NWPF

News ArchivesRead News

Sleep improves working memory in people with Parkinson's disease

Monday August 20, 2012

Emory news center - People with Parkinson's disease performed markedly better on a test of working memory after a night's sleep, and sleep disorders can interfere with that benefit, researchers have shown.

While the classic symptoms of Parkinson's disease include tremors and slow movements, Parkinson's can also affect someone's memory, including "working memory." Working memory is defined as the ability to temporarily store and manipulate information, rather than simply repeat it. The use of working memory is important in planning, problem solving and independent living.

The findings underline the importance of addressing sleep disorders in the care of patients with Parkinson's, and indicate that working memory capacity in patients with Parkinson's potentially can be improved with training. The results also have implications for the biology of sleep and memory.

The results were published this week in the journal Brain.

"It was known already that sleep is beneficial for memory, but here, we've been able to analyze what aspects of sleep are required for the improvements in working memory performance," says postdoctoral fellow Michael Scullin, PhD, who is the first author of the paper. The senior author is Donald Bliwise, PhD, professor of neurology at Emory University School of Medicine.

The performance boost from sleep was linked with the amount of slow wave sleep, or the deepest stage of sleep. Several research groups have reported that slow wave sleep is important for synaptic plasticity, the ability of brain cells to reorganize and make new connections.

Sleep apnea, the disruption of sleep caused by obstruction of the airway, interfered with sleep's effects on memory. Study participants who showed signs of sleep apnea, if it was severe enough to lower their blood oxygen levels for more than five minutes, did not see a working memory test boost.

In this study, participants took a "digit span test," in which they had to repeat a list of numbers forward and backward. The test was conducted in an escalating fashion: the list grows incrementally until someone makes a mistake. Participants took the digit span test eight times during a 48-hour period, four during the first day and four during the second. In between, they slept.

Repeating numbers in the original order is a test of short-term memory, while repeating the numbers in reverse order is a test of working memory.

"Repeating the list in reverse order requires some effort to manipulate the numbers, not just spit them back out again," Scullin says. "It's also a purely verbal test, which is important when working with a population that may have motor impairments."

54 study participants had Parkinson's disease, and 10 had dementia with Lewy bodies: a more advanced condition, where patients may have hallucinations or fluctuating cognition as well as motor symptoms. Those who had dementia with Lewy bodies saw no working memory boost from the night's rest. As expected, their baseline level of performance was lower than the Parkinson's group.

Participants with Parkinson's who were taking dopamine-enhancing medications saw their performance on the digit span test jump up between the fourth and fifth test. On average, they could remember one more number backwards. The ability to repeat numbers backward improved, even though the ability to repeat numbers forward did not.

Patients needed to be taking dopamine-enhancing medications to see the most performance benefit from sleep. Patients not taking dopamine medications, even though they had generally had Parkinson's for less time, did not experience as much of a performance benefit. This may reflect a role for dopamine, an important neurotransmitter, in memory.

Scullin and Bliwise are planning an expanded study of sleep and working memory, in healthy elderly people as well as patients with neurodegenerative diseases.

"Many elderly people go through a decline in how much slow wave sleep they experience, and this may be a significant contributor to working memory difficulties," Scullin says.

The research was supported by the National Institute of Neurological Disorders and Stroke (R01 NS050595) and the National Institute of Aging (F32 AG041543).

Reference:
M.K. Scullin, L.M. Trotti, A.G. Wilson, S.A. Greer and D.L. Bliwise. Nocturnal sleep enhances working memory training in Parkinson's disease but not Lewy body dementia. Brain (2012) doi: 10.1093/brain/aws192

Recent News

Jul 7 - Parkinson’s Patients Have a Higher Risk of Developing Melanoma — and Vice Versa, Study Finds
Jun 27 - The rogue protein behind Parkinson’s disease may also protect your gut
Jun 26 - Do Statins Increase Risk of Parkinson’s Disease? Some Researchers Think So
Jun 22 - A Confused Immune System Could Be Behind Parkinson's Disease
Jun 21 - Predicting cognitive deficits in people with Parkinson’s disease
Jun 20 - Gym offers classes in noncontact boxing for Parkinson’s patients
Jun 19 - Human Limitations Could Prevent Us From Advancing in Science. AI Could Help.
Jun 13 - Brain Cell Transplants Are Being Tested Once Again For Parkinson's
Jun 12 - Smell Test May Sniff Out Oncoming Parkinson's and Alzheimer's
Jun 8 - Smartphones Track Motor Function in Parkinson's Disease
Jun 8 - GKC Enrolls First Patient in Personal KinetiGraph Trial as Part of NPF’s Parkinson’s Outcomes Project
Jun 8 - Low-fat dairy intake may raise Parkinson's risk
Jun 6 - Patient Voices: Parkinson's Disease
Jun 1 - World-First Trials Have Been Launched to Treat Parkinson's And Blindness With Embryonic Stem Cells
Jun 1 - LIFE Shared This Remarkable Parkinson's Disease Story in 1959.
May 24 - Survival Rates Differ Widely in Parkinson's, MSA, Lewy Bodies
May 22 - Discovery may offer hope to Parkinson's disease patients
May 15 - Study offers answers on life expectancy for people with Parkinson's disease, Lewy body dementia
May 5 - Parkinson's in a dish: Researchers reproduce brain oscillations
May 5 - ‘Hunger Hormone’ Could Help Treat Parkinson’s Disease