Rats with electrodes in the lateral hypothalamus, which elicit both self-stimulation and drinking, were presented with quinine solutions, saccharine solutions, and water while self-stimulating. Quinine significantly reduced the volume ingested during electrically-induced drinking, whereas saccharin increased the volume; a significant decrease in concurrent self-stimulation rate accompanied electrically-induced drinking of quinine solution and a significant increase accompanied ingestion of saccharine solution. An experiment to study the effects of no water, water, and saccharin on self-stimulation rate revealed a significant increase while Ss were drinking water and an additional increase when Ss were drinking saccharine solution.Satiated rats with electrodes terminating in a small region of the lateral hypothalamus will self-stimulate and drink water (Mogenson & Stevenson, 1966. The electrical stimulation reinforces lever presses and, because of the unique locus of stimulation, it also induces the animal to drink. From Pfaffmann (1960) it is thought that the "affective consequences of sensory stimulation [p. 265]" are mediated by the visceral brain. Sweet taste, which produces positive affect, and bitter taste, which produces negative affect, should influence the integrative systems in the visceral brain concerned with intracranial stimulation (ICS) and drinking behavior. In order to investigate this possibility, saccharin or quinine were added to the water ingested during ICS. METHOD SubjectsMale Wistar rats, 3-5 mo. of age and weighing 450-575 gm., were housed in individual wire mesh cages in a controlled environment of 40%1 The authors wish to thank J. A. F. Stevenson for critically reading the manuscript and providing valuable comments. Thanks are also extended to M. Dinning for her technical assistance.

Rats on a 23-hr food and water deprivation schedule were tested for preference between lever pressing for electrical stimulation of the lateral hypothalamus and liquid rewards, which varied in taste and caloric content. Preference for self-stimulation diminished as the alternative liquid became more palatable: with a saccharineglucose solution as the alternative the animals showed an equal preference for hypothalamic stimulation and the liquid reward. In longer 6-hr tests, rats deprived of water for 24 and 48 hr initially showed a preference for self-stimulation over water but eventually satisfied their water deficit by pressing for water. Neglect of physiological needs during self-stimulation appears to be more a function of the alternatives available and the length of the test session than intrinsic properties of the brain stimulation.

The present experiment has demonstrated that rats with simultaneously prepared septal-neocortieal ablations maintained states of hyperemotionality if they were not rated for 3 weeks. However, such was not the case for

An investigation was carried out to compare avoidance learning in four test situations: bar pressing, wheel turning, shuttle box, and rotor. The effects of delayed secondary reinforcement on avoidance learning and performance were also studied. Delayed secondary reinforcement was produced by delaying the termination of the CS after the avoidance response. Differences were observed in behaviour among response groups during the habituation period and the inter-trial intervals as well as in the rates of avoidance learning. The effects of delayed reinforcement appeared to vary with the response required. When initiated during acquisition, delayed CS termination produced a deficit only for the shuttle-box animals. When the delayed reinforcement was introduced during performance there was a decrement in all groups, but it was greatest for shuttle-box animals. It was suggested that a deficit in avoidance responding occurs if the CS delay interval is not spanned by "perseverative responding." WELL-KNOWN STIMULUS VABIABLES are considered responsible for a great deal of the variance observed in avoidance learning. Most experimental studies have been concerned with investigating these variables (Kimble, 1961). Response factors are undoubtedly important also (Meyer, Cho, & Wesemann, 1960) but they have received relatively little attention. The present investigation was undertaken to study more systematically the role of response requirements in avoidance learning. Four avoidance learning situations, and thus four different avoidance responses, were used in the experiment described below.Since grid shock does not occur when avoidance responses are made, several theorists have suggested that avoidance responses are maintained by secondary reinforcement (cessation of the CS). This hypothesis has empirical support, including the demonstration of a delay of reinforcement gradient (Kamin, 1957). Delaying secondary reinforcement, which may be achieved by postponing the termination of the CS after the appropriate or adequate response, typically produces an avoidance learning decrement (Kamin, 1957; Mullin, 1963; Verhave, 1959). A decrement x

10 rats were trained to press a lever for brain stimulation. Then they were given intraperitoneal injections of sodium pentobarbital (15 mg/kg) in order to determine the effects of this drug upon brain self-stimulation. For 8 Ss there was a nonsignificant decrease in self-stimulation rate. This result is consistent with previous findings. 2 rats in which brain self-stimulation was accompanied by convulsions no longer had convulsions following the sodium pentobarbital injection but self-stimulated at markedly increased rates. This finding is not consistent with the view that the reward effects of brain stimulation are related to seizures or convulsive-like effects.