ELECTRICAL STIMULATION ‘TUNES’ VISUAL ATTENTION


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“Existing theories of visual attention propose that working memory representations, also known as short-term memory, typically control how attention is focused on targets in our visual field,” Geoffrey Woodman, assistant professor of psychology at Vanderbilt University and co-author of the study along with Ph.D. candidate Robert M.G. Reinhart, said. “These new findings provide evidence that long-term memory representations can also underlie our ability to rapidly configure attention to focus on certain objects, and that long-term memory performance can be sharply accelerated using electrical stimulation.”

Researchers have long known that attention could be tuned, like a radio dial, to hone in on specific features, but how and where in the brain this tuning occurs has remained an open question.

By passing very weak electrical current through the brains of healthy volunteers using a process called transcranial direct-current stimulation, researchers were able to cause the volunteers to much more quickly find target objects embedded in arrays of distracting objects. The study showed that after 20 minutes of passing safe levels of weak electrical current through electrodes placed on the head, the volunteers were able to more effectively focus attention on the searched-for targets, with dramatic increases in speed.

To determine the source of the attentional improvements, the researchers examined the recordings of the volunteers’ brain activity for the neurophysiological signatures of visual working memory and long-term memory. They found that the rapid improvement in attention was most closely related to increased activity in long-term, rather than working, memory. Their findings further indicate that long-term memory more immediately integrates information that is used to control attention than was previously thought, offering new insights into the relationship between working and long-term memory in controlling attention.

Sleep and Working Memory in Parkinson Disease.


Slow-wave sleep may be an important modulator of dopamine-related improvement in working memory among patients with PD.

To investigate whether sleep parameters are associated with improvement in working memory among patients with Parkinson disease (PD) or dementia with Lewy bodies (DLB), researchers conducted overnight polysomnography for 2 nights, followed by cognitive testing, in 53 patients with PD (most without dementia) and 10 patients with DLB. After each night of polysomnography, participants performed digit-span testing four times, beginning 2 hours after awakening and repeated every 2 to 3 hours. The digit-span forward task tested short-term memory, and the digit-span backward task tested working memory.

Sleep parameters did not differ among PD patients who were or were not taking dopaminergic medication and DLB patients. Based on the mean difference in digit-span scores from day 1 and day 2, the PD patients who were taking dopaminergic medications improved significantly on the digit-span backward task; the PD group not taking dopaminergic medications and the DLB patients did not show improvement. On the digit-span forward test, the PD patients did not improve significantly and the DLB patients’ scores declined significantly. In PD patients taking dopaminergic medication, improvement in digit-span backward performance correlated positively with the percentage of sleep that was slow-wave sleep and correlated negatively with duration of time with an oxygen saturation level <90%.

The authors concluded that (1) improvements in working memory based on digit-span backward performance can be seen in PD patients, particularly in those taking dopaminergic medications; (2) slow-wave sleep may be important for these improvements; and (3) nocturnal oxygen desaturation may impede these improvements.

Comment: These findings offer insight into the potential for cognitive improvement in patients with Parkinson disease, particularly those who do not have dementia and who are taking dopaminergic medications. Slow-wave sleep may be an important modulator of this improvement. Increasing slow-wave sleep may improve working memory in people with PD, although the clinical utility of using dopaminergic medications specifically to enhance cognition requires further investigation. Future research should examine the exact mechanisms by which dopamine may enhance working memory, determine whether dopaminergic medications increase slow-wave sleep, and clarify how nocturnal oxygen desaturation can impede this cognitive process.

Source: Journal Watch Neurology