Eunjoo Kang

Regional cerebral blood flow in children with attention deficit hyperactivity disorder: Comparison before and after methylphenidate treatment

Differences in brain activity of children with attention deficit hyperactivity disorder (ADHD) have been compared to normal healthy controls, suggesting neural correlates of cognitive/behavioral symptoms. Symptoms are improved with methylphenidate treatment but limited sources can be cited to show how brain activity in ADHD is altered after pharmacologic treatment. We investigated how long‐term oral medication of methylphenidate affects the resting regional cerebral blood flow (rCBF) in ADHD children, using single photon emission computerized tomography (SPECT). rCBF was decreased in the orbitofrontal cortex and middle temporal gyrus in the right hemisphere whereas it was increased in the dorsomedial prefrontal and somatosensory area bilaterally in drug‐naïve ADHD children compared to control child subjects. After treatment with methylphenidate, the extent of hyperperfusion in the somatosensory area was reduced and significant reduction of rCBF was found in the right striatum for the first time. Methylphenidate treatment also resulted in rCBF increase in superior prefrontal and reduction in ventral higher visual areas bilaterally. The results indicated that improving ADHD symptom after methylphenidate is associated with normalization of abnormally reduced orbitofrontal activity and abnormally increased somatosensory cortical activity. These changes were accompanied with reduced striatum activity lower than that of normal controls. These changes might be associated with improving ADHD to control attention and motor response to irrelevant environmental stimuli after methylphenidate treatment. Hum. Brain Mapp 24:157–164, 2005.

Prediction of the Clinical Outcome of Pediatric Moyamoya Disease With Postoperative Basal/Acetazolamide Stress Brain Perfusion SPECT After Revascularization Surgery

Background and Purpose— We evaluated whether basal/acetazolamide stress brain perfusion SPECT performed after revascularization surgery can predict the further clinical outcome of patients with pediatric moyamoya disease. Methods— A total of 77 (31 males, 46 females, age 6.6±3.2 years) patients with postoperative pediatric moyamoya disease who underwent basal/acetazolamide stress brain perfusion SPECT 6 to 12 months after revascularization surgery and who were followed-up >12 months after SPECT were included. Mean follow-up period after SPECT was 36±19 months. Sixty-two patients underwent bilateral ribbon encephaloduroarteriosynangiosis (EDAS), 14 bilateral EDAS, and 1 unilateral EDAS. Ordinal logistic regression analysis using 5 independent variables (infarction on preoperative MRI, age at the first operation, highest Suzuki stage on cerebral angiography, and regional cerebrovascular reserve on postoperative SPECT) against postoperative clinical outcomes was performed. Results— Fifty-one patients had preserved reserve on postoperative SPECT and their clinical outcomes were excellent (30), good (15), fair (4), and poor (2); 26 patients had decreased reserve (excellent, 1; good, 7; fair, 14; poor, 4). On ordinal logistic regression analysis, age at the first operation (P=0.033) and reserve on postoperative SPECT (P<0.001) were statistically significant. Conclusion— Basal/acetazolamide stress brain perfusion SPECT performed at 6 to 12 months after the indirect bypass operation could predict the further clinical outcome of pediatric patients with moyamoya disease. Patients with decreased cerebrovascular reserve will have remaining neurological deficit and ischemic attacks on follow-up.

Preoperative differences of cerebral metabolism relate to the outcome of cochlear implants in congenitally deaf children

In congenitally deaf children, chronological age is generally accepted as a critical factor that affects successful rehabilitation following cochlear implantation (CI). However, a wide variance among patients is known to exist regardless of the age at CI [Sarant, J.Z., Blamey, P.J., Dowell, R.C., Clark, G.M., Gibson, W.P., 2001. Variation in speech perception scores among children with cochlear implants. Ear Hear. 22, 18-28]. In a previous study, we reported that prelingually deaf children in the age range 5-7 years at implantation showed greatest outcome variability [Oh S.H., Kim C.S., Kang E.J., Lee D.S., Lee H.J., Chang S.O., Ahn S.H., Hwang C.H., Park H.J., Koo J.W., 2003. Speech perception after cochlear implantation over a 4-year time period. Acta Otolaryngol. 123, 148-153]. Eleven children who underwent CI between the age of 5 and 7 1/2 years were subdivided into a good (above 65%: GOOD) and a poor (below 45%: POOR) group based on the performance in a speech perception test given 2 years after CI. The preoperative (18)F-FDG-PET (F-18 fluorodeoxyglucose positron emission tomography) images were compared between the two groups in order to examine if regional glucose metabolic difference preexisted before the CI surgery. In the GOOD group, metabolic activity was greater in diverse fronto-parietal regions compared to the POOR group. In the POOR group, the regions related to the ventral visual pathway showed greater metabolic activity relative to the GOOD group. These findings suggest that the deaf children who had developed greater executive and visuospatial functions subserved by the prefrontal and parietal cortices might be successful in auditory language learning after CI. On the contrary, greater dependency on the visual function subserved by the occipito-temporal region due to auditory deprivation may interfere with acquisition of auditory language after CI.

Development of Korean Standard Brain Templates

We developed age, gender and ethnic specific brain templates based on MR and Positron-Emission Tomography (PET) images of Korean normal volunteers. Seventy-eight normal right-handed volunteers (M/F=49/29) underwent 3D T1-weighted SPGR MR and F-18-FDG PET scans. For the generation of standard templates, an optimal target brain that has the average global hemispheric shape was selected for each gender. MR images were then spatially normalized by linear transformation to the target brains, and normalization parameters were reapplied to PET images. Subjects were subdivided into 2 groups for each gender: the young/midlife (<55 yr) and the elderly groups. Young and elderly MRI/PET templates were composed by averaging the spatially normalized images. Korean templates showed different shapes and sizes (mean length, width, and height of the brains were 16.5, 14.3 and 12.1 cm for man, and 15.6, 13.5 and 11.4 cm for woman) from the template based on Caucasian (18.3, 14.2, and 13.3 cm). MRI and PET templates developed in this study will provide the framework for more accurate stereotactic standardization and anatomical localization.

Tractography-guided statistics (TGIS) in diffusion tensor imaging for the detection of gender difference of fiber integrity in the midsagittal and parasagittal corpora callosa

Parasagittal or off-midsagittal structures of the interhemispheric fiber tracts, i.e., the corpus callosum (CC), have a tendency to form structures which diverge from the midsagittal CC (mCC). This has led to mild inconsistencies in terms of defining parasagittal structures as region of interest for diffusion tensor imaging (DTI) analysis. Moreover, it is a labor-intensive work with potential inconsistencies and inaccuracies to define the parasagittal structure slice by slice using currently available methods. In the present study, to better cope with these problems, a new method was developed to construct the extended parasagittal structure of the CC using diffusion tensor tractography-guided (TGI) parameterization methods based on tract-length-based and parasagittal plane-based extensions. Using extended ROIs, fractional anisotropy (FA) values, as the indicators of fiber integrity in DTI, were compared between normal 14 male (25.7+/-4.7 years) and 17 female (25.9+/-4.6 years) groups for investigating the gender difference. Both TGI parameterization methods showed that men have significantly higher regional FA values than women for global CC structure areas in parasagittal and midsagittal space. In contrast, women showed significantly higher FA values in the partial areas of the rostrum, genu and splenium. Our findings based on TGI statistics (TGIS) of fiber integrity could serve as a frame of reference for assessing the group differences of the CCs in finer scale and in more extended space or parasagittal space.

Blocking of irrelevant memories by posterior alpha activity boosts memory encoding

In our daily lives, we are confronted with a large amount of information. Because only a small fraction can be encoded in long‐term memory, the brain must rely on powerful mechanisms to filter out irrelevant information. To understand the neuronal mechanisms underlying the gating of information into long‐term memory, we employed a paradigm where the encoding was directed by a “Remember” or a “No‐Remember” cue. We found that posterior alpha activity increased prior to the “No‐Remember” stimuli, whereas it decreased prior to the “Remember” stimuli. The sources were localized in the parietal cortex included in the dorsal attention network. Subjects with a larger cue‐modulation of the alpha activity had better memory for the to‐be‐remembered items. Interestingly, alpha activity reflecting successful inhibition following the “No‐Remember” cue was observed in the frontal midline structures suggesting preparatory inhibition was mediated by anterior parts of the dorsal attention network. During the presentation of the memory items, there was more gamma activity for the “Remember” compared to the “No‐Remember” items in the same regions. Importantly, the anticipatory alpha power during cue predicted the gamma power during item. Our findings suggest that top‐down controlled alpha activity reflects attentional inhibition of sensory processing in the dorsal attention network, which then finally gates information to long‐term memory. This gating is achieved by inhibiting the processing of visual information reflected by neuronal synchronization in the gamma band. In conclusion, the functional architecture revealed by region‐specific changes in the alpha activity reflects attentional modulation which has consequences for long‐term memory encoding. Hum Brain Mapp 35:3972–3987, 2013.

Altered neural circuit for working memory before and after symptom provocation in patients with obsessive-compulsive disorder

Objective:  The authors compared the neural circuits recruited for working memory (WM) in obsessive–compulsive disorder (OCD) patients both at a neutral state and at a symptom provoked state.

Neural changes associated with speech learning in deaf children following cochlear implantation

Brain plasticity was investigated, which underlies the gaining of auditory sensory and/or auditory language in deaf children with an early onset deafness after cochlear implantation (CI) surgery. This study examined both the glucose metabolism of the brain and the auditory speech learning using 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) and the Central Institute of Deaf (CID) test, respectively, both before and after the CI surgery. In a within analysis comparing the pre-CI and the post-CI PET results, CI itself resulted in an increase in the glucose metabolism in the medial visual cortex, the bilateral thalamus, and the posterior cingulate. Compared with the normal hearing controls, the brain activity of the deaf children was greater in the medial visual cortex and bilateral occipito-parietal junctions after the CI. The better speech perception ability was associated with increases in activity in the higher visual areas such as middle occipito-temporal junction (hMT/V5) and posterior inferior temporal region (BA 21/37) in the left hemisphere and associated with decreases in activity in the right inferior parieto-dorsal prefrontal region. These findings suggest that the speech learning resulted in a greater demand of the visual and visuospatial processings subserved by the early visual cortex and parietal cortices. However, only those deaf children who successfully learned the auditory language after CI used more visual motion perception for mouth movement in the left hMT/V5 region and less somatosensory function in the right parieto-frontal region.

Age-associated changes of cerebral glucose metabolic activity in both male and female deaf children: parametric analysis using objective volume of interest and voxel-based mapping.

Quantitative analysis of brain activity in the brains of children requires the establishment of age-associated norms. We investigated regional differences in age-associated changes in fluorodeoxyglucose (FDG) uptake in the developmental brains. From 87 (44 male and 43 female) deaf children from the age of 1 to 15, brain FDG positron emission tomography (PET) images were examined after spatial normalization, smoothing, and global normalization to identify brain regions showing a correlation between FDG uptake and age. Using population-based probabilistic volume of interests (VOIs), an objective VOI analysis was performed where normalized relative FDG uptake was measured and their correlations with age were examined in both genders. For the voxel-based analyses, the correlations with age were examined in a general linear model using statistical parametric mapping (SPM99). Both methods revealed that FDG uptake linearly increases with age both in the bilateral inferior prefrontal/orbitofrontal gyri and the right dorsomedial frontal gyrus and decreases in the inferior temporal gyrus and internal capsule white matter. Male children showed age-associated increases of FDG uptake in the right dorsomedial frontal gyrus, and female children in the left dorsolateral prefrontal cortex and thalamus. These changes in FDG uptake in various brain regions may suggest changes in synaptic density or regional activity resulting from normal maturation or deaf-induced adaptation. Caution should be exercised in interpreting the differences in the brain of child patients when compared with adult controls or with a different gender. Further research will be needed to examine if gender difference is manifested in the development rate of behavioral/cognitive functions in association with the age-associated changes of the right medial frontal (male) or the left dorsolateral prefrontal cortices.

The neural correlates of cross-modal interaction in speech perception during a semantic decision task on sentences: A PET study

Speech perception in face-to-face conversation involves processing of speech sounds (auditory) and speech-associated mouth/lip movements (visual) from a speaker. Using PET where no scanner noise was present, brain regions involved in speech cue processing were investigated with the normal hearing subjects with no previous lip-reading training (N = 17) carrying out a semantic plausibility decision on spoken sentences delivered in a movie file. Multimodality was ensured at the sensory level in all four conditions. Sensory-specific speech cue of one sensory modality, i.e., auditory speech (A condition) or mouth movement (V condition), was delivered with a control stimulus of the other modality whereas speech cues of both sensory modalities (AV condition) were delivered during bimodal condition. In comparison to the control condition, extensive activations in the superior temporal regions were observed bilaterally during the A condition but these activations were reduced in extent and left lateralized during the AV condition. Polymodal region such as left posterior superior temporal sulcus (pSTS) involved in cross-modal interaction/integration of audiovisual speech was found to be activated during the A and more so during the AV conditions but not during the V condition. Activations were observed in Brocas (BA 44), medial frontal (BA 8), and anterior ventrolateral prefrontal (BA 47) regions in the left during the V condition, where lip-reading performance was less successful. Results indicated that the speech-associated lip movements (visual speech cue) rendered suppression on the activity in the right auditory temporal regions. Overadditivity (AV > A + V) observed in the right postcentral region during the bimodal condition relative to the sum of unimodal speech conditions was also associated with reduced activity during the V condition. These findings suggested that visual speech cue could exert an inhibitory modulatory effect on the brain activities in the right hemisphere during the cross-modal interaction of audiovisual speech perception.