Current approaches to characterize micro- and macroscale circuit mechanisms of Parkinson's disease in rodent models

The Basal Ganglia and Mesencephalic Locomotor Region Connectivity Matrix

Although classically considered a relay station for basal ganglia (BG) output, the anatomy, connectivity, and function of the mesencephalic locomotor region (MLR) were redefined during the last two decades. In striking opposition to what was initially thought, MLR and BG are actually recip- rocally and intimately interconnected. New viral-based, optogenetic, and mapping technologies re- vealed that cholinergic, glutamatergic, and GABAergic neurons coexist in this structure, which, in ad- dition to extending descending projections, send long-range ascending fibers to the BG. These MLR projections to the BG convey motor and non-motor information to specific synaptic targets throughout different nuclei. Moreover, MLR efferent fibers originate from precise neuronal subpopulations locat- ed in particular MLR subregions, defining independent anatomo-functional subcircuits involved in particular aspects of animal behavior such as fast locomotion, explorative locomotion, posture, fore- limb-related movements, speed, reinforcement, among others. In this review, we revised the literature produced during the last decade linking MLR and BG. We conclude that the classic framework con- sidering the MLR as a homogeneous output structure passively receiving input from the BG needs to be revisited. We propose instead that the multiple subcircuits embedded in this region should be taken as independent entities that convey relevant and specific ascending information to the BG and, thus, actively participate in the execution and tuning of behavior.

Store-Operated Ca2+ Channels Contribute to the Generation of Ca2+ Waves in Interdental Cells in the Cochleae

Cochlear calcium (Ca2+) waves are vital regulators of the cochlear development and establishment of hearing function. Inner supporting cells are believed to be the main region generating Ca2+ waves that work as internal stimuli to coordinate the development of hair cells and the mapping of neurons in the cochlea. However, Ca2+ waves in interdental cells (IDCs) that connect to inner supporting cells and spiral ganglion neurons are rarely observed and poorly understood. Herein, we reported the mechanism of IDC Ca2+ wave formation and propagation by developing a single-cell Ca2+ excitation technology, which can easily be accomplished using a two-photon microscope for simultaneous microscopy and femtosecond laser Ca2+ excitation in any target individual cell in fresh cochlear tissues. We demonstrated that the store-operated Ca2+ channels in IDCs are responsible for Ca2+ wave formation in these cells. The specific architecture of the IDCs determines the propagation of Ca2+ waves. Our results provide the mechanism of Ca2+ formation in IDCs and a controllable, precise, and noninvasive technology to excite local Ca2+ waves in the cochlea, with good potential for research on cochlear Ca2+ and hearing functions.

Real-Life Experience on Directional Deep Brain Stimulation in Patients with Advanced Parkinson’s Disease

Directional deep brain stimulation (dDBS) is preferred by patients with advanced Parkinson’s disease (PD) and by programming neurologists. However, real-life data of dDBS use is still scarce. We reviewed the clinical data of 53 PD patients with dDBS to 18 months of follow-up. Directional stimulation was favored in 70.5% of dDBS leads, and single segment activation (SSA) was used in 60% of dDBS leads. Current with SSA was significantly lower than with other stimulation types. During the 6-month follow-up, a 44% improvement in the Unified Parkinson’s Disease Rating Scale (UPDRS-III) points and a 43% decline in the levodopa equivalent daily dosage (LEDD) was observed. After 18 months of follow-up, a 35% LEDD decrease was still noted. The Hoehn and Yahr (H&Y) stages and scores on item no 30 “postural stability” in UPDRS-III remained lower throughout the follow-up compared to baseline. Additionally, dDBS relieved non-motor symptoms during the 6 months of follow-up. Patients with bilateral SSA had similar clinical outcomes to those with other stimulation types. Directional stimulation appears to effectively reduce both motor and non-motor symptoms in advanced PD with minimal adverse effects in real-life clinical care.