Networking and structural differences

From: <a href="https://neurocritic.blogspot.com/2011/04/mental-imagery-and-right-parietal-lobe.html">The Neurocritic: Mental Imagery and the Right Parietal Lobe in OCD</a>

Neuroanatomical circuit models of the underlying brain dysfunction have implicated fronto-striatal loops that control thoughts and actions. For example, OCD has been associated with overactivity in the <a href="http://en.wikipedia.org/wiki/Orbitofrontal_cortex">orbitofrontal cortex</a> (<a href="http://www.ncbi.nlm.nih.gov/pubmed/18061263">Menzies et al., 2008</a>), overactive error monitoring processes in the <a href="http://en.wikipedia.org/wiki/Anterior_cingulate_cortex">anterior cingulate cortex</a> (<a href="http://www.ncbi.nlm.nih.gov/pubmed/15691530">Fitzgerald et al., 2005</a>), and reduced activation in dorsal prefrontal-striatal regions during planning (<a href="http://www.ncbi.nlm.nih.gov/pubmed/15753243">van den Heuvel et al., 2005</a>) and task switching (<a href="http://www.ncbi.nlm.nih.gov/pubmed/18065438">Gu et al., 2008</a>). In summary, OCD has been conceptualized as an impulse control disorder marked by a breakdown of high-level executive control over behavior.

However, a new study by <a href="http://dx.doi.org/10.1016/j.bandc.2011.03.020">Koçak et al. (2011)</a> has expanded the range of cognitive processes and brain regions that might be implicated in OCD.

From: <a href="https://www.sciencedirect.com/science/article/pii/S2444866416300319">Cognitive and emotional impairments in obsessive–compulsive disorder: Evidence from functional brain alterations - ScienceDirect</a>

OCD patients show alterations in connectivity in regions associated with the CSTC pathways, with evidence for a dissociation/imbalance between patterns of connectivity in the dorsal versus ventral CSTC loops.

</dd>

There is also evidence for connectivity abnormalities between CSTC loops and other brain regions.

</dd>

Different nodes of the DMN showed altered connectivity in OCD.

</dd>

There is evidence for altered connectivity in several resting state brain networks (e.g., top-down network, salience network, fronto-parietal network).

</dd>

Impaired inhibitory control in OCD has been associated with functional abnormalities in the CSTC loops, and fronto-parietal networks. Additionally, anterior cingulate seems to be particularly active in overmonitoring performance in these tasks.

</dd>

OCD's cognitive flexibility impairments are related with decreased activations not only in the OCD loops but also extended temporal, parietal and <a title="Learn more about Occiput" href="https://www.sciencedirect.com/topics/medicine-and-dentistry/occiput">occipital regions</a>.

</dd>

Working memory performance in OCD patients is affected by functional abnormalities in the CSTC and frontal parietal networks. Again, the dorsal anterior cingulate seems to modulate the activity the remaining brain regions during the course of working memory tasks.

</dd>

The predominance of fear/defensive affective motivational system is associated with increased amygdala responsiveness but also increased activity in additional brain regions associated with perceptual (e.g., parietal, occipital) and higher level cognitive processing (e.g. prefrontal, temporal).

</dd>

Increased activity in the insula seems to be a brain marker of increased OCD sensitivity to disgust, while propensity for shame and guilt may be attributed to an increase in widespread brain (e.g. frontal, limbic, temporal) and a deactivation in other regions such as the middle frontal gyrus and inferior parietal <a title="Learn more about Lobe (anatomy)" href="https://www.sciencedirect.com/topics/medicine-and-dentistry/lobe-anatomy">lobe</a> (shame) and anterior cingulate (guilt).

</dd>

</dl>

The studies reported here bring evidence for regional and <a title="Learn more about Resting state fMRI" href="https://www.sciencedirect.com/topics/medicine-and-dentistry/resting-state-fmri">connectivity functional</a>abnormalities evident during resting state and task conditions that may help understand OCD as both an emotional (i.e., anxiety) and cognitive (i.e. inhibitory control) disorder with a diversity of psychological and symptomatic expressions. Despite this evidence little is known about the specificity of the present results for OCD. It remains to be known if these findings are transdiagnostic to other psychiatry disorders (particularly within the OCRD and anxiety spectra). Additionally, distinct OCD subtypes (e.g., washers, hoarders, checkers) and <a title="Learn more about Endophenotype" href="https://www.sciencedirect.com/topics/medicine-and-dentistry/endophenotype">endophenotypes</a> (genetic risk versus environmental) were reported to be associated with specific brain activation patterns.<a class="workspace-trigger" href="https://www.sciencedirect.com/science/article/pii/S2444866416300319#bib0865" name="bbib0865">86</a>, <a class="workspace-trigger" href="https://www.sciencedirect.com/science/article/pii/S2444866416300319#bib0870" name="bbib0870">87</a> Future studies should try to differentiate distinct OCD subtypes and endophenotypes as well as including as comparison groups from other psychiatry disorders within and outside the OCRD and anxiety spectra.

From: <a href="https://www.nature.com/articles/tp201722">Abnormal white matter structural connectivity in adults with obsessive-compulsive disorder | Translational Psychiatry</a>

In conclusion, the present study showed widespread microstructural alterations in the brains of patients diagnosed with OCD, predominantly in the CC and SLF, areas which may have important roles in OCD pathogenesis. Our findings suggest that OCD may involve abnormalities affecting a broader network of regions than commonly believed, that is, beyond the frontal–striatal–thalamic circuitry. Longitudinal studies are needed to elucidate the underlying mechanisms of WM changes in patients with OCD.