Mood modulates auditory laterality of hemodynamic mismatch responses during dichotic listening

CDDO-Im exerts antidepressant-like effects via the Nrf2/ARE pathway in a rat model of post-stroke depression

Increasing evidence suggests that oxidative damage and neuroinflammation play a critical role in the pathogenesis of post-stroke depression (PSD). These pathologic processes are tightly regulated by the NF-E2-related factor 2/antioxidant response element (Nrf2/ARE) signaling pathway. The synthetic triterpenoid, 2-Cyano-3,12-dioxooleana-1,9-dien-28-imidazolide (CDDO-Im), is a potent Nrf2 activator. This study investigated whether CDDO-Im exhibited antidepressant-like activity and elucidated its protective mechanisms in a rat model of PSD, which was produced by middle cerebral artery occlusion (MCAO) followed by 28 days of chronic unpredictable mild stress (CUMS) in conjunction with solitary housing. The results demonstrated that CDDO-Im treatment markedly improved the depressive-like behaviors and reduced neuronal cell loss in the hippocampus, through decreasing the malondialdehyde (MDA) content (indicative of lipid peroxidation), superoxide dismutase (SOD), NF-kB activation, interleukin-6 (IL-6) and interleukin-1b (IL-1β) in PSD rats. CDDO-Im treatment alleviated the oxidative stress and inflammatory response in PSD rats by promoting Nrf2 nuclear import and increasing the protein levels of Nrf2 downstream target genes, including heme oxygenase-1(HOMX1) and, quinone oxidoreductase-1(NQO1).These findings suggested that CDDO-Im treatment exhibited antidepressant-like effects and protected PSD rats from oxidative and inflammatory injury via the Nrf2/ARE pathway. Therefore, CDDO-Im treatment is worthy of further study.

[Structural features of intestinal flora in preterm rats with cognitive impairment: an analysis based on high-thorough sequencing]

OBJECTIVE

To study the structural features of intestinal flora in preterm rats with cognitive impairment and the association of the change in intestinal flora with cognitive impairment in preterm rats.

METHODS

Sprague-Dawley rats at 16-17 days of gestation were intraperitoneally injected with lipopolysaccharide for two consecutive days to establish a model of cognitive impairment, and the rats treated with intraperitoneally injected phosphate-buffered saline were established as the control group. Cesarean section was performed on day 21 of gestation, and preterm rats were randomly assigned to healthy maternal rats for feeding. The place navigation test in the Morris water maze was used to evaluate cognition on day 30 after birth. According to the result, the preterm rats were divided into cognitive impairment group with 21 rats and normal control group with 10 rats. Hematoxylin and eosin staining was used to observe pathological changes of the hippocampus, and fecal samples were collected for 16S rRNA sequencing and analysis. A principal component analysis (PCA) was performed for intestinal flora.

RESULTS

Compared with the normal control group, the cognitive impairment group showed degeneration and necrosis of a large number of neurons in the hippocampus. Compared with the normal control group, the cognitive impairment group had significant reductions in the abundance and diversity of intestinal flora (P<0.05), with a significant increase in the abundance of Proteobacteria at the phylum level (P<0.05), as well as significant reductions in the abundance of Prevotella and Lactobacillus and significant increases in the abundance of Staphylococcaceae and Oligella at the order, family, and genus levels (P<0.05). PCA showed a significant difference in the composition of intestinal flora between the two groups.

CONCLUSIONS

There is a significant change in the structure of intestinal flora in preterm rats with cognitive impairment, which provides a basis for the treatment and intervention of microecological changes due to cognitive impairment after preterm birth.

Comparative Aspects of Hearing in Vertebrates and Insects with Antennal Ears

The evolution of hearing in terrestrial animals has resulted in remarkable adaptations enabling exquisitely sensitive sound detection by the ear and sophisticated sound analysis by the brain. In this review, we examine several such characteristics, using examples from insects and vertebrates. We focus on two strong and interdependent forces that have been shaping the auditory systems across taxa: the physical environment of auditory transducers on the small, subcellular scale, and the sensory-ecological environment within which hearing happens, on a larger, evolutionary scale. We briefly discuss acoustical feature selectivity and invariance in the central auditory system, highlighting a major difference between insects and vertebrates as well as a major similarity. Through such comparisons within a sensory ecological framework, we aim to emphasize general principles underlying acute sensitivity to airborne sounds.

Auditory mismatch impairments are characterized by core neural dysfunctions in schizophrenia

Major theories on the neural basis of schizophrenic core symptoms highlight aberrant salience network activity (insula and anterior cingulate cortex), prefrontal hypoactivation, sensory processing deficits as well as an impaired connectivity between temporal and prefrontal cortices. The mismatch negativity is a potential biomarker of schizophrenia and its reduction might be a consequence of each of these mechanisms. In contrast to the previous electroencephalographic studies, functional magnetic resonance imaging may disentangle the involved brain networks at high spatial resolution and determine contributions from localized brain responses and functional connectivity to the schizophrenic impairments. Twenty-four patients and 24 matched control subjects underwent functional magnetic resonance imaging during an optimized auditory mismatch task. Haemodynamic responses and functional connectivity were compared between groups. These data sets further entered a diagnostic classification analysis to assess impairments on the individual patient level. In the control group, mismatch responses were detected in the auditory cortex, prefrontal cortex and the salience network (insula and anterior cingulate cortex). Furthermore, mismatch processing was associated with a deactivation of the visual system and the dorsal attention network indicating a shift of resources from the visual to the auditory domain. The patients exhibited reduced activation in all of the respective systems (right auditory cortex, prefrontal cortex, and the salience network) as well as reduced deactivation of the visual system and the dorsal attention network. Group differences were most prominent in the anterior cingulate cortex and adjacent prefrontal areas. The latter regions also exhibited a reduced functional connectivity with the auditory cortex in the patients. In the classification analysis, haemodynamic responses yielded a maximal accuracy of 83% based on four features; functional connectivity data performed similarly or worse for up to about 10 features. However, connectivity data yielded a better performance when including more than 10 features yielding up to 90% accuracy. Among others, the most discriminating features represented functional connections between the auditory cortex and the anterior cingulate cortex as well as adjacent prefrontal areas. Auditory mismatch impairments incorporate major neural dysfunctions in schizophrenia. Our data suggest synergistic effects of sensory processing deficits, aberrant salience attribution, prefrontal hypoactivation as well as a disrupted connectivity between temporal and prefrontal cortices. These deficits are associated with subsequent disturbances in modality-specific resource allocation. Capturing different schizophrenic core dysfunctions, functional magnetic resonance imaging during this optimized mismatch paradigm reveals processing impairments on the individual patient level, rendering it a potential biomarker of schizophrenia.

Emotional valence and spatial congruency differentially modulate crossmodal processing: an fMRI study

Salient exogenous stimuli modulate attentional processes and lead to attention shifts-even across modalities and at a pre-attentive level. Stimulus properties such as hemispheric laterality and emotional valence influence processing, but their specific interaction in audio-visual attention paradigms remains ambiguous. We conducted an fMRI experiment to investigate the interaction of supramodal spatial congruency, emotional salience, and stimulus presentation side on neural processes of attention modulation. Emotionally neutral auditory deviants were presented in a dichotic listening oddball design. Simultaneously, visual target stimuli (schematic faces) were presented, which displayed either a negative or a positive emotion. These targets were presented in the left or in the right visual field and were either spatially congruent (valid) or incongruent (invalid) with the concurrent deviant auditory stimuli. According to our expectation we observed that deviant stimuli serve as attention-directing cues for visual target stimuli. Region-of-interest (ROI) analyses suggested differential effects of stimulus valence and spatial presentation on the hemodynamic response in bilateral auditory cortices. These results underline the importance of valence and presentation side for attention guidance by deviant sound events and may hint at a hemispheric specialization for valence and attention processing.

Involvement of the dorsal and ventral attention networks in oddball stimulus processing: a meta-analysis

The aim of this study was to provide the first, comprehensive meta-analysis of the neuroimaging literature regarding greater neural responses to a deviant stimulus in a stream of repeated, standard stimuli, termed here oddball effects. The meta-analysis of 75 independent studies included a comparison of auditory and visual oddball effects and task-relevant and task-irrelevant oddball effects. The results were interpreted with reference to the model in which a large-scale dorsal frontoparietal network embodies a mechanism for orienting attention to the environment, whereas a large-scale ventral frontoparietal network supports the detection of salient, environmental changes. The meta-analysis yielded three main sets of findings. First, ventral network regions were strongly associated with oddball effects and largely common to auditory and visual modalities, indicating a supramodal "alerting" system. Most ventral network components were more strongly associated with task-relevant than task-irrelevant oddball effects, indicating a dynamic interplay of stimulus saliency and internal goals in stimulus-driven engagement of the network. Second, the bilateral inferior frontal junction, an anterior core of the dorsal network, was strongly associated with oddball effects, suggesting a central role in top-down attentional control. However, other dorsal network regions showed no or only modest association with oddball effects, likely reflecting active engagement during both oddball and standard stimulus processing. Finally, prominent oddball effects outside the two networks included the sensory cortex regions, likely reflecting attentive and preattentive modulation of early sensory activity, and subcortical regions involving the putamen, thalamus, and other areas, likely reflecting subcortical involvement in alerting responses.