and behavioral measures. Patients were imaged with MRI and SPECT. Charts were reviewed by a social psychologist to determine patients who exhibited a dramatic change in their self as defined by changes in political, social, or religious values. The brain areas with the most severe atrophy or hypoperfusion on neuroimaging were noted.

RESULTS

Seven of 72 patients exhibited a dramatic change in self. In six of the seven, the selective dysfunction involved the nondominant frontal region. In contrast, only one of the other 65 patients without selective nondominant frontal dysfunction showed a change in self.

CONCLUSIONS

FTD patients with asymmetric loss of function in the nondominant frontal lobe often exhibit a diminished maintenance of previously learned self-concepts despite intact memory and language. Normal nondominant frontal function is important for the maintenance of the self.

An event-related fMRI study of overt and covert word stem completion

In fMRI studies of language processing, it would be extremely useful to obtain high-quality images during tasks requiring spoken output. Recent studies have suggested that this may be possible, particularly if event-related fMRI methods are used. This study assesses the feasibility of acquiring interpretable images during speech by applying event-related methods to visual word stem completion, a task that has been studied extensively. On each trial, a different three-letter word stem (e.g., COU) was presented visually and subjects were required to generate a word beginning with that stem (e.g., COUSIN). In covert runs, subjects were instructed to say the word once to themselves, without moving their lips. In overt runs, subjects were instructed to say the word once aloud. Ten subjects were scanned during six overt runs and six covert runs at three presentation rates. Data were analyzed using an implementation of the general linear model making no assumptions about response shape. Images were relatively free of artifacts, and regions demonstrating task-related activation were similar to those reported in previous imaging studies. Regions active during overt task performance were similar to those active during covert task performance, with the addition of several regions commonly associated with motor aspects of speech production. Consistent with other studies, magnitude of activation was greater in the overt condition than in the covert condition, and there was a modest decrease in magnitude at the fastest presentation rate. Together, these results help to validate the use of event-related fMRI during tasks that require spoken output. Press

Neural correlates of recovery from aphasia after damage to left inferior frontal cortex

OBJECTIVE

To determine neural correlates of recovery from aphasia after left frontal injury.

METHODS

The authors studied the verbal performance of patients with infarcts centered in the left inferior frontal gyrus (IFG), using a battery of attention-demanding lexical tasks that normally activate the left IFG and a simpler reading task that does not normally recruit the left IFG. The authors used positron emission tomography (PET) and functional MRI (fMRI) to record neural activity in the same group of patients during word-stem completion, one of the attention-demanding lexical tasks. To identify potential neural correlates of compensation/recovery, they analyzed the resulting data for the group as a whole (PET, fMRI) and also for each participant (fMRI).

RESULTS

Patients with damage to the left IFG were impaired on all attention-demanding lexical tasks, but they completed the word-reading tasks normally. The imaging studies demonstrated a stronger-than-normal response in the right IFG, a region homologous to the damaged left IFG. The level of activation in the right IFG did not correlate with verbal performance, however. In addition, a perilesional response within the damaged left IFG was localized in the two patients who gave the best performance in the word-stem completion task and showed the most complete recovery from aphasia.

CONCLUSIONS

Right-IFG activity may represent either the recruitment of a preexisting neural pathway through alternative behavioral strategies or an anomalous response caused by removal of the left IFG. Perilesional activity in the left IFG may represent sparing or restoration of normal function in peri-infarctual tissue that was inactive early on after injury. This activity may be of greater functional significance than right IFG activity because it was associated with more normal verbal performance.

Frontotemporal dementia

Frontotemporal dementia (FTD) is a unique neurodegenerative disease that can be differentiated from Alzheimer's disease and other diseases that result in cognitive complaints. The primary anatomic focus of degeneration determines the clinical presentation, which can vary from aphasia to behavioral symptoms. Expanding knowledge about the genetics and biochemistry of FTD may lead to specific treatments.

Comparison of brain activation during word retrieval done silently and aloud using fMRI

Using functional MRI we compared the patterns of activation in an effortful word retrieval task (stem completion) performed both silently and aloud. The silent and overt conditions showed expected differences in activation magnitude in regions such as primary motor cortex. Some regions, such as frontal operculum and dorsolateral frontal cortex, showed similar activation magnitude across conditions. Thalamus was more active on the left in both conditions and showed a symmetric drop in activity in the silent compared with the overt condition. Putamen was also more active in the overt condition and showed a larger decrease in activity on the right than on the left in the silent compared with the overt condition. Thus it appears that silent and overt performance of this task engage the thalamus and putamen in different ways.

Mental decline in the elderly: pharmacotherapy (ergot alkaloids versus papaverine)

This is the first double-blind study in outpatients to evaluate the effectiveness of dihydrogenated ergot alkaloids (DEA) (Hydergine) versus papaverine in the treatment of selected symptoms associated with mental aging. In addition, this is the first study comparing these two pharmacologic agents in relatively young geriatric patients, with a mean age in the mid-sixties. After twelve weeks of treatment, ratings of overall clinical condition and global change showed that the 26 patients given DEA improved more than twice as much as the 27 patients given papaverine. Of the 14 individual symptoms rated, 13 improved significantly more in the DEA group than in the papaverine group. These symptoms included confusion, dizziness, unsociability, depressive mood, and mental alertness. Other data confirmed the generally superior results with DEA. In view of its demonstrated beneficial clinical actions and of its notable scarcity of contraindications or side effects, DEA appears to represent a significant pharmacologic contribution to the care of elderly persons showing selected symptoms of mental and functional decline.