[Neural substrates underlying cognitive expertise]

Recent behavioral and neuro-anatomical studies of cognitive expertise have suggested that that superior performance in memory experts is neither due to extraordinary general intelligence nor anatomical brain difference. Furthermore, functional neuro-imaging studies have revealed that expert performance in mental abacus and memory experts is not attributable to increased brain activities of the process that exists in non-experts or to hyper-activity in the prefrontal cortex. On the contrary, cognitive experts utilize brain areas that are not used by non-experts. These brain regions are directly related to exceptional knowledge and unique strategies that are acquired by experts through extensive practice. These neuro-imaging findings support psychological theories that cognitive expertise is achieved by developing extensive knowledge and novel cognitive strategies not used by non-experts. These lines of evidence suggest that ordinary people could become experts through appropriate practice.

Cross-modal integration during vowel identification in audiovisual speech: a functional magnetic resonance imaging study

To investigate the neural substrates of the perception of audiovisual speech, we conducted a functional magnetic resonance imaging study with 28 normal volunteers. We hypothesized that the constraint provided by visually-presented articulatory speech (mouth movements) would lessen the workload for speech identification if the two were concordant, but would increase the workload if the two were discordant. In auditory attention sessions, subjects were required to identify vowels based on auditory speech. Auditory vowel stimuli were presented with concordant or discordant visible articulation movements, unrelated lip movements, and without visual input. In visual attention sessions, subjects were required to identify vowels based on the visually-presented vowel articulation movements. The movements were presented with concordant or discordant uttered vowels and noise, and without sound. Irrespective of the attended modality, concordant conditions significantly shortened the reaction time, whereas discordant conditions lengthened the reaction time. Within the neural substrates that were commonly activated by auditory and visual tasks, the mid superior temporal sulcus showed greater activity for discordant stimuli than concordant stimuli. These findings suggest that the mid superior temporal sulcus plays an important role in the auditory-visual integration process underlying vowel identification.

Source of nonlinearity of the BOLD response revealed by simultaneous fMRI and NIRS

The nonlinearity of the blood oxygenation level-dependent (BOLD) response to stimuli of different duration, particularly those of short duration, has been well studied by functional magnetic resonance imaging (fMRI). This nonlinearity is assumed to be due to neural adaptation and the nonlinearity of the response in the oxygen extraction fraction (OEF); the latter has not been examined quantitatively in humans. To evaluate how the OEF response contributes to the nonlinearity of the BOLD response to neural activity, we used simultaneous fMRI and near-infrared spectroscopy (NIRS). The responses to visual stimuli of four different durations were measured as changes in the BOLD signal and the NIRS-derived hemoglobin concentrations. The hemodynamic response nonlinearity was quantified using an impulse response function model with saturation nonlinearity scaling in the response amplitude, assuming that the unknown neural adaptation parameters varied within a physiologically feasible range. Independent of the degree of neural adaptation, the BOLD response consistently showed saturation nonlinearity similar to that of the OEF response estimated from the NIRS measures, the nonlinearity of which was greater than that of the response in the total hemoglobin concentration representing the cerebral blood volume (CBV). We also found that the contribution of the OEF response to the BOLD response was four to seven times greater than the contribution of the CBV response. Thus, we conclude that the nonlinearity of the BOLD response to neural activity originates mainly from that of the OEF response.

Tactile-visual integration in the posterior parietal cortex: a functional magnetic resonance imaging study

To explore the neural substrates of visual-tactile crossmodal integration during motion direction discrimination, we conducted functional magnetic resonance imaging with 15 subjects. We initially performed independent unimodal visual and tactile experiments involving motion direction matching tasks. Visual motion discrimination activated the occipital cortex bilaterally, extending to the posterior portion of the superior parietal lobule, and the dorsal and ventral premotor cortex. Tactile motion direction discrimination activated the bilateral parieto-premotor cortices. The left superior parietal lobule, intraparietal sulcus, bilateral premotor cortices and right cerebellum were activated during both visual and tactile motion discrimination. Tactile discrimination deactivated the visual cortex including the middle temporal/V5 area. To identify the crossmodal interference of the neural activities in both the unimodal and the multimodal areas, tactile and visual crossmodal experiments with event-related designs were also performed by the same subjects who performed crossmodal tactile-visual tasks or intramodal tactile-tactile and visual-visual matching tasks within the same session. The activities detected during intramodal tasks in the visual regions (including the middle temporal/V5 area) and the tactile regions were suppressed during crossmodal conditions compared with intramodal conditions. Within the polymodal areas, the left superior parietal lobule and the premotor areas were activated by crossmodal tasks. The left superior parietal lobule was more prominently activated under congruent event conditions than under incongruent conditions. These findings suggest that a reciprocal and competitive association between the unimodal and polymodal areas underlies the interaction between motion direction-related signals received simultaneously from different sensory modalities.

Human brain activation in response to olfactory stimulation by intravenous administration of odorants

To identify the BOLD effects related to olfaction in humans, we recorded functional magnetic resonance imaging (fMRI) scans in response intravenously instilled thiamine propyl disulfide (TPD) and thiamine tetrahydrofurfuryl disulfide monohydrochloride (TTFD). TPD and TTFD evoked a strong and weak odor sensation, respectively. Since we did not spray the odor stimuli directly, this method is expected to reduce the effect caused by direct stimulation of the trigeminal nerve. For the analysis of fMRI data, statistical parametric mapping (SPM2) was employed and the areas significantly activated during olfactory processing were located. Both strong and weak odorants induced brain activities mainly in the orbitofrontal gyrus (Brodmann's area: BA 11) in the left hemisphere. TPD (a strong odorant) induced activity in the subthalamic nucleus in the left hemisphere and the precentral gyrus (BA 6) and insula in the right hemisphere. TTFD (a weak odorant) induced activity in the superior frontal gyrus (BA 11) in the right hemisphere. In both circumstances, there was an increase in blood flow at the secondary olfactory cortex (SOC) but not the primary olfactory cortex (POC), probably due to a habituation effect in the POC. From the present results, we found brain activity in not only odor-specific regions but also regions whose levels of activity were changed by an intensity difference of odor stimuli.

Role of alpha2C-adrenoceptors in the reduction of skin blood flow induced by local cooling in mice

BACKGROUND AND PURPOSE

The reduction of skin blood flow induced by local cooling results from a reflex increase in sympathetic output and an enhanced vasoconstrictor activity of cutaneous vessels. The present study investigated the latter local response in vivo in tetrodotoxin-treated mice, in which the sympathetic nerve tone was abolished.

EXPERIMENTAL APPROACH

Male ddY mice, anaesthetized with pentobarbitone, were treated with tetrodotoxin and artificially ventilated. The plantar skin blood flow (PSBF) was measured by laser Doppler flowmetry.

KEY RESULTS

Cooling the air temperature around the left foot from 25 to 10 degrees C decreased the PSBF of the left foot. Bunazosin, an alpha (1)-adrenoceptor antagonist, RS79948, an alpha (2)-adrenoceptor antagonist, and MK-912, an alpha (2C)-adrenoceptor antagonist, all significantly inhibited the cooling-induced reduction of PSBF; the inhibition by bunazosin was relatively small compared with that by RS79948 and MK-912. The response was not affected by guanethidine or bretylium, but was diminished in adrenalectomized mice. An intra-arterial injection of clonidine, an alpha (2)-adrenoceptor agonist, to the left iliac artery of adrenalectomized mice caused a transient decrease in PSBF, which was significantly augmented at 10 degrees C. MK-912 suppressed only the augmented portion at 10 degrees C. Y-27632, H-1152 and fasudil, Rho kinase inhibitors, also inhibited the cooling-induced reduction of PSBF. RS79948 caused no further reduction of the cooling-induced response after the inhibition by Y-27632.

CONCLUSIONS AND IMPLICATIONS

Local cooling-induced reduction of skin blood flow in mice primarily results from increased reactivity of alpha (2C)-adrenoceptors to circulating catecholamines, in which the Rho/Rho kinase pathway is involved.

Control of lead polluted leachate in a box-scale phytoremediation test using common buckwheat (Fagopyrum esculentum Moench) grown on lead contaminated soil

The remediation of heavy metal contaminated soil using plants is a technology worth developing. However, the overall effect of phytoremediation in high-density Pb polluted sites remains unknown. Especially, little information is available about the effects of using plants to control lead polluted leachate. Thus, we investigated the control of leachate in a box-scale phytoremediation test using common buckwheat, a Pb hyperaccumulator, grown on Pb contaminated soil. In the presence of buckwheat, the change in volumetric water content was smaller than that of the control with rainfall. The total amount of Pb in the leachate strongly correlated with the amount of leachate and the decrease in the density of Pb in the leachate. During the cultivation period, the total amount of Pb leached in the control was 1.28mg per container, while in the presence of buckwheat the total amount of Pb was approximately 22.7% of the control. Moreover, with buckwheat cultivation, Pb polluted leachate resulting from rainwater was prevented. The results suggested that buckwheat was a Pb hyperaccumulator and also had a high ability for phytostabilization. Control of Pb polluted leachate using buckwheat was shown to be a phytoremediation technology applicable to heavily Pb contaminated sites.

Cognitive slowing in Parkinson disease is accompanied by hypofunctioning of the striatum

Objective: To investigate whether cognitive slowing in Parkinson disease (PD) reflects disruption of the basal ganglia or dysfunction of the frontal lobe by excluding an influence of abnormal brain activity due to motor deficits.

Methods: We measured neuronal activity during a verbal mental-operation task with H215O PET. This task enabled us to evaluate brain activity change associated with an increase in the cognitive speed without an influence on motor deficits.

Results: As the speed of the verbal mental-operation task increased, healthy controls exhibited proportional increase in activities in the anterior striatum and medial premotor cortex, suggesting the involvement of the corticobasal ganglia circuit in normal performance of the task. By contrast, patients with PD lacked an increase in the striatal activity, whereas the medial premotor cortex showed a proportional increase.

Conclusions: Although the present study chose a liberal threshold and needs subsequent confirmation, the findings suggest that striatal disruption resulting in abnormal processing in the corticobasal ganglia circuit may contribute to cognitive slowing in Parkinson disease, as is the case in motor slowing.

Genes involved in oxidative phosphorylation are coordinately upregulated with fasting hyperglycaemia in livers of patients with type 2 diabetes

AIMS/HYPOTHESIS

Mitochondrial oxidative phosphorylation (OXPHOS) plays an important role in the pathophysiology of type 2 diabetes. Genes involved in OXPHOS have been reported to be down-regulated in skeletal muscle from patients with type 2 diabetes; however, hepatic regulation is unknown.

MATERIALS AND METHODS

We analysed expression of genes involved in OXPHOS from the livers of 14 patients with type 2 diabetes and 14 subjects with NGT using serial analysis of gene expression (SAGE) and DNA chip analysis. We evaluated the correlation between expression levels of genes involved in OXPHOS and the clinical parameters of individuals with type 2 diabetes and NGT.

RESULTS

Both gene analyses showed that genes involved in OXPHOS were significantly upregulated in the type 2 diabetic liver. In the SAGE analysis, tag count comparisons of mitochondrial transcripts showed that ribosomal RNAs (rRNA) were 3.5-fold over-expressed, and mRNAs were 1.2-fold over-expressed in the type 2 diabetes library. DNA chip analysis revealed that expression of genes involved in OXPHOS, which correlated with several nuclear factors, including estrogen-related receptor-alpha or peroxisome proliferator-activated receptor-gamma, was a predictor of fasting plasma glucose levels, independently of age, BMI, insulin resistance and fasting insulin levels (p = 0.04). Surprisingly, genes involved in OXPHOS did not correlate with peroxisome proliferator-activated receptor-gamma coactivator-1alpha or nuclear respiratory factor 1.

CONCLUSIONS/INTERPRETATION

Our results indicate that upregulation of genes involved in OXPHOS in the liver, which are regulated by different mechanisms from genes in the skeletal muscle, is associated with fasting hyperglycaemia in patients with type 2 diabetes.

The synthetic TRH analogue taltirelin exerts modality-specific antinociceptive effects via distinct descending monoaminergic systems

BACKGROUND AND PURPOSE

Exogenously administered thyrotropin-releasing hormone (TRH) is known to exert potent but short-acting centrally-mediated antinociceptive effects. We sought to investigate the mechanisms underlying these effects using the synthetic TRH analogue taltirelin, focusing on the descending monoaminergic systems in mice.

EXPERIMENTAL APPROACH

The mice received systemic or local injections of taltirelin combined with either central noradrenaline (NA) or 5-hydroxytryptamine (5-HT) depletion by 6-hydroxydopamine (6-OHDA) or DL-p-chlorophenylalanine (PCPA), respectively, or blockade of their receptors. The degree of antinociception was determined using the tail flick and tail pressure tests.

KEY RESULTS

Subcutaneously (s.c.) administered taltirelin exhibited dose-dependent antinociceptive effects in the tail flick and tail pressure tests. These effects appeared to be primarily supraspinally mediated, since intracerebroventricularly (i.c.v.) but not intrathecally (i.t.) injected taltirelin generated similar effects. Depletion of central NA abolished only the analgesic effect of taltirelin (s.c. and i.c.v.) on mechanical nociception. By contrast, depletion of central 5-HT abolished only its analgesic effect on thermal nociception. Intraperitoneal (i.p.) and i.t. injection of the alpha2-adrenoceptor antagonist yohimbine respectively reduced the analgesic effect of taltirelin (s.c. and i.c.v.) on mechanical nociception. By contrast, the 5-HT1A receptor antagonist WAY-100635 (i.p. and i.t.) reduced the effect of taltirelin (s.c. and i.c.v.) on thermal nociception. Neither the 5-HT2 receptor antagonist ketanserin nor the opioid receptor antagonist naloxone altered the antinociceptive effect of taltirelin.

CONCLUSIONS AND IMPLICATIONS

These findings suggest that taltirelin activates the descending noradrenergic and serotonergic pain inhibitory systems, respectively, to exert its analgesic effects on mechanical and thermal nociception.

Transient elevation of intracellular calcium ion levels as an early event in T-2 toxin-induced apoptosis in human promyelotic cell line HL-60

Recently we have reported that T-2 toxin, a trichothecene mycotoxin produced by Fusarium species, is a potent inducer of apoptosis in the human promyelotic cell line HL-60. To clarify the signal transduction pathway of apoptosis primed by T-2 toxin, T-2 toxin-induced apoptosis was investigated in detail using confocal laser microscopy and flow cytometry. Apoptosis in HL-60 cells induced by T-2 toxin was dose dependent when the cells were treated with concentrations of 5-100 ng/ml for more than 2 hr. The apoptosis proceeds through various cell cycle stages of HL-60 cells. Prior to apoptosis, the intracellular calcium ion (Ca+2i) level was markedly elevated within 3-5 min after exposure to T-2 toxin and returned to normal level thereafter. A well-known chelator for Ca+2i, ethylene-N,N,N', N'-tetraacetic acid 4K acetoxymethyl ester (BAPTA-AM), a Ca+2-dependent endonuclease inhibitor ZnCl2, and calpain inhibitor 1 sharply blocked T-2 toxin-induced apoptosis. These results strongly suggest that the Ca+2 signal triggered by T-2 toxin is transduced by the activation of endonuclease and protease, and ultimately evokes apoptosis.

Cutaneous immunological activation elicited by a low-fluence pulsed dye laser

BACKGROUND

Three years ago, the nonablative wrinkle reduction laser (a 585-nm laser, Chromogenex V3; Chromogenex Light Technologies, Llanelli, U.K.) was developed, and there have already been several reports about its clinical effectiveness. The Chromogenex V3 laser has also been reported to be effective in treating acne and atopic dermatitis. These results suggest that the Chromogenex V3 laser has some immunological role. In this study, we investigated immunological changes elicited by laser irradiation at the ultrastructural level and by analysis of interleukin (IL)-2 and IL-4 mRNA in skin homing T lymphocytes.

MATERIALS AND METHODS

Eight healthy adult volunteers (mean age 56.3 years, range 25-66 years) were recruited for this study. Ultrastructural analysis was done 3 h after the laser irradiation, as well as 1 day, 3 days, 1 week, 2 weeks, 4 weeks and 5 weeks later. IL-2 and IL-4 mRNAs in skin homing T cells cultured for 6 weeks were semiquantitatively measured using reverse transcriptase-polymerase chain reaction.

RESULTS

Ultrastructural observations revealed that at 3 h after laser therapy, neutrophils, monocytes and mast cells could already be seen in the extravascular dermis. These dermal acute inflammatory changes were observed also at 1 week after laser treatment. Two weeks after laser treatment, the capillaries showed an almost normal structure. Four weeks after laser treatment, many lymphocytes and fibroblasts were observed. The numbers of these lymphocytes increased further at 5 weeks after the laser treatment. One week after the laser irradiation, all subjects were positive for IL-2 mRNA and for IL-4 mRNA. The level of IL-4 mRNA was larger compared with that of IL-2 mRNA in all subjects.

CONCLUSION

The Chromogenex V3 is a 585-nm visible light laser, and it may affect the skin not only by selective photothermolysis but also by direct cutaneous immunological activation.

Prime-boost vaccination with plasmid DNA and a chimeric adenovirus type 5 vector with type 35 fiber induces protective immunity against HIV

Immunization involving a DNA vaccine prime followed by an adenovirus type 5 (Ad5) boost elicited a protective immune response against SHIV challenge in monkeys. However, the hepatocellular tropism of Ad5 limits the safety of this viral vector. This study examines the safety and immunogenicity of a replication-defective chimeric Ad5 vector with the Ad35 fiber (Ad5/35) in BALB/c mice and rhesus monkeys. This novel Ad5/35 vector showed minimal hepatotoxicity after intramuscular administration with the novel Ad5/35 vector. In addition, an Ad5/35 vector expressing HIV Env gp160 protein (Ad5/35-HIV) generated strong HIV-specific immune responses in both animal models. Priming with a DNA vaccine followed by Ad5/35-HIV boosting yielded protection against a gp160-expressing vaccinia virus challenge in BALB/c mice. The Ad5/35-HIV vector was significantly less susceptible to the pre-existing Ad5 immunity than a comparable Ad5 vector. These findings indicate that an Ad5/35 vector-based HIV vaccine may be of considerable value for clinical use.

Functionally segregated neural substrates for arbitrary audiovisual paired-association learning

To clarify the neural substrates and their dynamics during crossmodal association learning, we conducted functional magnetic resonance imaging (MRI) during audiovisual paired-association learning of delayed matching-to-sample tasks. Thirty subjects were involved in the study; 15 performed an audiovisual paired-association learning task, and the remainder completed a control visuo-visual task. Each trial consisted of the successive presentation of a pair of stimuli. Subjects were asked to identify predefined audiovisual or visuo-visual pairs by trial and error. Feedback for each trial was given regardless of whether the response was correct or incorrect. During the delay period, several areas showed an increase in the MRI signal as learning proceeded: crossmodal activity increased in unimodal areas corresponding to visual or auditory areas, and polymodal responses increased in the occipitotemporal junction and parahippocampal gyrus. This pattern was not observed in the visuo-visual intramodal paired-association learning task, suggesting that crossmodal associations might be formed by binding unimodal sensory areas via polymodal regions. In both the audiovisual and visuo-visual tasks, the MRI signal in the superior temporal sulcus (STS) in response to the second stimulus and feedback peaked during the early phase of learning and then decreased, indicating that the STS might be key to the creation of paired associations, regardless of stimulus type. In contrast to the activity changes in the regions discussed above, there was constant activity in the frontoparietal circuit during the delay period in both tasks, implying that the neural substrates for the formation and storage of paired associates are distinct from working memory circuits.

The role of biological system other than auditory air-conduction in the emergence of the hypersonic effect

Although human beings cannot perceive elastic vibrations in the frequency range above 20 kHz, nonstationary sounds containing a wealth of inaudible high-frequency components (HFC) above the human audible range activate deep-lying brain structures, including the brainstem and thalamus and evoke various physiological, psychological, and behavioral responses. In the previous reports, we have called these phenomena collectively "the hypersonic effect." It remains unclear, however, if vibratory stimuli above the audible range are transduced and perceived solely via the conventional air-conducting auditory system or if other mechanisms also contribute to mediate transduction and perception. In the present study, we have examined the emergence of the hypersonic effect when inaudible HFC and audible low-frequency components (LFC) were presented selectively to the ears, the entrance of an air-conducting auditory system, or to the body surface including the head which might contain some unknown vibratory sensing mechanisms. We used two independent measurements based on differing principles; one physiological (alpha 2 frequency of spontaneous electroencephalogram [alpha-EEG]) and the other behavioral (the comfortable listening level [CLL]). Only when the listener's entire body surface was exposed to HFC, but not when HFC was presented exclusively to the air-conducting auditory system, did both the alpha-EEG and the CLL significantly increase compared to the presentation of LFC alone, that is to say, there was an evident emergence of the hypersonic effect. The present findings suggest that the conventional air-conducting auditory system alone does not bring about the hypersonic effect. We may need to consider the possible involvement of a biological system distinct from the conventional air-conducting auditory nervous system in sensing and transducing high-frequency elastic vibration above the human audible range.

Brain activity during visuomotor behavior triggered by arbitrary and spatially constrained cues: an fMRI study in humans

Rule-based behavior associating nonspatial visual stimuli with learned responses is called arbitrary visuomotor mapping, an ability that enriches behavioral repertoire. To better understand the underlying neural correlates, the present functional magnetic resonance imaging (fMRI) study explored brain activity during visually informed movement involving two different types of cues and two different effectors. After being trained on the tasks, six healthy subjects performed right or left finger tapping tasks according to either arbitrary cues or spatially constrained cues. An event-related fMRI experiment was conducted on a 3-T MRI. The image data were analyzed with statistical parametric mapping. With the aid of the probabilistic architectonic map in the stereotaxic space, we identified three types of task-related brain activity: cue-selective, effector-selective, and nonselective. The left ventrolateral prefrontal cortex and the rostral part of the right dorsal premotor cortex (PMd) exhibited cue-selective activity, which was greater during the arbitrary condition than the spatially constrained condition. The left ventral prefrontal activity may reflect retrieval of visuomotor association from memory in arbitrary context. The rostral part of the left PMd showed nonselective activity while the caudal part of the PMd on each side showed conspicuous effector-selective activity to the contralateral movement. These findings suggest functional demarcation of the PMd between its rostral and dorsal parts during visuomotor mapping.

Suppression of the non-dominant motor cortex during bimanual symmetric finger movement: A functional magnetic resonance imaging study

Patterns of bimanual coordination in which homologous muscles are simultaneously active are more stable than those in which homologous muscles are engaged in an alternating fashion. This may be attributable to the stronger involvement of the dominant motor cortex in ipsilateral hand movements via interaction with the non-dominant motor system, known as neural crosstalk. We used functional magnetic resonance imaging to investigate the neural representation of the interhemispheric interaction during bimanual mirror movements. Thirteen right-handed subjects completed four conditions: sequential finger tapping using the right and left index and middle fingers, bimanual mirror and parallel finger tapping. Auditory cues (3 Hz) were used to keep the tapping frequency constant. Task-related activation in the right primary motor cortex was significantly less prominent during mirror than unimanual left-handed movements. This was mirror- and non-dominant side-specific; parallel movements did not cause such a reduction, and the left primary motor cortex showed no such differential activation across the unimanual right, bimanual mirror, and bimanual parallel conditions. Reducing the contralateral innervation of the left hand may increase the fraction of the force command to the left hand coming from the left primary motor cortex, enhancing the neural crosstalk.