Biomedical subjects

Todd D Watson

Publications and source records attributed to Todd D Watson.

5 recordsLinked to original sources

PubMed2006

Event-related potential correlates of extradimensional and intradimensional set-shifts in a modified Wisconsin Card Sorting Test.

Event-related potentials (ERPs) were recorded in healthy adult participants during the performance of a modified version of the Wisconsin Card Sorting Test that was designed to isolate the effects of extradimensional (ED) and intradimensional (ID) set-shifts. ERP averages were created for ED- and ID-Shift trials, as well as for the 5th trial in each block (Maintain-Rule). Differences in sensory and longer latency ERP components were found between the ED- and ID conditions, and between the two shift conditions and the Maintain-Rule trials. Consistent with the previous literature, these data indicated that ED- and ID-Shifts require different levels of neural resources. A secondary goal of this experiment was to use the excellent temporal resolution of ERPs to examine the neural correlates of various other aspects of the performance of a set-shift task, including differences between correct shifts and the commission of errors, and the differences between the reception of correct and error feedback. Comparisons were made between ERP averages to correct ED-Shift trials and ED-Error trials, and to feedback following a correct ED-Shift compared to feedback following an error. As expected, ERP differences were found between correct trials and error trials, and between the ERP correlates of receiving different types of feedback. Overall, these data further indicate the utility of using ERP methodology to study various aspects of complex neuropsychological paradigms.

Adolescent↗

PubMed2006

Time course of processes underlying picture and word evaluation: an event-related potential approach.

A substantial body of research suggests that the cognitive mechanisms for picture and word processes are functionally and anatomically distinct. In spite of significant advancements in the understanding of pictures and words, the electrophysiological activities mediating these processes are not well known. To address this issue, we examined event-related brain potentials (ERPs) to pictures and their printed names in a modified dual-target oddball task. ERPs were recorded while participants classified schematic pictures and their corresponding names into target and nontarget categories. Results showed that pictures and words were associated with electrophysiological responses that differed temporally and topographically. In comparison to words, P300s to pictures were characterized by shorter latency and larger amplitude at parietal electrodes. In contrast, words produced greater P200 amplitude at frontal areas. The results are consistent with the view that categorization of pictures is faster than words. Findings are discussed in relation to stimulus evaluation and the time course for picture and word classification.

Adult↗

PubMed2005

Event-related potentials as an index of similarity between words and pictures.

This report examines the ERP correlates of processing nontarget stimuli that are conceptually, but not perceptually, similar to a target. In two studies, the P300 component was examined in healthy adults during a multistimulus oddball paradigm. The stimuli were pictures of five objects and their five corresponding names. Participants were required to keep a mental count of number of target presentations. In Experiment 1, the target was the word "globe." Both the word target and the nontarget picture of the globe elicited large P300s, though the P300 to the picture was smaller in amplitude. No other stimulus elicited a prominent P300. In Experiment 2, the target was the picture of the globe, and the word was considered to be the related nontarget. Again, the target elicited a large P300. However, in this case the related nontarget stimulus failed to elicit a P300. The relevance of the data to theories of word/picture processing is discussed.

Adult↗

PubMed2003

Age differences in factor analysis of EEG.

This study examined age differences in the factor structure of EEG using a 128-electrode system. Running EEG records were obtained from healthy younger and healthy older adults before, during, and after they performed a 13-minute Continuous Performance Task. Factor analyses were conducted on each five-second segment of EEG data by treating the voltages obtained at each electrode site as variables and each measurement epoch as a case. Results showed that the EEG records of older adults yielded significantly more factors than those of younger adults in every task condition. In addition, eigenvalues for the first common factor derived from EEG data sets were significantly larger in the EEG recordings of younger adults than older adults. The results are interpreted to indicate a greater degree of complexity in the spatial distribution of EEG activity in older adults, possibly reflecting an age-related decrease in the degree of coordination among cortical areas.

Acoustic Stimulation↗

PubMed2002

Different activation dynamics in multiple neural systems during simulated driving.

Driving is a complex behavior that recruits multiple cognitive elements. We report on an imaging study of simulated driving that reveals multiple neural systems, each of which have different activation dynamics. The neural correlates of driving behavior are identified with fMRI and their modulation with speed is investigated. We decompose the activation into interpretable pieces using a novel, generally applicable approach, based upon independent component analysis. Some regions turn on or off, others exhibit a gradual decay, and yet others turn on transiently when starting or stopping driving. Signal in the anterior cingulate cortex, an area often associated with error monitoring and inhibition, decreases exponentially with a rate proportional to driving speed, whereas decreases in frontoparietal regions, implicated in vigilance, correlate with speed. Increases in cerebellar and occipital areas, presumably related to complex visuomotor integration, are activated during driving but not associated with driving speed.

Adult↗