| |
Abstract:
A novel serial search task was used to obtain combined
behavioral, electrophysiological, and neuropsychological evidence
for implicit learning of spatio-motor and nonspatial phoneme
sequences. On each trial a visual array of four letters (e.g.,
CDBA) was presented, followed by the auditory presentation of a
single letter (e.g., D). Participants indicated the location of the
auditory letter in the visual array by pressing one out of four
response keys. The visual array was changed from trial to trial
such that both the locations and the auditory letters followed
repeating, but uncorrelated sequences. Occasionally inserted
deviants that violated either the spatio-motor or the phoneme
sequence produced reliable and increasing reaction time costs
compared to regular events. This was true even when participants
with explicit knowledge were excluded. Moreover, learning effects
for the two sequences were uncorrelated across participants. In an
electrophysiological study, event-related potentials for deviants
showed an enhanced early negativity compared to regular events.
This deviance-related negativity exhibited a left-frontal maximum
for phoneme deviants and a right-central maximum for spatial
deviants. Finally, patients with left-anterior lesions, who
suffered from Broca's aphasia, did learn the spatio-motor, but not
the phoneme sequence. These results are consistent with the
assumption that implicit learning of spatial and nonspatial
sequences is mediated by experience-dependent changes that take
place within separate domain-specific representation
systems.
|
