Does ventrolateral prefrontal cortex help in searching for the lost key? Evidence from an fNIRS study
The Key Search Task (KST) is a neuropsychological
test that requires strategies for searching a lost key in an
imaginary field. This request may involve different cognitive
processes as mental imagery and navigation planning. This
study was aimed at investigating, by a twenty-channel functional
near-infrared spectroscopy (fNIRS) system, the hemodynamic
response (i.e., oxygenated-hemoglobin (O2Hb) and
deoxygenated-hemoglobin (HHb) changes) of the prefrontal
cortex in navigation planning. A right ventrolateral prefrontal
cortex (rVLPFC) activation during the KST was hypothesized.
Thirty-eight volunteers performed the KST and a
Control Task (CT), the latter requiring the volunteers to mark
the X letter. An activation (i.e., increase/decrease in O2Hb/
HHb) of: 1) rVLPFC during the KST execution, and 2) bilateral
dorsolateral prefrontal cortex (DLPFC) during the CT
execution was found. The present study provides a contribution
in localizing the rVLPFC as the critically active region,
within the frontal lobes, that was found maximally activated
during mental navigation in the mind’s eye of healthy participants
while performing the KST. Considering the contribution
of rVLPFC in spatial navigation, its activation suggests
that the KST could be adopted in the clinical routine for investigating
navigation planning. Compared to other neuroimaging
techniques, fNIRS (with its relatively low physical constraints)
contributes to better clarifying the role of rVLPFC in
some aspects of human navigation. Therefore, the combined
use of the fNIRS and the KST could be considered as an
innovative and valid tool to evaluate fundamental functions
for everyday life, such as spatial navigation planning.