Optimal deep brain stimulation sites and networks for stimulation of the fornix in Alzheimer's disease.

Deep brain stimulation (DBS) to the fornix is an investigational treatment for patients with mild Alzheimer's Disease. Outcomes from randomized clinical trials have shown that cognitive function improved in some patients but deteriorated in others. This could be explained by variance in electrode placement leading to differential engagement of neural circuits. To investigate this, we performed a post-hoc analysis on a multi-center cohort of 46 patients with DBS to the fornix (NCT00658125, NCT01608061). Using normative structural and functional connectivity data, we found that stimulation of the circuit of Papez and stria terminalis robustly associated with cognitive improvement (R = 0.53, p < 0.001). On a local level, the optimal stimulation site resided at the direct interface between these structures (R = 0.48, p < 0.001). Finally, modulating specific distributed brain networks related to memory accounted for optimal outcomes (R = 0.48, p < 0.001). Findings were robust to multiple cross-validation designs and may define an optimal network target that could refine DBS surgery and programming.

Mapping autonomic, mood and cognitive effects of hypothalamic region deep brain stimulation.

Because of its involvement in a wide variety of cardiovascular, metabolic and behavioural functions, the hypothalamus constitutes a potential target for neuromodulation in a number of treatment-refractory conditions. The precise neural substrates and circuitry subserving these responses, however, are poorly characterized to date. We sought to retrospectively explore the acute sequelae of hypothalamic region deep brain stimulation and characterize their neuroanatomical correlates. To this end we studied-at multiple international centres-58 patients (mean age: 68.5 ± 7.9 years, 26 females) suffering from mild Alzheimer's disease who underwent stimulation of the fornix region between 2007 and 2019. We catalogued the diverse spectrum of acutely induced clinical responses during electrical stimulation and interrogated their neural substrates using volume of tissue activated modelling, voxel-wise mapping, and supervised machine learning techniques. In total 627 acute clinical responses to stimulation-including tachycardia, hypertension, flushing, sweating, warmth, coldness, nausea, phosphenes, and fear-were recorded and catalogued across patients using standard descriptive methods. The most common manifestations during hypothalamic region stimulation were tachycardia (30.9%) and warmth (24.6%) followed by flushing (9.1%) and hypertension (6.9%). Voxel-wise mapping identified distinct, locally separable clusters for all sequelae that could be mapped to specific hypothalamic and extrahypothalamic grey and white matter structures. K-nearest neighbour classification further validated the clinico-anatomical correlates emphasizing the functional importance of identified neural substrates with area under the receiving operating characteristic curves between 0.67 and 0.91. Overall, we were able to localize acute effects of hypothalamic region stimulation to distinct tracts and nuclei within the hypothalamus and the wider diencephalon providing clinico-anatomical insights that may help to guide future neuromodulation work.

Are certain lifestyle habits associated with lower Alzheimer's disease risk?

As the number of patients with Alzheimer's disease (AD) is expected to grow, finding ways to prevent and lower the risk of AD becomes a crucial matter. Risk factors for developing AD have been identified including health conditions, dietary habits, genetics and heredity, gender, education, age, and lifestyle. Interventions targeted at some of these risk factors may offer opportunities for development of an optimal preventive strategy. Lifestyle habits which include dietary habits and physical activities appear to have positive effect on modifying many risk factors. Studies have shown controversial results when it comes to the relation between the adherence to a Mediterranean diet and /or physical activity and the incidence of AD. Many population-based studies reported the positive association between antioxidants intake (like vitamin E and C), and polyunsaturated fatty acids whether it is from the diet or supplements on the cognitive performance. Future investigations should aim to determine objectively whether lifestyle modification through diet, exercise, or vitamins/supplements truly exert risk reduction or outright prevention. In this review, lifestyle habits are reviewed as they pertain to influence on risk of developing AD as well as on cognitive decline. Epidemiological studies and animal studies are reviewed.

Latrepirdine, a potential novel treatment for Alzheimer's disease and Huntington's chorea.

Latrepirdine (Dimebon) is a small-molecule compound under development by Medivation Inc and Pfizer Inc for the treatment of Alzheimer's disease and Huntington's chorea. Originally developed and marketed as an antihistamine in Russia, latrepirdine has since demonstrated potential for the treatment of neurodegenerative diseases. Early research suggested that the mechanism of action was centered on AChE inhibition and NMDA antagonism. More recent research questions these early findings, and other mechanisms of action have been proposed and investigated. In phase II clinical trials, latrepirdine demonstrated clinically relevant improvements in patients with Alzheimer's disease and Huntington's chorea. At the time of publication, phase III clinical trials had been initiated. Given the robustness of the phase II clinical data, latrepirdine has a high likelihood of success in phase III trials and in subsequently being granted regulatory approval.

Donepezil: potential neuroprotective and disease-modifying effects.

BACKGROUND: There is substantial evidence from preclinical studies that cholinesterase inhibitors affect basic processes that have been implicated in Alzheimer's disease (AD) pathogenesis, suggesting that these drugs should have both disease-modifying and neuroprotective effects in humans. The evidence seems to be strongest in relation to donepezil, which is the focus of this review. OBJECTIVE: To summarize the preclinical literature regarding the effects of donepezil on cellular and molecular processes underlying AD. Second, to suggest reasons for the apparent disparity between robust preclinical effects and modest clinical effects of this drug and others in its class. METHODS: Articles retrieved from PubMed searches were critically reviewed and selected for relevance to the current topic. RESULTS/CONCLUSION: Donepezil has numerous cellular and molecular effects that should influence AD progression.