The Acoustic Cortex in Frontal Dementia

Abstract

Frontal dementia is a clinical entity of cognitive impairment, characterized mostly by progressive loss of fluency in speech, eventually resulting in aphasia or anomia, associated frequently with early loss of insight and many forms of inappropriate behavior. Hyperphosphorylation of the isoforms of tau protein, a microtubule-associated protein, which plays an important role in the pathogenetic mechanisms of Alzheimer's disease, is mainly involved in the pathogenesis of frontal dementia. In the present study, the morphological alterations of the acoustic cortex are described in three cases of dementia who fulfilled all the clinical and neuropathological criteria of frontal dementia. Specimens from the acoustic area of the temporal cortex were processed with Golgi silver impregnation techniques, Cajal and Rio Hortega stainings and electron microscopy. A tremendous loss of Cajal-Retzius neurons in layer I of the acoustic cortex was noticed in Golgi staining, associated with dense reactive astrocytosis, visualized clearly in Cajal gold impregnation technique. Loss of dendritic spines was extensively seen in layers III, V, and VI in correlation with normal controls. The electron microscopy revealed numerous Pick bodies, whose tau protein was the main protein constituent. Paired helical filaments were seen in the perikaryon and the axons of the neurons of layers IV, V, and VI. Synaptic alterations were extensively seen in the acoustic cortex consisting mainly of degeneration of the postsynaptic components. The authors think that the impressive morphological alterations of the acoustic cortex in frontal dementia might explain the early onset of deficiency of communication that most of the patients demonstrate in the initial stage of the disease.

Cholinergic Hypofunction in Presbycusis-Related Tinnitus With Cognitive Function Impairment: Emerging Hypotheses

“…Chronic white noise (100 dB SPL, 4 h/day × 14 day) persistently increased tau hyperphosphorylation at the same sites that are typically phosphorylated in the AD brain and glycogen synthase kinase 3β (GSK3β), as well as increased the formation of pathological NFT tau in the hippocampus and prefrontal cortex (Cui et al, 2012 ). Such changes in the frontal cortex also play an important role in the pathogenesis of frontal dementia, while changes in the frontal acoustic cortex are seen in the early onset of communication deficiency (Baloyannis et al, 2001 ).…”

Synaptopathy Mechanisms in ALS Caused by C9orf72 Repeat Expansion

“…Moreover, synapse loss in AD is accompanied by a compensatory increase in synaptic bouton's size (Scheff et al, 1990;Scheff and Price, 1993). A similar neuronal loss and extensive dendritic spine loss in the cortex have also been found in FTD (Baloyannis et al, 2001), in neocortical neurons in Pick's disease (Ferrer, 1999), and ALS (Ferrer et al, 1991). Moreover, a reduction in dendritic spines in dopaminergic projections of striatal neurons in PD (McNeill et al, 1988) and in locus ceruleus and substantia nigra in rodent models for PD (Shors et al, 2001) have been also observed.…”