VARIATION IN HIPPOCAMPAL THETA SHOULDERS ALONG THE LONGITUDINAL AXIS OF THE HIPPOCAMPAL CA1 SUBREGION.
1. ARL NSMA
2. Evelyn F. McKnight Brain Inst., Univ. Arizona, Tucson, AZ
The hippocampal theta oscillation is typically not purely sinusoidal. In many recordings, a distinct shoulder appears on each theta wave, which likely gives rise to the second harmonic component often seen in hippocampal EEG power spectra from behaving animals. Terrazas et al. (2005) showed that the amplitude of the theta shoulder is more strongly dependent on running speed than the fundamental wave, and thus the waveshape changes substantively with running speed. Maurer et al. (2005) showed that both theta amplitude and neuronal firing rates increased more steeply with running speed in the dorsal, compared to the middle hippocampus, suggesting that the gain of some self-motion signal might vary systematically along this axis, leading to a change in the scale of the spatial representations (place fields). Further analysis of the data from Maurer et al. (2005) now shows that the shoulder component of the theta wave is much weaker in the middle region of the CA1 field than more dorsally, suggesting that this component may be the primary factor in the septotemporal variation in slope of the theta amplitude versus running-speed function
Supported by NS020331; AG012609; NS054465
Keyword (Complete): EEG; memory; rat; spatial