Auditory motion: perception and cortical response

Summary The localization of sound sources in humans is based on the binaural cues, interaural time and level differences (ITDs, ILDs) and the spectral cues (Blauert 1997). The ITDs relate to the timing of sound arrival at the two ears. For example, a sound located at the right side will arrive at the right ear earlier than at the left ear. The ILDs refer to the difference of sound pressure-level between the two ears. In the example mentioned above, if the sound located at the right has short wavelength then it will arrive at the right ear with higher sound-pressure than at the left ear. This is because a sound with short wavelength cannot bypass the head. In other words, the head creates an obstacle that diffracts the waves and that is why the sound arriving at the ear closer to the sound source will receive the sound with higher sound-pressure. Due to the association of each of the binaural cues with the wavelength of a sound, Rayleigh (1907) proposed the ‘duplex theory’ of sound source localization suggesting that on the azimuth, the ITDs is the main localization cue for low frequency sounds and the ILDs is the main localization cue for high frequency sounds. The spectral cues are based on the shape of the pinna’s folds and they are very useful for sound source localization in elevation but they also help in azimuthal localization (Schnupp et al. 2012). The contribution of the spectral cues on the azimuthal localization arises from the fact that due to the symmetrical position of the ears on the head, the binaural cues vary symmetrically as a function of spatial location (King et al. 2001). Whereas the ITDs have a very symmetrical distribution, the ILDs become more symmetrical the higher the sound frequency is. This way, there are certain locations within the left-frontal and left-posterior hemifield, as well as the right-frontal and the right-posterior hemifield that share the same binaural cues, which makes the binaural cues ambiguous and so the auditory system cannot depend solely on these for sound source localization. To resolve this ambiguity, our auditory system uses the spectral cues that help to disambiguate frontal-back confusion (King et al. 2001, Schnupp et al. 2012). The role of these cues in localizing sounds in our environment is well established. But their role in acoustic motion localization is not yet clear. This is the topic of the current thesis. The auditory localization cues are processed on the subcortical and cortical level. The ITDs and ILDs are processed from different neurons along the auditory pathway (Schnupp et al. 2012). Their parallel processing stages seem to converge at the inferior colliculus as evidence shows from cat experiments (Chase and Young 2005). But in humans, an electroencephalographic (EEG) study measuring the mismatch negativity (MMN; Schröger 1996) and a study using magnetoencephalographie (MEG; Salminen et al. 2005) showed that these cues are not integrated. One of the models of the spatial representation of sound sources is Jeffress’ place code (1948). This model suggests that each location of the azimuthal space is encoded differently, thus the name ‘place code’. Evidence in support of this model comes from studies on the cat (Yin and Chan 1990). However, arguments against this model come from studies in gerbils whose results showed that their subcortical neurons respond maximally to locations that are outside the physiological range based on the size of their heads (Pecka et al. 2008). An alternative model of auditory spatial encoding is the hemifield code (von Bekesy 1960). This model proposes that subcortical neurons are separated into two populations, one tuned to the left hemifield and another tuned to the right. Thus, the receptive field of the neurons is wide and the estimation of the sound source location is derived from the balance of activity of these two populations. Evidence from human studies support this model. Salminen and colleagues (2009) employed an adaptation paradigm during MEG recording. They presented sets of adaptor and probe stimuli that either had the same or different spatial location. Their results showed that the response to the probe was more reduced when the adaptor was located at the far left location and not when the adaptor and probe shared the exact same location. Also, an EEG study on auditory motion showed that sounds that move from central to lateral locations elicit higher amplitudes than when the move in the opposite direction (Magezi and Krumbholz 2010). The authors concluded that these results are based on the movement of the sound source towards the location of the maximal activity of the neurons (also in Salminen et al. 2012). The ability to detect moving objects is well-embedded into our nature. Whereas it enriches predators and prey with the skills to survive, in everyday life it enables us to interact with our environment. For example, the task of crossing a street (without traffic signs) safely is based on the encoding of visual and auditory features of moving vehicles. In the visual modality, the capability of the system to encode motion is based on motion-specific neurons (Mather 2011). In the auditory modality, the debate over whether these sensors exist is still ongoing. One theory on how the auditory system encodes motion is the ‘snapshot’ theory (Chandler and Grantham 1991, Grantham 1986). In a series of experiments, Grantham (1986) showed that auditory perception was not affected by features of motion such as velocity, but it was more sensitive on distance as a spatial cue. Thus, what he suggested is that the encoding of auditory motion is based on the mechanisms that encode stationary sounds. In other words, when a sound is moving it activates the neurons that correspond to the points that are located along the trajectory of that sound but in a serial manner. This way, the perception of auditory motion is based on ‘snapshots’ instead of processing motion as a complete feature. This mechanism of auditory motion processing corroborates with Jeffress’ place code (1948). Animal studies on monkeys (Ahissar et al. 1992) and owls (Wagner et al. 1994) showed that neurons responded similarly to moving and stationary sounds. Evidence against this theory come from a recent behavioural study that introduced velocity changes within acoustic motion and showed that participants were able to detect them (Locke et al. 2016). The authors concluded that if ‘snapshot’ theory would be true, then these detections of velocity change would not occur. Another theory of auditory motion was evolved that supports the motion-specific mechanisms in the brain (Warren et al. 2002, Docummun et al. 2004, Poirier et al. 20017). A human study using functional magnetic resonance imaging (fMRI) and positron-emission tomography (PET) showed evidence of a motion-specific cortical network that includes the planum temporale and the parietotemporal operculum (Warren et al. 2002). The authors suggested that these areas are part of a posterior processing stream that is responsible for analysis of auditory moving objects. Moreover, a recent primate fMRI study provided evidence of motion-specificity in the activity of the posterior belt and parabelt regions of the primary auditory cortex (Poirier et al. 2017). The authors contrasted cortical response to auditory motion with stationary and spectrotemporal sounds and found that the aforementioned cortical areas were only activated by moving sounds. All in all, the neuronal mechanism underlying auditory motion perception has been vaguely described. However, there is an increasing number of evidence that show that specialized motion areas and mechanisms exist in the cortex. To study how exactly these mechanisms function, it is important to know which aspects of the stimulus paradigm affect the response. Study 1. In this study, I focused on eliciting the cortical motion-onset response (MOR) in the freefield. This specific response is measured with EEG and it is elicited when a sound motion follows a stationary sound without any temporal gaps between them. The stationary part serves as an adaptive sound and the onset of motion provides a release-of-adaptation, which gives rise to the MOR. One of the focus was to investigate the effect on the MOR when the initial part is moving in space instead of being stationary. In addition, a secondary focus was the effect of the stimuli frequency on the MOR. I hypothesized that, due to the adaptation provided by the initial stimulus part, the motion response would be smaller after moving than after stationary adaptation. Also, I expected that the effects of frequency would follow the literature and since the motion response is a late response, the amplitude would be smaller after the high frequency than low frequency stimulus presentation. The results showed that the current paradigm did not elicit the MOR. Comparison of the current experimental settings with those used previously in the literature showed that the MOR is strongly depended on the adaptation time provided by the first part of the stimuli. Study 2. In this study, the stimulus characteristics were adapted after failing to elicit the response in the previous study. In addition, I employed an active instead of a passive paradigm, since data from the literature show that the motion response is strongly dependent on the allocation of attention on auditory motion. Thus, in this study, the elicitation of the MOR was successful. The current study examines the modulation of the MOR based on the frequency-range of sound stimuli. Higher amplitude on the motion response was expected after the presentation of stimuli with high frequency spectrum. Also, I studied the effects of hemifield presentation and the direction of motion on the MOR. The results showed that the early part of the motion response (cN1) was modulated by the frequency range of the sounds with stronger amplitudes elicited by stimuli with high frequency range. Study 3. This study is focused on analysis from data collected in the previous study. The focus, however, is on the effects of the stimulus paradigm on the MOR. I hypothesized that after the adaptation provided by an initial moving part, lower amplitude was expected in comparison to the stimuli with an initial stationary part. These responses were also analysed based on the effects of stimulus frequency. The results showed that the stimulus paradigm with the initial moving part elicited a response that resembles the MOR but has lower amplitude. In addition, the effects of stimulus frequency evident from the previous analysis apply here as well, with high frequency stimuli eliciting higher MOR amplitude than low frequency stimuli. Study 4. This study examined further the effects of stimuli characteristics on the MOR. Since the latency of the MOR in the previous study was a bit later than what is usually reported in the literature, the focus here was to test the effects of motion velocity and adaptation duration on the MOR. The results showed that faster velocity elicited higher amplitudes on the peak-to-peak comparison. Separate analysis on the MOR components, showed that this effect was based on higher cN1 amplitude. A separate analysis between the electrodes over the left and right hemisphere, showed that the peak-to-peak amplitude was stronger on the electrodes over the right hemisphere. Lastly, the strong adaptation created by the long duration of the initial stationary part provided abundant evidence of auditory motion, which led to the separation of the cP2 into its constituent parts. Study 5. This behavioural study focused on the effect of motion adaptation on the rear field to the presentation of motion in the frontal field. Thus, the presentation of adaptors and probes within the left-frontal and left-rear fields aimed at locations that share the same ITDs and ILDs. The disambiguation of auditory localization of motion is based on how these interaural cues interact with the spectral cues. A moving probe was presented in the left hemifield, following an adaptor that spanned either the same trajectory or a trajectory located in the opposite field (frontal/ rear). Participants had to indicate the direction of the probe. The results showed that performance was worse when adaptor and probe were sharing the same binaural cues, even if they were in different hemifields and their direction was opposite. But the magnitude of the adaptation effect when the pair was in different hemifields was smaller, thus showing motion-direction detection depends on the integration of interaural and spectral cues

A Trib2-p38 axis controls myeloid leukaemia cell cycle and stress response signalling

Trib2 pseudokinase is involved in the etiology of a number of cancers including leukaemia, melanoma, ovarian, lung and liver cancer. Both high and low Trib2 expression levels correlate with different types of cancer. Elevated Trib2 expression has oncogenic properties in both leukaemia and lung cancer dependent on interactions with proteasome machinery proteins and degradation of transcription factors. Here, we demonstrated that Trib2 deficiency conferred a growth and survival advantage both at steady state and in stress conditions in leukaemia cells. In response to stress, wild type leukaemia cells exited the cell cycle and underwent apoptosis. In contrast, Trib2 deficient leukaemia cells continued to enter mitosis and survive. We showed that Trib2 deficient leukaemia cells had defective MAPK p38 signalling, which associated with a reduced γ-H2Ax and Chk1 stress signalling response, and continued proliferation following stress, associated with inefficient activation of cell cycle inhibitors p21, p16 and p19. Furthermore, Trib2 deficient leukaemia cells were more resistant to chemotherapy than wild type leukaemia cells, having less apoptosis and continued propagation. Trib2 re-expression or pharmacological activation of p38 in Trib2 deficient leukaemia cells sensitised the cells to chemotherapy-induced apoptosis comparable with wild type leukaemia cells. Our data provide evidence for a tumour suppressor role of Trib2 in myeloid leukaemia via activation of p38 stress signalling. This newly identified role indicates that Trib2 may counteract the propagation and chemotherapy resistance of leukaemia cells

Species-specific secondary metabolites from Primula veris subsp. veris obtained In Vitro adventitious root cultures: an alternative for sustainable production

Primula veris subsp. veris L. is a perennial herbaceous and medicinal plant species the roots and flowers of which are a source of valuable pharmaceutical raw materials. The plant tissues are used to produce expectorant and diuretic drugs due to their high content of triterpene saponins and phenolic glycosides. Underground roots of P. veris can be obtained only through a destructive process during the plant’s harvesting. In the present study, an in vitro adventitious root production protocol was developed as an alternative way of production, focused on four species-specific secondary metabolites. Root explants were cultured in Murashing & Skoog liquid medium supplemented with 5.4 µM α-naphthaleneacetic acid, 0.5 µM kinetin, L-proline 100 mg/L, and 30 g/L sucrose, in the dark and under agitation. The effect of temperature (10, 15 and 22 ◦C) on biomass production was investigated. The content of two flavonoid compounds (primeverin and primulaverin), and two main triterpene saponins (primulic acid I and II) were determined after 60 days of culture and compared with 1.5-year-old soil-grown plants. The accumulated content (mg/g DW) of bioactive compounds of in vitro adventitious roots cultured under 22 ◦C was significantly higher than the other two temperatures of the study, being 9.71 mg/g DW in primulaverin, 0.09 mg/g DW in primeverin, 6.09 mg/g DW in primulic acid I, and 0.51 mg/g DW in primulic acid II. Compared to the soil-grown roots (10.23 mg/g DW primulaverin, 0.28 mg/g DW primeverin, 17.01 mg/g DW primulic acid I, 0.09 mg/g DW primulic acid II), the in vitro grown roots at 22 ◦C exhibited a 5.67-fold higher content in primulic acid II. However, primulic acid I and primeverin content were approximately three-fold higher in soil-grown roots, while primulaverin content were at similar levels for both in vitro at 22 ◦C and soil-grown roots. From our results, tissue culture of P. veris subsp. veris could serve not only for propagation but also for production of species-specific secondary metabolites such as primulic acid II through adventitious root cultures. This would therefore limit the uncontrolled collection of this plant from its natural environment and provide natural products free from pesticides in a sustainable wa

Crystal structures of native cytochrome c 6 from Thermosynechococcus elongatus in two different space groups and implications for its oligomerization

Native cytochrome c (6) was purified from an extract of strain BP-1 of the thermophilic cyanobacterium Thermosynechococcus elongatus. The protein was crystallized, and with only slight modifications of the buffer and vapour-diffusion conditions two different space groups were observed, namely H3 and C2. Both crystal structures were solved; they contained three and six molecules per asymmetric unit and were refined to 1.7 and 2.25 Å resolution, respectively. To date, the structure of native cytochrome c (6) from T. elongatus has only been reported as a monomer using NMR spectroscopy, i.e. without addressing putative oligomerization, and related structures have only previously been solved using X-ray crystallography after recombinant gene overexpression in Escherichia coli. The reported space groups of related cyanobacterial cytochrome c (6) structures differ from those reported here. Interestingly, the protein–protein interfaces that were observed utilizing X-ray crystallography could also explain homo-oligomerization in solution; specifically, trimerization is indicated by infra-red dynamic light scattering and blue native gel electrophoresis in solution. Trimers were also detected by mass spectrometry. Furthermore, there is an indication of post-translational methylation in the crystal structure. Additionally, the possibility of modifying the crystal size and the redox activity in the context of photosynthesis is shaping the investigated cytochrome as a highly suitable model protein for advanced serial crystallography at highly brilliant X-ray free-electron laser sources

Protein hydrolysates supplement in the nutrient solution of soilless grown fresh peppermint and spearmint as a tool for improving product quality

7openInternationalInternational coauthor/editorThe present study investigated the potential of fresh peppermint (Mentha × piperita L.) and spearmint (Mentha spicata L.) production on a floating raft system combined with a commercial protein hydrolysate supplement (Amino16®) in a nutrient solution aiming to improve plant product quality. Three levels of the protein hydrolysate solution (0, 0.25 and 0.50%) were added in the nutrient solution, and the plants were harvested after twenty-four days. Plant growth characteristics were recorded, and nutritional, essential oil and polyphenolic composition were determined in fresh tissue. The addition of protein hydrolysates did not affect the fresh or dry weight but reduced plant height. Nitrate content significantly decreased, while total chlorophyll and essential oil content increased in both species. Moreover, the protein hydrolysate solution further increased total antioxidant capacity, total soluble phenol and carotenoid contents in spearmint plants, while it did not affect the essential oil and polyphenolic composition in both species. In conclusion, protein hydrolysates solution may be added in the nutrient solution, to improve the quality of peppermint and spearmint grown in a floating system, without adverse effects on crop yield or the essential oil and polyphenolic profile.openAktsoglou, D.; Kasampalis, D.; Sarrou, E.; Tsouvaltzis, P.; Chatzopoulou, P.; Martens, S.; Siomos, A.Aktsoglou, D.; Kasampalis, D.; Sarrou, E.; Tsouvaltzis, P.; Chatzopoulou, P.; Martens, S.; Siomos, A

Foliar calcium effects on quality and primary and secondary metabolites of white-fleshed ‘Lemonato’ peaches

‘Lemonato’ is a Greek peach melting-flesh white-flesh cultivar with high nutritional value highly appreciated by the consumers. This study aimed to evaluate the effect of pre-harvest foliar calcium application on fruit quality, primary metabolite profile, antioxidant activity, total phenolic content, and phenolic profile of the ‘Lemonato’ peach, clone ‘Stamatis’. The experiment was conducted for two years, 2019 and 2020, in two commercial orchards at Kato Lehonia and Agios Vlasios regions, central Greece, where the ‘Lemonato’ clone ‘Stamatis’ is traditionally cultivated. The treatments were organic calcium (Ca), calcium–silicate in nanoparticles (Ca–Si), and calcium chloride (CaCl2). Foliar application of the different Ca formulations, commonly used as a horticultural practice, were not effective at improving the fruit quality characteristics in this clone, which is characterized by fruit softening during ripening. The study revealed the sugars and organic acid composition and phenolic profile of the ‘Lemonato’ peach, clone ‘Stamatis’. Peach fruit quality, primary metabolites, and phenolic compounds of the two orchards showed a different response to organic Ca and Ca–Si, indicating that genetic or environmental factors may also be involved. A higher concentration of organic Ca and CaCl2 increased the peach fruit phenolic compounds content and the total antioxidant activity, improving the fruit nutritional qualit

Age-specific biological and molecular profiling distinguishes paediatric from adult acute myeloid leukaemias

Acute myeloid leukaemia (AML) affects children and adults of all ages. AML remains one of the major causes of death in children with cancer and for children with AML relapse is the most common cause of death. Here, by modelling AML in vivo we demonstrate that AML is discriminated by the age of the cell of origin. Young cells give rise to myeloid, lymphoid or mixed phenotype acute leukaemia, whereas adult cells give rise exclusively to AML, with a shorter latency. Unlike adult, young AML cells do not remodel the bone marrow stroma. Transcriptional analysis distinguishes young AML by the upregulation of immune pathways. Analysis of human paediatric AML samples recapitulates a paediatric immune cell interaction gene signature, highlighting two genes, RGS10 and FAM26F as prognostically significant. This work advances our understanding of paediatric AML biology, and provides murine models that offer the potential for developing paediatric specific therapeutic strategies

Chemical and Biological Characterization of the Anticancer Potency of \u3ci\u3eSalvia fruticosa\u3c/i\u3e in a Model of Human Malignant Melanoma

Malignant melanoma is one of the most aggressive types of skin cancer with an increasing incidence worldwide. Thus, the development of innovative therapeutic approaches is of great importance. Salvia fruticosa (SF) is known for its anticancer properties and in this context, we aimed to investigate its potential anti-melanoma activity in an in vitro model of human malignant melanoma. Cytotoxicity was assessed through a colorimetric-based sulforhodamine-B (SRB) assay in primary malignant melanoma (A375), non-malignant melanoma epidermoid carcinoma (A431) and non-tumorigenic melanocyte neighbouring keratinocyte (HaCaT) cells. Among eight (8) different fractions of S. fruticosa extracts (SF1-SF8) tested, SF3 was found to possess significant cytotoxic activity against A375 cells, while A431 and HaCaT cells remained relatively resistant or exerted no cytotoxicity, respectively. In addition, the total phenolic (Folin–Ciocalteu assay) and total flavonoid content of SF extracts was estimated, whereas the antioxidant capacity was measured via the inhibition of tert-butyl hydroperoxide-induced lipid peroxidation and protein oxidation levels. Finally, apoptotic cell death was assessed by utilizing a commercially available kit for the activation of caspases - 3, - 8 and - 9. In conclusion, the anti-melanoma properties of SF3 involve the induction of both extrinsic and intrinsic apoptotic pathway(s), as evidenced by the increased activity levels of caspases - 8, and - 9, respectively

Pre- and Post-harvest Melatonin Application Boosted Phenolic Compounds Accumulation and Altered Respiratory Characters in Sweet Cherry Fruit

The aim of the present study was to investigate the impact of exogenous melatonin (0. 5 mM) application through pre-harvest foliar spray and postharvest immersion, alone or in combination, on ripening parameters of sweet cherry (cv. Ferrovia) fruit and their relationship with bioactive compounds and gene expression at harvest as well after cold storage (0°C) for 12 days and subsequent room temperature (20°C) exposure for 8 h. Although several ripening traits were not influenced by melatonin, the combining pre- and post-harvest treatments delayed fruit softening at post-cold period. Preharvest spray with melatonin depressed fruit respiration at time of harvest while all applied treatments induced respiratory activity following cold, indicating that this anti-ripening action of melatonin is reversed by cold. Several genes related to the tricarboxylic acid cycle, such as PaFUM, PaOGDH, PaIDH, and PaPDHA1 were upregulated in fruit exposed to melatonin, particularly following combined pre- and post-harvest application. The accumulation of phenolic compounds, such as neochlorogenic acid, chlorogenic acid, epicatechin, procyanidin B1, procyanidin B2+B4, cyanidin-3-O-galactoside, and cyanidin-3-O-rutinoside along with the expression of several genes involved in phenols biosynthesis, such as PaSK, PaPAL, Pa4CL, PaC4H, and PaFNR were at higher levels in melatonin-treated cherries at harvest and after cold exposure, the highest effects being observed in fruits subjected to both pre- and post-harvest treatments. This study provides a comprehensive understanding of melatonin-responsive ripening framework at different melatonin application conditions and sweet cherry stages, thereby helps to understand the action of this molecule in fruit physiology