Feature type effects in semantic memory: An event related potentials study

G. Sartori et al. /Neuroscience Letters 390 (2005) 139-144

Fig. 2. Grand average ERPs in response to descriptions of Sensory and Non-sensory concepts. No difference in the N400 windows at any site.

[12], close to vertex. In accordance with the literature [12],
the N400 peak was defined as the negative deflection in the
time range between 300 and 500 ms after target onset.

A first ANOVA was performed on average voltage of the
time window 300-500 ms after target onset. Category (Living
versus Non-living), Relevance (High versus Low), Feature
Type (Sensory versus Non-sensory), Congruency (Yes versus
No) and Midline (FPZ, FZ, FCZ, CZ, CPZ, PZ, POZ, OZ)
were the within-subject factors. In this analysis we observed
a significant effect of the Midline factor (F(7,161) = 15.24;
p < 0.001) and, as reported in previous studies [11,12], the
maximum N400 effect (i.e. the difference in N400 ampli-
tude between congruent and incongruent targets [10]) was
detected in CZ, CPZ and PZ. Hence, we repeated the same
analysis using CZ, CPZ and PZ as levels of the Midline
factor, which was not significant (F(2,46) = 1.10; p= 0.34)
and did not interact with any other factor. The N400 did
not differ between Categories (F(1,23) = 1.76; p = 0.20) and,
except for the interaction with Feature Type, no other effect
involving Category was significant. More specifically, the
interaction between Category and Congruency was not sig-
nificant (F(1,23) = 2.89; p = 0.10). The N400 did not show
any significant difference (F(1,23) = 1.25; p = 0.28) between
Feature Type and, no other interaction with Feature Type was
significant. Particularly, interaction of Feature Type by Con-
gruency was not significant (F(1,23) = 0.46; p= 0.50). The
N400 to low relevance was larger than to high relevance
semantic features (F(1,23) = 29.81; p < 0.001). Given that the
N400 indexes semantic incongruity [12], the differing effect
to high and low relevance shows that low relevance descrip-
tions index with more difficulty the target concept and this
is consistent with previous behavioural observations.⁷ The
significant interaction between Relevance and Congruency
(F(1,23) = 9.04; p < 0.01) indicates that the N400 is larger for

⁷ Confronting concepts with their high relevance descriptions is accu-
rate and fast. In contrast, confronting concepts with their low relevance
descriptions is harder, yielding inaccurate and slow responses. The seman-
tic incongruity that gives rise to the N400 is therefore characteristic of low
relevance descriptions.

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