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G. Sartori et al. / Neuroscience Letters 390 (2005) 139-144
shows up in larger N400, then larger N400 are expected for
these two types of items if relevance is not controlled. In
contrast, when relevance is matched, any category or fea-
ture type effect should vanish; and this is what we found. At
neural level, we showed that relevance matched categories
had similar N400 and that relevance matched feature types
had also similar N400. In other words, no difference between
Living and Non-living and between Sensory and Non-sensory
descriptions may be found when relevance is matched. These
results confirmed the view that the previously reported dis-
sociations observed using ERPs could be spurious.
In our view, the larger N400 for Living [11] and for Sen-
sory features [3] may not be genuine effects if we consider
that: (i) low relevance semantic features elicit larger N400 and
(ii) Living items have, on average, many Sensory features of
lower relevance as compared to Non-living [19]. Therefore,
any uncontrolled set of stimuli is likely to result in larger,
spurious N400 for items belonging to the Living category
and in larger N400 for Sensory descriptions.
These results increase credibility to the general claim that
the organising principles of conceptual representation in the
brain are semantic features rather than categories (see also
[17]). Aside from a clear relevance effect, also the absence of
any category effect is in accord with this view. With regard
to semantic features, we present results at neural level that
parallel those previously reported at behavioural level [19].
Taken together our results seem to indicate that semantic
features may not be organised on the basis of their content
(Sensory versus Non-sensory) but rather on the basis of their
importance in facilitating concept retrieval. Relevance, an
effective index of this importance, may account for many
effects previously believed to characterise the organisation at
neural level. Instead, feature content per se does not affect
ERPs. Our data raise the possibility that it is the impor-
tance of semantic features (relevance), which is the basis
of behavioural and neural effects of category and feature
types that were previously reported. In sum, this investigation
adds credibility to the sceptic views on category-specificity
as researchers are looking more closely at criteria used in
defining the phenomenon. In fact, credibility of semantic
memory dissociations, at behavioural level, is reduced by a
number of methodological problems concerning the methods
through which dissociations are established [4]. Experimen-
tal approaches to the neural basis of semantic memory are
just beginning to control the effect of such variables on pro-
cessing requirements after a period in which the only variable
manipulated was category (see [9]).
References
[1] S.F. Cappa, D. Perani, T. Schnur, M. Tettamanti, F. Fazio, The effects
of semantic category and knowledge type on lexical-semantic access:
a PET study, Neuroimage 8 (1998) 350-359.
[2] A. Caramazza, J.R. Shelton, Domain-specific knowledge systems in
the brain, J. Cogn. Neurosci. 10 (1998) 1-34.
[3] M. Coltheart, L. Inglis, L. Cupples, P. Michie, A. Bates, B. Budd,
A semantic subsystem of visual attributes, Neurocase 4 (1998)
353-370.
[4] G.S. Cree, K. McRae, Analyzing the factors underlying the structure
and computation of the meaning of chipmunk, cherry, chisel, and
cello (and many other such concrete nouns), J. Exp. Psychol.: Gen.
132 (2003) 163-201.
[5] R. Dell’Acqua, L. Lotto, R. Job, Naming time and standard-
ized norms for the Italian PD/DPSS of 266 pictures: direct com-
parisons with American, English, French, and Spanish published
databases, Behav. Res. Methods Instrum. Comput. 32 (2000) 588-
612.
[6] J.T. Devlin, C.J. Moore, C.J. Mummery, M.L. Gorno-Tempini, J.A.
Phillips, U. Noppeney, R.S.J. Frackowiak, K.J. Friston, C.J. Price,
Anatomic constraints on cognitive theories of category specificity,
Neuroimage 15 (2002) 675-685.
[7] M.J. Farah, J.L. McClelland, A computational model of seman-
tic memory impairment: modality specificity and emergent category
specificity, J. Exp. Psychol.: Gen. 120 (1991) 339-357.
[8] K.D. Federmeier, M. Kutas, A rose by any other name: long-term
memory structure and sentence processing, J. Mem. Lang. 41 (1999)
469-495.
[9] J. Joseph, Functional neuroimaging studies of category specificity in
object recognition: a critical review and meta-analysis, Cogn. Affect.
Behav. Neurosci. 1 (2001) 119-136.
[10] M. Kiang, M. Kutas, Association of schizotypy with seman-
tic processing differences: an event-related brain potentials study,
Schizophr. Res. (2005) 329-342.
[11] M. Kiefer, Perceptual and semantic source of category-specific
effects: event-related potentials during picture and word categoriza-
tion, Mem. Cogn. 29 (2001) 100-116.
[12] M. Kutas, K.D. Federmeier, Electrophysiology reveals semantic
memory use in language comprehension, Trends Cogn. Sci. 4 (2000)
463-470.
[13] M. Kutas, S.A. Hillyard, Reading senseless sentences: brain poten-
tials reflect semantic incongruity, Science 297 (1980) 203-205.
[14] A. Martin, L.L. Chao, Semantic memory and the brain: structure and
processes, Curr. Opin. Neurobiol. 11 (2001) 194-201.
[15] A. Martin, C.L. Wiggs, L.G. Ungerleider, J.V. Haxby, Neural cor-
relates of category-specific knowledge, Nature 379 (1996) 649-
652.
[16] R. McCarthy, E.K. Warrington, Category specificity in an agram-
matic patient: the relative impairment of verb retrieval and compre-
hension, Neuropsychologia 23 (1985) 709-727.
[17] C.J. Mummery, T. Shallice, C.J. Price, Dual-process model in seman-
tic priming: a functional imaging perspective, Neuroimage 9 (1999)
516-525.
[18] E. Saffran, The organization of semantic memory: in support of a
distributed model, Brain Lang. 71 (2000) 204-212.
[19] G. Sartori, L. Lombardi, Semantic relevance and semantic disorders,
J. Cogn. Neurosci. 16 (2004) 439-452.
[20] G. Sartori, L. Lombardi, L. Mattiuzzi, Semantic relevance best pre-
dicts normal and abnormal name retrieval, Neuropsychologia (2005)
754-770.
[21] S.L. Thompson-Schill, G.K. Aguirre, M. Desposito, M.J. Farah, A
neural basis for category and modality specificity of semantic knowl-
edge, Neuropsychologia 37 (1999) 671-676.
[22] E.K. Warrington, T. Shallice, Category specific semantic impair-
ments, Brain 107 (1999) 829-854.
[23] T. Yano, M. Kaga, Semantic category discrimination and N400, Psy-
chol. Rep. 87 (2000) 415-422.