Bilateral cingulotomy
Neuroimaging also uncovered different sub-regions in the anterior cingulate cortex itself based on their function. These studies showed that the caudal part of the anterior cingulate cortex plays a more important function in cognitive activities that involve attention, salience, interference and response competition. These results combined with electrophysiological investigation of the function of neurons in the anterior cingulate cortex have provided insights that can be used in the improvement of cingulotomy performed on patients treated for OCD. The basis behind this idea is the fact that a variation of certain tasks, Emotional Stroop tasks (ES), which have been particularly identified as exerting effects in OCD patients activate neurons in the more rostral part of the anterior cingulate cortex. Thus, theoretically if bilateral cingulotomy is performed in such patient in the rostral anterior cingulate cortex, better results should be obtained.
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.