Mild Probable Alzheimer's Disease Research Articles

Replication of a study of frequency analysis of the resting awake EEG in mild probabke Alzheimer's disease

In the resting EEG, the percentage power in the delta, theta, alpha, and beta bands and the mean frequency were computed in an occipital-vertex derivation for two samples of subjects. Theoriginal sample ( n = 79) and the new sample ( n = 43) each contained a mild probable Alzheimer's disease (SDAT) group and a healthy elderly control group. Group medians in both samples were higher in the SDAT than in the healthy subjects for percentage delta and theta, and were lower for percentage alpha and beta and for mean frequency. Percentage theta and mean frequency were consistent across the two samples in showing statistically significant differences between SDAT and healthy groups. The ability of each EEG measure to detect individual subjects with SDAT was assessed. The most effective measure, percentage theta, had only modest sensitivity (about 20%),but this was attained at a specificity of 100%. The accurate detection of an individual at the mildstage requires that the predictive value of a positive test be hight to avoid misclassification of non-SDAT subjects as SDAT. This,in turn, requires a specificity of virtually 100% when the prevalence is low. The low sensotivity puts several constrainss on the usefulness of the EEG. For this reason, when the dementia is at the mild stage the EEG would be a useful detector Af probable Alzheimer's disease only under certain limiting conditions, including high prevalence, high specificity, and a willingness to accept a high rate of falsely negative tests.

51. Dopamine and homovanillic acid concentrations and monoamine oxidase-B activities in the brain tissue of patients with Alzheimer's disease

Brain oscillatory responses can be used for non-invasive analyses of cortico-cortical connectivity, local neuronal synchronization, and coherence of oscillations in many neuropsychiatric conditions including Alzheimer's disease (AD). In the present paper, we examine sensory-evoked and event-related gamma coherences elicited by visual stimuli in three sub-gamma bands in two sub-groups of patients with AD (i.e., acetylcholinesterase-inhibitor treated and untreated) and healthy controls.We studied a total of 39 patients with probable mild AD (according to NINCDS-ADRDA criteria) who had been sub-divided into untreated (n = 21) and treated (n = 18) (patients either on cholinergic monotherapy or combined therapy with memantine) AD groups, and 21 age-, gender-, and education-matched healthy elderly controls. A simple flash visual paradigm was applied for the acquisition of sensory-evoked coherences. Event-related coherences were elicited using a classical visual oddball paradigm. Both sensory-evoked and event-related gamma coherences were calculated for long-distance intrahemispheric pairs for three frequency ranges: 25–30 Hz, 30–35 Hz, and 40–48 Hz in post-stimulus 0–800 ms duration. The long-distance intrahemispheric pairs from both sides were fronto-parietal, fronto-temporal, fronto-temporoparietal, fronto-occipital, centro-occipital and parieto-occipital.The sensory-evoked or event-related gamma coherences revealed that both treated and untreated AD patients had significantly increased values compared to healthy controls in all three sub-gamma bands. Moreover, the treated AD patients demonstrated significantly higher fronto-parietal gamma coherences during both sensory stimulation and oddball paradigm and lower occipito-parietal coherences during oddball paradigm in comparison to untreated AD patients.The present study demonstrated that an increase of gamma coherences was present in response to both visual sensory and cognitive stimulation in AD patients in all gamma sub-bands. Therefore, gamma oscillatory activity seems to be fundamental in brain functions at both the sensory and cognitive levels. The increase of gamma coherence values was not due to cholinergic treatment to any significant extent, as both treated and untreated AD patients had increased gamma coherence values compared to healthy controls. The use of coherence values reflecting brain connectivity holds potential for neuroimaging of AD and understanding brain dynamics related to the effects of medication.