A Neuroanatomy of Positive Affect Display – Subcortical Fiber Pathways Relevant for Initiation and Modulation of Smiling and Laughing

Abstract

BackgroundWe here report two cases of stimulation induced pathological laughter (PL) under thalamic deep brain stimulation (DBS) for essential tremor and interpret the effects based on a modified neuroanatomy of positive affect display (PAD).Objective/HypothesisThe hitherto existing neuroanatomy of PAD can be augmented with recently described parts of the motor medial forebrain bundle (motorMFB). We speculate that a co-stimulation of parts of this fiber structure might lead to a non-volitional modulation of PAD resulting in PL.MethodsWe describe the clinical and individual imaging workup and combine the interpretation with normative diffusion tensor imaging (DTI)-tractography descriptions of motor connections of the ventral tegmental area (VTA) (n = 200 subjects, HCP cohort), [[18F] fluorodeoxyglucose (18FDG)] positron emission tomography (PET), and volume of activated tissue simulations. We integrate these results with literature concerning PAD and the neuroanatomy of smiling and laughing.ResultsDBS electrodes bilaterally co-localized with the MB-pathway (“limiter pathway”). The FDG PET activation pattern allowed to explain pathological PAD. A conceptual revised neuroanatomy of PAD is described.ConclusionEliciting pathological PAD through chronic thalamic DBS is a new finding and has previously not been reported. PAD is evolution driven, hard wired to the brain and realized over previously described branches of the motorMFB. A major relay region is the VTA/mammillary body complex. PAD physiologically undergoes conscious modulation mainly via the MB branch of the motorMFB (limiter). This limiter in our cases is bilaterally disturbed through DBS. The here described anatomy adds to a previously described framework of neuroanatomy of laughter and humor.

The anterior perforated substance (APS) revisited: Commented anatomical and imagenological views

“…It is not clear after the descriptions of those authors how the ascending or descending fibers reach the cortex or the top of MFB, respectively. Recently, a superolateral division of the MFB (slMFB) has been proposed that from the prefrontal cortex would reach the bundle through the anterior limb of the internal capsule (Cho et al, 2013;Coenen et al, 2009Coenen et al, , 2022Hosp et al, 2019;Hurwitz et al, 2006;Panksepp, 2015). It has the drawback of having been traced only by tractography (Haber & Knutson, 2010;Haber et al, 2011Haber et al, , 2020Haynes & Haber, 2013), in a zone like the hypothalamus that has uncountable fiber systems passing anteroposteriorly.…”

“The Heart Asks Pleasure First”—Conceptualizing Psychiatric Diseases as MAINTENANCE Network Dysfunctions through Insights from slMFB DBS in Depression and Obsessive–Compulsive Disorder

“…It is one focus of our research to look at monoaminergic and other transmitters' transmissions in a translational approach [17,20,75,[91][92][93][94]. The region of stimulation-the mesencephalic ventral tegmentum-as the seat of the A10 DA cellular group in conjunction with the mammillary bodies, forms a complex basal regulation center, relevant as a basis for the MAINTENANCE system but also for positive affect display [95].…”