Control of the rat's sniffing behavior by response-independent and dependent schedules of reinforcing brain stimulation.

The rat's sniffing response occurs in continuous bursts, at approximately 5-11 Hz. In the present experiments, the analog signal from a thermo-couple probe in the nasal cavity was digitized to provide a discrete logic pulse, defining a sniff, and permitting on-line presentations of reinforcing brain stimulation contingent on momentary sniffing patterns. Schedules of reinforcer presentation included response-independent fixed interval (temporal conditioning), continuous reinforcement (CRF), and differential reinforcement of low rates (DRL 10 sec). Under temporal conditioning, bursts of sniffing were observed immediately after stimulation, and an acceleration in sniffing developed preceding stimulation. Under CFR, operant rate-intensity functions were found to be similar to traditional bar-press data. Under DRL, sniffs were effectively paced by the criterion interval, and interresponse time analyses revealed evidence of temporal discrimination. The behavioral patterns were interpreted in terms of the interplay of operant and respondent functions.