Self-paced Paradigm Research Articles

Effects of Working Memory Capacity and Tasks in Processing L2 Complex Sentence: Evidence from Chinese-English Bilinguals.

Two experiments aimed at investigating how working memory capacity (WMC) related to processing wh-extractions in both a grammatical judgment and a translation task by using the Operation Span task. A self-paced paradigm was used to collect response times and accuracy rates. In Experiment 1, results showed that high WMC was related to faster grammatical judgment of the critical region in subject- and object-extractions. In Experiment 2, high WMC was only related to high accuracy in translating wh-extractions. These results indicate that individual differences in WMC play a certain role during L2 sentence processing, and experimental tasks can modulate this effect.

A "one size fits all" approach to language fMRI: increasing specificity and applicability by adding a self-paced component.

We have previously established an fMRI task battery suitable for mapping the language processing network in children. Among the tasks used, the synonyms and the vowel identification task induced robust task-related activations in children with average language abilities; however, the fixed presentation time seems to be a drawback in participants with above- or below-average language abilities. This feasibility study in healthy adults (n=20) was aimed at adapting these tasks to the individual level of each patient by implementing a self-paced stimulus presentation. The impact of using a block- versus an event-related statistical approach was also evaluated. The self-paced modification allowed our participants with above-average language abilities to process stimuli much faster than originally implemented, likely increasing task adherence. A higher specificity of the event-related analysis was confirmed by stronger left inferior frontal and crossed cerebellar activations. We suggest that self-paced paradigms and event-related analyses may both increase specificity and applicability.

Sitting and standing intention can be decoded from scalp EEG recorded prior to movement execution.

Low frequency signals recorded from non-invasive electroencephalography (EEG), in particular movement-related cortical potentials (MRPs), are associated with preparation and execution of movement and thus present a target for use in brain-machine interfaces. We investigated the ability to decode movement intent from delta-band (0.1–4 Hz) EEG recorded immediately before movement execution in healthy volunteers. We used data from epochs starting 1.5 s before movement onset to classify future movements into one of three classes: stand-up, sit-down, or quiet. We assessed classification accuracy in both externally triggered and self-paced paradigms. Movement onset was determined from electromyography (EMG) recordings synchronized with EEG signals. We employed an artifact subspace reconstruction (ASR) algorithm to eliminate high amplitude noise before building our time-embedded EEG features. We applied local Fisher's discriminant analysis to reduce the dimensionality of our spatio-temporal features and subsequently used a Gaussian mixture model classifier for our three class problem. Our results demonstrate significantly better than chance classification accuracy (chance level = 33.3%) for the self-initiated (78.0 ± 2.6%) and triggered (74.7 ± 5.7%) paradigms. Surprisingly, we found no significant difference in classification accuracy between the self-paced and cued paradigms when using the full set of non-peripheral electrodes. However, accuracy was significantly increased for self-paced movements when only electrodes over the primary motor area were used. Overall, this study demonstrates that delta-band EEG recorded immediately before movement carries discriminative information regarding movement type. Our results suggest that EEG-based classifiers could improve lower-limb neuroprostheses and neurorehabilitation techniques by providing earlier detection of movement intent, which could be used in robot-assisted strategies for motor training and recovery of function.

Independent component analysis applied to self-paced functional MR imaging paradigms

Self-paced functional MR imaging (fMRI) paradigms, in which the task timing is determined by the subject's performance, can offer several advantages over commonly applied paradigms with predetermined stimulus timing. Independent component analysis (ICA) does not require specification of a timed response function, and could be an advantageous method of deriving results from fMRI data sets with varying response timings and durations. In this study normal volunteers ( N = 10) each performed two self-paced fMRI motor and arithmetic paradigms. Individual data sets were analyzed with the Infomax spatial ICA algorithm. Conventional regression analysis was performed for comparison purposes. Spatial ICA effectively produced task-related components from each of the self-paced data sets, even in a few cases where regression analysis yielded non-specific functional maps. For the motor paradigm, these components consistently mapped to primary motor areas. ICA of the arithmetic paradigm yielded multiple task-related components that variably mapped to regions of parietal and frontal lobes. Regression analysis generally yielded similar spatial maps. The multiple task-related ICA components that were sometimes produced from each self-paced data set can be challenging to identify and evaluate for significance. These preliminary results indicate that ICA is useful as an exploratory and complementary method to conventional regression analysis for fMRI of self-paced paradigms.

327. Functional MRI of implicit learning in Huntington’s disease

Patients with Huntington’s disease (HD) are impaired in some implicit learning tasks. This has been taken as evidence that the striatum plays an important role in implicit learning. Other evidence comes from several functional neuroimaging reports showing that the serial reaction time task (SRTT), a well-studied example of implicit learning, activates the ventral striatum in healthy subjects. There are conflicting reports, however, on whether patients with HD are able to learn the SRTT. To assess this, we tested mildly affected HD subjects during two versions of the SRTT to address the role of the striatum in this type of implicit learning. In the first version, the inter-stimulus interval (ISI) remained constant (1.5 sec; fixed ISI); while in the second version, the ISI depended on the subject’s reaction time (reaction time + 0.5 sec; self-paced). We found that HD patients do show robust learning in the SRTT, but only when tested with the self-paced paradigm. We are now testing HD patients and normal controls on both versions of the SRTT while using blood oxygen-dependent functional magnetic resonance imaging. fMRI results to date show activation of the right ventral striatum that is correlated with learning in both healthy controls and HD patients. More results will be reported at the meeting.

The impact of a decision process upon scalp recorded premovement potential

Twelve normal subjects were asked to select one finger after a warning signal and to move it. Using different modes of averaging the EEG responses, it is shown that: (i) the selection of a finger is accompanied by a distinct negative slow potential consisting of a rapid set-up and a following plateau which is the most prominent under the F z electrode, and (ii) the decision process, when dispersed within a large interval in repeated trials, gives rise to a slow progressive increase of negativity resembling the early component of premovement slow cortical potential from the classical self-paced paradigm.

Use of verb information in syntactic parsing: Evidence from eye movements and word-by-word self-paced reading.

We investigated whether readers use verb information to aid in their initial parsing of temporarily ambiguous sentences. In the first experiment, subjects' eye movements were recorded. In the second and third experiments, subjects read sentences by using a noncumulative and cumulative word-by-word self-paced paradigm, respectively. The results of the first two experiments supported Frazier and Rayner's (1982) garden-path model of sentence comprehension: Verb information did not influence the initial operation of the parser. The third experiment indicated that the cumulative version of the self-paced paradigm is not appropriate for studying on-line parsing. We conclude that verb information is not used by the parser to modify its initial parsing strategies, although it may be used to guide subsequent reanalysis.