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PubMed2004

Endogenous task shift processes in relapsing-remitting multiple sclerosis.

This paper reports a study that was aimed to evaluate executive functions in relapsing-remitting multiple sclerosis patients. The groups tested comprised 22 relapsing-remitting multiple sclerosis patients, and 22 non-brain damaged controls. When one is engaged in two speeded tasks, not simultaneously but with some form of alternation, it is slower to respond to an item of task A if it was preceded by an item of task B, than when it was preceded by an item of task A. Shifts between sets of cognitive operations can be internally or externally generated. Endogenous task shift refers to advance preparation for the new task. In the present study, we tested endogenous shift cost in relapsing-remitting multiple sclerosis patients. The results indicate a greater shift cost for patients than for non-brain damaged controls.

Adaptation, Psychological↗

PubMed2003

Multitasking costs in close-head injury patients. A fine-grained analysis.

The issue of whether severe close-head injury (CHI) patients suffer from disproportionate dual-task deficits compared with matched controls was investigated in two experiments. In the first experiment, either one or three masked letters were presented at the center of a monitor, followed by a pure tone at variable stimulus-onset asynchronies (SOAs). In half of the blocks of trials, the task on the letters required a delayed report of the letters at the end of each trial; in the other half of the blocks, the letters had to be ignored. The tone task always required an immediate manual response based on the tone pitch. In the second experiment, either three masked letters or three masked digits were presented with equal probability in each trial, followed by a tone at variable SOAs. The task required the delayed report of the characters only if they were letters, or ignoring the characters if they were digits. In both experiments, CHI patients and matched controls both exhibited an SOA-locked slowing of the reaction time (RT) to the tone: When characters had to be encoded for delayed report, tone RT increased progressively as SOA was decreased. The SOA effect on tone RT was more pronounced for CHI patients than for controls, suggesting that a substantial component of the slower processing time for CHI patients was related to a selective increase at a central stage of processing shared by the two tasks. Implications for models of the CHI effects on human performance are discussed.

Acoustic Stimulation↗