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PubMed1994

Localization of atrophy-prone areas in the aging mouse brain: comparison between the brain atrophy model SAM-P/10 and the normal control SAM-R/1.

Mouse inbred strain "SAM-P/10" (Senescence Accelerated Mouse) is a model of age-related brain atrophy. In this strain there is an earlier and more severe age-related deterioration in the conditional avoidance learning than the normal control inbred SAM-R/1 strain. The present study analysed age-related changes in brain area size using a computerized morphometric method. The region most vulnerable to age-related atrophy in SAM-P/10 was the frontal region of the cerebral cortex, including the prefrontal cortex. Other neocortical regions underwent diffuse atrophy. Posterior piriform cortex, entorhinal cortex, anterior olfactory nucleus, amygdala, caudate-putamen, nucleus accumbens and cerebellar cortex were atrophy-prone regions. The septum also underwent atrophy but other basal forebrain structures were intact. The hippocampus, diencephalon and brainstem structures showed no atrophic change. White matter structures did not change in size with aging except for the forceps minor of the corpus callosum, which showed age-related atrophy. On the contrary, SAM-R/1 showed a significant age-related atrophy only in a restricted part of the cerebral cortex, mainly in the parietal region. Other cortical regions, subcortical structures, diencephalon, brainstem structures, cerebellum and white matter were atrophy-resistant in SAM-R/1. The prefrontal cortex, entorhinal cortex, piriform cortex and striatum are closely interconnected and also connect with the amygdala which plays a key role in conditioning in the rodent. Age-related atrophy in all these structures in SAM-P/10 presumably accounts for the age-related deficits in conditional avoidance learning in this strain of mouse. Comparison between SAM-P/10 and SAM-R/1 or other well-known rodents indicates that SAM-P/10 is a unique rodent that spontaneously and rapidly develops progressive generalized cerebral atrophy, which is considered to be a pathological process rather than an accelerated aging process.

Aging↗

PubMed1998

The uterine environment enhances cognitive competence.

Genetically identical mouse embryos were transferred into same-strain uteri (transfer controls) or into hybrid uteri. A third group was not transferred. When adult, the mice were given a series of behavioral tests. In-strain transfer controls differed from non-transfer mice only on two activity measures, and did not differ on any cognitive variable. In contrast, mice reared in hybrid uteri were found to be superior to in-strain transfer mice on discrimination learning. Lashley maze learning and Morris maze learning; they also showed better adaptation in an avoidance learning shuttlebox. To our knowledge this is the first study showing that the uterine environment can have a general enhancing effect upon cognitive competence across a broad range of behaviors.

Animals↗

PubMed1989

A quantitative analysis of the synaptic development of the lobus parolfactorius of the chick (Gallus domesticus).

The lobus parolfactorius (LPO) of the chick has been shown to undergo an increase in the mean synaptic numerical density (Nvsyn) in response to one-trial passive avoidance learning (Stewart et al. 1987). The present study was undertaken in order to describe the pattern of normal development of synapses in the LPO, to further investigate the significance of this plastic response. The LPO's from each hemisphere of pre-hatch (16 days), and post-hatch (1 day, 9 day and 22 day old) chicks were processed for electron microscopy. Synapses were classified into asymmetric spine, asymmetric shaft, symmetric spine, and symmetric shaft synapses, on the basis of the density of the post-synaptic thickening and the nature of the post-synaptic target. A 3-dimensional stereological probe was used (the 'disector') to calculate Nvsyn, and mean projected height (Hsyn) of the post-synaptic density (PSD). Mean values for each age and hemisphere were compared with a 2-way analysis of variance test using paired samples. A six-fold increase in Nvsyn was seen between 16 days in ovo, and 9 days post-hatch. There was a hemispheric asymmetry at 9 days post-hatch, with the left hemisphere LPO containing 1.6 times as many synapses per micron-3. There was a subsequent period of reduction in synaptic density in the left hemisphere LPO between 9 and 22 days post-hatch. The Nv of all classes of synapse increased with age, but the proportions of the symmetrical synapses with respect to the total number of synapses, decreased with age. This decrease was of a similar magnitude for each hemisphere. A hemispheric difference was seen in post-hatch asymmetric synapses, with a greater proportion of asymmetric spine synapses in the left hemisphere. The magnitude of the hemispheric asymmetry was constant throughout the 3 week period of post-hatch development, but was not present in pre-hatch chicks. The PSD increased in length in each hemisphere by approximately 40% between post-hatch day 1 and post-hatch day 9. These data show that the LPO contains a synaptic population which undergoes substantial modification during the first week post-hatch. An asymmetry exists at post-hatch day 9 which is not present at the earlier ages investigated, nor indeed after 22 days post-hatch. This may have significance with regard to studies of passive avoidance learning in the one-day old chick, where an increase in both the size and number of synapses in the LPO has been demonstrated (Stewart et al. 1987).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2000

The adolescents training and learning to avoid steroids program: preventing drug use and promoting health behaviors.

BACKGROUND: Use of alcohol and other illicit drugs by adolescent male athletes is a significant problem. Participation in sports may encourage use of drugs that enhance athletic performance, especially anabolic steroids (AS). Because, to our knowledge, no other intervention has successfully altered substance abuse by athletes, we developed and assessed the efficacy of a team-centered, sex-specific education program designed to reduce adolescent athletes' intentions to use and use of AS and alcohol and other illicit drugs. METHODS: We studied 31 high school football teams that comprised 3207 athletes in 3 successive annual cohorts (1994-1996). The intervention included interactive classroom and exercise training sessions given by peer educators and facilitated by coaches and strength trainers. Program content included discussion of sports nutrition, exercise alternatives to AS and sport supplements, and the effects of substance abuse in sports, drug refusal role-playing, and the creation of health promotion messages. Questionnaires assessing AS, the use of sport supplements and alcohol and other illicit drugs, and potential risk and protective factors were administered before and after the intervention (before and after the football season) and up to 1 year after the program. RESULTS: At season's end, intentions to use (P<.05) and actual AS use (P<.04) were significantly lower among students who participated in the study. Although AS reduction did not achieve significance at 1 year (P<.08), intentions to use AS remained lower (P = .02). Illicit drug use (marijuana, amphetamines, and narcotics) was reduced at 1 year, whether alcohol was included (P = .04) or excluded (P = .02) from the index. Other long-term effects included fewer students reporting drinking and driving (P = .004), less sport supplement use (P = .009), and improved nutrition behaviors (P<.02). CONCLUSIONS: Use of alcohol and other illicit drugs and associated harmful activities can be prevented with a sex-specific, team-centered education. School athletic teams provide an optimal environment in which to provide drug prevention and health promotion education.

Adolescent↗

PubMed1996

The Adolescents Training and Learning to Avoid Steroids (ATLAS) prevention program. Background and results of a model intervention.

OBJECTIVE: To develop and test a school-based intervention to prevent anabolic androgenic steroid use among high-risk adolescent athletes. DESIGN: Nonrandom controlled trial. SETTING: Two urban high schools. PARTICIPANTS: Fifty-six adolescent football players at the experimental school and 24 players at the control school. INTERVENTION: Eight weekly, 1-hour classroom sessions delivered by the coach and adolescent team leaders, and eight weight-room sessions delivered by research staff. The intervention addressed sports nutrition and strength training as alternatives to steroid use, drug refusal role play, and antisteroid media campaigns. OUTCOME MEASURES: A preintervention and postintervention questionnaire that assessed attitudes toward and intent to use steroids and other drugs; knowledge of drug effects; and diet, exercise, and related constructs. RESULTS: Compared with controls, experimental subjects were significantly less interested in trying steroids after the intervention, were less likely to want to use them even if their friends used them, were less likely to believe steroid use was a good idea, believed steroids were more dangerous, had better knowledge of alternatives to steroid use, had improved body image, increased their knowledge of diet supplements, and had less belief in these supplements as beneficial. CONCLUSIONS: Significant beneficial effects were found despite the sample size, suggesting that the effects of the intervention was large. This outcome trial demonstrates an effective anabolic androgenic steroid prevention program for adolescent athletes, and the potential of team-based interventions to enhance adolescents' health.

Adolescent↗

PubMedDate not supplied

Heart rate reactivity in HAD and LAD rats during Pavlovian fear conditioning.

Recently, we reported that High-Alcohol-Drinking (HAD) rats exhibited selective deficits in active avoidance learning under alcohol-naive conditions, and that administration of moderate doses of alcohol (0.5 and 1.0 g/kg) facilitated learning in these rats (Blankenship et al., 2000; Rorick et al., 2003b). We hypothesized that the deficits resulted from excessive fear in the aversive learning context and that the anxiolytic properties of alcohol may have contributed to the improved learning that was observed after alcohol administration. This hypothesis was supported by a recent study in which prolonged freezing in HAD rats was seen after a classical fear conditioning procedure (Rorick et al., 2003a). To provide additional evidence that HAD rats indeed exhibit behaviors consistent with the expression of increased fear in aversive learning contexts, we employed a Pavlovian fear conditioning task to measure heart rate in HAD and Low-Alcohol-Drinking (LAD) rats. In this study, HAD (HAD-1 and HAD-2) and LAD (LAD-1 and LAD-2) rats were assigned to one of three pre-exposure conditions: Context Only, Context/Tone, or Sequential (Context Only followed by Context/Tone) Pre-Exposure. Following pre-exposure, fear conditioning acquisition and extinction procedures were identical for all groups. Results indicated that although no baseline differences were observed between HAD and LAD rats, HAD rats receiving Context-Only pre-exposure exhibited excessive heart rate reactivity to the tone conditional stimulus during fear conditioning acquisition, compared to LAD rats receiving the same pre-exposure conditions. These findings support the hypothesis that HAD rats exhibit behaviors consistent with increased fear in aversive learning contexts, as measured by autonomic conditioning.

Acoustic Stimulation↗

PubMed1995

Amphetamine enhances memory retention and facilitates norepinephrine release from the hippocampus in rats.

The present study investigated the effects of intrahippocampal amphetamine on memory retention and the role of hippocampal norepinephrine (NE) in memory consolidation in rats. One-way inhibitory avoidance learning paradigm was adopted. Animals were trained to avoid the foot shock. The latency to step into the shock compartment was recorded as the retention measure. The ceiling score (full retention) was 600 s. Results indicated that intra-hippocampal injections of amphetamine produced a dose-dependent enhancement of memory retention with doses at 0.6 micrograms and 1.6 micrograms reaching a significant effect. The beta-adrenergic blocker propranolol, at a dose which did not affect retention alone (80 ng), antagonized the memory-enhancing effect of amphetamine. Along with this memory-enhancing effect, amphetamine also elevated the level of NE release, and this effect was significant in animals not showing a full retention score (nonresponders) than in animals showing a full retention score (responders), as assayed by in vivo microdialysis. Within the control group, the responders also had a higher level of NE than the nonresponders. All these results are probably due to the fact that responders have a higher level of NE release than nonresponders. The effect of amphetamine on NE release is, therefore, not as obvious in responders. These results together support our hypothesis that NE plays a facilitatory role in the memory process and amphetamine enhances retention performance, at least in part, through facilitation of hippocampal NE release.

Amphetamine↗

PubMed2002

Comparison of sonohysterography and hysteroscopy: lessons learned and avoiding pitfalls.

We compared ultrasound images of the uterine cavity obtained by sonohysterography (SHG) with those of hysteroscopy in an attempt to avoid inaccurate interpretations. Women referred for abnormal bleeding or infertility underwent SHG before treatment. Those with an abnormal study underwent hysteroscopy for confirmation and treatment. Abnormal SHG studies are frequent, with false positive images including blood clots, mucus plugs, and shearing of normal endometrium relatively common. Uterine pathology generally seen on SHG, including anomalies, polyps, and myomas, is consistent with that seen at hysteroscopy. Performing intraoperative SHG concomitantly with hysteroscopy adds value due to SHG's three-dimensional images to confirm depth of pathology and false negative hysteroscopy findings.

Diagnosis, Differential↗

PubMed1998

Organization of projections of rat retrosplenial cortex to the anterior thalamic nuclei.

The organization of the projections from the retrosplenial cortex (Brodmann's area 29) to the anterior thalamic nuclei was examined in the rat with retrograde transport of the cholera toxin B subunit and anterograde transport of biotinylated dextran amine. Areas 29a and 29b project mainly ipsilaterally to the rostral two-thirds of the anteroventral nucleus, with area 29a projecting more rostrodorsally than area 29b. Area 29c projects bilaterally to the ventromedial part of the anteroventral nucleus. The projections from area 29c are organized in a topographic pattern such that the rostral area 29c projects to the caudoventral part of the anteroventral nucleus, whereas the caudal area 29c projects to the more rostrodorsal parts. Caudal area 29d projects mainly ipsilaterally to the rostrodorsal part of the anteromedial nucleus, and the rostral and dorsal parts of the anteroventral nucleus, whereas rostral area 29d projects bilaterally to the caudodorsal part of the anteromedial nucleus and the caudolateral part of the anteroventral nucleus. All the areas of the retrosplenial cortex provide sparse projections, mainly ipsilateral, to the anterodorsal nucleus, with a crude topographic pattern such that the rostrocaudal axis of the retrosplenial cortex corresponds to the caudorostral axis of the anterodorsal nucleus. The results indicate that each area of the retrosplenial cortex has a distinct projection field within the anterior thalamic nuclei. This suggests that each of these projections transmits distinct information that is important for complex memory and learning functions, e.g. discriminative avoidance learning and spatial memory.

Animals↗

PubMed1996

Problems of conditioning Xenopus laevis tadpoles with standard avoidance-response learning paradigms.

The amphibian Xenopus laevis embryo (tadpole) provides a satisfactory alternative to mammalian screening for structural teratogens. Testing was undertaken to extend the usefulness of this species for behavioral teratogenicity testing. One simple and eight operant conditioning paradigms were examined: none elicited learning in Xenopus embryos. Adaptation to the conditioning stimulus (light) and freezing in response to the unconditioned stimulus (shock) were responses incompatible with conditioned learning.

Animals↗

PubMed1996

Effects of a multidimensional anabolic steroid prevention intervention. The Adolescents Training and Learning to Avoid Steroids (ATLAS) Program.

OBJECTIVE: To test a team-based, educational intervention designed to reduce adolescent athletes' intent to use anabolic androgenic steroids (AAS). DESIGN: Randomized prospective trial. SETTING: Thirty-one high school football teams in the Portland, Ore, area. PARTICIPANTS: Seven hundred two adolescent football players at experimental schools; 804 players at control schools. INTERVENTION: Seven weekly, 50-minute class sessions were delivered by coaches and student team leaders, addressing AAS effects, sports nutrition and strength-training alternatives to AAS use, drug refusal role play, and anti-AAS media messages. Seven weight-room sessions were taught by research staff. Parents received written information and were invited to a discussion session. MAIN OUTCOME MEASURES: Questionnaires before and after intervention and at 9- or 12-month follow-up, assessing AAS use risk factors, knowledge and attitudes concerning AAS, sports nutrition and exercise knowledge and behaviors, and intentions to use AAS. RESULTS: Compared with controls, experimental subjects at the long-term follow-up had increased understanding of AAS effects, greater belief in personal vulnerability to the adverse consequences of AAS, improved drug refusal skills, less belief in AAS-promoting media messages, increased belief in the team as an information source, improved perception of athletic abilities and strength-training self-efficacy, improved nutrition and exercise behaviors, and reduced intentions to use AAS. Many other beneficial program effects remained significant at the long-term follow-up. CONCLUSIONS: This AAS prevention program enhanced healthy behaviors, reduced factors that encourage AAS use, and lowered intent to use AAS. These changes were sustained over the period of 1 year. Team-based interventions appear to be an effective approach to improve adolescent behaviors and reduce drug use risk factors.

Adolescent↗

PubMed1994

Possible involvement of central cholinergic system in ameliorating effects of indeloxazine, a cerebral activator, on disturbance of learning behavior in rats.

Effects of indeloxazine, a cerebral activator, on passive avoidance learning by disruption of cholinergic transmission were studied in rats. The shortened latency was prolonged when indeloxazine was administered before training in rats subjected to scopolamine-injection, ethylcholine aziridinium ion (AF64A)-treatment and nucleus basalis magnocellularis (NBM) lesion. Indeloxazine administered immediately after training also showed ameliorating effects on passive avoidance in NBM-lesioned rats. Indeloxazine increased extracellular acetylcholine concentration in the frontal cortex of rats. Indeloxazine possesses facilitatory effects on cerebral function in part due to activation of the central cholinergic system.

Acetylcholine↗

PubMed2004

Effects of aversive stimuli on learning and memory in Arctic ground squirrels.

The present study was designed to assess effects of aversive stimuli on learning and memory in wild-caught Arctic ground squirrels (AGS, Spermophilus parryii) using an active avoidance learning paradigm. Results indicate that animals trained with low-value aversive stimuli (air puffs and lights) retained the task better than animals trained with high-value aversive stimuli (air puffs, lights, and foot shock). Poor retention could not be explained by learning impairment, fear-induced freezing behavior or the effects of massed versus spaced training trials. Wild-caught AGS readily hibernate under laboratory conditions and provide a model of pronounced adult synaptic plasticity associated with emergence from hibernation. Characterization of learning and retention using active avoidance as well as other learning paradigms is a first step towards developing behavioral paradigms to assess cognitive function in this wild-trapped species. The present study shows that captive AGS are sensitive to aversive stimuli, argues for a direct effect on retention and suggests that high baseline levels of stress in a captive population may influence behavioral measures. The results further suggest that future studies of the effects of hibernation on learning and retention of active avoidance tasks employ low-level aversive stimuli.

Animals↗

PubMed1988

Strength of scopolamine-induced amnesia as a function of time between training and testing.

Variations in the strength of scopolamine-induced amnesia as a function of age of the habit were studied in Swiss Webster mice. Animals were trained in an active avoidance task to a criterion of 9/10 avoidances and immediately following training injected with scopolamine hydrochloride (1.0 mg/kg) or saline. Retention of the avoidance learning was evaluated by testing different groups of animals 1, 3, 7, 10, 14, and 28 days following training. The retention test consisted of five trials in which the CS but not the UCS was presented. Results indicated that saline-treated mice exhibited near-perfect retention up to 14 days post-training with forgetting beginning to be apparent at 28 days. Scopolamine treatment produced strong amnesia in animals tested 1 and 3 days post-training but normal retention in animals tested 7 and 10 days after learning. The amnesia abruptly reappeared at 14 days after which time it remained stable. The marked similarity of the scopolamine retention curve to changes in the strength of memory of discrimination learning in undertrained rats reported by Deutsch suggested that scopolamine resulted in the storage of a weak memory of the avoidance response. To explore this idea further we trained mice to a criterion (4/5) which would result in a weak avoidance response and tested different groups 1, 3, 10, 14, and 28 days following learning. Results showed that strength of the memory of avoidance learning increased up to 10 days and then decreased abruptly at 14 days thus replicating the general shape of the retention curve produced by injecting scopolamine following strong training. These data suggest that scopolamine disrupts processes essential for the formation of durable memories.

Animals↗

PubMed1997

Effect of chronic treatment with piracetam and tacrine on some changes caused by thymectomy in the rat brain.

Thymectomized rats, 5 weeks after surgery, showed a significant impairment in learning and memory as shown by deficits in passive avoidance and in the Morris water maze test. The behaviour of the thymectomized rats in the "open field" apparatus was largely unchanged. Following treatment for 20 days with either piracetam (500 mg/kg) or tacrine (3.0 mg/kg), the deficit in passive avoidance learning was largely reversed. Chronic treatment with tacrine also reversed the deficit in the behaviour of the thymectomized rats in the Morris water maze. The effects of thymectomy on the biogenic amines and some of their metabolites in the amygdaloid cortex, hypothalamus, striatum and olfactory bulbs were also determined. Relative to the sham-operated controls, thymectomy resulted in a reduction in the noradrenaline concentration in the amygdala, hypothalamus, and olfactory bulbs. This effect was reversed by chronic piracetam and tacrine treatments. The concentration of dopamine was also reduced in the olfactory bulbs after thymectomy whereas in the striatum the concentration of 5-hydroxytryptamine (5-HT; serotonin) was increased. The concentration of gamma amino butyric acid (GABA) was determined in amygdaloid cortex and hippocampus only. The only significant change occurred following chronic treatment of thymectomized rats with tacrine, when a significant elevation of GABA was found. Neither piracetam nor tacrine produced any change in the amines of their metabolites in the sham-operated controls. Tacrine, however, elevated the dopamine and reduced the 5-HT content of the hypothalamus and increased the 3,4-dihydroxylphenylacetic acid concentration of the striatum of thymectomized rats. Examination of the differential white blood cell count of the thymectomized rats showed that the percentage of lymphocytes was decreased, and the percentage of neutrophils increased, relative to the sham-operated controls. Chronic lacrine, but not piracetam, treatment reversed the lesion-induced changes.

Animals↗

PubMed2001

Behavioral effects following subacute inhalation exposure to m-xylene or trimethylbenzene in the rat: a comparative study.

Trimethylbenzene (TMB), like xylene (dimethylbenzene), is a significant constituent of some industrial solvent mixtures. In earlier studies, we found that in the rat a subacute low-level inhalation exposure to some of the TMB isomers may result in behavioral alterations detectable weeks after the exposure [Neurotoxicol Teratol 19;1997:327; Int J Occup Med Environ Health 11;1998:319]. The purpose of the present study was to compare m-xylene (XYL) and each of the TMB isomers: 1,2,3-TMB (hemimellitene - HM), 1,2,4-TMB (pseudocumene - PS), and 1,3,5-TMB (mesitylene - MES) with respect to the ability for inducing behavioral effects in the rat. The rats (10-11 animals per group) were exposed repeatedly for 4 weeks (6 h per day, 5 days per week) to XYL (XYL group), HM (HM group), PS (PS group) or MES (MES group) at 100 ppm, or sham exposed (C group) in 1.3 cu/m dynamic inhalation chambers. Starting 2 weeks after exposure the following forms of rat's behavior were assessed: radial maze performance, spontaneous activity in an open field, learning and retention of passive and active (two-way) avoidance response, and heat-induced paw licking before and after a 2 min footshock (a test for assessment of the stress response). None of the solvent-exposed groups differed considerably from the control one with respect to the radial maze performance. Compared to control rats, the rats of the XYL, PS and MES groups, but not those of HM group, showed a significantly higher spontaneous locomotor activity in the open field, an impaired passive avoidance learning and significantly longer paw-lick latencies 24 h after footshock. Acquisition, but not retention, of the two-way active avoidance response was significantly impaired in all solvent-exposed groups. The XYL group did not differ significantly from PS, MES or HM group in any of the behavioral parameters. The above results show that a short-term exposure to any of the TMB isomers or m-xylene at concentration as low as 100 ppm may induce persistent behavioral alterations in the rat.

Administration, Inhalation↗

PubMed1986

The effect of substance P and its fragments on passive avoidance retention and brain monoamine activity.

It has been shown that substance P(SP), as well as its carboxy and amino terminal fragments, affects a wide range of behaviors. In order to test the CNS activity of these fragments, we measured their effects on passive avoidance learning and monoamine activity. Following one-trial passive avoidance training, mice were injected intraventricularly with either a carboxy or amino terminal SP fragment (SP-C or SP-N), SP itself or phosphate-buffered saline (PBS). SP-N enhanced avoidance retention, which was tested 24 h after training. In a second experiment, monoamine activity was measured one hour after intraventricular injection of SP, PBS or SP fragments. SP-C decreased both nigral 5-hydroxyindoleacetic acid/5-hydroxytryptamine (5-HIAA/5-HT) and, to a lesser extent, 3,4-dihydroxyphenylacetic acid/dopamine, while SP-N increased nigral 5-HIAA/5-HT. It was concluded that SP-N and SP-C can exert behavioral and neurochemical effects that may be independent of the parent SP molecule.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1992

Retention of massed vs distributed response-prevention treatments in rats and a revised training procedure.

Two experiments were conducted to estimate the retention of response-prevention effects using massed vs distributed treatments in a model of animal avoidance-learning. In Exp. I, 120 rats were trained to avoid shock in a one-way platform avoidance apparatus. Groups received response-prevention treatment or nontreatment in a 36-min. massed session or in several sessions distributed over a four-day period. In Exp. II, 160 rats were given two trials of escape training in a one-way shuttle box. Groups received response-prevention treatment or nontreatment in a 24-min. session of massed or distributed treatments delivered in one day. Subjects in both studies were tested using a passive-avoidance paradigm immediately following treatment, 24 hours later, and 30 days later. Analysis showed that response-prevention treatments were effective in reducing avoidance behavior and there were no significant differences in retention of avoidance associated with massed vs distributed response-prevention treatments. Implications for animals and humans are discussed, and researchers are encouraged to change from a criterion training procedure to an escape procedure since the latter is a closer analogue to the human condition.

Animals↗