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Advanced Neurology Neuroimaging regarding spatial navigation in AD

a large effect on global cognition [131] . The study suggested methodologies from clinical trials and incorporates
that VR-based cognitive stimulation is effective for behavioral and neurophysiological data are required to
neurocognitive stimulation in older adults with dementia, provide clear evidence on the effectiveness of VR-based
contributing to the maintenance of cognitive function training for cognitive and spatial navigation impairments
in patients with AD. A case study of healthy older adults in AD.
and MCI patients with unilateral vestibular hypoactivity
suggested that participants who played a VR racing game 5.2. Neuromodulation
in the treated condition (including those with MCI) Due to the unsatisfactory effect of drug therapy for AD,
showed greater improvements in vestibular function neuromodulation technology has gradually attracted
than those in the untreated condition [132] . Another study the attention of neurologists and physical therapists.
showed that the cognitive function and balancing ability Neuromodulation is defined as an intervention intended
of MCI patients showed a significant increase after to alter nervous system function using energy fields,
exposure to the VR program, which involved 20 sessions such as electricity, magnetism, or both, with the goal of
for 4 weeks, 30 min/experiment [133] . The results indicated improving psychiatric symptoms or related conditions [138] .
that the VR program is also an effective intervention for Neuromodulation techniques include deep brain
elderly individuals with MCI. stimulation (DBS), transcranial magnetic stimulation
More importantly, the VR technique also offers the (TMS), transcranial direct current stimulation (tDCS),
opportunity to create complex individualized and natural transcranial alternating current stimulation, and
simulated environments in which spatial navigation transcranial focused ultrasound (tFUS). DBS has been
impairment could be treated precisely. Kober et al. found widely used to treat Parkinson’s disease and essential
that different aspects of spatial abilities in neurologic tremors, while its application in AD is still under research.
patients with focal brain lesions were improved after In study of DBS targeting the fornix to improve cognition
VR training in comparison to their spatial performance in AD patients, Deeb et al. found that a total of 20 patients
before VR training [134] . This study showed that guided (48%) spontaneously reported having vivid experiences
passive navigation training in VR could enhance general of ostensible previous events in their lives after DBS [139] .
spatial cognition in neurological patients with spatial The high-frequency repetitive TMS (rTMS) protocol at
disorientation as well as in NCs and can thus be used in the the left DLPFC has been approved for treatment-resistant
rehabilitation of spatial navigation impairments associated depression therapy in the United States, and its effectiveness
with spatial disorientation. Moreover, VR training has been in AD has also been investigated. Of note, after treating
thought of as an advanced embodied tool for the treatment aMCI and AD patients with neuro-navigated rTMS
of spatial memory impairment in patients with AD. Serino targeting the left angular gyrus for 4 weeks, Yang et al.
et al. recruited 20 AD patients who were randomly assigned observed significant improvement in episodic memory of
to either the VR-based training group or the control group, aMCI patients and general cognition of both groups [140] .
and observed a significant improvement in long-term tDCS is the most common choice for transcranial
spatial memory after VR-based training [135] . Another study electrical stimulation for treating AD. Another recent
demonstrated that after experiencing a VR environment, study revealed that tDCS to the left DLPFC can enhance
the skill of a man at the onset of AD in navigating while verbal episodic memory performance by modulating the
driving improved noticeably in a cognitive treatment memory reconsolidation process in subjects with SCD [141] .
program based on spatial navigation [136] . Interestingly, In addition, a study suggested that without opening the
another study showed that the spatial navigation of older blood-brain barrier, the regional cerebral metabolic rate
adults was enhanced after VR-based physical exercise with of glucose in the superior frontal gyrus, middle cingulate
two-dimensional exergames [137] . gyrus, and fusiform gyrus increased, and the memory,
executive, and global cognitive function improved in
In general, VR training could serve as a promising [142]
approach to treat cognitive and spatial navigation patients with AD who received tFUS .
impairments in AD. A big advantage of VR is that it A few studies have assessed the effectiveness of
enables the development of customized cognitive exercises neuromodulation on the neural circuits of spatial navigation.
in meaningful environments, which is especially important Spatial navigation is a complex process that associates with
since cognitive training can be particularly demanding for various navigational skills, such as spatial memory. Fyock
AD patients [135] . More specifically, in a virtual environment, et al. found that tDCS could modulate spatial memory in
cognitive training can be implemented based on specific cognitively intact adults [143] . The study by Krishnamurthy
rehabilitation mechanisms. Despite the preliminary et al. revealed that tDCS enhanced functional connectivity
studies mentioned above, further research that adopts between the medial superior parietal lobule seeds and

Volume 1 Issue 2 (2022) 9 https://doi.org/10.36922/an.v1i2.145