The DMN is active when not engaged in a goal-oriented activity and at rest. Resting DNM
is especially active when the mind is busy with introspective situations (Barkhof et al.,
2014; Mak et al., 2017). Although the posterior parts of the DMN consisting of the
posterior cingulate/precuneus and bilateral parietal cortex regions are associated with
memory functions, memory functions are not unique to DMN and the parietal regions are not
functionally homogeneous (Sestieri et al., 2011). At this point, a new network called the
parietal memory network (PMN) was defined in a study by Gilmore (Gilmore et al., 2015).
This network is a system that diverges from the posterior parts of the DMN and consists
of the middle cingulate cortex, precuneus and inferior parietal lobule/angular gyrus
structures and has overlapping regions with the DMN. This network appears to differ from
the DMN in different types of recall memory functions. Accordingly, when recalling
autobiographical information, DMN; PMN seems to be active in encoding and recall tasks
related to recognition memory (McDermott et al., 2009; Chen et al., 2017; Nelson et al.,
2013; Hu et al., 2016; Manenti et al., 2010; Kragel et al., 2016) . A double dissociation
appears to occur between these two network systems in memory processes, and furthermore,
the spacial proximity of PMN to the DMN suggests that some of the cognitive dysfunctions
attributed to the DMN of these two systems are due to PMN. The fact that PMN is
associated with memory encoding and recall functions even in different types of tasks
(de-activity in perceiving new stimulus but being active in perceiving familiar stimulus)
differentiates it from other network systems. Stimulation of the parietal region with
repetitive transcranial magnetic stimulation (rTMS) resulted in improved visual
recognition memory performance (Velioğlu et al., 2021).

The dorsolateral prefrontal cortex (DLPFC) is the central region associated with
executive functions, and damage to this region is associated with difficulty in
regulating behavioral responses, memory-retrieval, and inability to demonstrate
appropriate motor behavior. Damages in this region are associated with cognitive loss in
related areas (Liu et al., 2021; Brak et al., 2022). tDCS, on the other hand, stands out
as a promising method for patients with Covid-19 infection and subjective cognitive
complaints, and appears to act by modulating functional connectivity (Baptista, 2020;
Linnhoff, 2023; Yulug B). Increased connectivity between the hippocampus and other DMN
nodes such as the dorsal attention network, control, attention-attractiveness network,
and sensori-motor networks was detected in fMRI with atDCS stimulation (Manenti et al.,
2020; Meinzer et al., 2015). In this context, improvement in neurocognitive tests and
changes in functional imaging can be detected with stimulation of the relevant regions of
the cortex with tDCS in patients who have had Covid-19 infection and have subjective
cognitive complaints. In patients with Covid-19 infection, stimulation of the relevant
regions with tDCS resulted in improvement in cognitive functions such as working memory
and cognitive control. (Baptista, 2020; Linnhoff, 2023; Yulug B,2023). At this point,
DLPFC stimulation may also result in improved cognitive functions regarding encoding and
recall.

From this point of view, in this study -based on the studies referenced in the text-,
bilateral stimulation of the DLPFC region with anodal tDCS (atDCS) increased performance
in neurocognitive abilities, especially memory and executive functions, in patients who
had Covid-19 infection and had subjective cognitive complaints. The methodical mesh is
shaped in the context of this template, hypothesizing that it will result in In addition,
in the fMRI studies mentioned above, it is aimed to point out that tDCS stimulation
increases the coherence between DMN networks and to examine the effect of tDCS
stimulation on DMN network connectivity and connectivity with the hippocampal region with
reference to the role of PMN in patients with Covid-19 infection and subjective cognitive
complaints. From this point of view, the aim of this study is dorsolateral prefrontal
cortex (DLPFC) active tDCS (transcranial direct stimulation/transcribed) in patients with
covid-19 infection and subjective cognitive complaints.