This project is devoted to measurement and description of the electroencephalographic (EEG) activity of the limbic system of the vertebrate brain that occurs during goal-directed behavior. The limbic system comprises cortical parts (e.g. olfactory bulb and cortex, septum, hippocampus) and nuclear parts (e.g. amydaloid, striatum) and is responsible for the basic organization and execution of teleological behavior. The cortical parts generate well-defined fields of EEG and evoked potential, and the fields are well known to undergo changes related to behavior. Recent studies supported by this grant have shown that the olfactory EEG has prominent spectral peaks in the theta (3-7Hz) and gamma (35-80Hz) frequency ranges. We postulate that behaviorally relevant information is carried by amplitude and phase modulation of gamma waves, which are gated from bulb to cortex in bursts at theta frequencies. Behavioral testing with olfactory stimuli has shown that amplitudes of gamma activity are invariant with respect to odorous stimuli, but change with conditioning to induce the search for odors. More generally, we postulate that animals maintain and update in the limbic system in internal image of the outside world, and that limbic EEG activity reflects aspects of information contained in the image. We propose to test this hypothesis by controlling animal behavior in simple, reproducible goal-directed tasks, while recording EEG activity simultaneously from up to 64 implanted electrodes, and making precise measurements of the space-time patterns of limbic EEG activity by use of advanced computer technology.
Our specific aim i s to determine the precise forms in which olfactory information is encoded in the olfactory bulb and cortex, and the manner in which it is transmitted and transformed from the bulb to the cortex. Assays will be made to determine whether similar techniques can be applied to analysis of similar informational transactions between these and other parts of the limbic system. The studies may provide insight into the same or similar mechanisms that operate in the human limbic system during normal behavior.
|Lefebvre, Vladimir A; Sanabria, Federico (2008) Matching by fixing and sampling: a local model based on internality. Behav Processes 78:204-9|