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Biomedical subjects

D C Riccio

Publications and source records attributed to D C Riccio.

At least 19 recordsLinked to original sources
PubMed1995

Differential effects of Ketaset/Rompun anesthesia on hypothermia-induced retrograde amnesia and its recovery.

A nonbarbiturate anesthetic consisting of ketamine HCl (Ketaset) and xlyazine (Rompun) was administered to assess the effects of anesthesia on hypothermia-induced retrograde amnesia in Long Evans hooded and Sprague-Dawley albino rats. Results from Experiment 1a indicate that this anesthetic does not attenuate retrograde amnesia, and the findings from Experiment 1b suggest that awakening from Ketaset/Rompun anesthesia at normal body temperature (following administration of deep body cooling) does not attenuate the resulting hypothermia-induced retrograde amnesia. Experiment 2 demonstrated that various delays between training and hypothermia resulted in a temporal gradient that was the same for animals cooled while either conscious or under anesthesia. The results of Experiment 3 showed that rats made amnesic while under anesthesia did not recover the target memory if given a recooling treatment, but rats that were made amnesic while conscious did recover the memory with the same reminder treatment. These findings indicate that the conscious processing of stimuli associated with hypothermia treatment is not necessary in inducing hypothermia-induced retrograde amnesia, but that conscious processing is an important factor if the amnesia is to be recovered with a recooling treatment.

Anesthetics, Dissociative↗
PubMed1995

State-dependent retention produced with estrus in rats.

State-dependent retention (SDR) has frequently been demonstrated with drug-induced physiological changes which apparently serve as contextual cues for memory. These support the assumption that commonly occurring endogenous dispositions play a role in memory, yet there are few reports showing SDR with states that are likely to be part of an organism's natural experiences. To determine if behavioral estrus could produce SDR, ovariectomized female rats were rendered estrus via hormone injections or remained anestrus via placebo injections, trained with quinine-laced apple juice, and later tested while in the same or different state for reactions towards pure juice. SDR was not evident in the amount of juice consumed; however, those tested in the same state as the initial experience were slower to initiate drinking than those tested in a different state revealing a state-dependent influence on memory related to phases of the ovarian cycle.

Animals↗
PubMed1995

Concussion-induced retrograde amnesia in rats.

Three experiments were conducted to investigate the characteristics of retrograde amnesia (RA) induced by concussion in rats. In Experiment 1, rats receiving experimental concussion shortly after training in a single punishment trial exhibited severe forgetting on a retention test 48 h later. In the second experiment, rats receiving a concussion within 6 h after training showed severe RA, while those receiving concussion one day to five days after training exhibited progressively weaker amnesia. In Experiment 3, amnesic animals in one group received pretest noncontingent foot shock as a reminder treatment. This pretest cue significantly increased the cross-through latency, thus indicating a reduction in the memory deficit resulting from concussion. These results suggest that experimental concussion can be an effective method to induce retrograde memory loss in rats; that the RA caused by concussion is time-dependent; and that concussion-induced RA can be alleviated by a pretest cue indicating that the underlying mechanism of concussion-induced RA is more likely to be a retrieval deficit than a consolidation failure.

Amnesia, Retrograde↗
PubMed1994

Memory. When less is more.

Loss of memory for the characteristics of stimuli (i.e., forgetting of stimulus attributes) can lead to increases in behavior, a consequence quite different from the impairments associated with the forgetting of responses. Evidence from animal and human research for the forgetting of stimuli as a distinct memory principle is presented, and the methodological and conceptual implications of this pervasive type of memory loss are considered. Malleability of eyewitness memory, cognitive confusions, sleeper and familiarity effects, and temporal distortions in inferences and attributions are among the varied behavioral phenomena that can be accounted for in terms of forgetting of stimulus attributes.

Cognition↗
PubMed1993

The effect of US preexposure on conditioned taste aversion: lack of postconditioning recovery of the aversion.

Although the CS preexposure effect in CTA was once viewed exclusively as an acquisition failure, recent studies have suggested that the latent inhibition phenomenon is the result of retrieval impairment. This interpretive challenge is based on the unexpected finding that recovery of the aversion occurs over a long retention interval following conditioning (Kraemer, Lariviere, & Spear, Animal Learning and Behavior, 16, 185-190, 1988; Bakner, Strohen, Nordeen, & Riccio, Physiology & Behavior, 50, 1269-1272, 1991). This study examined whether a similar recovery occurs after US preexposure. Following preexposure to the US (LiCl), rats received a sucrose-illness pairing and were subsequently tested after either short or long training-to-test intervals. In contrast to the findings with the CS preexposure effect, US-preexposed subjects did not show a spontaneous increase in CTA following the long retention interval.

Animals↗
PubMed1992

Reinstatement of latent inhibition following a reminder treatment in a conditioned taste aversion paradigm.

Reminder treatments have been shown to facilitate the retrieval of a variety of conditioned responses. Whether or not similar results would occur with an experimental paradigm which involves primarily memory for a stimulus, i.e., where no particular response is specified, is unclear. Accordingly, using Sprague-Dawley rats, we employed a latent inhibition paradigm with a long (10 days) retention interval between sucrose (CS) preexposure and sucrose-illness pairing (training). The results demonstrated a loss of latent inhibition following the 10-day retention interval suggesting "forgetting" of the CS preexposure. However, placing a single reminder exposure to the CS within the preexposure-to-training interval reinstated the preexposure effect. Controls indicated that in the absence of the initial preexposure the reminder per se did not produce latent inhibition. Thus, a reminder can reinstate a stimulus attribute (flavor representation) and explicit conditioned responses.

Animals↗
PubMed1992

Forgetting of stimulus attributes: methodological implications for assessing associative phenomena.

Differential responding to changes in the stimulus situation, long central to the concept of stimulus control, also provides the implicit conceptual basis for assessing the nature of a variety of associative relationships. However, there is substantial evidence that the perception of stimulus similarity is not a static property. Generalization gradients to contextual as well as discriminative stimuli flatten over time, and this increase in perceived similarity presumably reflects forgetting of the detailed characteristics or attributes of stimuli. Methodologically, the flattening of the gradient imposes an important constraint: The effect of a stimulus shift will be highly sensitive to the length of the delay interval between training and testing. Conceptually, the loss of memory for stimulus attributes also implies that the sources of interference in retention can increase over time.

Animals↗
PubMed1991

The effects of preexposure to the drug on state dependent retention.

The present experiment examined whether previous experience with a drug would decrease the potential of the drug to produce state dependent retention (SDR) for a passive avoidance response in rats. In the first experiment, a single injection of sodium pentobarbital (20 mg/kg) given on six consecutive days before the training day slightly reduced, but did not block, pentobarbital-induced SDR. In Experiment Two, four preexposure injections of 5 IU/kg insulin reduced the magnitude of memory loss produced by administration of the hormone prior to training. As with pentobarbital, however, preexposure to insulin did not completely block the amnestic effect of the hormone. A subsequent experiment demonstrated that the decrease in the strength of insulin-induced SDR in insulin preexposed rats was not the result of enhanced acquisition. Collectively, these data indicate that noncontingent preexposure to an amnestic treatment may decrease the magnitude of memory loss that would normally result from the administration of that treatment during training.

Animals↗
PubMed1991

Postconditioning recovery from the latent inhibition effect in conditioned taste aversion.

Two experiments were conducted examining the effects of flavor (CS) preexposure on the retention of conditioned taste aversion. In Experiment 1, rats received preexposure to sucrose solution followed by a sucrose-illness pairing. The expected "latent inhibition" effect was obtained when testing occurred after a two-day but not an eleven-day training-to-test interval. Experiment 2 extended these results by employing five- and twenty-one-day training-to-test interval parameters and provided evidence that the stronger taste aversion displayed by preexposed subjects following long retention intervals is not attributable to differences in training consumption of sucrose solution. This posttraining increase in conditioned taste aversion (CTA) suggests that preexposure blocks expression of memory.

Animals↗
PubMed1991

Increased generalization between drug-related interoceptive stimuli with delayed testing.

Although the flattening of generalization gradients over time has been widely investigated using exteroceptive stimuli, little attention has been given to generalization involving interoceptive stimuli. To investigate generalization between internal states, Sprague-Dawley rats were given either 0.835 ml/kg chloropent or 15 mg/kg sodium pentobarbital. Both drugs produced asymmetrical state-dependent retention of a passive avoidance response, that is, good retention in the "same state" conditions (i.e., the drug-drug and no drug-no drug conditions) as well as in the no drug-drug conditions but poor retention in the drug-no drug conditions, at both 1- and 7-day retention intervals. Furthermore, subjects trained in one drug state (pentobarbital or chloropent) demonstrated disrupted performance when tested 1 day later in another drug state, but good performance when tested 7 days later in the other drug state, indicating a decrement in the discriminability of the two drug states after 7 days. This outcome demonstrates that generalization gradients between drug states flatten over time. Moreover, these results suggest that memory for attributes of internal stimuli undergoes changes similar to those found for exteroceptive stimuli. Implications for contextual cues models of forgetting are considered.

Anesthetics↗
PubMed1991

Associative processes in adaptation to repeated cold exposure in rats.

Learning processes have been implicated in drug tolerance, but the role of associative mechanisms in adaptation to stressors has not previously been determined. Rats that received daily brief cold exposures demonstrated adaptation to the cold as measured by an attenuation of hypothermia. Tolerance to the cold was disrupted by changing the context in which the subject experienced the cold. These findings provide evidence of associative processes in adaptation to cold exposure and illustrate that these processes are not limited to drug tolerance.

Acclimatization↗
PubMed1990

Homeostatic disruption and memory: effect of insulin administration in rats.

The present study examined the effect of insulin-induced hypoglycemia on 24-h retention of passive avoidance in rats. In the initial experiment, rats received either insulin (50 U/kg) or saline injections 30 min prior to training and testing. Impairments in retention were observed when animals were trained with insulin and tested with saline. This anterograde memory loss was attenuated, however, when insulin was administered prior to both training and testing. A subsequent experiment further explored the disruptive effect of hypoglycemia on memory. Data from this study indicated that lower doses of insulin at training (5 and 10 U/rat) yielded impairments in 24-h retention of passive avoidance. It is concluded that disruption of glucoregulation can produce state-dependent anterograde memory losses in rats. Possible implications for the effects of hypoglycemia on cognitive functioning in humans are discussed.

Animals↗
PubMed1989

ACTH produces long-lasting recovery following partial extinction of an active avoidance response.

Recent data suggest that ACTH administration produces recovery of an extinguished passive avoidance response at an unusually long injection-to-test interval. The present experiment sought to explore further the durability of recovery by examining the effect of ACTH following extinction of one-way active avoidance. Adult rats were injected with 16 IU ACTH, an equivalent volume of the ACTH vehicle gel, or saline 48 h after a previously learned active avoidance response was partially extinguished. Different groups from each treatment condition were tested 15 min, 24 h, or 7 days after injection. ACTH improved avoidance performance at all injection-to-test intervals relative to saline and vehicle gel injected controls. These data indicate that unlike reversal of other types of performance decrements, in which the effect of ACTH appears to be transient, administration of the hormone following an extinction treatment can produce enduring improvement of avoidance performance.

Adrenocorticotropic Hormone↗
PubMed1989

Role of ACTH in recovery from retrograde amnesia induced by hypothermia in rats.

The present investigation assessed whether increased congruency between ACTH state present shortly after training and that at testing contributed to memory recovery. If recovery were related to an increased correspondence between internal state present after training and that at testing, then suppressing ACTH release should block memory recovery. This was the hypothesis that was examined in the present investigation. Specifically, animals were trained on a passive avoidance task, administered hypothermia (the amnestic agent) and, shortly prior to testing, given treatments known to be effective in reversing memory loss induced by hypothermia. Before training (Experiment 1) or testing (Experiment 2) animals were injected with either dexamethasone (an agent that suppresses ACTH release) or saline. Results, in general, indicated that when ACTH release was suppressed, a blunted recovery effect was obtained. This reduction in the extent of memory recovery was observed when ACTH was suppressed either at training or at testing. These data are interpreted as providing support for an ACTH-related, state-dependent retention mechanism contributing to recovery from hypothermia-induced retrograde amnesia in rats.

Adrenocorticotropic Hormone↗
PubMed1988

Stimulus attributes of reactivated memory: alleviation of ontogenetic forgetting in rats is context specific.

Numerous studies have shown that ontogenetic forgetting (infantile amensia) can be alleviated by a number of different types of reminder treatment. The present study extends the information about the alleviation of infantile amnesia by examining the "content" of the reactivated memory. Toward this purpose, one attribute of memory (environmental context) was examined in rats tested either shortly after training (preamnesic) or after 1-week retention interval. For the latter, a reactivation treatment was used to reverse infantile amnesia. At both intervals, a context shift resulted in impaired performance of a conditioned fear response. These findings demonstrate that environment context is an important component of the originally encoded memory as well as the reactivated amnestic memory. The implications of these results for both the reactivation of memory and general memory processes are discussed.

Aging↗
PubMed1987

ACTH- and noncontingent footshock-induced recovery of an extinguished passive avoidance response.

The effectiveness of both exogenous adrenocorticotropic hormone and noncontingent footshock as agents for the recovery of an extinguished passive avoidance response was assessed. Six groups of male Holtzman rats were administered either adrenocorticotropic hormone (4IU), or a single noncontingent footshock, either 15 minutes, 24 hours, or 7 days prior to retention testing. Two control groups received an injection of the inactive gel vehicle either 15 minutes or 7 days prior to test. Adrenocorticotropic hormone administered either 15 minutes or 24 hours prior to test, as well as noncontingent footshock delivered 24 hours (but not 15 minutes) prior to test, served as effective reinstatement agents. Substantial "spontaneous recovery" of responding precluded evaluation of reinstatement effects at the 7 day retention interval. The persistence of the recovery for at least 24 hours is consistent with the notion that both adrenocorticotropic hormone and noncontingent footshock not only enhance memory retrieval of the original fear conditioning, but also cause the training memory to be further processed.

Adrenocorticotropic Hormone↗
PubMed1987

Hypothermia-induced anterograde amnesia: is memory loss attributable to impaired acquisition?

The present investigation examined whether the poor test performance observed in studies of anterograde amnesia reflects a memory deficit or is a by-product of weaker initial learning resulting from impaired sensory, motivational, or associative processes. Two experiments were performed which utilized latent extinction (Experiment 1) and delay of punishment (Experiment 2) manipulations in order to assess the nature of original learning in rats trained under either hypothermic (29 degrees C) or normothermic conditions. Results from both experiments provided evidence that hypothermia treatment administered prior to training had relatively little influence on the animal's ability to acquire a passive avoidance response. Therefore, the rapid forgetting observed in hypothermia-induced anterograde amnesia is most likely due to memory deficits rather than an artifact of poorer acquisition.

Amnesia↗