The granule cell islands in the olfactory tubercle (islands of Calleja) and the insula magna of Calleja are present in all species examined in this study: cat, rat, mouse, rabbit, hedgehog, monkey, man, and dolphin, displaying the same basic morphology. They appear as rather undifferentiated neurons with a poorly developed dendritic tree and a short unramified axon that does not leave the island. The larger islands and the insula magna are associated with medium-sized neurons often lying in cell-sparse core regions; they probably represent the efferent component of the islands. The distribution of granule cell islands in the olfactory tubercle varies from species to species: in the cat, they are restricted to the superficial cap regions; in the hedgehog and rabbit, they lie in cap regions and in the deep polymorph layer. In the rat, they are confined mainly to the deep polymorph layer, whereas in the mouse they extend through the three layers. In most species, the lateral islands form part of the cap regions, and they may receive fibers from the lateral olfactory tract. However, the consistent relationship between dwarf cells in the cap regions and granule cells seems to be a merely topographical one. The variable location of granule cell islands indicates that they are not related to specific cell types or cell groups in the olfactory tubercle, except to the large neurons in the hilus zones, which send their dendrites into the islands. Another close and constant relationship exists between granule islands and fibers of the medial forebrain bundle. The medial islands and the insula magna are the largest and most constant aggregations of granule cells. They are present even in the dolphin, which lacks lateral islands. Medial islands and insula magna are continuous in the hedgehog and the newborn kitten and seem to belong to a medial system of granule cells that is independent from the olfactory tubercle and from olfactory fibers. Aggregations of granule cells occur also outside the olfactory tubercle and the insula magna: in the hedgehog and the rabbit, clusters lie scattered in the n. accumbens. Distribution of granule cells outside the olfactory tubercle is related to ontogenetic development: in newborn kittens, granule cells extend from the subependymal layer of the lateral ventricle, where they probably originate, to the medioventral border of the hemisphere, and also distribute throughout the n. accumbens and the ventral pallidum. Thus, the granule cell territory is initially wider, and the original distribution is maintained in some species.(ABSTRACT TRUNCATED AT 400 WORDS)

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Background and purpose: Reduced facial expression of emotions is a very frequent symptom of Parkinson's disease (PD) and has been considered part of the motor features of the disease. However, the neural correlates of hypomimia and the relationship between hypomimia and other non-motor symptoms of PD are poorly understood. Methods:The clinical and structural brain correlates of hypomimia were studied. For this purpose, cross-sectional data from the COPPADIS study database were used. Age, disease duration, levodopa equivalent daily dose, Unified Parkinson's Disease Rating Scale part III (UPDRS-III), severity of apathy and depression and global cognitive status were collected. At the imaging level, analyses based on gray matter volume and cortical thickness were used.Results: After controlling for multiple confounding variables such as age or disease duration, the severity of hypomimia was shown to be indissociable from the UPDRS-III speech and bradykinesia items and was significantly related to the severity of apathy (β = 0.595; p < 0.0001). At the level of neural correlates, hypomimia was related to motor regions brodmann area 8 (BA 8) and to multiple fronto-temporo-parietal regions involved in the decoding, recognition and production of facial expression of emotions. Conclusion:Reduced facial expressivity in PD is related to the severity of symptoms of apathy and is mediated by the dysfunction of brain systems involved in motor control and in the recognition, integration and expression of emotions. Therefore, hypomimia in PD may be conceptualized not exclusively as a motor symptom but as a consequence of a multidimensional deficit leading to a symptom where motor and non-motor aspects converge.

Background Identifying modifiable risk factors for cognitive impairment in the early stages of Parkinson’s disease (PD) and estimating their impact on cognitive status may help prevent dementia (PDD) and the design of cognitive trials. Methods Using a standard approach for the assessment of global cognition in PD and controlling for the effects of age, education and disease duration, we explored the associations between cognitive status, comorbidities, metabolic variables and lifestyle variables in 533 PD participants from the COPPADIS study. Results Among the overall sample, 21% of participants were classified as PD-MCI (n = 114) and 4% as PDD (n = 26). The prevalence of hypertension, diabetes and dyslipidemia was significantly higher in cognitively impaired patients while no between-group differences were found for smoking, alcohol intake or use of supplementary vitamins. Better cognitive scores were significantly associated with regular physical exercise (p < 0.05) and cognitive stimulation (< 0.01). Cognitive performance was negatively associated with interleukin 2 (Il2) (p < 0.05), Il6 (p < 0.05), iron (p < 0.05), and homocysteine (p < 0.005) levels, and positively associated with vitamin B12 levels (p < 0.005). Conclusions We extend previous findings regarding the positive and negative influence of various comorbidities and lifestyle factors on cognitive status in early PD patients, and reinforce the need to identify and treat potentially modifiable variables with the intention of exploring the possible improvement of the global cognitive status of patients with PD.

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