Complex Brain Networks: A Graph-Theoretical Analysis

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subjects. The authors postulate that these findings imply that a shift from a

balanced small-world structure to a weaker small-world occurs in PD.

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental

disorder with general symptoms of hyperactivity, inattention, impulsivity and

emotional dysregulation. Individuals with ADHD have abnormal interactions

in macro- and micro-scale functional networks of the brain. Functional motif

patterns in patients with ADHD is investigated in [50] to validate informa-

tion flow and interaction modes. The results showed that the interaction be-

tween right hippocampus and the right amygdala were significantly increased

which may cause the mood disorders in patients. Changes in the information

interaction of the bilateral thalamus were noted, influencing and modifying

behavioral results.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with

symptoms such as impairments in social interaction and restricted, repetitive

patterns of behavior, interests, or activities. Graph-theoretic analysis of the

weighted and unweighted structural brain networks of 14 adult male highly

functioning ASD patients and 19 matching control subjects is investigated

in [51]. The findings are that global efficiency was significantly decreased

in both unweighted and weighted networks, normalized characteristic path

length was significantly increased in the unweighted networks, and strength

was significantly decreased in the weighted networks of ASD patients. Be-

tweenness centrality of the right caudate was significantly increased in the

weighted networks in local structure analyses, and the strength of the right

superior temporal pole was significantly decreased in the unweighted ASD

patient networks.

Primary Angle Closure Glaucoma (PACG) is a chronic optic neuropathy

with a loss of retinal ganglion cells and their axons commonly affecting the el-

derly populations. Topological brain network properties of resting-state fMRI

data in 33 patients with PACG and 33 healthy controls were investigated in

[52]. The findings are that there are no significant differences between the

global topological measures between the two groups. However, significant re-

gional changes were detected in PACG patients within visual and nonvisual

(somatomotor and cognition-emotion) regions.

A recent survey on the importance of brain network hubs in neurological

disease formation is reviewed in [53]. The author notes that pathological hubs

may play a role in spreading of seizure activity in patients with epilepsy and

removal of such hubs may provide improved healing. It is also postulated

that optimal network organization is damaged in multiple sclerosis possibly

causing cognitive dysfunction and damaged hubs in stroke may be the reason

for impaired cognitive recovery. Amyloid beta and tau pathology in AD are

directly related to hyperactive hub nodes in this disorder as stated.