Place de l'inhibition dans le trouble obsessionnel-compulsif

On the theoretical level, it is the model of attention that was used in explaining the OCD hypothesis. In the model of attention control of action, described by Norman, Shallice and Burgess, three systems were emphasized: one that takes care of routine actions, and the second that takes over the first in situations where automatic activities must stop in order to establish an attention control and therefore inhibit automatic responses. When selection of everyday and automatic activities is not sufficient to accomplish a task, it is the third system, that of cognitive control, which takes over. This supervisory attentional system operates in non-routine and ambiguous activities. The cognitive control is charged with detecting potential or emitted cognitive errors and resolving ambiguous situations. Neurocognitive studies show that cingular anterior cortex and prefrontal lateral cortex are engaged in ambiguous and conflicting situations. These two regions are considered essential for inhibition of routine actions, adjustment to change and, more generally, for an efficient and flexible behaviour. Repetitive nature of verification rituals in OCD could be explained in terms of lack of relationship between two systems, leaving in action the one that regulates automatic activities. Therefore, the rituals are considered to be under particular influence of the system which, being in charge of automatic actions, has a deficit in disengagement. Another model of attention, described by Posner, gives a further explanation of OCD. Mental inhibition has the capacity to treat information, either by applying strategies to control it (i.e. trying not to remember an unpleasant event) or leaving it to automatic control (i.e. incapacity to experience an emotion in relation to a particular event). In this way, the effort to suppress an intrusive thought is considered as controlled and deliberate cognitive treatment of emotionally charged information. In OCD, in the context of heightened anxiety, the assumed negative valence of information would influence habitual suppression of thought during controlled treatment. As a result, controlled efforts to suppress obsessions in emotionally stressful situations, would lead to the production of repetitive thoughts, as controlled treatment of information has failed in this action. On a clinical and experimental level, these studies have led to a better understanding and conceptualization of OCD. In spite of some conflicting results, there are concordant data in favour of hypotheses of the role of sub-cortical and frontal regions and their function in inhibition/desinhibition implied in the onset and maintenance of OCD. Functional neuroimagery anomalies are also in favour of the role of sub-cortical-frontal region in clinical manifestations of OCD. They are often associated with low performance in cognitive tasks, especially those implying frontal functions, which are, in turn, dependent on a necessary level of attention in order to guide or inhibit motor and cognitive programs.