Bilateral cingulotomy
Studies in patients that were a subject to bilateral cingulotomy, that involved fMRI analyses, showed that the anterior cingulate cortex has a key role in cognitive control and is highly likely to be involved in the control of attentional response, whereas the dorsal part of that region of the brain was not identified to be involved in such a process, although this is still under dispute. The function of the dorsal part of the cingulate cortex was connected to the sorting out and processing of conflicting information signals. In addition, neuroimaging studies also indicated that the anterior cingulate cortex participates in the modulation of cortical regions that are of higher order as well as sensory processing areas.
Bilateral cingulotomy
Moreover, OCD has been associated with a malformation of the basal ganglia. The function of this part of the human brain has been mapped to be composed of fiber tracks associated with numerous parallel cortico-striato-thalamocortical circuits (CSTC), which are involved in sensorimotor, motor, oculomotor as well as the cognitive processes that are manifested by the limbic system. This pathway involves GABAergic inhibitory projections that serve as one of the means of communication between the different structures involved. It has been hypothesized that some forms of OCD are a result of disinhibition of one or several of the circuits that operate in the CSTC. This is also indicated by a finding that showed a significant decrease in intracortical inhibition in OCD patients. Thus, lesions in the anterior cingulate cortex might contribute to the lessening of the disinhibition effect. This theory has been confirmed by another study which assessed the cortical inhibitory and excitatory mechanisms in OCD. The study measured the excitability of motor cortex, as well as intracortical inhibition in OCD patients and a control of healthy individuals. The results showed a significant decrease in intracortical inhibition, which resulted in a slowdown of interstimulus intervals by 3 ms.
In addition to its proximity to and association with the limbic system and the amygdala in particular, which plays a key role in emotional experience, the anterior cingulate cortex shares afferent and efferent pathways with a number of thalamic nuclei as well as the posterior cingulate and part of some parietal, frontal and supplementary motor cortex. All these underline the high likelihood that the anterior cingulate cortex must be linked to OCD.