title: The special status of verbal knowledge in semantic memory: evidence from performance of semantically impaired subjects on verbalizable and non-verbalizable versions of the object decision task.
abstract: According to the semantic hub hypothesis, a supramodal semantic hub is equally needed to deal with verbal and extraverbal "surface" representations. Damage to the supramodal hub is thought to underlie the crossmodal impairment observed in selective semantic deficits. In the present paper, we provide evidence supporting an alternative view: we hold that semantic impairment is not equal across domains but affects verbal behavior disproportionately. We investigated our hypothesis by manipulating the verbal load in an object decision task. Two pathological groups showing different levels of semantic impairment were enrolled together with their normal controls. The severe group included 10 subjects with semantic dementia and the mild group 10 subjects with Alzheimer's disease. In keeping with our hypothesis, when shifting from the low verbal load to the high verbal load condition, brain-damaged individuals, as compared to controls, showed a disproportionate impairment as a function of the severity of their semantic deficit.
authors.affiliation: I.R.C.C.S. Fondazione Santa Lucia, Roma, Italy. Electronic address: g.zannino@hsantalucia.it.
authors.forename: Gian Daniele
authors.initials: GD
authors.lastname: Zannino
authors.affiliation: I.R.C.C.S. Fondazione Santa Lucia, Roma, Italy. Electronic address: r.perri@hsantalucia.it.
authors.forename: Roberta
authors.initials: R
authors.lastname: Perri
authors.affiliation: I.R.C.C.S. Fondazione Santa Lucia, Roma, Italy. Electronic address: m.monaco@hsantalucia.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Monaco
authors.affiliation: I.R.C.C.S. Fondazione Santa Lucia, Roma, Italy; Clinica Neurologica, Università di Roma Tor Vergata, Italy. Electronic address: c.caltagirone@hsantalucia.it.
authors.forename: Carlo
authors.initials: C
authors.lastname: Caltagirone
authors.affiliation: Dipartimento di Medicina Sperimentale e Clinica-Polytechnic University of Marche, Ancona, Italy. Electronic address: s.luzzi@univpm.it.
authors.forename: Simona
authors.initials: S
authors.lastname: Luzzi
authors.affiliation: I.R.C.C.S. Fondazione Santa Lucia, Roma, Italy; Clinica Neurologica, Università di Roma Tor Vergata, Italy. Electronic address: memolab@hsantalucia.it.
authors.forename: Giovanni A
authors.initials: GA
authors.lastname: Carlesimo
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000523:psychology*; D003657:Decision Making; D005260:Female; D057180:Frontotemporal Dementia / Q000523:psychology*; D006801:Humans; D019359:Knowledge; D008297:Male; D008568:Memory; D010364:Pattern Recognition, Visual; D012660:Semantics; D014705:Verbal Behavior
keywords: Alzheimer’s disease; Semantic dementia; Semantic memory