INVESTIGADORES
WAINSELBOIM Alejandro Javier
congresos y reuniones científicas
Título:
ERP markers of semantic and grammatical statistical information processing in the absence of learning
Autor/es:
ÁNGEL TABULLO; PAMELA LOPES DA CUNHA; ENRIQUE SEGURA; SILVANO ZANUTTO; ALEJANDRO WAINSELBOIM
Lugar:
Florianópolis
Reunión:
Congreso; Language and Neuroscience Conference; 2012
Institución organizadora:
Universidade Federal de Santa Catarina
Resumen:
First
language acquisition occurs by mere exposure to the linguistic context. During
this process, infants must solve among other problems, two basic issues: i)
infer word meanings by pairing specific aspects of their perceptual experience
with particular segments of the concurrent linguistic input (semantics); and
ii) acquire the combinatorial rules that allow to convey a coherent message
within that language (grammar). The ability to solve these issues requires to
statistically analyze cross-situational information, i.e. to associate
information that is concurrent along multiple events or situations.
Experimentally, it has been shown that adults are able to infer new noun
meanings by cross-situational pairings of images and auditory non-words (Yu
& Smith 2007). Similarly, we analyzed whether adults are also able to infer
new verbal meanings by associating concurrent visual and formal information
(Lopes da Cunha et al. 2010). In this experiment training consisted of 70
different visual scenes presented on a computer screen (two geometrical
figures, one static and the other performing one of 6 possible movements). A
sentence describing the scene in an artificial language was presented
audio-visually in simultaneous. Participants had to learn which word denoted
each movement. During testing 80 new scenes were shown, 40 of them presented a
mismatch between the movement and the presented verb. Subjects decided on-line
whether each sentence correctly described the scene. Simultaneous EEG
recordings were obtained in this stage. Most subjects responded significantly
above chance level during testing. In those who learned, the appearance of a
mismatch between verb and referent elicited an N400-like wave. Thus, under
controlled experimental conditions, subjects infer new verbal meanings by
conscious cross-situational pairing of images and audiovisual non-words, if
they are given the explicit instruction to learn the presented terms. In a
second experiment we studied if new verbal meanings could be learned in the
absence of intention to acquire regularities between linguistic and contextual
information. 22 right-handed healthy adults volunteered for the experiment. The
training protocol followed that of Lopes da Cunha et al 2010, but participants
were told not to pay attention to the sentences and concentrate on classifying
the movements they saw as horizontal or non-horizontal. During the test stage
(as in Lopes da Cunha et al. 2010), subjects were told to decide on-line
whether each sentence correctly described the scene. Simultaneous EEG
recordings were obtained in this stage. Results showed that participants were
completely unable to classify the sentences as correct or not. Nevertheless,
the appearance of a mismatch between verb and referent elicited an ELAN-like
potential. Thus, although no behavioral evidence could be found of new semantic
knowledge, at the neurobiological level evidence was found that an association
was achieved between movements and their corresponding terms. Finally, in a
third experiment we eliminated the semantic (visual) referent and asked
participants to learn the combinatorial rules of the artificial grammar. During
testing, subjects were asked to classify as grammatical or ungrammatical 160
new sentences that followed or not the
trained combinatorial rules. Results showed that certain sequence types
elicited a late positive component which was modulated by different factors in
two distinct time windows. In an earlier window, the component was higher for
sequences which had a low or null probability of occurrence during training,
while in a later window, the component was higher for incorrect than correct
sequences. Although the late window effect was absent in subjects that were
unable to learn the trained rules, these subjects presented the earlier
positive component that was sensitive to the probability of occurrence during
training. Thus, even in the absence of knowledge, neurobiological evidence was
found showing that statistical information was acquired of the possible
combinations between items.