Activity, startle magnitude, and prolonged food and water deprivation: Two further failures to duplicate

Abstract

Studies from one laboratory have shown deprivation-induced attenuation of startle response magnitudes, but another laboratory has reported failures to show any relationship between these variables. In an attempt to locate possible procedural contributions to this discrepancy in outcomes, our Experiment 1 involved 20 massed startle-stimulus presentations (30-sec lSI) to rats that had gone either 43 h or 1 h since eating (80% body weights equated for groups). Experiment 2 entailed spaced presentations (four trials per five bidaily sessions, 20-min lSI) to rats that had gone either 43 h or 1 h since drinking (80% weights also equated). Activity prior to, during, and after startle presentations also was recorded. Although group startle magnitudes differed on some trial blocks of both experiments, these differences were not systematically related to either of the deprivation conditions. Mean activity level was sensitive to startle-stimulus presentations, and showed systematic trial-block rates of decline for periods prior to, during, and following startle presentations that were identical for all groups.In a frequently cited but unpublished study, Meryman (1952) reported that a stimulus previously paired respectively with electric shock (a fear CS) and with prolonged food deprivation could intensify startle reactions to an intense , punctate acoustic stimulus . He further showed that even larger startle magnitudes resulted from the combined presence of both stimuli . Anderson, Crowell, and Brown (1985) more recently published a detailed exposition of Meryman 's (1952) study and duplicated its essential features . They similarly found lower startle magnitudes to a fear CS alone than to a fear CS presented in combination with food deprivation. However, in contrast to Meryman, they reported that food deprivation alone was ineffective in facilitating startle magnitude. Anderson et al. (1985) explained the latter disparity by proposing that augmented startle magnitude was occasioned exclusively by the fear CS in these studies, and that satiation may have served to attenuate fear rather than that deprivation intensified startle. They further deduced that Meryman's alleged nonfearful groups probably were modestly fearful but, because of a procedural modification, their groups were not. Because of the postulations that satiation in the absence of fear, along with deprivation per se, should exert null influence on startle magnitude , we then applied Anderson et al . 's (1985) satiation, fear-attenuation proposal to explain the startle differences associated with these two studies.