Using a Bioluminescent Bacterial Bioreporter to Assess Iron Bioavailability in the Oceans

Recent improvements in modern analytical methods have considerably increased our understanding of Fe biogeochemistry in the Ocean. Compiled data have shown that Fe concentrations are low in most open ocean surface waters and that the bioavailability of this Fe is influenced by organic complexation. Of presumed biotic origin, the importance of this organic complexation to Fe availability remains to be elucidated. Unfortunately, current analytical tools do not allow for a linkage to be established between Fe speciation to Fe bioavailability. To supplement chemical analyses, we have developed a bioanalytical tool: a heterotrophic bacterial bioluminescent reporter system that responds quantitatively to bioavailable Fe concentrations. Data collected during one field study in a freshwater system as well as three independent field studies in marine systems demonstrate that these whole-cell biosensors are a powerful tool for environmental monitoring, providing both qualitative and quantitative insights on Fe biogeochemistry. To complement this work, laboratory studies have been carried out to characterize the influence of various sources of Fe-complexing organic ligands, including synthetic chelators, bacterial and fungal siderophores and virus-mediated bacterial lysis products. The results of this study will be presented in the context of attempting to clarify the role that the organic complexation of Fe may play in regulating Fe bioavailability to the diverse planktonic components of the aquatic microbial community. To improve our abilities to standardize this tool in the field, a green fluorescent protein gene expressed under control of a constitutive promoter has been introduced in the genomic DNA of P. putida FeLux. The resulting dual bioreporter will allow for the enumeration of bioreporter cells in environmental samples in parallel to the detection the bioluminescent signal in response to changes in Fe bioavailability

Dissociating Explicit and Implicit Timing in Parkinson\u2019s Disease Patients: Evidence from Bisection and Foreperiod Tasks

A consistent body of literature reported that Parkinson\u2019s disease (PD) is marked by severe deficits in temporal processing. However, the exact nature of timing problems in PD patients is still elusive. In particular, what remains unclear is whether the temporal dysfunction observed in PD patients regards explicit and/or implicit timing. Explicit timing tasks require participants to attend to the duration of the stimulus, whereas in implicit timing tasks no explicit instruction to process time is received but time still affects performance. In the present study, we investigated temporal ability in PD by comparing 20 PD participants and 20 control participants in both explicit and implicit timing tasks. Specifically, we used a time bisection task to investigate explicit timing and a foreperiod task for implicit timing. Moreover, this is the first study investigating sequential effects in PD participants. Results showed preserved temporal ability in PD participants in the implicit timing task only (i.e., normal foreperiod and sequential effects). By contrast, PD participants failed in the explicit timing task as they displayed shorter perceived durations and higher variability compared to controls. Overall, the dissociation reported here supports the idea that timing can be differentiated according to whether it is explicitly or implicitly processed, and that PD participants are selectively impaired in the explicit processing of time

Interval discrimination across different duration ranges with a look at spatial compatibility and context effects

In the present study, a time discrimination task was used to investigate the effect of different contexts for intervals varying from 400 to 1600 ms. A potential time-space interaction was controlled, and participants used both manual responses (Experiments 1 and 2) and vocal responses (Experiment 3). Three ranges of durations were employed (short, middle and long), and within each range condition, three standard values were used (400, 700, and 1000 ms; 700, 1000, and 1300 ms; and 1000, 1300, and 1600 ms). Within each range, standard intervals were randomized (Experiments 1 and 3) or remained constant (Experiment 2) within a block of trials. Our results suggest that context influences time discrimination performances only when the temporal range under investigation is below 1300 ms and the temporal intervals varied within blocks. In the case of temporal intervals longer than 1300 ms, participants presented a tendency to respond “long” independently of the procedure used. Moreover, our results suggested that performances in a discrimination task are mainly influenced by the fact of varying standard durations within blocks, and not much by the time-space compatibility. -- Keywords : time discrimination, context effect, spatial compatibility, temporal intervals, manual responses, verbal response

Me, myself and you: How self-consciousness influences time perception

Several investigations have shown that the processing of self-relevant information differs from processing objective information. The present study aimed to investigate the effect of social stimuli on subjective time processing. Here, social stimuli are images of an unknown male and female person and an image of participants' self. Forty university students were tested with a time reproduction task in which they were asked to reproduce the duration of the stimulus previously presented. Images of others or themselves were used to mark the temporal intervals. Participants also performed questionnaires to evaluate the level of anxiety and depression as well as self-consciousness. A generalised linear mixed-effects model approach was adopted. Results showed that male participants with higher Private Self-Consciousness scores showed higher time perception accuracy than females. Also, female participants reported higher scores for the Public Self-Consciousness subscale than male participants. The findings are discussed in terms of social context models of how attention is solicited and arousal is generated by social stimuli, highlighting the effect of social context on subjective perception of time

The effect of emotion intensity on time perception: a study with transcranial random noise stimulation

Emotional facial expressions provide cues for social interactions and emotional events can distort our sense of time. The present study investigates the effect of facial emotional stimuli of anger and sadness on time perception. Moreover, to investigate the causal role of the orbitofrontal cortex (OFC) in emotional recognition, we employed transcranial random noise stimulation (tRNS) over OFC and tested the effect on participants' emotional recognition as well as on time processing. Participants performed a timing task in which they were asked to categorize as "short" or "long" temporal intervals marked by images of people expressing anger, sad or neutral emotional facial expressions. In addition, they were asked to judge if the image presented was of a person expressing anger or sadness. The visual stimuli were facial emotional stimuli indicating anger or sadness with different degrees of intensity at high (80%), medium (60%) and low (40%) intensity, along with neutral emotional face stimuli. In the emotional recognition task, results showed that participants were faster and more accurate when emotional intensity was higher. Moreover, tRNS over OFC interfered with emotion recognition, which is in line with its proposed role in emotion recognition. In the timing task, participants overestimated the duration of angry facial expressions, although neither emotional intensity not OFC stimulation significantly modulated this effect. Conversely, as the emotional intensity increased, participants exhibited a greater tendency to overestimate the duration of sad faces in the sham condition. However, this tendency disappeared with tRNS. Taken together, our results are partially consistent with previous findings showing an overestimation effect of emotionally arousing stimuli, revealing the involvement of OFC in emotional distortions of time, which needs further investigation

Effects of observing hand motor action on number processing: an online study

In this online study we hypothesized that hand pointing might specifically contribute to the processing of number ordinality, since we learn to list, order, and count series of items through pointing. To test this hypothesis, we asked participants to observe hand pointing or grasping prior to executing number comparison. In experiment 1, participants (N=77) indicated whether a number was larger/smaller than a reference number (magnitude task), therefore processing number cardinality. In Experiment 2, participants (N=75) processed number ordinality, judging whether a number came before/after a reference number in a mental number line (order task). The results showed that response times in the magnitude task (Exp. 1) were faster after grasping as compared to pointing. In the order task (Exp. 2), response times did not differ between grasping and pointing conditions. These results suggest that hand action contribute to specific aspects of numerical processing, in line with embodied accounts of cognition

Young adults and multisensory time perception: Visual and auditory pathways in comparison

: The brain continuously encodes information about time, but how sensorial channels interact to achieve a stable representation of such ubiquitous information still needs to be determined. According to recent research, children show a potential interference in multisensory conditions, leading to a trade-off between two senses (sight and audition) when considering time-perception tasks. This study aimed to examine how healthy young adults behave when performing a time-perception task. In Experiment 1, we tested the effects of temporary sensory deprivation on both visual and auditory senses in a group of young adults. In Experiment 2, we compared the temporal performances of young adults in the auditory modality with those of two samples of children (sighted and sighted but blindfolded) selected from a previous study. Statistically significant results emerged when comparing the two pathways: young adults overestimated and showed a higher sensitivity to time in the auditory modality compared to the visual modality. Restricting visual and auditory input did not affect their time sensitivity. Moreover, children were more accurate at estimating time than young adults after a transient visual deprivation. This implies that as we mature, sensory deprivation does not constitute a benefit to time perception, and supports the hypothesis of a calibration process between senses with age. However, more research is needed to determine how this calibration process affects the developmental trajectories of time perception

Understanding, Assessing and Treating Prospective Memory Dysfunctions in Traumatic Brain Injury Patients

Our capacity to shape and direct our future behaviour is of fundamental importance in the development, pursuit, and maintenance of independence and autonomy from early childhood to late adulthood. A cognitive ability required for those functions is prospective memory (PM), which is the ability to form and remember to prospectively perform the intended action. Researchers have extensively focused on PM impairment in patients with traumatic brain injury (TBI). However, there has been limited research into the assessment and treatment of PM impairment in TBI patients. Reliable and valid tests with normative data are necessary for health professionals working with people with PM impairments. This chapter reviews the principal findings on PM impairment in TBI patients, and the main procedures used to assess and rehabilitate PM