Human brain mechanisms of auditory and audiovisual selective attention

Selective attention refers to the process in which certain information is actively selected for conscious processing, while other information is ignored. The aim of the present studies was to investigate the human brain mechanisms of auditory and audiovisual selective attention with functional magnetic resonance imaging (fMRI), electroencephalography (EEG) and magnetoencephalography (MEG). The main focus was on attention-related processing in the auditory cortex. It was found that selective attention to sounds strongly enhances auditory cortex activity associated with processing the sounds. In addition, the amplitude of this attention-related modulation was shown to increase with the presentation rate of attended sounds. Attention to the pitch of sounds and to their location appeared to enhance activity in overlapping auditory-cortex regions. However, attention to location produced stronger activity than attention to pitch in the temporo-parietal junction and frontal cortical regions. In addition, a study on bimodal attentional selection found stronger audiovisual than auditory or visual attention-related modulations in the auditory cortex. These results were discussed in light of Näätänen s attentional-trace theory and other research concerning the brain mechanisms of selective attention.

Dynamics of contour, object and face processing in the human visual cortex

The neural basis of visual perception can be understood only when the sequence of cortical activity underlying successful recognition is known. The early steps in this processing chain, from retina to the primary visual cortex, are highly local, and the perception of more complex shapes requires integration of the local information. In Study I of this thesis, the progression from local to global visual analysis was assessed by recording cortical magnetoencephalographic (MEG) responses to arrays of elements that either did or did not form global contours. The results demonstrated two spatially and temporally distinct stages of processing: The first, emerging 70 ms after stimulus onset around the calcarine sulcus, was sensitive to local features only, whereas the second, starting at 130 ms across the occipital and posterior parietal cortices, reflected the global configuration. To explore the links between cortical activity and visual recognition, Studies II III presented subjects with recognition tasks of varying levels of difficulty. The occipito-temporal responses from 150 ms onwards were closely linked to recognition performance, in contrast to the 100-ms mid-occipital responses. The averaged responses increased gradually as a function of recognition performance, and further analysis (Study III) showed the single response strengths to be graded as well. Study IV addressed the attention dependence of the different processing stages: Occipito-temporal responses peaking around 150 ms depended on the content of the visual field (faces vs. houses), whereas the later and more sustained activity was strongly modulated by the observers attention. Hemodynamic responses paralleled the pattern of the more sustained electrophysiological responses. Study V assessed the temporal processing capacity of the human object recognition system. Above sufficient luminance, contrast and size of the object, the processing speed was not limited by such low-level factors. Taken together, these studies demonstrate several distinct stages in the cortical activation sequence underlying the object recognition chain, reflecting the level of feature integration, difficulty of recognition, and direction of attention.

Delivering superior forage oat varieties for sub-tropical Australia

This full application seeks ongoing funding for the Agri-Science Queensland's forage oat breeding program through the Meat and Livestock Australia Partners in Innovation program with Heritage Seeds as the Donor Company and the commercial collaborator. The focus of the breeding program will shift to the use of minor genes that confer partial resistance or adult plant resistance to leaf rust. Accumulation of several minor genes in a single variety should produce a high level of effective field resistance, and better durability of resistance, with less likelihood of a mutational change in the pathogen.

Pre-emptive breeding to combine superior eating quality in tropical super sweet corn with resistance to major diseases

This report presents the process and outcomes of a five year project, which employed genetics and breeding approach for integrating disease resistance,agronomy and quality traits that enhances sustainable productivity improvement in sweet corn production. The report outlines a molecular markers based approach to introgress quantitative traits loci that are believed to contribute to resistance to downy mildew, a potentially devastating disease that threatens sweet corn and other similar crops. It also details the approach followed to integrate resistances for other major diseases such as southern rust (caused by Puccinia polysora Underw), Northern Corn Leaf Blight (Exserohilum turcicum) with improved agronomy and eating quality. The report explains the importance of heterosis (hybrid vigour) and combining ability in the development of useful sweet corn hybrids. It also explains the relevance of parental performance to predict its breeding value and the performance of its hybrids.

A Probabilistic Approach to the Primary Visual Cortex

What can the statistical structure of natural images teach us about the human brain? Even though the visual cortex is one of the most studied parts of the brain, surprisingly little is known about how exactly images are processed to leave us with a coherent percept of the world around us, so we can recognize a friend or drive on a crowded street without any effort. By constructing probabilistic models of natural images, the goal of this thesis is to understand the structure of the stimulus that is the raison d etre for the visual system. Following the hypothesis that the optimal processing has to be matched to the structure of that stimulus, we attempt to derive computational principles, features that the visual system should compute, and properties that cells in the visual system should have. Starting from machine learning techniques such as principal component analysis and independent component analysis we construct a variety of sta- tistical models to discover structure in natural images that can be linked to receptive field properties of neurons in primary visual cortex such as simple and complex cells. We show that by representing images with phase invariant, complex cell-like units, a better statistical description of the vi- sual environment is obtained than with linear simple cell units, and that complex cell pooling can be learned by estimating both layers of a two-layer model of natural images. We investigate how a simplified model of the processing in the retina, where adaptation and contrast normalization take place, is connected to the nat- ural stimulus statistics. Analyzing the effect that retinal gain control has on later cortical processing, we propose a novel method to perform gain control in a data-driven way. Finally we show how models like those pre- sented here can be extended to capture whole visual scenes rather than just small image patches. By using a Markov random field approach we can model images of arbitrary size, while still being able to estimate the model parameters from the data.

Structural and functional roles of KCC2 in developing cortex

Cation chloride cotransporters (CCCs) are critical for controlling intracellular chloride homeostasis. The CCC family is composed of four isoforms of K-Cl cotransporters (KCC1-4), two isoforms of Na-K-2Cl cotransporters (NKCC1-2), one Na-Cl cotransporter (NCC) and two the structurally related proteins with unknown function, CCC8 also known as cation-chloride cotransporter interaction protein, CIP, and CCC9. KCC2 is a neuron-specific isoform, which plays a prominent role in controlling the intracellular Cl- concentration in neurons and is responsible for producing the negative shift of GABAA responses from depolarizing to hyperpolarizing during neuronal maturation. In the present studies we first used in situ hybridization to examine the developmental expression patterns of the cation-chloride cotransporters KCC1-4 and NKCC1. We found that they display complementary expression patterns during embryonic brain development. Most interestingly, KCC2 expression in the embryonic central nervous system strictly follows neuronal maturation. In vitro data obtained from primary and organotypic neuronal cultures support this finding and revealed a temporal correlation between the expression of KCC2 and synaptogenesis. We found that KCC2 is highly expressed in filopodia and mature spines as well as dendritic shaft and investigated the role of KCC2 in spine formation by analyzing KCC2-/- neurons in vitro. Our studies revealed that KCC2 is a key factor in the maturation of dendritic spines. Interestingly, the effect of KCC2 in spine formation is not due to Cl- transport activity, but mediated through the interaction between KCC2 C-terminal and intracellular protein associated with cytoskeleton. The interacting protein we found is protein 4.1N by immunoprecipitation. Our results indicate a structural role for KCC2 in the development of functional glutamatergic synapses and suggest KCC2 as a synchronizer for the functional development of glutamatergic and GABAergic synapses in neuronal network. Studies on the regulatory mechanisms of KCC2 expression during development and plasticity revealed that synaptic activity of both the glutamatergic and GABAergic system is not required for up-regulation of KCC2 during development, whereas in acute mature hippocampal slices which undergo continuous synchronous activity induced by the absence of Mg2+ solution, KCC2 mRNA and protein expression were down-regulated in CA1 pyramidal neurons subsequently leading to a reduced capacity for neuronal Cl- extrusion. This effect is mediated by endogenous BDNF-TrkB down-stream cascades involving both Shc/FRS-2 and PLCγ-CREB signaling. BDNF mediated changes in KCC2 expression indicate that KCC2 is significantly involved in the complex mechanisms of neuronal plasticity during development and pathophysiological conditions.

Functional imaging of peripheral vision and dorsal stream function in the human cerebral cortex

Visual information processing in brain proceeds in both serial and parallel fashion throughout various functionally distinct hierarchically organised cortical areas. Feedforward signals from retina and hierarchically lower cortical levels are the major activators of visual neurons, but top-down and feedback signals from higher level cortical areas have a modulating effect on neural processing. My work concentrates on visual encoding in hierarchically low level cortical visual areas in human brain and examines neural processing especially in cortical representation of visual field periphery. I use magnetoencephalography and functional magnetic resonance imaging to measure neuromagnetic and hemodynamic responses during visual stimulation and oculomotor and cognitive tasks from healthy volunteers. My thesis comprises six publications. Visual cortex forms a great challenge for modeling of neuromagnetic sources. My work shows that a priori information of source locations are needed for modeling of neuromagnetic sources in visual cortex. In addition, my work examines other potential confounding factors in vision studies such as light scatter inside the eye which may result in erroneous responses in cortex outside the representation of stimulated region, and eye movements and attention. I mapped cortical representations of peripheral visual field and identified a putative human homologue of functional area V6 of the macaque in the posterior bank of parieto-occipital sulcus. My work shows that human V6 activates during eye-movements and that it responds to visual motion at short latencies. These findings suggest that human V6, like its monkey homologue, is related to fast processing of visual stimuli and visually guided movements. I demonstrate that peripheral vision is functionally related to eye-movements and connected to rapid stream of functional areas that process visual motion. In addition, my work shows two different forms of top-down modulation of neural processing in the hierachically lowest cortical levels; one that is related to dorsal stream activation and may reflect motor processing or resetting signals that prepare visual cortex for change in the environment and another local signal enhancement at the attended region that reflects local feed-back signal and may perceptionally increase the stimulus saliency.

Studies on the assessment of the adequacy of anesthesia

Several hypnosis monitoring systems based on the processed electroencephalogram (EEG) have been developed for use during general anesthesia. The assessment of the analgesic component (antinociception) of general anesthesia is an emerging field of research. This study investigated the interaction of hypnosis and antinociception, the association of several physiological variables with the degree of intraoperative nociception, and aspects of EEG Bispectral Index Scale (BIS) monitoring during general anesthesia. In addition, EEG features and heart rate (HR) responses during desflurane and sevoflurane anesthesia were compared. A propofol bolus of 0.7 mg/kg was more effective than an alfentanil bolus of 0.5 mg in preventing the recurrence of movement responses during uterine dilatation and curettage (D C) after a propofol-alfentanil induction, combined with nitrous oxide (N2O). HR and several HR variability-, frontal electromyography (fEMG)-, pulse plethysmography (PPG)-, and EEG-derived variables were associated with surgery-induced movement responses. Movers were discriminated from non-movers mostly by the post-stimulus values per se or normalized with respect to the pre-stimulus values. In logistic regression analysis, the best classification performance was achieved with the combination of normalized fEMG power and HR during D C (overall accuracy 81%, sensitivity 53%, specificity 95%), and with the combination of normalized fEMG-related response entropy, electrocardiography (ECG) R-to-R interval (RRI), and PPG dicrotic notch amplitude during sevoflurane anesthesia (overall accuracy 96%, sensitivity 90%, specificity 100%). ECG electrode impedances after alcohol swab skin pretreatment alone were higher than impedances of designated EEG electrodes. The BIS values registered with ECG electrodes were higher than those registered simultaneously with EEG electrodes. No significant difference in the time to home-readiness after isoflurane-N2O or sevoflurane-N2O anesthesia was found, when the administration of the volatile agent was guided by BIS monitoring. All other early and intermediate recovery parameters were also similar. Transient epileptiform EEG activity was detected in eight of 15 sevoflurane patients during a rapid increase in the inspired volatile concentration, and in none of the 16 desflurane patients. The observed transient EEG changes did not adversely affect the recovery of the patients. Following the rapid increase in the inhaled desflurane concentration, HR increased transiently, reaching its maximum in two minutes. In the sevoflurane group, the increase was slower and more subtle. In conclusion, desflurane may be a safer volatile agent than sevoflurane in patients with a lowered seizure threshold. The tachycardia induced by a rapid increase in the inspired desflurane concentration may present a risk for patients with heart disease. Designated EEG electrodes may be superior to ECG electrodes in EEG BIS monitoring. When the administration of isoflurane or sevoflurane is adjusted to maintain BIS values at 50-60 in healthy ambulatory surgery patients, the speed and quality of recovery are similar after both isoflurane-N2O and sevoflurane-N2O anesthesia. When anesthesia is maintained by the inhalation of N2O and bolus doses of propofol and alfentanil in healthy unparalyzed patients, movement responses may be best avoided by ensuring a relatively deep hypnotic level with propofol. HR/RRI, fEMG, and PPG dicrotic notch amplitude are potential indicators of nociception during anesthesia, but their performance needs to be validated in future studies. Combining information from different sources may improve the discrimination of the level of nociception.

Herpes Simplex Virus Infection, Pathological Pain and Recurrent Lymphocytic Meningitis

Background: Aims of the study were: (i) to characterise the clinical picture, immunological features and changes in brain morphology and function in patients with widespread unilateral pain and HSV-infections, and (ii) to analyse the prevalence, clinical symptoms and immunological predisposing factors of HSV-2 induced recurrent lymphocytic meningitis (RLM) in Southern Finland. Patients and methods: Patients for the studies were recruited from the Pain Clinic, and from the Department of Neurology, at Helsinki University Central Hospital. Plasma concentrations of IgM, IgA, IgG, and IgG1-4, and serum concentrations of C3, C4 were measured. Serological anti-HSV-1 and -2 antibody status was tested. C4 genotyping, HLA-A, HLA-B and HLA-DRB1 typing, MBL2 genotyping, and IgG1 and IgG3 allotyping (Gm) were performed. Clinical neurological examination, quantitative sensory testing, skin biopsy, and functional magnetic resonance imaging were also performed. Results: HSV probably has a role in the generation of a pathological pain state. Low serum IgG1 and IgG3 levels, made the patients vulnerable for recurring HSV infections. Both functional and structural changes were observed in the brain pain-processing areas in the patients: they had less pain-related activity in the insular cortices bilaterally, in the anterior cingular cortex (ACC), and in the thalamus, and the gray matter density was lower in the ACC, in the frontal and prefrontal cortices. In the meningitis studies it was shown that RLM is more common and less benign than previously reported, and that neuropathic pain is frequently present both during and after meningitis episodes. HLA-DRB1*01, HLA-B*27, and low IgG1 levels are predisposing factors for RLM. Conclusions: Patients are vulnerable to recurrent HSV infections because of subtle immunological abnormalities. HSV causes diverse clinical manifestations. First, the herpes simplex virus, or the inflammatory process triggered by it, may cause pathological widespread pain probably by activating glial cells in the CNS. In these patients, signs of alterations in the brain pain-processing areas can be demonstrated by functional brain imaging methods. Secondly, HSV-2 induced RLM is a rare complication of HSV-2 virus. The predisposing factors include low IgG1 subclass levels, HLA-DRB1*01 and HLA –B*27 genotypes. Neuropathic pain is frequently associated with RLM.

Aqueous colloidal stability evaluated by zeta potential measurement and resultant TiO2 for superior photovoltaic performance

Controlling the morphological structure of titanium dioxide (TiO 2) is crucial for obtaining superior power conversion efficiency for dye-sensitized solar cells. Although the sol-gel-based process has been developed for this purpose, there has been limited success in resisting the aggregation of nanostructured TiO2, which could act as an obstacle for mass production. Herein, we report a simple approach to improve the efficiency of dye-sensitized solar cells (DSSC) by controlling the degree of aggregation and particle surface charge through zeta potential analysis. We found that different aqueous colloidal conditions, i.e., potential of hydrogen (pH), water/titanium alkoxide (titanium isopropoxide) ratio, and surface charge, obviously led to different particle sizes in the range of 10-500 nm. We have also shown that particles prepared under acidic conditions are more effective for DSSC application regarding the modification of surface charges to improve dye loading and electron injection rate properties. Power conversion efficiency of 6.54%, open-circuit voltage of 0.73 V, short-circuit current density of 15.32 mA/cm2, and fill factor of 0.73 were obtained using anatase TiO 2 optimized to 10-20 nm in size, as well as by the use of a compact TiO2 blocking layer.

Task-dependent activations of human auditory cortex during pitch discrimination and pitch memory tasks

"The functional organization of auditory cortex (AC) is still poorly understood. Previous studies suggest segregation of auditory processing streams for spatial and nonspatial information located in the posterior and anterior AC, respectively (Rauschecker and Tian, 2000; Arnott et al., 2004; Lomber and Malhotra, 2008). Furthermore, previous studies have shown that active listening tasks strongly modulate AC activations (Petkov et al., 2004; Fritz et al., 2005; Polley et al., 2006). However, the task dependence of AC activations has not been systematically investigated. In the present study, we applied high-resolution functional magnetic resonance imaging of the AC and adjacent areas to compare activations during pitch discrimination and n-back pitch memory tasks that were varied parametrically in difficulty. We found that anterior AC activations were increased during discrimination but not during memory tasks, while activations in the inferior parietal lobule posterior to the AC were enhanced during memory tasks but not during discrimination. We also found that wide areas of the anterior AC and anterior insula were strongly deactivated during the pitch memory tasks. While these results are consistent with the proposition that the anterior and posterior AC belong to functionally separate auditory processing streams, our results show that this division is present also between tasks using spatially invariant sounds. Together, our results indicate that activations of human AC are strongly dependent on the characteristics of the behavioral task."