Describing brain activity of persons with AD and depressive symptoms

Electrical stimulation of the vmPFC serves as a remote control to affect VTA activity and improve depressive-like behavior

Despite progress in elucidating mechanisms of depression, the efficacy of different treatments remains inadequate. Recent small-scale clinical studies suggested anti-depressant treatment using deep brain stimulation (DBS) of the ventral capsule/ventral striatum or subgenual cingulate cortex (SCC), yet controlled, multi-center trials were unsuccessful. We recently suggested the ventral tegmental area (VTA) as an important intersection for treating depression. We also found that stimulation of the VTA of a genetic rat model of depression (Flinders Sensitive Line (FSL) rats) with a programmed pattern designed to mimic the burst firing of normal rats decreases depressive-like behavior. Herein, we examined the possibility of reaching the VTA - located deep in the brain stem - through its direct connection to the ventro-medial prefrontal cortex (vmPFC), which parallels the human SCC. Thus, we compared treatment of FSLs with modified versions of DBS - either chronic-intermittent low-frequency electrical stimulation of the vmPFC, or patterned acute electrical stimulation (pAES), which integrates transcranial magnetic stimulation properties, namely, bursts of pulse trains and low frequency stimulation, applied to the VTA. We found that stimulation of the vmPFC (20Hz, 15min/day, 10days) improved depressive-like behavior and VTA local field potential (LFP) activity of FSLs, yet it had only a partial long-term effect on behavior. In particular, vmPFC stimulation decreased theta band activity, which correlated with the improvement in depressive-like behavior of all treated FSLs at day 1, and in ~50% of treated FSLs at day 28 post treatment. pAES of the VTA (10Hz, 20min) caused significant, long-term improvement of depressive-like behavior of FSLs, concurrently with normalizing intra-VTA LFP activity, and increasing VTA LFP synchronicity and hippocampal BDNF mRNA levels. Thus, although low-frequency electrical stimulation of the PFC alters VTA activity, leading to attenuation of depressive-like manifestations, a specific stimulation pattern affecting VTA cell programming is important for long-term efficacy.

The Electrophysiological Phenomenon of Alzheimer's Disease: A Psychopathology Theory

The current understanding of Alzheimer's disease (AD) is based on the Aβ and tau pathology and the resulting neuropathological changes, which are associated with manifested clinical symptoms. However, electrophysiological brain changes may provide a more expansive understanding of AD. Hence, the objective of this systematic review is to propose a theory about the electrophysiological phenomenon of Alzheimer's disease (EPAD). The review of literature resulted from an extensive search of PubMed and MEDLINE databases. One-hundred articles were purposively selected. They provided an understanding of the concepts establishing the theory of EPAD (neuropathological changes, neurochemical changes, metabolic changes, and electrophysiological brain changes). Changes in the electrophysiology of the brain are foundational to the association or interaction of the concepts. Building on Berger's Psychophysical Model, it is evident that electrophysiological brain changes occur and affect cortical areas to generate or manifest symptoms from onset and across the stages of AD, which may be prior to pathological changes. Therefore, the interaction of the concepts demonstrates how the psychopathology results from affected electrophysiology of the brain. The theory of the EPAD provides a theoretical foundation for appropriate measurements of AD without dependence on neuropathological changes. Future research is warranted to further test this theory. Ultimately, this theory contributes to existing knowledge because it shows how electrophysiological changes are useful in understanding the risk and progression of AD across the stages.