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Mitsutoshi Nakada

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3 papers

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YNICL Journal 2025 Journal Article

Broader functionality of language areas at the left middle frontal gyrus in patients with Broca’s area tumors

Riho Nakajima
Akitoshi Ogawa
Masashi Kinoshita
Takahiro Osada
Hirokazu Okita
Seiki Konishi
Mitsutoshi Nakada

The frontal language area (FLA; left posterior inferior frontal gyrus [pIFG] or Broca's area), critical for language processing can reorganize in response to lesion progression. While reorganization in the contralateral hemisphere is well known, how reorganization occurs within the ipsilateral hemisphere, especially in the perilesional region, remains unclear. Direct electrical stimulation (DES) during awake surgery enables identification of causal relationships between brain regions and language functions with high spatial resolution. In this study, we investigated cortical reorganization within the ipsilateral hemisphere of the FLA. Seventy-two patients with left hemisphere gliomas were studied. Patients were divided into FLA and non-FLA groups based on whether lesions included the pIFG (n = 10 and n = 62, respectively). All patients underwent DES during a picture-naming task, as recommended by awake surgery guidelines. A subset also underwent resting-state functional MRI (rsfMRI) before surgery to calculate betweenness centrality, an index of network importance of brain areas. DES revealed that the pIFG exhibited positive (impaired) responses to the picture-naming task in both groups. Notably, the frequency of positive responses in the middle frontal gyrus (MFG) was significantly higher in the FLA group than in the non-FLA group. RsfMRI-based network analyses revealed that two areas in the MFG, one in the anterior part and the other in the posterior part, showed higher centrality than surrounding frontal areas in both groups, especially the posterior one. These results suggest that language areas can be observed in the perilesional MFG regions following tumor progression, and raise the possibility that network hubs contribute to maintaining cognitive functions after brain lesions.

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YNICL Journal 2022 Journal Article

Posterior-prefrontal and medial orbitofrontal regions play crucial roles in happiness and sadness recognition

Riho Nakajima
Masashi Kinoshita
Hirokazu Okita
Mitsutoshi Nakada

The core brain regions responsible for basic human emotions are not yet fully understood. We investigated the key areas responsible for emotion recognition of facial expressions of happiness and sadness using data obtained from patients who underwent local brain resection. A total of 44 patients with right cerebral hemispheric brain tumors and 33 healthy volunteers were enrolled and subjected to a facial expression recognition test. Voxel-based lesion-symptom mapping was performed to investigate the relationship between the accuracy of emotion recognition and the resected regions. Consequently, trade-off relationships were discovered: the posterior-prefrontal region was related to a low score of happiness recognition and a high score of sadness recognition (disorder-of-happiness group), whereas the medial orbitofrontal region was related to a low score of sadness recognition and a high score of happiness recognition (disorder-of-sadness group). The emotion recognition score in both the happiness and sadness disorder groups was significantly lower than that in the control group (p = 0.0009 and p = 0.021, respectively). Interestingly, the deficit in happiness recognition was temporary, whereas the deficit in sadness recognition persisted during the chronic phase. Using graph theoretical analysis, we identified structural connectivity between the posterior-prefrontal and medial orbitofrontal regions. When either of these regions was damaged, the tract volume connecting them was significantly reduced (p = 0.013). These results indicate that the posterior-prefrontal and medial orbitofrontal regions may be crucial for maintaining a balance between happiness and sadness recognition in humans. Investigating the clinical impact of certain area resections using lesion studies combined with connectivity analysis is a useful neuroimaging method for understanding neural networks.

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YNICL Journal 2020 Journal Article

Does the superior fronto-occipital fascicle exist in the human brain? Fiber dissection and brain functional mapping in 90 patients with gliomas

Xiaoliang Liu
Masashi Kinoshita
Harumichi Shinohara
Osamu Hori
Noriyuki Ozaki
Mitsutoshi Nakada

The presence of the superior fronto-occipital fascicle (SFOF) has been reported in the Rhesus monkey; however, it is a subject of controversy in humans. The aim of this study is to identify the SFOF using both in vitro and in vivo anatomo-functional analyses. This study consisted of two approaches. First, one acallosal brain and 12 normal postmortem hemispheres (five left and seven right sides) were dissected under a microscope using Klingler's fiber dissection technique. We focused on the medial subcallosal area superior to the Muratoff bundle, which has been indicated as a principal target area of the SFOF in previous studies. Second, 90 patients underwent awake craniotomy for gliomas with direct electrical stimulations. Functional examinations for visual, ataxic, and cognitive tasks were performed and 453 positive mapping sites were investigated by voxel-based morphometry analysis to establish the functions of the SFOF. The corticostriatal fibers, or the Muratoff bundle, and thalamic peduncle fibers joined in the area of the caudate nucleus, making thalamic peduncle/ corticostriatal bundles, which ran antero-posteriorly in the anterior subcallosal area and radiated from the caudate superior margin in the posterior subcallosal area. However, no SFOF fiber bundle crossed perpendicular to the thalamic peduncle/ corticostriatal bundles in the posterior subcallosal area. In the acallosal hemispheres, Probst bundles were confirmed and the subcallosal areas did not show a specific organization different from the normal brain. Hence, we could not detect a long and continuous association fascicle connecting the frontal lobe and occipital or parietal lobe in the target areas. Furthermore, in the in vivo functional mappings of awake surgery and voxel-based morphometry analysis, eight positive points on the SFOF were selected from the total 453 positive points, but their functions were not related with visual processing and spatial awareness, as has been reported in previous studies. In conclusion, in the present study we attempted to investigate the existence of the SFOF using an anatomical and functional approach. According to our results, the SFOF may not exist in the human brain.

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