The prefrontal cortex (PFC) , which is most developed in humans among mammals, plays important roles in: (1) cognitive/executive control of behavior, (2) theory of mind/social behavior, and (3) emotional and motivational control of behavior. There are two kinds of functional axis within PFC: up-down and anterior-posterior axes. As for the up-down axis, the lateral PFC (upper part) is more concerned with role (1), the medial PFC (middle part) with role (2), and the ventral (orbital) PFC (lower part) with role (3). As for the anterior-posterior axis, the more anterior area within PFC is concerned with more abstract and higher information processing. The ventromedial PFC, which consists of the anterior parts of both the ven tral and medial PFC, is specifically concerned with emotion-motivation based decision-making. The most anterior part of PFC is called the frontal pole. The lateral part of the frontal pole is unique to humans, and plays the most important role in abstract and complex cognitive operations. In our studies using monkeys as subjects, we have found that: (1) there are PFC neurons that are related to social behavior by coding the winning and losing of face-to-face competition, and are considered to be related to facilitating competitive behavior, (2) the regional cerebral blood flow (as measured by PET) increases during rest compared with during cognitive task performance in the medial PFC, which is a major part of the default network, (3) do pamine, which is the most important neurotransmitter for cognitive operations in PFC, shows a decreased release in the lateral PFC and increased release in the medial PFC during rest compared with during cogni tive task performance. The increase of dopamine during rest in the medial PFC is considered to be related to internal thought processes.
It is generally thought that the mechanism underlying word-meaning deafness (WMD) is impairment in access from auditory word form to semantics. In Japanese writing, words usually written in kanji (morphograms) can alternately also be written in kana (syllabograms) . Some researchers have hypothesized that such atypically kana-written words undergo letter-by-letter conversion via the auditory word form before accessing semantics. If so, patients with WMD would have difficulty in the comprehension of atypically kana-written words as well as aurally presented words. We studied comprehension of words printed in the atypical kana-written form in a patient with WMD. A right-handed Japanese male in his early 60s presented with WMD following traumatic brain injury. He showed impaired comprehension of aurally presented words but flawless comprehension of visually pre sented words. His ability to perform the phoneme discrimination task, the auditory and written lexical decision task, and repetition of words and non-words were preserved. We considered these performances as those typical of WMD. When he was unable to comprehend aurally presented words, he sometimes wrote them down exactly and understood their meanings. We investigated whether he could comprehend words written atypically in kana letters. He pointed to the pictures that corresponded to the presented words swiftly, showing flawless acquisition of their meanings. For individual kana letters and kana-written non-words, however, his reading aloud was moderately impaired. These findings suggest that in WMD, aurally perceived word forms may neither access semantic memory nor directly retrieve visual word forms that would be understood flawlessly. By contrast, written words may access semantic memory via orthographic word form, even if they are printed in an unusual style with kana letters. Brain magnetic resonance imaging revealed abnormal-intensity areas in the anterior part of the left superior and middle temporal gyri and in the posterior superior temporal region around the superior temporal sulcus. We believe that the semantic memory was preserved, as the anterior temporal lesion was partial and due to traumatic etiology. The posterior superior temporal lesion may be responsible for the disconnection between the auditory word form and the semantic memory, while the preservation of the inferior part of the left temporal lobe may explain the flawless access from the visual word form to the semantic memory
In this study, factors associated with the arrangement of numbers on a clock drawing were investigated in cases of unilateral spatial neglect (USN) . The subjects were 32 patients with USN who could not draw a clock correctly. The transposition index (TI) , which refers to distribution rate of outer numbers in the outer number on the left and right sides, was used to analyze number placement. We analyzed the following four items: 1) the association between TI and the site of damage, 2) association between TI and laterality index (LI) in a line cancellation task, 3) reaction when numbers were placed in the counter-clockwise direction, and 4) reaction when a single number was placed. The results indicated that deviations in number placement differed according to cases and TI was widely distributed. Furthermore, in cases in which numbers were only distributed only on the right side in the outer circle, two different reactions were confirmed; some subjects placed ≤6 numbers and other subjects filled in ≥6 numbers, representing cases of parietal lobe impairment and extensive brain damage including the frontal lobe, respectively. No correlation was observed between TI and LI. When placing numbers counter-clockwise or a single number, some cases did not show any deviation in number placement. These results suggested that errors in figure placement in a clock drawing by USN cases are affected by other impairments accompanying USN.
We report the patient that shown compulsive manipulation of tools with the right leg. The patient was a right handed and right-legged man in his 60s, who had graduated from high school. He had suffered a stroke in his left hemisphere resulting in lesions in medial prefrontal cortex, as well as the genu and sple nium of the corpus callosum. He displayed right hemiplegia. However, disorders of consciousness, aphasia, visuo-spatial disorders, or amnesia were not present. His right hand displayed compulsive manipulation of tools and left hand displayed pantomime apraxia. His right leg moved compulsively, when walking, when climbing stairs, when putting on shoes, and when kicking a ball. Tools used for the symptoms were limited to tools for treating leg. The symptoms were not present in the left leg. It is suggested that the left hand, which reflected his intentions, might control the compulsive movements of the right leg. It is possible that the symptoms of his right leg were identical to the characteristics of compulsive manipulation of tools with the hand. However, further investigations of the relationship between the observed symptoms and the le sion and the grasp reflection should be conducted in the future, in order to better understand.
Recollection of routes requires mental rotation ability to construct spatial information associated with a townscape, and spatial orientation ability to represent the direction and distance of the target destination on a map. We experienced a patient who did not present heading disorientation despite suffering brain damage that impaired her mental rotation and spatial orientation abilities. The 48-year-old, right-handed female patient exhibited subcortical hemorrhage of the right parietal cortex; however, damage did not extend to the retrosplenial region. Although the patient had difficulties with mental rotation and spatial orientation tasks, she did not show heading disorientation. This case indicates that impairment of mental rotation and spatial orientation abilities is not a necessary precursor for heading disorientation.
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