Habitat associations of shovelnose sturgeon \u3ci\u3eScaphirhynchus platorynchus\u3c/i\u3e (Rafinesque, 1820) in the lower Platte River, Nebraska

Human induced alterations of river systems are ubiquitous throughout the world. Alterations have reduced riverine habitat and negatively affected riverine species; therefore, it is crucial to understand what habitats are important to riverine fish at multiple scales. Most research has focused around microhabitats (i.e., depth) with little effort on how the reach scale habitat (i.e., geomorphic landscape) influences riverine fish abundance. We examined habitat associations of shovelnose sturgeon sampled with two gears (trotlines and trammel nets) at multiple spatial scales in the lower Platte River, NE, a system that has not been overtly altered in physical description. At a microhabitat scale, shovelnose sturgeon abundance was influenced by velocities and temperatures within the lower Platte River. The influence of velocity was contradictory between gears suggesting that gear limitations may have been present. Shovelnose sturgeon abundance increased in close proximity to a tributary interaction with the lower Platte River in both gears. Portions of the river with a relatively medium valley width, low-medium sinuosity, and wide channel had the lowest shovelnose sturgeon abundance for both gears. Our results provide insight at multiple habitat scales on the landscape that may help managers and policy makers develop sound approaches to protecting and mitigating habitat for shovelnose sturgeon and other riverine species

Neural activity associated with episodic memory for emotional context

To address the question of which brain regions subserve retrieval of emotionally-valenced memories, we used event-related fMRI to index neural activity during the incidental retrieval of emotional and non-emotional contextual information. At study, emotionally neutral words were presented in the context of sentences that were either negatively, neutrally or positively valenced. At test, fMRI data were obtained while participants discriminated between studied and unstudied words. Recognition of words presented in emotionally negative relative to emotionally neutral contexts was associated with enhanced activity in right dorsolateral prefrontal cortex, left amygdala and hippocampus, right lingual gyrus and posterior cingulate cortex. Recognition of words from positive relative to neutral contexts was associated with increased activity in bilateral prefrontal and orbitofrontal cortices, and left anterior temporal lobe. These findings suggest that neural activity mediating episodic retrieval of contextual information and its subsequent processing is modulated by emotion in at least two ways. First, there is enhancement of activity in networks supporting episodic retrieval of neutral information. Second, regions known to be activated when emotional information is encountered in the environment are also active when emotional information is retrieved from memory. Copyright © 2001 Elsevier Science Ltd

Remembrance of Odors Past Human Olfactory Cortex in Cross-Modal Recognition Memory

AbstractEpisodic memory is often imbued with multisensory richness, such that the recall of an event can be endowed with the sights, sounds, and smells of its prior occurrence. While hippocampus and related medial temporal structures are implicated in episodic memory retrieval, the participation of sensory-specific cortex in representing the qualities of an episode is less well established. We combined functional magnetic resonance imaging (fMRI) with a cross-modal paradigm, where objects were presented with odors during memory encoding. We then examined the effect of odor context on neural responses at retrieval when these same objects were presented alone. Primary olfactory (piriform) cortex, as well as anterior hippocampus, was activated during the successful retrieval of old (compared to new) objects. Our findings indicate that sensory features of the original engram are preserved in unimodal olfactory cortex. We suggest that reactivation of memory traces distributed across modality-specific brain areas underpins the sensory qualities of episodic memories

Population characteristics of Shovelnose Sturgeon during low- and high-water conditions in the lower Platte River, Nebraska

Cycles of low- and high-water periods (i.e., years) in river systems are natural occurrences, but understanding how cyclical climatological patterns affect fishes, especially long-lived species, is unclear. We assessed Shovelnose Sturgeon population dynamics between a period of low- (2001-2004) and high- (2009-2012) water years in the lower Platte River, Nebraska. Low-flow periods in the lower Platte River can cause disconnection(s) between upstream and downstream reaches resulting in isolated pools and elevated water temperatures leading to stressful situations for aquatic life and possible mortality. Our data show no measurable differences between key population indices between flow condition periods which is consistent with current paradigms for long-lived fish species. Shovelnose Sturgeon relative weights were generally \u3e 80 during both low- and high-water periods and the size structure did not differ between the two periods. Shovelnose Sturgeon abundances, however, were greater during high-water conditions compared to low-water conditions (Kruskal-Wallis: χ2 = 6.15, d.f. = 1, P = 0.01). Shovelnose Sturgeon may have migrated to more suitable habitats during low-water periods to seek refuge allowing these individuals to return during more suitable conditions. Shovelnose Sturgeon and other riverine fish have evolved in a variable environment and have been able to endure relatively minor anthropogenic changes within the lower Platte River. Rivers like the lower Platte River that have retained much of their original physical features and flow regimes are likely key components for the resistance and resilience of riverine species. However, as alterations to landscapes continue and uncertainty exists surrounding future climate predictions, it is unknown how these riverine species will be able to adapt to future changes. The reduction in anthropogenic changes that disrupt flow regimes and increasing connectivity among river systems could provide more fish refuge during stressful conditions helping to protect these riverine species

Changes in brain electrical activity during extended continuous word recognition

Twenty healthy subjects (10 men, 10 women) participated in an EEG study with an extended continuous recognition memory task, in which each of 30 words was randomly shown 10 times and subjects were required to make old vs. new decisions. Both event-related brain potentials (ERPs) and induced band power (IBP) were investigated. We hypothesized that repeated presentations affect recollection rather than familiarity. For the 300- to 500-ms time window, an 'old/new' ERP effect was found for the first vs. second word presentations. The correct recognition of an 'old' word was associated with a more positive waveform than the correct identification of a new word. The old/new effect was most pronounced at and around the midline parietal electrode position. For the 500- to 800-ms time window, a linear repetition effect was found for multiple word repetitions. Correct recognition after an increasing number of repetitions was associated with increasing positivity. The multiple repetitions effect was most pronounced at the midline central (Cz) and fronto-central (FCz) electrode positions and reflects a graded recollection process: the stronger the memory trace grows, the more positive the ERP in the 500- to 800-ms time window. The ERP results support a dual-processing model, with familiarity being discernable from a more graded recollection state that depends on memory strengths. For IBP, we found 'old/new' effects for the lower-2 alpha, theta, and delta bands, with higher bandpower during 'old' words. The lower-2 alpha 'old/new' effect most probably reflects attentional processes, whereas the theta and delta effects reflect encoding and retrieval processes. Upon repeated word presentations, the magnitude of induced delta power in the 375- to 750-ms time window diminished linearly. Correlation analysis suggests that decreased delta power is moderately associated with faster decision speed and higher accurac

Divergent density feedback control of migratory predator recovery following sex-biased perturbations

Uncertainty in risks posed by emerging stressors such as synthetic hormones im-pedes conservation efforts for threatened vertebrate populations. Synthetic hor-mones often induce sex-biased perturbations in exposed animals by disrupting gonad development and early life-history stage transitions, potentially diminishing per capita reproductive output of depleted populations and, in turn, being manifest as Allee effects. We use a spatially explicit biophysical model to evaluate how sex-biased perturbation in life-history traits of individuals (maternal investment in egg production and male-skewed sex allocation in offspring) modulates density feedback control of year-class strength and recovery trajectories of a long-lived, migratory fish—shovelnose sturgeon (Scaphirhynchus platorynchus)—under spatially and tempo-rally dynamic synthetic androgen exposure and habitat conditions. Simulations show that reduced efficiency of maternal investment in gonad development prolonged maturation time, increased the probability of skipped spawning, and, in turn, shrunk spawner abundance, weakening year-class strength. However, positive density feed-back disappeared (no Allee effect) once the exposure ceased. By contrast, responses to the demographic perturbation manifested as strong positive density feedback; an abrupt shift in year-class strength and spawner abundance followed after more than two decades owing to persistent negative population growth (a strong Allee effect), reaching an alternative state without any sign of recovery. When combined with the energetic perturbation, positive density feedback of the demographic perturbation was dampened as extended maturation time reduced the frequency of producing male-biased offspring, allowing the population to maintain positive growth rate (a weak Allee effect) and gradually recover. The emergent patterns in long-term population projections illustrate that sex-biased perturbation in life-history traits can interactively regulate the strength of density feedback in depleted populations such as Scaphirhynchus sturgeon to further diminish reproductive capacity and abundance, posing increasingly greater conservation challenges in chemically altered river scapes