Dendritic right/left asymmetries in the neurons of the human hippocampal formation: a quantitative Golgi study

Abstract

-Objective: To search for right/left asymmetries in the dendritic trees of the neuronal populations and in the cell-free layer volumes of the human hipoccampal formation. Method: In necropsic material obtained from six male individuals we performed a quantitative Golgi study of the dendritic trees of dentate granules, CA3 and CA1 pyramidal neurons and a volumetric analysis of dentate gyrus molecular layer, strata oriens plus alveus and strata lacunosum-moleculare plus radiatum of CA3 and CA1 fields. Results: We found inter-hemispheric asymmetries in the dendrites trees of all neurons, reaching the significant level in the number of granule cells dendritic segments (higher in the left than in the right hemisphere), dendritic branching density of CA3 pyramidal cells and mean dendritic length of CA1 apical terminal segments (higher in the right than in the opposite side). No volumetric differences were observed. Conclusion: This study points to different anatomical patterns of connectivity in the hippocampal formations of both hemispheres which may underlie functional asymmetries.KEY WORDS: brain asymmetries, hippocampal formation, dendritic asymmetries. Assimetrias dendríticas direita/esquerda nos neurónios da formação do hipocampo humano: estudo quantitativo GolgiRESUMO -Objectivo: Pesquisar a existência de assimetrias direita/esquerda nas arborizações dendríticas neuronais e nos volumes das camadas não celulares da formação do hipocampo humano. Método: Efectuamos estudo quantitativo Golgi das arborizações dendríticas dos grânulos da fascia denteada e das células piramidais de CA3 e CA1, e uma análise estereológica dos volumes da camada molecular da fascia denteada, do strata oriens + alveus e do strata lacunosum-moleculare + radiatum de CA3 e de CA1 em material necrópsico colhido em 6 indivíduos do sexo masculino. Resultados: Encontrámos assimetrias inter-hemisféri-cas nas arborizações dendríticas de todos os neurónios, significativas no número de segmentos dendríticos das células granulares (maior à esquerda do que à direita) na densidade de ramificação dendrítica das pirâmides de CA3 e no comprimento dendrítico médio dos segmentos apicais terminais das pirâmides de CA1 (maiores à direita do que à esquerda). Não encontramos diferenças volumétricas. Conclusão: Estes resultados alertam para diferentes padrões anatómicos de conectividade nas formações do hipocampo de ambos os hemisférios que podem fundamentar assimetrias funcionais. PALAVRAS-CHAVE: assimetrias cerebrais, formação do hipocampo, assimetrias dendríticas. Porto -Portugal. E-mail: mjsa@med.up.pt The existence of anatomical inter-hemispheric asymmetries has since long been described in several regions of the normal human brain, mainly in those related to the processing of language functions [1][2][3][4] . In effect, most studies addressing this issue were centered in the neocortex where right/left differences were observed in macroscopic features, such as the shape and confi guration of cerebral sulci and specific cortical areas, as well as...

Radiation-induced gray matter atrophy in patients with nasopharyngeal carcinoma after intensity modulated radiotherapy: a MRI magnetic resonance imaging voxel-based morphometry study

“…We speculate that hippocampus on two sides show different sensitivity to radiation and chemotherapy toxicity due to subtle lateralized differences in cytoarchitecture. The hippocampal formation is more complex in the left side than the right, as it has been reported the total number of granule cells of dendritic segments is larger in the left than that in the right, suggesting that they have a larger receptor surface (17). Radiation or chemotherapy induces toxicity shows a decrease of dendritic branching and spine volume, which are more obvious in the left hippocampus than in its counterpart.…”

“…To our knowledge, ours is the first study that reveals the findings of GM volume deficit in hippocampus of NPC patients who received IMRT and the imaging evidence confirming that the RT damage to hippocampus. As is known, left hippocampus plays a particular role in verbal memory (17). The RTOG 0933 study (18), a single arm phase II multi-institutional trial, was conducted to evaluate the efficiency of the hippocampus sparing in brain metastasis patients who underwent wholebrain radiotherapy (WBRT).…”

MR Image Changes of Normal-Appearing Brain Tissue after Radiotherapy

“…Similarly, no significant hippocampal volume change in low-dose areas was also reported in 15 low-dose radiated head and neck cancer patients four to ten years after RT [43]. Interestingly, Shi et al [40] found GM atrophy only in the left hippocampus, suggesting that the left side has a larger receptor surface as the granule cells show a larger amount of dendritic segments [58]. GM was also significantly lower in the right pulvinar and the right middle temporal gyrus.…”

Enigma of Pyramidal Neurons: Chirality-Centric View on Biological Evolution. Congruence to Molecular, Cellular, Physiological, Cognitive, and Psychological Functions

“…The evolutionary selected system for space-time information processing, including the morphology and spatial orientation of PyrNs, is the fundamental feature underlying the function of CNS. Experimentally observed hemispheric asymmetry of synaptic morphology of PyrNs explains well-known functional laterality of human perceptual and cognitive functions [158][159][160]. The morphology of PyrNs concerning the function was the focus of long-term attention in neuroscience.…”