Page 12 - JCBP-1-1

Journal of Clinical and
Basic Psychosomatics Brain MRI alterations in MDD

biomarkers for depression treatment [41-45] . Several directed activity; the thalamus is involved in processing
studies have demonstrated an obvious association emotional distress, and its altered function may lead to
between decreased amygdala activation and positive suicidal ideation in patients . The postcentralgyrus is
[58]
treatment outcomes in emotional tasks involving the somatosensory information center of the brain that
negative stimuli [46,47] . Improved treatment outcomes have receives and integrates external stimuli, and the precentral
been associated with higher activation of the subgenual and paracentralgyri are associated with somatomotor
anterior cingulate cortex (ACC) in the studies using function [58,59] .
the gender discrimination task of sad faces, the higher The network interactions might be broadly involved
activation of the pregenual ACC for sad versus happy in MDD mechanisms. The posterior DMN is implicated
faces in a backward masking paradigm [48,49] , the higher in consciousness and memory processing through its
activation of the pregenual ACC to negative pictures [50] , connections with hippocampal formation, spontaneous
and the lower activation in the dorsal ACC during thoughts, and mind-wandering. The pregenual ACC,
negative word processing [51] . Godlewska et al. also found parahippocampal gyrus, and DMN activity has been
decreased activation of the dorsal ACC while viewing related to increased self-referential processing, particularly
fearful faces, compared to viewing happy faces 1 week with spontaneous and self-related negative thoughts .
[60]
after starting treatment, predicted treatment response [47] . Changes in the ReHo and ALFF values and functional
A task-fMRI study focusing on a facial expression alterations of the DMN, CEN, and SN may lead to
recognition task revealed increased activation in the abnormalities in spontaneous activity and connectivity
left parietal lobe, pre-central gyrus, and bilateral insula functions in cognitive and emotion-processing brain
in patients with MDD after 1 week of treatment [52] . In regions, which coincide with clinical symptoms such
another study, following 4 weeks of treatment, patients
with MDD showed significantly increased activation as cognitive impairment and depressed mood in MDD.
Although results of FC within the DMN in patients with
in the anterior cingulate gyrus, dorsomedial prefrontal MDD are heterogeneous, the previous fMRI analysis has
cortex, dorsolateral prefrontal cortex, and basal ganglia shown that the severity of depression could modulate
during a facial expression recognition task [53] . However,
Reed et al. found significantly reduced activation DMN in depressive patients, and the severity of rumination
[55,60]
in the frontal, temporal, precuneus, and posterior may be predicted by the relative dominance of DMN .
cingulate gyrus bilaterally in patients with MDD after It has been indicated that the anterior DMN shows
hyperconnectivity with the insula and amygdala, while the
the treatment. The differences between the studies may
be attributed to variations in the stimulation tasks, the posterior DMN shows hypoconnectivity with cognitive
[55,61,62]
heterogeneity of MDD, and differences in the sensitivity control areas .
of patients to spines. Antidepressants may improve the functional activity
of relevant brain regions and restore the regulation
4.2. Possible mechanisms of function albrain of emotion processing by altering relevant excitatory
changes synaptic functions or increasing the concentration
Different brain regions have been highlighted for distinct of neurotransmitters such as 5-HT and NE in the
function involvement during MDD. For example, the synaptic gap, inhibiting the excitation of dopamine
right superior frontal gyrus is associated with executive neurons, regulating neuronal connectivity functions,
functions. It controls internally contradictory impulse and promoting neuroplasticity and anti-inflammatory
responses, while the dorsolateral prefrontal lobe is a key effects [4,7,25,26] so that the resting-state FC of the DMN,
area for regulating attention, cognitive control, motivation, CEN, and SN gradually returns to normal. Moreover,
and emotion [54,55] . The right inferior frontal gyrus triangle the symptoms of enhanced negative self-concern, self-
is an important component of the dorsolateral prefrontal regurgitation, abnormal cognition, and emotional control
lobe. The prefrontal cortex is associated with emotion and caused by abnormalities in FC are improved. However,
cognitive regulation and its abnormal function causes the reduced ReHo and ALFF values in the precuneus
negative emotions and reduces cognitive performance . following anti depressant treatment could be attributed
[56]
The cingulate gyrus is associated with emotion and self- to the extended duration (8 – 12 weeks) required for the
control; the precuneus regulates self-awareness and effects of antidepressants to become evident. Further
memory and is associated with low self-esteem and investigation involving long-term treatment is necessary
memory loss in patients . The hippocampus is associated to investigate the abnormal changes in the precuneus
[57]
with memory function, regulating emotional responses, activity. Notably, activation in brain regions such as the
executive function, sensorimotor integration, and goal- parietal cortex and insula imparts task-related changes

Volume 1 Issue 1 (2023) 4 https://doi.org/10.36922/jcbp.0896