We assessed working memory load during computer use with neural network pattern recognition applied to EEG spectral features. Eight participants performed high-, moderate-, and low-load working memory tasks. Frontal theta EEG activity increased and alpha activity decreased with increasing load. These changes probably reflect task difficulty-related increases in mental effort and the proportion of cortical resources allocated to task performance. In network analyses, test data segments from high and low load levels were discriminated with better than 95% accuracy. More than 80% of test data segments associated with a moderate load could be discriminated from high- or low-load data segments. Statistically significant classification was also achieved when applying networks trained with data from one day to data from another day, when applying networks trained with data from one task to data from another task, and when applying networks trained with data from a group of participants to data from new participants. These results support the feasibility of using EEG-based methods for monitoring cognitive load during human-computer interaction.

Perhaps the most basic issue in the study of cognitive workload is the problem of how to actually measure it. The electroencephalogram (EEG) continues to be the clinical method of choice for monitoring brain function in assessing sleep disorders, level of anaesthesia and epilepsy. This preference reflects the EEG's high sensitivity to variations in alertness and attention, the unimposing conditions under which it can be recorded, and the low cost of the technology it requires. These characteristics also suggest that EEG-based monitoring methods might provide a useful tool in ergonomics. This paper reviews a long-term programme of research aimed at developing cognitive workload monitoring methods based on EEG measures. This research programme began with basic studies of the way neuroelectric signals change in response to highly controlled variations in task demands. The results yielded from such studies provided a basis on which to develop appropriate signal processing methodologies to automatically differentiate mental effort-related changes in brain activity from artifactual contaminants and for gauging relative magnitudes of mental effort in different task conditions. These methods were then evaluated in the context of more naturalistic computerbased work. The results obtained from these studies provide initial evidence for the scientific and technical feasibility of using EEG-based methods for monitoring cognitive load during human-computer interaction.

Decisions regarding whether an item has been previously encountered are typically accompanied by one of two distinct forms of subjective awareness: either a general sense of familiarity, or conscious recollection of specific details from a prior study episode. To examine the neurophysiological concomitants of these different types of internal experience, event-related potentials (ERPs) were recorded while subjects engaged in a modified recognition memory procedure that required them to describe their subjective response during each testtrial. Stimuli that evoked recollection were accompanied by waveforms distinct from those that evoked only a sense of familiarity, and waveforms for both categories of correctly classified old items differed from correctly rejected distractor items and incorrectly classified (missed) studied items. These ERP responses are interpreted with respect to current knowledge concerning the neural structures and processes intimately involved in the capacity to engage in recollection.

Sound is an important means of communication in aquatic environments because it can be propagated rapidly (five times faster than in air) over great distances and it is not attenuated as quickly as other signals such as light or chemicals (Hawkins and Myrberg, 1983). Thus, it is not surprising that fishes and marine mammals make considerable use of sound for communication, for detection of predators and prey and for learning about their environment (Au and Nachtigall, 1997;Edds-Walton, 1997;Zelick et al., 1999;Fay and Popper, 2000).Within the past decade, there has developed an increased awareness that underwater anthropogenic (human-generated) sounds may be detrimental to marine organisms by masking the detection of biologically relevant signals and/or even damaging the exposed animals (NRC, 2000(NRC, , 2003. These sounds may be associated with shipping, dredging, drilling, seismic surveys, sonar, recreational boating and many other human-made sources. As a result of these human-generated sounds, ambient noise levels in the ocean are thought to be growing (NRC, 2003). Early estimates by Ross (1993) suggest a 10·dB increase from 1950 to 1975 alone or more than a doubling in noise level. This is likely to have risen further with increases in shipping and uses of other acoustic sources in parts of the oceans (NRC, 2003). Indeed, recent forecasts by the National Oceanographic and Atmospheric Administration's Marine Transportation System indicate that foreign oceanborne trade is expected to double by the year 2020 (US Department of Transportation, 1999), and this could result in even greater ocean noise levels in shipping lanes unless there are dramatic changes in ship acoustics.Substantial exposure of fish to acoustical stress is also found in many aquaculture facilities (Bart et al., 2001) that are important sources of food, ornamental species and stock enhancement of wild populations. While considerable effort has been made to optimize growth of aquaculture species by manipulating many environmental parameters such as temperature, food quality, photoperiod, water chemistry and stock density, little or no concern has been directed to determining the appropriate acoustic environment for optimal growth and development. Rearing conditions in aquaculture tanks can produce sound levels within the frequency range of fish hearing that are 20-50·dB higher than in natural habitats (Bart et al., 2001). The few studies that have examined the Fishes are often exposed to environmental sounds such as those associated with shipping, seismic experiments, sonar and/or aquaculture pump systems. While efforts have been made to document the effects of such anthropogenic (human-generated) sounds on marine mammals, the effects of excess noise on fishes are poorly understood. We examined the short-and long-term effects of increased ambient sound on the stress and hearing of goldfish (Carassius auratus; a hearing specialist). We reared fish under either quiet (110-125·dB re 1·µPa) or noisy (white noise, 160-170·dB re 1·µPa) conditions a...

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