PRESENTISM,PERSISTENCE AND COMPOSITION

Pace Benovsky's ‘Presentism and Persistence,’ presentism is compatible with perdurantism, tropes and bundle‐of‐universals theories of persisting objects. I demonstrate how the resemblance, causation and precedence relations that tie stages together can be accommodated within an ersatzer presentist framework. The presentist account of these relations is then used to delineate a presentist‐friendly account of the inter‐temporal composition required for making worms out of stages. The defense of presentist trope theory shows how properties with indexes other than t may be said to exist at t. This involves an account of how times other than t exist at t, and how times may be multiply located at any given time. Benovsky's objection to bundles of universals is shown to assume that a bundle of properties must have the properties of its element properties.     

Clamped Corticosterone (B) Reveals the Effect of Endogenous B on Both Facilitated Responsivity to Acute Restraint and Metabolic Responses to Chronic Stress

To determine the effects of both corticosterone (B) and chronic stressors on acute ACTH responses to restraint, young male rats were exposed to streptozotocin-induced diabetes, cold (5-7 degreesC) or intracerebroventricular (icv) neuropeptide Y (NPY) for 5 d and then exposed to restraint within 2 h after lights on. Two groups of rats were studied: intact and adrenalectomized replaced with B pellets that maintained plasma B in the normal mean 24-h range of intact rats. In addition to ACTH and B responses to restraint on d 5, body weight, food intake, fat depots, glucose and other hormones were measured to determine the role of stress-induced elevations in B on energy balance. ACTH responses to restraint were normal in intact rats subjected to diabetes or cold. By contrast, there was no ACTH or B response to restraint in NPY-infused intact rats. All 3 groups of chronically stimulated adrenalectomized rats with clamped B had facilitated ACTH responses to restraint compared to their treatment controls. Overall food intake increased in all groups of stressed rats; however, augmented intake occurred only during the light in intact rats and equally in the light and dark in B-clamped rats. White adipose depot weights were decreased by both diabetes and cold and increased by NPY in intact rats; the decreases with cold and increases with NPY were both blunted and changes in fat stores were not significant in adrenalectomized, B-clamped rats. We conclude that: 1. diabetes- and cold-induced facilitation of restraint-induced afferent input to hypothalamic control of the hypothalamo-pituitary-adrenal (HPA) axis is opposed in intact rats by the elevated feedback signal of B secretion; 2. NPY does not induce facilitation of afferent stress pathways; 3. chronic stimulation of the HPA axis induces acute hyperresponsiveness of hypothalamic neurons to restraint provided that the afferent input of this acute stimulus is not prevented by B feedback; 4. stimulus-induced elevations in B secretion result in day-time feeding; 5. insensitivity of both caloric efficiency and white fat stores to chronic stress in adrenalectomized, B-clamped rats results from loss of normally variable B levels.     

Rats place greater value on rewards produced by high effort: An animal analogue of the “effort justification” effect

The effort justification phenomenon, in which greater value is given to rewards that require more effort to obtain, is frequently explained in terms of cognitive dissonance (Festinger & Carlsmith, 1959). Here, we employed a novel combination of operant and lick analysis techniques to show that rats place more value on a sucrose reward when it follows high effort than when the same reward follows low effort. This is the first demonstration of a direct analogue of the effort justification phenomenon in nonhuman animals. As the behavior of rats is normally considered in terms of relatively simple mechanisms, the current results question the need for complex cognitive accounts for the effort justification phenomenon (in rats or humans). As an alternative, we examine the possibility that high effort produces an aversive state that enhances reward value by a process of contrast.     

Simultaneous contrast: evidence from licking microstructure and cross-solution comparisons

The microstructure of rats' licking responses was analyzed to investigate both "classic" simultaneous contrast (e.g., Flaherty & Largen, 1975) and a novel discrete-trial contrast procedure where access to an 8% test solution of sucrose was preceded by a sample of either 2%, 8%, or 32% sucrose (Experiments 1 and 2, respectively). Consumption of a given concentration of sucrose was higher when consumed alongside a low rather than high concentration comparison solution (positive contrast) and consumption of a given concentration of sucrose was lower when consumed alongside a high rather than a low concentration comparison solution (negative contrast). Furthermore, positive contrast increased the size of lick clusters while negative contrast decreased the size of lick clusters. Lick cluster size has a positive monotonic relationship with the concentration of palatable solutions and so positive and negative contrasts produced changes in lick cluster size that were analogous to raising or lowering the concentration of the test solution respectively. Experiment 3 utilized the discrete-trial procedure and compared contrast between two solutions of the same type (sucrose-sucrose or maltodextrin-maltodextrin) or contrast across solutions (sucrose-maltodextrin or maltodextrin-sucrose). Contrast effects on consumption were present, but reduced in size, in the cross-solution conditions. Moreover, lick cluster sizes were not affected at all by cross-solution contrasts as they were by same-solution contrasts. These results are consistent with the idea that simultaneous contrast effects depend, at least partially, on sensory mechanisms.