Activation of prefrontal cortex in elderly people from Okinawa in comparison to elderly from the Nederlands

Aging is characterized by the decline of certain cognitive functions. More
specifically, key cognitive functions such as memory and executive functioning
(e.g., planning, mental flexibility, inhibition and working memory updating)
have consistently been shown to decline with age (Ardila et al., 2000).
Okinawan elderly have been reported to be in better health in comparison to
elderly in Western Europe, the United States of America, or even in comparison
to mainland Japan (Willcox & Willcox, 2014). That is, Okinawan elderly suffer
significantly less from age-related diseases, including neurodegenerative
disorders such as senile dementia (Ogura et al. 1995). Okinawa also counts with
a disproportionate number of centenarians. Indeed, by several measures of
health and longevity the Okinawans can claim to be the world's healthiest and
longest-lived people (Willcox et al., 2016). This can be attributed in small
part to genetic differences and to a larger extent to environmental variables,
such as diet (Willcox et al., 2016).
However, there is a lack of research studying functional brain characteristics
of successful aging as found in Okinawan elderly. The current study is designed
to take the first step in this regard. Specifically, we want to investigate
brain activation during executive functioning in Okinawan elderly as compared
to Western-European elderly (in this case, Dutch elderly).

We aim to investigate, for the first time, differences in frontal activation
between healthy elderly people from Okinawa and the Netherlands. We predict
that the Western European elderly will show an "MCI-light" pattern, whereas the
Okinawan elderly may have a more "youthful pattern" (i.e. need less activation
to perform the task and the activation will be lateralised more to the left
hemisphere during verbal fluency).
Another aim is to investigate memory functioning in the same groups, given its
sensitivity to aging. Memory functioning has also been investigated in elderly
people using fNIRS during memory encoding (Ferreri et al., 2014) and memory
retrieval (Obayashi and Hara, 2013).Here we will investigate differences in the
right PFC activation in elderly Western European and Okinawan subjects during
this memory retrieval of meaningless shapes task.

Eighty healthy elderly adults (age 65-80) will participate in two research
centra: Groningen (n=40) and Okinawa (n=40). They will perform two cognitive
tasks while their brain activation is recorded over the dorsolateral prefrontal
cortex (bilaterally) using fNIRS.
Cognitive tests
We will include a brief cognitive assessment to be able to characterise the
sample in terms of neuropsychological functioning. This test battery will
include the Digit Symbol Substition test (from the WAIS-I), the Trail Making
Test A and B, the Stroop color-word test and a verbal memory test (WMS
paired-associates). For all mentioned tests validated Dutch and Japanese
versions are available. In addition, the Mini-Mental State Evaluation (MMSE)
will be included as a screening measure for general cognitive functioning, and
for sake of comparison with extant research on cognitive aging and dementia.

fNIRS
The fNIRS cap will be placed on the participant*s head. Concentration changes
of oxygenated (oxyHb) and deoxygenated (Hb) haemoglobin will be recorded using
NIRS with 8 source and 8 detector optodes. Sources and detectors will be
distributed on the PFC and FC on the following positions of the international
10/20 EEG system: from F1 to F5 and F7 on the left and from F2 to F6 and F8 on
the right side.
Tasks
During fNIRS recordings, patients will perform a verbal fluency category task
(VFC) and episodic memory task.

The study will consist of two sessions: the first for explaining the study to
the participant and screening whether the all inclusion criteria are met (and
no exclusion criteria). This will usually not take longer than 30 min. The
second session concerns the neuropsychological testing and NIRS measurements,
with a total duration of 70 min. The experiment will not involve more than
minimal risks for the participants. NIRS is a standard brain mapping technique
with no known negative effects on health.
The study is not intended to benefit the participants directly. Participants
will receive a compensation for their contribution.