The Japanese journal of neuropsychology

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ArticleTitle	The role of medial frontal cortices in the mechanism of "conflict of intentions"
Language	J
AuthorList	Takashi Nishikawa
Affiliation	School of Comprehensive Rehabilitation, Osaka Prefecture University
Publication	Japanese Journal of Neuropsychology: 26 (1), 35-46, 2010
Received
Accepted
Abstract	"Conflict of intentions" is a rare callosal disconnection symptom in that patients are unable to perform intended whole body actions because another intention emerged in competition with the original one. This symptom is regarded as a fragment of diagonistic dyspraxia, although it can occur independently of intermanual conflict. The author presented three own cases of conflict of intentions, and discussed the role of medial frontal cortices involved in the mechanism of this symptom. All the patients have no significant lesion in the medial frontal cortices including the supplementary motor areas. Conflict of intentions manifests several weeks after callosal damage, and often appears along with the resolution of such involuntary hand actions as intermanual conflict or compulsive manipulation of tools. These symptomatic features suggest that it arises during the reorganization of hemispheric function after callosal disconnection. Each hemisphere would attain an increase of function above that in the former, intact state, because both hemispheres are released from regulation by the contralateral side. Then, the intrinsic traits of each hemisphere would be independently exaggerated and this will lead to a state of interhemispheric competition, whereas the preserved medial control system prevents involuntary manual responses by maintaining a balance with the lateral premotor system within each hemisphere. Involuntary actions limited to one hand are not accompanied by a conscious sense of intention, even if the dominant hand is involved. Thus, a conscious experience of self decided action may be produced only when the hemisphere is functionally well preserved and wholly activated including not only the responsive system but also the inhibitory system. In normal behaviour, it may be that the specialised characteristics of the two hemispheres act complementarily to achieve consistency when pursuing a purpose as well as flexibility when it is necessary to respond to environmental changes: information from both hemispheres would be integrated to dismiss either of the alternatives or to set up a new intention by combining both of them. In the case of conflict of intentions, because of the lack of interhemispheric harmonisation due to callosal disconnection and, moreover, the traits of each hemisphere being exaggerated, the tendencies of the two hemispheres would remain disintegrated. Such double, often contrary, behavioural tendencies may sometimes simultaneously enter the patient's awareness. These pathologies in conflict of intentions suggest that medial frontal cortices do not originally exist as conscious agents who cause and control intentional actions, but may come to generate the senses of agency in consequence of those unconscious inhibitory effects on involuntary actions through enduring a certain period of conflicting state.
Keywords	conflict of intentions, diagonistic dyspraxia, corpus callosum, supplementary motor area, sense of agency