FOCUSED ULTRASOUND MODIFICATIONS OF NEURAL CIRCUIT ACTIVITY IN A MAMMALIAN BRAIN

The application of focused, pulsed ultrasound was studied as a method of modifying the activity of a local neural circuit of the mammalian b rain. An in vitro hippocampal preparation was used to facilitate deliv ery, dosimetry and assessment of mechanisms of ultrasound effects. Ext racellular evoked potentials were recorded from cell and dendritic lay ers of the rat hippocampal dentate gyrus, Focused pulses of ultrasound with center frequency of 500 kHz and repetition rate of 200 kHz were studied and found both to enhance and to depress electrically evoked f ield potentials. The fiber volley and cell population potentials were depressed, whereas the dendritic potential was enhanced. Results sugge st a simultaneous mechanical and thermal mechanism of ultrasound in mo difying evoked field potentials of dentate local circuits. (C) 1998 Wo rld Federation for Ultrasound in Medicine & Biology.