The Retrograde Connections and Anatomical Segregation of the Göttingen Minipig Nucleus Accumbens

Anterograde Tracing From the Göttingen Minipig Motor and Prefrontal Cortex Displays a Topographic Subthalamic and Striatal Axonal Termination Pattern Comparable to Previous Findings in Primates

Background: Deep brain stimulation (DBS) of the dorsal subthalamic nucleus (STN) is a validated neurosurgical treatment of Parkinson’s Disease (PD). To investigate the mechanism of action, including potential DBS induced neuroplasticity, we have previously used a minipig model of Parkinson’s Disease, although the basal ganglia circuitry was not elucidated in detail.

Aim: To describe the cortical projections from the primary motor cortex (M1) to the basal ganglia and confirm the presence of a cortico-striatal pathway and a hyperdirect pathway to the subthalamic nucleus, respectively, which is known to exist in primates.

Materials and Methods: Five female Göttingen minipigs were injected into the primary motor cortex (n = 4) and adjacent prefrontal cortex (n = 1) with the anterograde neuronal tracer, Biotinylated Dextran Amine (BDA). 4 weeks later the animals were sacrificed and the brains cryosectioned into 30 μm thick coronal sections for subsequent microscopic analysis.

Results: The hyperdirect axonal connections from the primary motor cortex were seen to terminate in the dorsolateral STN, whereas the axonal projections from the prefrontal cortex terminated medially in the STN. Furthermore, striatal tracing from the motor cortex was especially prominent in the dorsolateral putamen and less so in the dorsolateral caudate nucleus. The prefrontal efferents were concentrated mainly in the caudate nucleus and to a smaller degree in the juxtacapsular dorsal putamen, but they were also found in the nucleus accumbens and ventral prefrontal cortex.

Discussion: The organization of the Göttingen minipig basal ganglia circuitry is in accordance with previous descriptions in primates. The existence of a cortico-striatal and hyperdirect basal ganglia pathway in this non-primate, large animal model may accordingly permit further translational studies on STN-DBS induced neuroplasticity of major relevance for future DBS treatments.

The Pathophysiology of Tics; An Evolving Story

Background:

Tics, defined as quick, rapid, sudden, recurrent, non-rhythmic motor movements or vocalizations are required components of Tourette Syndrome (TS) - a complex disorder characterized by the presence of fluctuating, chronic motor and vocal tics, and the presence of co-existing neuropsychological problems. Despite many advances, the underlying pathophysiology of tics/TS remains unknown.

Objective:

To address a variety of controversies surrounding the pathophysiology of TS. More specifically: 1) the configuration of circuits likely involved; 2) the role of inhibitory influences on motor control; 3) the classification of tics as either goal-directed or habitual behaviors; 4) the potential anatomical site of origin, e.g. cortex, striatum, thalamus, cerebellum, or other(s); and 5) the role of specific neurotransmitters (dopamine, glutamate, GABA, and others) as possible mechanisms (Abstract figure).

Methods:

Existing evidence from current clinical, basic science, and animal model studies are reviewed to provide: 1) an expanded understanding of individual components and the complex integration of the Cortico-Basal Ganglia-Thalamo-Cortical (CBGTC) circuit - the pathway involved with motor control; and 2) scientific data directly addressing each of the aforementioned controversies regarding pathways, inhibition, classification, anatomy, and neurotransmitters.

Conclusion:

Until a definitive pathophysiological mechanism is identified, one functional approach is to consider that a disruption anywhere within CBGTC circuitry, or a brain region inputting to the motor circuit, can lead to an aberrant message arriving at the primary motor cortex and enabling a tic. Pharmacologic modulation may be therapeutically beneficial, even though it might not be directed toward the primary abnormality.

Online histological atlas of the Göttingen minipig brain

Background

The cytoarchitecture of the Göttingen minipig telencephalon has recently been elucidated in the published article (Bjarkam et al., 2017). The aim of the current paper is to describe how such data can be presented in an online histological atlas of the Gottingen minipig brain and how this atlas was constructed.

Methods

Two sets of histological sections were used. One set was photographed in high resolution and labelled, the other set in low resolution (resized first set) was used for reference on the computer screen. The two sets of microphotographs enable, using the freely available JQuery Image Zoom Plugin, the subsequent construction of a simple HTML-based atlas web page with a “virtual microscope like” style, which allowed magnifying of the base image (low-resolution image) up to the maximum resolution of the high-resolution image. In addition, we describe how the established histological atlas can be accompanied by a set of similar T1-weighted MRI pictures.

Results and conclusion

Histological and MRI pictures are presented in atlas form on www.cense.dk/minipig_atlas/index.html. The described pipeline represent a cheap and freely available way to present histological images, in online virtual microscopic atlas form, and may thus be of general interest to anyone who would like to present histological data accordingly.

Anatomic Review of the Ventral Capsule/Ventral Striatum and the Nucleus Accumbens to Guide Target Selection for Deep Brain Stimulation for Obsessive-Compulsive Disorder

BACKGROUND

Disturbances in the reward network of the brain underlie addiction, depression, and obsessive-compulsive disorder. The ventral capsule/ventral striatum and nucleus accumbens (NAc) region is a clinically approved target for deep brain stimulation for obsessive-compulsive disorder.

METHODS

We performed a comprehensive literature review to define clinically relevant anatomy and connectivity of the ventral capsule/ventral striatum and NAc region to guide target selection for deep brain stimulation.

RESULTS

Architecturally and functionally, the NAc is divided into the core and the shell, with each area having different connections. The shell primarily receives limbic information, and the core typically receives information from the motor system. In general, afferents from the prefrontal cortex, hippocampus, and amygdala are excitatory. The dopaminergic projections to the NAc from the ventral tegmental area modulate the balance of these excitatory inputs. Several important inputs to the NAc converge at the junction of the internal capsule (IC) and the anterior commissure (AC): the ventral amygdalofugal pathways that run parallel to and underneath the AC, the precommissural fornical fibers that run anterior to the AC, axons from the ventral prefrontal cortex and medial orbitofrontal cortex that occupy the most ventral part of the IC and embedding within the NAc and AC, and the superolateral branch of the medial forebrain bundle located parallel to the anterior thalamic radiation in the IC.

CONCLUSIONS

The caudal part of the NAc passing through the IC-AC junction may be an effective target for deep brain stimulation to improve behavioral symptoms associated with obsessive-compulsive disorder.