COMPARATIVE NEUROPHYSIOLOGY

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The long term objectives are to give perspective on the human brain and how it evolved, in respect to mechanisms of integration of neural activity in organized assemblies of neurons in the central nervous system, including macro- and local circuits. The specific aims are to use the comparative approach with model systems in lower vertebrates to examine selected neural achievements or structures, including in particular sensory processing, encoding, decoding, filtering, parallel information channels, interactions among modalities and extraction of useful signals at various levels, from first order to cerebral. The octavolateralis system of senses (eighth nerve and lateral line) and the cerebellum and higher centers receiving its modalities are a special focus. Receptors and brain structures analyzing acoustic, vibratory, gravity, acceleration, water movement and weak electric field stimuli, in favorable species of elasmobranchs, teleosts and other vertebrates will be the materials. They will be studied with the following, mainly physiological but partly anatomical methods. (i) Recording from single units and multiple units with single electrodes and arrays of multiple electrodes. (ii) Recording from populations of cells as extracellular fields of ongoing as well as evoked activity, with computer displays of histograms, cross correlations, averaged activity, power spectra, coherence, envelopes of bandpass filtered activity, spectra and cross correlations of the envelopes of different bands and other descriptors that might distinguish lower and higher levels of organization. (iii) Injection of peroxidase, cobalt, fluorescent dyes or radioactive amino acids and histochemical visualization of sites of lesions. This project will normally occupy 2 students, 3 postdoctoral visitors, the P.I., an engineer, technician and secretary. Continued collaboration with former visiting scientists as well as new collaboration with local and distant colleagues are planned.