ABR multielectrode recording: Determination of source position movement through cat brainstem

Abstract

The click-evoked acoustic brainstem response (ABR), average of 512 responses, was recorded at 18 sites on the scalp of anesthetized cats. Scalp recordings were used to determine source position by attributing the scalp-surface potential field at each instant to the presence of a single current-dipole equivalent source, immersed within a spherical, homogeneous volume conductor. At each sampling instant, equivalent source position was determined by the method of Schneider [IEEE Trans. BME-21, 52–54 (1974)]. At those instants corresponding to vertex-positive response peaks, the single-source model was generally consistent with observed field patterns. Plots of equivalent source position along the axis from head center through vertex between 2.5 and 6.0 ms following the click. Movement along other axes is less prominent. Lack of movement along the centro-lateral axis may reflect the activity of sources arrayed symmetrically along either side of the brainstem, while the lack of expected ventral movement is attributed to limitations of the spherical head model assumed. [Work supported by the Whitaker Foundation.]