Effects of Spatial Attention on the Visual-Evoked Neuromagnetic Response

A number of studies have shown that selective attention to spatial location modulates the amplitudes of several visual evoked potential components recorded from posterior regions of the head (e.g., Eason, Harter White, 1969; Harter, Aine, Schroeder, 1982; Hillyard Munte, 1984; Mangun Hillyard, 1988). The early components, P1 and N1 (peak latencies: 90--135 and 140--170 msec, respectively), are thought to arise in one or more areas of visual cortex. Although it is generally assumed that such ERP effects reflect differential activation of populations of neurons at successive levels of the nervous system, little information is available about the neural structures responsible for such effects. We have employed neuromagnetic techniques in an attempt to identify more precisely the neural structures involved in selective attention to spatial location within the P1-N1 time sequence. In this study, effects of attention were assessed by comparing neural responses evoked by stimuli at a specified spatial location when subjects were required to attend and respond behaviorally to that location with neural responses to the same stimuli when subjects were required to attend and respond behaviorally to another location in the visual field. 7 refs., 3 figs

Behavioural Thermoregulatory Tactics in Lacustrine Brook Charr, Salvelinus fontinalis

The need to vary body temperature to optimize physiological processes can lead to thermoregulatory behaviours, particularly in ectotherms. Despite some evidence of within-population phenotypic variation in thermal behaviour, the occurrence of alternative tactics of this behaviour is rarely explicitly considered when studying natural populations. The main objective of this study was to determine whether different thermal tactics exist among individuals of the same population. We studied the behavioural thermoregulation of 33 adult brook charr in a stratified lake using thermo-sensitive radio transmitters that measured hourly individual temperature over one month. The observed behavioural thermoregulatory patterns were consistent between years and suggest the existence of four tactics: two “warm” tactics with both crepuscular and finer periodicities, with or without a diel periodicity, and two “cool” tactics, with or without a diel periodicity. Telemetry data support the above findings by showing that the different tactics are associated with different patterns of diel horizontal movements. Taken together, our results show a clear spatio-temporal segregation of individuals displaying different tactics, suggesting a reduction of niche overlap. To our knowledge, this is the first study showing the presence of behavioural thermoregulatory tactics in a vertebrate

Finding Text Information in the Ocean of Electronic Documents

Information management in natural resources has become an overwhelming task. A massive amount of electronic documents and data is now available for creating informed decisions. The problem is finding the relevant information to support the decision-making process. Determining gaps in knowledge in order to propose new studies or to determine which proposals to fund for maximum potential is a time-consuming and difficult task. Additionally, available data stores are increasing in complexity; they now may include not only text and numerical data, but also images, sounds, and video recordings. Information visualization specialists at Pacific Northwest National Laboratory (PNNL) have software tools for exploring electronic data stores and for discovering and exploiting relationships within data sets. These provide capabilities for unstructured text explorations, the use of data signatures (a compact format for the essence of a set of scientific data) for visualization (Wong et al 2000), visualizations for multiple query results (Havre et al. 2001), and others (http://www.pnl.gov/infoviz ). We will focus on IN-SPIRE, a MS Windows vision of PNNL’s SPIRE (Spatial Paradigm for Information Retrieval and Exploration). IN-SPIRE was developed to assist information analysts find and discover information in huge masses of text documents