The Japanese journal of neuropsychology

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ArticleTitle	Neural pathways and their impairments behind emerging actions and behaviors
Language	J
AuthorList	Toshiya Fukui
Affiliation	Kawasaki Memorial Hospital
Publication	Japanese Journal of Neuropsychology: 39 (1), 54-64, 2023
Received
Accepted
Abstract	This review article aims to seek electro-physiological and psychological mechanisms behind intended (with the sense of volition) vs. non-intended (without the sense of volition) motor behaviors often observed in patients with alien hand signs. The representative patient was a 41-year old woman who suffered from a ruptured pericallosal artery that resulted in the damage to the anterior and middle portions of the corpus callosum as well as the mesial frontal cortices bilaterally. Two months after the rupture, she presented left-sided ideomotor apraxia and diagonistic apraxia, diagonistic-like dyspraxia in the systemic behaviors, and an intermittent freezing phenomenon of the left arm. Extensive review of the previous publication on diagnostic apraxia revealed that there can be "two minds" contributory to antagonizing behaviors, one belonging to the normal self and the other to the anarchic left arm. For the purpose of clarifying electro-physiological and psychological backgrounds of the "two minds", we first discussed the functional neural connections of the inferior parietal lobule (IPL), pre-supplementary motor area (pre-SMA) and supplementary motor area (SMA), believed to be the primary sites for directing and determining purposeful actions/behaviors. The presence of sense of volition or sense of agency alternatively, that signifies awareness of certain behaviors belonging to the self, may depend on the appearance of electroencephalographic "Bereitschaftspotential (BP) " that was found to be generated in the SMA in the Libet's clock experiments. Conversely, the presence of BP may not suffice for the sense of volition; as normal subjects were asked to dorsiflex their right wrist at will while recording both EEG and EMG, 13 percent performed without noticing the presence of volition even in the presence of BP, especially when the subjects were day-dreaming or thinking about something irrelevant to the experimental task. In the same line, overlearned behaviors (habits) may be put into action and can overtake the intended behaviors. Normal subjects may often experience situations of the kind when they are in low attention, distracted by external stimulation or internal thoughts. It has been well documented that activation of the default mode network may elicit these states of minds. Though highly speculative, "two minds" in diagonistic apraxia may result from intermingling imbalance of the IPL-preSMA-SMA axis, BP generation, and habit presentation that may be related to abnormal status of the default mode network.
Keywords	diagonistic apraxia, (pre)supplementary motor area, inferior parietal lobule, bereitschaftspotential, default mode network