[No abstract]

Total sleep deprivation (TSD) leads to neurobehavioral changes in experimental tasks of alertness, attention, learning, and motor responses. However, results from working memory (WM) studies are more equivocal. WM comprises multiple cognitive processes and the cerebral basis of this differential vulnerability is not known. The current experiment utilized tasks employing parametric manipulations within an event-related functional magnetic resonance imaging (fMRI) design to better understand the cerebral basis for the differential effects of TSD on WM components. Specifically, the current study utilized fMRI with healthy young adults (n = 20, ages 20-35), who were scanned 12 hours after their habitual wake time and again 36 hours after their habitual wake time in a counterbalanced design. For an attention component, results demonstrated activation in neural regions implicated in selective visual attention and frontal top- down control of the attentional system when participants were attending to the stimuli. For a rehearsal span component, results demonstrated activation in neural regions subserving rehearsal and episodic encoding when maintaining information in WM. The attention component parameter estimates from a mathematical model correlated with selective visual attention brain regions; whereas, the rehearsal span component estimates from the mathematical model correlated with brain regions subserving rehearsal processes. Following TSD, there was a decrease in behavioral performance for the attention component coinciding with decreases in activation (relative to when participants were rested) in the selective visual attention system. For the rehearsal span component, there was intact behavioral performance coinciding with increased activation (relative to when participants were rested) in brain areas subserving rehearsal processes. Results from the mathematical model demonstrated a shift from the use of both rehearsal span and episodic encoding when participants were rested to use of rehearsal span during TSD. These data suggest that a mechanism for decreased performance and activation in verbal WM following TSD lies in impairment of the supervisory attentional system. Alternatively, behavioral performance related to the phonological loop and associated neural substrates compensate in the face of TSD. The compensatory mechanism seems to be related to rehearsal processes as participants shifted from using episodic encoding to phonological rehearsal during TSD

The extent to which low-frequency noise from large vessels is a part of the coastal marine environment and the ramifications of this for blue whale (Balaenoptera musculus) communication ranges and vocal behavior was investigated in the Santa Barbara Channel (SBC), a region off the coast of southern California. Analysis of noise from individual ships transiting the region, identified unique spectral characteristics, and radiated noise levels related to ship-type. Predicting radiated underwater noise from container ships under normal operating conditions proved to be challenging given the high dimensionality of the problem. Generalized additive models of radiated ship noise in relation to design characteristics, operational conditions, and oceanographic features revealed the most relevant parameters associated with ship noise. The statistical approach provided a comprehensive view of radiated ship noise in a coastal environment. Increased background noise levels from commercial ship traffic altered the low-frequency acoustic environment in which large whales are communicating. A comparison of long term averages of ambient noise at different sites revealed that blue whales utilizing this region are exposed to diverse acoustic environments and ranges at which they can communicate acoustically. A significant reduction in average noise levels in the SBC, related to changes in the economy and unintended consequences of an air quality improvement rule, was observed from 2007 to 2010. The decrease in ocean noise provided direct evidence for the impact on the ecosystem from the human activity and presented a unique opportunity to understand the magnitude of change necessary to improve the acoustic habitat quality for blue whales. Although the vocalizations of blue whales continued in the presence of ships, changes in call level and rate were observed. Understanding the interactions between human activity and the marine ecosystem is vital to its sustainability. The results of this research advance scientific understanding of human produced noise in the marine environment, and serves as a model for addressing noise pollution in a coastal region on both an ecosystem and individual species basis