Historical and phrenologic reflections on the nonmotor functions of the cerebellum: love under the tent?

What is the function of the cerebellum? Since the pioneering studies of Reil, Flourens, Magendie, BrownSequard, and their contemporaries,‘ neuroanatomic analyses have emphasized the overriding importance of the cerebellum and its efferent and afferent tracts in proprioception and the integration of purposeful movement. Yet, over the last two decades, a substantial body of knowledge has begun to suggest a more subtle role for the cerebellum in behavioral patterning and as a part of a cognitive regulatory network extending to the hippocampus, septum, amygdala, and the limbic system.2 This regulatory network may be capable of modifying various emotion-laden psychological processes such as sensory integration, aggression, and reproductive arousaL3-’l Some subjects suffering from diffuse psychopathologic states such as senile dementia and autism demonstrate significant abnormalities in cerebellar morphology and histoanatomy.“$) In autism, for example, some postmortem histopathologic and morphometric analyses have revealed gross hypoplasia within the cerebellar vermis, diffuse loss of Purkinje cells throughout the cerebellar hemispheres, and a 50% to 90% loss of Purkinje cells in the archicerebellum.x,9 While these data are controversial and apparently at odds with recent correlative MRI studies performed on autistic children, I n the reported histopathologic patterns are provocative and suggest that the cerebellum and its projections may be implicated in important nonmotor functions. The hypothesis that the cerebellum is involved in emotive processing and cognitive activities is not new.“ In fact, this supposition was at the center of an acrimonious dispute between the 19th-century phrenological movement and its skeptical detractors from the academic mainstream.” According to Franz Joseph Gall ( 1758-1828), t h e peripatetic Swiss neuroanatomist, psychologist, iconoclast, and international impresario who founded phrenology some two centuries ago,l2-l4 the motor functions of the cerebellum were entirely secondary. For Gall and his followers, the cerebellum was nothing less than the primary anatomic locus of love.’:’ To understand the basis of Gall’s conjecture, it is necessary to appreciate the intellectual context of the phrenologic movement.’:’ Born into an era that was heavily influenced by Rousseau and the neoclassic Naturphilosophie movement (which emphasized detailed comparative anatomy studies aimed at deciphering the hidden relationships between biological structure and function), Gall postulated the existence of an orderly neuronal hierarchy composed of a series of relatively autonomous intracerebral ganglia, each devoted to a certain type of thought process or activity and each capable of reciprocal reinforcement or inhibition through an interconnecting network (figure l).l:I The relative importance of each type of thought process in the overall psychologic make-up of the individual could be inferred, Gall claimed, by cranioscopic examin ation of the indentations in the skull overlying each of these neurologic loci. A well-trained phrenologist could thus pass judgment on the character of an unknown individual either anteor postmortem merely by taking certain key measurements of skull topography (figure 2). The cerebellum was considered the primary node in this hierarchy, and was considered the locus of sexual (“amative”) love, while the overlying occipital pole and cuneus was considered the locus of maternawpaternal love for one’s children and dependents (“philoprogenitive” love 1. The surface anatomy correlates of these centers are depicted in figure 3.