High-quantum yield alloy-typed core/shell CdSeZnS/ZnS quantum dots for bio-applications.

BACKGROUND: Quantum dots (QDs) have been used as fluorophores in various imaging fields owing to their strong fluorescent intensity, high quantum yield (QY), and narrow emission bandwidth. However, the application of QDs to bio-imaging is limited because the QY of QDs decreases substantially during the surface modification step for bio-application. RESULTS: In this study, we fabricated alloy-typed core/shell CdSeZnS/ZnS quantum dots (alloy QDs) that showed higher quantum yield and stability during the surface modification for hydrophilization compared with conventional CdSe/CdS/ZnS multilayer quantum dots (MQDs). The structure of the alloy QDs was confirmed using time-of-flight medium-energy ion scattering spectroscopy. The alloy QDs exhibited strong fluorescence and a high QY of 98.0%. After hydrophilic surface modification, the alloy QDs exhibited a QY of 84.7%, which is 1.5 times higher than that of MQDs. The QY was 77.8% after the alloy QDs were conjugated with folic acid (FA). Alloy QDs and MQDs, after conjugation with FA, were successfully used for targeting human KB cells. The alloy QDs exhibited a stronger fluorescence signal than MQD; these signals were retained in the popliteal lymph node area for 24 h. CONCLUSION: The alloy QDs maintained a higher QY in hydrophilization for biological applications than MQDs. And also, alloy QDs showed the potential as nanoprobes for highly sensitive bioimaging analysis.

Gamma analysis dependence on specified low-dose thresholds for VMAT QA.

The American Association of Physicists in Medicine Task Group 119 instructed institutions to use a low-dose threshold of 10% or a region of interest determined by the jaw setting when they collected gamma analysis quality assurance (QA) data for the planar dose distribution. However, there are no clinical data to quantitatively demonstrate the impact of the low-dose threshold on the gamma index. Therefore, we performed a gamma analysis with various low-dose thresholds in the range of 0% to 15% according to both global and local normalization and different acceptance criteria (3%/3 mm, 2%/2 mm, and 1%/1 mm). A total of 30 treatment plans--10 head and neck, 10 brain, and 10 prostate cancer cases--were randomly selected from the Varian Eclipse treatment planning system (TPS). For the gamma analysis, a calculated portal image was acquired through a portal dose calculation algorithm in the Eclipse TPS, and a measured portal image was obtained using an electronic portal-imaging device. Then, the gamma analysis was performed using the Portal Dosimetry software (Varian Medical Systems, Palo Alto, CA). The gamma passing rate (%GP) for the global normalization decreased as the low-dose threshold increased, and all low-dose thresholds led to %GP values above 95% for both the 3%/3 mm and 2%/2 mm criteria. However, for the local normalization, %GP for a low-dose threshold of 10% was 7.47%, 10.23%, and 6.71% greater than the low-dose threshold of 0% for head and neck, brain, and prostate for the 3%/3 mm criteria, respectively. The results indicate that applying the low-dose threshold to global normalization does not have a critical impact on patient-specific QA results. However, in the local normalization, the low-dose threshold level should be carefully selected because the excluded low-dose points could cause the average %GP to increase rapidly.

Tumor targeting and imaging using cyclic RGD-PEGylated gold nanoparticle probes with directly conjugated iodine-125.

Radioactive iodine-labeled, cyclic RGD-PEGylated gold nanoparticle (AuNP) probes are designed and synthesized for targeting cancer cells and imaging tumor sites. These iodine-125-labeled cRGD-PEG-AuNP probes are stable in various conditions including a range of pHs and high salt and temperature conditions. These probes can target selectively and be taken up by tumor cells via integrin αvß3-receptor-mediated endocytosis with no cytotoxicity. The probes show a significant increase in the avidity of αvß3 integrin compared to the corresponding free cRGD peptides. In-vivo SPECT/CT imaging results show that the iodine-125-labeled cRGD-PEG-AuNP probes can target the tumor site as soon as 10 min after injection, and also that cyclic RGD peptides are needed for efficient and long-term in-vivo monitoring. The results suggest that the probes circulate through the whole body, including renal filtration, and are excretable. These promising results show that radioactive-iodine-labeled gold nanoprobes have potential for highly specific and sensitive tumor imaging or for use as angiogenesis-targeted SPECT/CT imaging probes.

Development of a deformable lung phantom for the evaluation of deformable registration.

The deformable lung phantom was developed to account for the patient breathing motion, and to evaluate for a deformable image registration algorithm. The phantom consisted of an acryl cylinder filled with water and a latex balloon located in the inner space of the cylinder. A silicon membrane was attached to the inferior end of the phantom. This silicon membrane was designed to simulate a real lung diaphragm and to reduce motor workload. This specific design was able to reduce the metal use which may prevent infrared sensing of the real position management (RPM) gating system on 4D CT image acquisition. Verification of intensity based 3D demon deformable registration was based on peak exhale and peak inhale breathing phases. The registration differences ranged from 0.85 mm to 1.47 mm, and accuracy was determined according to inner target deformation. This phantom was able to simulate the features and deformation of real human lung and has the potential for wide application in 4D radiation treatment planning.

Clinical implication of 18F-NaF PET/computed tomography indexes of aortic calcification in coronary artery disease patients: correlations with cardiovascular risk factors.

OBJECTIVE: Vascular calcification is known to be associated with cardiovascular risk factors. Recently, F-NaF PET has been reported to be effective for detecting early and active vascular calcification. In this study, correlations between F-NaF PET/computed tomography (CT) findings and cardiovascular risk factors were investigated in patients with suspected coronary artery disease. PATIENTS AND METHODS: Forty patients with suspected coronary artery disease underwent F-NaF PET/CT. The maximum and overall burden of calcifying activity, and the overall burden of calcium deposition in the descending thoracic aorta (DTA) were measured on F-NaF PET/CT and they were compared with cardiovascular risk factors, particularly, with those related to metabolic syndrome. RESULTS: The maximum and overall burden of calcifying activity in DTA measured on F-NaF PET were significantly correlated with diabetes mellitus (P = 0.030 and 0.049, respectively) and serum HbA1c level (ρ = 0.433 and 0.344, respectively). In contrast, the overall burden of calcium deposition measured on CT was significantly correlated with hypertension (P < 0.001). The overall burden of calcium deposition was also significantly correlated with metabolic syndrome (P = 0.002) and 10-year cardiovascular disease risk score (P = 0.004) CONCLUSION: F-NaF uptake is closely related to diabetes mellitus, whereas aortic calcification on CT is closely related to hypertension. Although F-NaF uptake in DTA can be a potential prognostic factor, aortic calcification on CT is a more significant prognostic factor for overall cardiovascular risk than F-NaF uptake.

Accelerated Blood Clearance Phenomenon Reduces the Passive Targeting of PEGylated Nanoparticles in Peripheral Arterial Disease.

Peripheral arterial disease (PAD) is a leading global health concern. Due to limited imaging and therapeutic options, PAD and other ischemia-related diseases may benefit from the use of long circulating nanoparticles as imaging probes and/or drug delivery vehicles. Polyethylene glycol (PEG)-conjugated nanoparticles have shown shortened circulation half-lives in vivo when injected multiple times into a single subject. This phenomenon has become known as the accelerated blood clearance (ABC) effect. The phenomenon is of concern for clinical translation of nanomaterials as it limits the passive accumulation of nanoparticles in many diseases, yet it has not been evaluated using inorganic or organic-inorganic hybrid nanoparticles. Herein, we found that the ABC phenomenon was induced by reinjection of PEGylated long circulating organic-inorganic hybrid nanoparticles, which significantly reduced the passive targeting of (64)Cu-labeled PEGylated reduced graphene oxide-iron oxide nanoparticles ((64)Cu-RGO-IONP-PEG) in a murine model of PAD. Positron emission tomography (PET) imaging was performed at 3, 10, and 17 days postsurgical induction of hindlimb ischemia. At day 3 postsurgery, the nanoparticles displayed a long circulation half-life with enhanced accumulation in the ischemic hindlimb. At days 10 and 17 postsurgery, reinjected mice displayed a short circulation half-life and lower accumulation of the nanoparticles in the ischemic hindlimb, in comparison to the naïve group. Also, reinjected mice showed significantly higher liver uptake than the naïve group, indicating that the nanoparticles experienced higher sequestration by the liver in the reinjected group. Furthermore, photoacoustic (PA) imaging and Prussian blue staining confirmed the enhanced accumulation of the nanoparticles in the liver tissue of reinjected mice. These findings validate the ABC phenomenon using long circulating organic-inorganic hybrid nanoparticles upon multiple administrations to the same animal, which may provide valuable insight into the future clinical applications of nanoparticles for imaging and treatment of PAD.

Plasmablastic lymphoma exclusively involving bones mimicking osteosarcoma in an immunocompetent patient: A case report.

BACKGROUND: It has been known that plasmablastic lymphoma (PBL) is a neoplasm of immunocompromised patients occurring in soft tissue of oral cavity or in the vicinity whereas bone is an unlikely site to harbor PBL. However, its occurrence is increasingly being reported in immunocompetent individuals in either osseous or extra-oral sites. To our best knowledge, F-18 FDG PET/CT findings of PBL involving bones in an immunocompetent patient have not been reported, yet . CASE SUMMARY: We report a case of PBL involving multiple bones in an immunocompetent patient. Features of different imaging modalities including F-18 Fluoro-deoxy glucose (FDG) positron emission tomography/computed tomography (PET/CT) were correlated well as findings of osteosarcoma in mandible with metastatic lesions. However, the histopathology and immunohistochemistry (IHC) of bone tissues from 2 separate biopsy sites revealed features of PBL. CONCLUSION: awareness to F-18 FDG PET/CT findings of PBL involving bones in an immunocompetent patient may prevent misdiagnosis.

Biomechanical and histomorphometric study on the bone-screw interface of bioactive ceramic-coated titanium screws.

The purpose of this study was to compare the osseointegration of 4 different kinds of bioactive ceramic-coated screws with uncoated screws by biomechanical and histomorphometric analysis. Calcium pyrophosphate (CPP), apatite-wollastonite 1:3 glass ceramic (W3G), apatite-wollastonite 1:1 glass ceramic (WAG) and bioactive CaO-SiO2-B2O3 glass ceramic (CSG) coatings were prepared and coated by the dipping method. Coated and uncoated titanium screws were inserted into the tibia of 18 adult mongrel male dogs for 2, 4, and 8 weeks. The insertion torques, radiographs, undecalcified histology, histomorphometric analysis, and extraction torques were evaluated. No difference of insertion torque was found among the five screw types. At 2 and 4 weeks after implantation, the extraction torque of ceramic-coated screws was significantly higher than that of uncoated screws (p < or = 0.0001). At 8 weeks, the extraction torques of CPP-, W3G-, and WAG-coated screws were significantly higher than those of CSG-coated and uncoated screws (p<0.0001). At 2, 4, and 8 weeks, the extraction torques of 4 different ceramic-coated screws were significantly higher than the corresponding insertion torque. Strong fixation was observed even at 2 weeks in the CPP-, W3G- and WAG-coated screws. The bone-screw contacts of the 4 different coated screws at 2 and 4 weeks were statistically higher than that of the uncoated screws, and the bone-screw contacts of the CPP-, W3G- and WAG-coated screws at 8 weeks were also statistically higher than that of the uncoated screws. The fixation strength was increased by the presence of osteoconductive coating materials, such as CPP, W3G, and WAG, which enabled to achieve higher fixation strength even as early as 2-8 weeks after the insertion.

Functionalized heparin-protamine based self-assembled nanocomplex for efficient anti-angiogenic therapy.

Angiogenesis is a key feature of cancer development, thus it is a good target for cancer therapy. However, drugs that have been designed to block angiogenesis mainly capture growth factors in circulation, resulting not only in the transient inhibition of tumor progression but also in producing undesirable side effects. Nanoparticular drug delivery systems, on the other hand, may help overcome such drawbacks and improve the efficacy of anti-angiogenic therapies by altering the biodistribution and pharmacokinetics, improving tumor targeting ability, and reducing side effects. In this light, we propose a new approach of anti-angiogenic therapy that combines strategies of long circulating, passive tumor targeting, and anti-angiogenesis efficacy using a new polyelectrolyte complex system that combines LHT7, a previously developed heparin-based angiogenesis inhibitor, with a protamine to form a self-assembling nanocomplex with a mean diameter of 200nm, which is effective for anti-angiogenesis therapy. At first, LHT7 was modified with polyethylene glycol (PEG). We observed that PEG-LHT7/protamine nanocomplex was stable in buffer and slowly dissociated in plasma (9% dissociation for 24h). Compared to the free form of PEG-LHT7, the mean residence time of PEG-LHT7/protamine nanocomplex was found higher (15.9h) with its increased accumulation in tumor. Most importantly, PEG-LHT7/protamine nanocomplex was diffused and extravasated through the dense collagen matrix of the tumor. Thus, the study describes a successful application of functionalized PEG-LHT/protamine nanocomplex that can inhibit angiogenesis with long circulating, passive targeting, and tumor extravasating ability.

In vitro and in vivo characteristics of a human colon cancer cell line, SNU-C5N, expressing sodium-iodide symporter.

Rat NIS (rNIS) genes were transfected into a human colon cancer cell line (SNU-C5) by lipofection. The transfected cells (SNU-C5N) exhibited an increase 125I uptake to a level 10 times higher than the untransfected SNU-C5 cells. The addition of 300 microM DIDS, an anion channel blocker, to the culture media led to a 2.35 times increase of 125I uptake in the cells. For the first 10 minutes, up to 70% of the cellular radioactivity was released into the medium. In the biodistribution study using SNU-C5N-xenografted mice, the %ID/g of the SNU-C5N tumors at 1, 3, 6, and 12 h after the 125I injection were 4.43%, 1.09%, 1.05%, and 0.05%, respectively, which were significantly higher than those for the SNU-C5 tumors (P<0.05). In tumor imaging, the SNU-C5N-xenografted tumor was clearly visible. In this study, NIS lipofection is efficient for triggering significant iodide uptake by a nonthyroidal tumor. However, for an increased therapeutic effect, the key issue is iodide retention in the target tissue.

Development of 99mTc-neomannosyl human serum albumin (99mTc-MSA) as a novel receptor binding agent for sentinel lymph node imaging.

BACKGROUND AND AIM: Various mannose receptor-binding agents, for example 99mTc-diethylenetriaminepentaacetic acid (DTPA)-mannosyl-polymer, have been developed for sentinel lymph node (SLN) imaging. In order to simplify the synthesis and labelling procedure and to improve the biological properties, we developed a novel mannose receptor-binding agent, 99mTc-neomannosyl human serum albumin (99mTc-MSA), for SLN imaging. METHODS: MSA was synthesized by conjugating mannopyranosylphenylisothiocyanate to human serum albumin (HSA). After reducing MSA with beta-mercaptoethanol and PD-10 column purification, a medronate solution containing stannous fluoride was added, divided into aliquots and freeze-dried. Reduced MSA was labelled with 99mTc-pertechnetate solution. The stability was checked for 24 h at 37 degrees C in human serum. The biodistribution of 99mTc-MSA in mice was investigated by intravenous injection through the tail vein and subcutaneous injection into the foot pad. The biodistributions of 99mTc-HSA and 99mTc-antimony sulphur colloid (99mTc-ASC) were also investigated for comparison. Dynamic whole-body images were obtained for 30 min after subcutaneous injection into the rats' foot pads. RESULTS: The number of mannose molecules conjugated per MSA was 15.9. The number of thiol groups produced was 19.4 per MSA after reduction with beta-mercaptoethanol. Labelling yields were always higher than 97%. 99mTc-MSA was stable for 24 h at 37 degrees C in human serum. The biodistribution in mice after intravenous injection showed high liver uptake (50.7+/-5.5% and 42.7+/-3.7% injected dose per gram at 10 and 60 min, respectively). 99mTc-MSA and 99mTc-ASC showed high accumulation in the lymph nodes after subcutaneous injection, whereas 99mTc-HSA and Tc-tin colloid did not, in both biodistribution and imaging studies. CONCLUSIONS: We have successfully developed a novel 99mTc-MSA for lymphoscintigraphy. The results of animal studies show that 99mTc-MSA has promising properties for SLN imaging.

Preparation of (188) Re-labeled paper for treating skin cancer.

For homogeneous delivery of beta radiation to skin cancer, we developed a simple method for preparing (188) Re-labeled nitrocellulose paper. The homogeneity and stability of the labeled paper were investigated. Absorbed dose estimates were calculated using the Monte-Carlo method. A 74-MBq (188) Re-labeled paper with 1-cm diameter delivered 147.2 Gy up to 1-mm depth after 2-h irradiation. Animal experiments on tumor-bearing mice showed that 50 Gy is an adequate dose for treating skin cancer. Tumors disappeared 7 days after irradiation in all the groups irradiated by 50 or 100 Gy. The (188) Re-labeled paper provided a convenient, economical, effective, and non-invasive method of treating skin cancer.

In vivo bioluminescence imaging for prolonged survival of transplanted human neural stem cells using 3D biocompatible scaffold in corticectomized rat model.

Stem cell-based treatment of traumatic brain injury has been limited in its capacity to bring about complete functional recovery, because of the poor survival rate of the implanted stem cells. It is known that biocompatible biomaterials play a critical role in enhancing survival and proliferation of transplanted stem cells via provision of mechanical support. In this study, we noninvasively monitored in vivo behavior of implanted neural stem cells embedded within poly-l-lactic acid (PLLA) scaffold, and showed that they survived over prolonged periods in corticectomized rat model. Corticectomized rat models were established by motor-cortex ablation of the rat. F3 cells expressing enhanced firefly luciferase (F3-effLuc) were established through retroviral infection. The F3-effLuc within PLLA was monitored using IVIS-100 imaging system 7 days after corticectomized surgery. F3-effLuc within PLLA robustly adhered, and gradually increased luciferase signals of F3-effLuc within PLLA were detected in a day dependent manner. The implantation of F3-effLuc cells/PLLA complex into corticectomized rats showed longer-lasting luciferase activity than F3-effLuc cells alone. The bioluminescence signals from the PLLA-encapsulated cells were maintained for 14 days, compared with 8 days for the non-encapsulated cells. Immunostaining results revealed expression of the early neuronal marker, Tuj-1, in PLLA-F3-effLuc cells in the motor-cortex-ablated area. We observed noninvasively that the mechanical support by PLLA scaffold increased the survival of implanted neural stem cells in the corticectomized rat. The image-guided approach easily proved that scaffolds could provide supportive effect to implanted cells, increasing their viability in terms of enhancing therapeutic efficacy of stem-cell therapy.

A case of ascending colon variceal bleeding treated with venous coil embolization.

A 38-year-old female with a history of alcoholic liver cirrhosis visited our hospital with a massive hematochezia. An esophagogastroduodenoscopy did not demonstrate any bleeding source, and a colonoscopy showed a massive hemorrhage in the ascending colon but without an obvious focus. The source of the bleeding could not be found with a mesenteric artery angiography. We performed an enhanced abdominal computed tomography, which revealed a distal ascending colonic varix, and assumed that the varix was the source of the bleeding. We performed a venous coil embolization and histoacryl injection to obliterate the colon varix. The intervention appeared to be successful because the vital signs and hemoglobin laboratory data remained stable and because the hematochezia was no longer observed. We report here on a rare case of colonic variceal bleeding that was treated with venous coil embolization.

Effect of dual-peak LED unit on the polymerization of coinitiator-containing composite resins.

The purpose of the present study was to evaluate the effect of dual-peak LED on the polymerization of coinitiator-containing composite resins. For this, microhardness, degree of conversion (DC), and polymerization shrinkage were evaluated. Specimens (coinitiator-containing: Aelite LS Posterior, Tetric EvoCeram, and Vit-l-escence; only camphorquinone-containng: Filtek Z350 and Grandio) were light cured using a quartz-tungsten-halogen (QTH: OP), a single-peak light-emitting diode (LED) (L. E. Demetron: DM), and a dual-peak LED (G-light: GL), respectively. All specimens light cured using GL showed the highest microhardness both on the top and bottom surfaces compared with the values obtained using the rest light-curing units (LCUs). DC had no consistent trend correspond to the LCU, but rather product specific. OP yielded the lowest polymerization shrinkage on the specimens. The coinitiator-containing composite resins achieved the highest microhardness by the dual-peak LED (GL). However, the influence of GL on DC and polymerization shrinkage of the specimens was not consistent.

Nanoparticles modified by encapsulation of ligands with a long alkyl chain to affect multispecific and multimodal imaging.

UNLABELLED: The attachment of specific ligands to the surfaces of nanoparticles is important for medical and biologic imaging. However, covalent modification of nanoparticles has inherent problems in reproducibility because of many factors such as temperature, pH, concentration, and reaction time. Thus, we developed a method for modifying nanoparticles by encapsulation with specific ligand-conjugated amphiphiles. METHODS: We synthesized special amphiphiles with a hydrophilic head and a long single-alkyl chain, such as arginine-glycine-aspartic acid-C(18), mannose-C(18), lactose-C(18), and 2-(p-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid-C(18). And then we produced stable quantum dots (QDs) encapsulated with polysorbate 60 (a branched polyethylene glycol head with a C(18) tail) and the synthesized special amphiphiles. The prepared encapsulated QDs were subject to in vitro and in vivo animal biodistribution studies and small-animal PET studies to confirm their specific binding. RESULTS: The encapsulated QDs could specifically bind to target cells in vitro and in vivo and could be labeled with (68)Ga (a positron emitter) easily and with high efficiency. CONCLUSION: The nanoparticles encapsulated with special amphiphiles could provide a straightforward and novel imaging solution with multimodality and multispecificity.

RVG peptide tethered bioreducible polyethylenimine for gene delivery to brain.

The work demonstrated the successful delivery of gene to mouse brain overcoming the blood-brain barrier (BBB) through expedient vector construct having RVG peptide as targeting ligand for neuronal cells. The newly developed delivery vector was designed to impart bioreducibility for greater intracellular pDNA release, higher serum stability and efficient complexing ability by incorporating disulfide linkage, PEG and low molecular weight polyethylenimine, respectively. The physiochemical properties of the polyplex, its cytotoxicity and the in vitro transfection efficiency on Neuro2a cell were studied prior to the successful in vivo study. In vivo fluorescence assay substantiated the permeation of the pDNA loaded polymeric vector through the BBB. The RVG-mediated target-specific cellular uptake of polymeric vector was established conclusively by competitive assay.

A brain-targeted rabies virus glycoprotein-disulfide linked PEI nanocarrier for delivery of neurogenic microRNA.

Recent advances in efficient microRNA (miRNA) delivery techniques using brain-targeted nanoparticles offer critical information for understanding the functional role of miRNAs in vivo, and for supporting targeted gene therapy in terms of treating miRNA-associated neurological diseases. Here, we report the rabies virus glycoprotein (RVG)-labeled non-toxic SSPEI nanomaterials capable of neuron-specific miR-124a delivery to neuron in vivo. The RVG-labeled BPEI-SS (RVG-SSPEI) nanocarrier showed less toxicity in acetylcholine receptor-positive Neuro2a cells, and electrostatic interaction of RVG-SSPEI with miR-124a exhibited optimal transfection efficacy. The RVG-SSPEI polymer specifically targeted Neuro2a using cy5.5-miR-124a mixed with RVG-SSPEI. The functional action of miR-124a oligomers released from polyplexes in the cytoplasmic region was evaluated by a reporter vector containing a miR-124a -binding sequence, and showed a significantly reduced reporter signal in a dose-dependent manner. Cy5.5-miR-124a/RVG-SSPEI- injected into mice via tail veins displayed the enhanced accumulation of miR-124a in the isolated brain. Hindrance of the efficient penetration of neuronal cells by size limitation of the miR-124a/RVG-SSPEI improved with the help of mannitol through blood-brain barrier disruption. These findings indicated that the RVG peptide combined with mannitol infusion using SSPEI polymer for neuron-specific targeting in vivo is sufficient to deliver neurogenic microRNA into the brain.

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 Broca's (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.

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.