2020 Volume 40 Issue 2 Pages 181-186
Frontotemporal lobar degeneration is a neurodegenerative disorder mainly damaged in the frontal and the anterior temporal lobe. Cerebral lateralization is often described in the context of the posterior functions such as symbolic or visuospatial manipulation, but there is also a lateralization in frontotemporal lobar degeneration. Progressive semantic memory impairment is characteristics in semantic dementia, that has damage in the anterior temporal lobe. In the left predominant cases, hearing comprehension impairment, naming impairment, and surface dyslexia are prominent from their early stage. In the right predominant cases, prosopagnosia often appears but not in all cases, behavioral changes like frontal symptoms are also exhibited. It is necessary to clarify the disease concept of right temporal dominant cases. Symptoms such as disinhibition, apathy, lack of empathy, stereotypy, changes in eating behavior, and executive dysfunction appear in behavioral variant frontotemporal dementia that have damage mainly in frontal lobe. Previous studies have proposed “right hemisphere hypothesis”, in which behavioral changes are associated with damages in the right hemisphere ventral side. However, hemispheres communication is also seemed to be important. Further neuropathological and network research are expected to elucidate the neural basis of semantic memory and behavioral changes beyond simple localization hypothesis.
