Frequency-response characteristics provide a functional separation between stimulation-bound feeding and self-stimulation

Generating rate-frequency curves for a range of current intensities for self-stimulation and stimulation-bound feeding, using bar press rate and ingestion rate, respectively, as behavioral measures suggest different processes of integrating neural activity in the directly activated substrates.

Abstract

Many lateral hypothalamic electrodes that support self-stimulation also elicit feeding. Refractory period and conduction velocity estimates for the axons supporting these behaviors appear identical, suggesting that these behaviors may be elicited by stimulation of a common directly activated substrate. However, it is not known if the substrate(s) for the two behaviors integrate activity in directly stimulated axons similarly in controlling their respective behaviors. This study generates rate-frequency curves for a range of current intensities for self-stimulation and stimulation-bound feeding, using bar press rate and ingestion rate, respectively, as behavioral measures. For self-stimulation, as is well established, increases in intensity shift rate-frequency curves toward lower frequencies. For stimulation-bound feeding, increases in intensity raise asymptotic ingestion rate, but do not always appreciably change the location of the curve along the frequency axis. The different parametric profiles obtained for the two behaviors suggest different processes of integrating neural activity in the directly activated substrates.