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PubMed2000

Conditioned compensatory response to ethanol as indicated by locomotor activity in rats.

Spontaneous motor activity (SMA) was used to investigate conditioned tolerance to the depressant effect of ethanol, and conditioned responses to stimuli predicting ethanol injection. Rats were injected with saline or ethanol at 800 or 1600 mg/kg, on alternate days, in two distinctly different locations, over a period of 20 conditioning days. The two ethanol doses were administered to separate groups of rats, but conditioned effects were determined by within-subject comparisons. Conditioned SMA responses (rearing and ambulatory activity) were measured after injection of saline in the location previously paired with ethanol treatment, and conditioned tolerance was determined by observing ethanol effects in rats tested in the environment previously paired with saline treatment. Ethanol-paired stimuli increased SMA (both activity measures, both dose-groups) during the conditioned response test. Absence of these conditioned stimuli during the tolerance test resulted in greater behavioral depression with the 800 mg/kg ethanol dose for both the rearing and ambulation measures; however, this effect was seen with the 1600 mg/kg dose for the rearing measure only. These results provide further evidence that Pavlovian conditioning is involved in tolerance to the depressant action of ethanol on overt behavior, and demonstrate the presence of such conditioned compensatory responses in the absence of ethanol treatment.

Animals↗
PubMedDate not supplied

Using pavlovian higher-order conditioning paradigms to investigate the neural substrates of emotional learning and memory.

In first-order Pavlovian conditioning, learning is acquired by pairing a conditioned stimulus (CS) with an intrinsically motivating unconditioned stimulus (US; e.g., food or shock). In higher-order Pavlovian conditioning (sensory preconditioning and second-order conditioning), the CS is paired with a stimulus that has motivational value that is acquired rather than intrinsic. This review describes some of the ways higher-order conditioning paradigms can be used to elucidate substrates of learning and memory, primarily focusing on fear conditioning. First-order conditioning, second-order conditioning, and sensory preconditioning allow for the controlled demonstration of three distinct forms of memory, the neural substrates of which can thus be analyzed. Higher-order conditioning phenomena allow one to distinguish more precisely between processes involved in transmission of sensory or motor information and processes involved in the plasticity underlying learning. Finally, higher-order conditioning paradigms may also allow one to distinguish between processes involved in behavioral expression of memory retrieval versus processes involved in memory retrieval itself.

Animals↗
PubMedDate not supplied

The cerebellum in maintenance of a motor skill: a hierarchy of brain and spinal cord plasticity underlies H-reflex conditioning.

Operant conditioning of the H-reflex, the electrical analog of the spinal stretch reflex, is a simple model of skill acquisition and involves plasticity in the spinal cord. Previous work showed that the cerebellum is essential for down-conditioning the H-reflex. This study asks whether the cerebellum is also essential for maintaining down-conditioning. After rats decreased the soleus H-reflex over 50 d in response to the down-conditioning protocol, the cerebellar output nuclei dentate and interpositus (DIN) were ablated, and down-conditioning continued for 50-100 more days. In naive (i.e., unconditioned) rats, DIN ablation itself has no significant long-term effect on H-reflex size. During down-conditioning prior to DIN ablation, eight Sprague-Dawley rats decreased the H-reflex to 57% (+/-4 SEM) of control. It rose after ablation, stabilizing within 2 d at about 75% and remaining there until approximately 40 d after ablation. It then rose to approximately 130%, where it remained through the end of study 100 d after ablation. Thus, DIN ablation in down-conditioned rats caused an immediate increase and a delayed increase in the H-reflex. The final result was an H-reflex significantly larger than that prior to down-conditioning. Combined with previous work, these remarkable results suggest that the spinal cord plasticity directly responsible for down-conditioning, which survives only 5-10 d on its own, is maintained by supraspinal plasticity that survives approximately 40 d after loss of cerebellar output. Thus, H-reflex conditioning seems to depend on a hierarchy of brain and spinal cord plasticity to which the cerebellum makes an essential contribution.

Animals↗
PubMed1997

Bilateral disruption of conditioned responses after unilateral blockade of cerebellar output in the decerebrate ferret.

1. Lesions of the cerebellar cortex can abolish classically conditioned eyeblink responses, but some recovery with retraining has been observed. It has been suggested that the recovered responses are generated by the intact contralateral cerebellar hemisphere. In order to investigate this suggestion, bilaterally acquired conditioned responses were studied after the unilateral blockade of cerebellar output. 2. Decerebrate ferrets were trained with ipsilateral electrical forelimb stimulation (300 ms, 50 Hz, 1 mA) as the conditioned stimulus and bilaterally applied peri-orbital stimulation (40 ms, 50 Hz, 3 mA) as the unconditioned stimulus. The conditioned and unconditioned eyeblink responses were monitored by EMG recordings from the orbicularis oculi muscle. The output from one cerebellar hemisphere was blocked either by injecting small amounts of lignocaine (lidocaine; 0.5-1.0 microliter) into the brachium conjunctivum, or by a restricted mechanical lesion of the brainstem rostral to the cerebellum. 3. As described by previous investigators, the unilateral blockade of cerebellar output abolished ipsilateral conditioned responses. 4. More importantly, such blockade also abolished or strongly depressed contralateral conditioned responses. When mechanical lesions of the brachium conjunctivum were made, contralateral responses, in contrast to ipsilateral responses, recovered within 1-2.5 h. 5. When the unconditioned stimulus was removed on one side, causing extinction of conditioned responses on this side, conditioned responses were temporarily depressed on the trained side as well. 6. Unilateral interruption of cerebellar output had no clear effect on contralateral unconditioned reflex responses. 7. The results demonstrate that one cerebellar hemisphere in ferrets exerts a marked control of contralateral conditioned eyeblink responses, probably via premotor neurones involved specifically in conditioned, and not in unconditioned, responses.

Anesthetics, Local↗
PubMed1993

Backward masking and skin conductance responses after conditioning to nonfeared but fear-relevant stimuli in fearful subjects.

The present study examined two issues. Are skin conductance responses conditioned to fear-relevant stimuli, as contrasted with responses conditioned to fear-irrelevant stimuli, elicited after merely an automatic, nonconscious analysis of the stimulus content? Do fearful subjects show better conditioning to nonfeared but fear-relevant stimuli (e.g., conditioning to spiders in snake-fearing subjects) than do nonfearful subjects? Subjects afraid of snakes, but not of spiders, or vice versa (n = 32) and nonfearful subjects (n = 32) were shown either fear-relevant stimuli (snakes or spiders and rats) or fear-irrelevant stimuli (flowers and mushrooms) in a differential conditioning paradigm, where one of the stimuli was followed by an electric shock. During a subsequent extinction phase, the conditioned stimuli were presented under backward masking conditions, preventing their conscious recognition. Consistent with our hypothesis, during the masked extinction of the conditioned stimuli, differential skin conductance responses to conditioning and control stimuli remained only for subjects conditioned to fear-relevant stimuli. Both fearful and nonfearful control subjects had significantly larger differential electrodermal responses to fear-relevant than to fear-irrelevant stimuli. However, contrary to our hypothesis, fearful subjects did not show enhanced conditionability to their nonfeared but fear-relevant stimuli as compared with nonfearful control subjects.

Adolescent↗
PubMed1995

Fear conditioning, preparedness, and the contingent negative variation.

Psychophysiological research on preparedness has previously focused on autonomic nervous system parameters. The present study used electrocortical indices of fear conditioning. Subjects (n = 10) were tested under fear-relevant and fear-irrelevant conditions (1 week apart, order of conditions counterbalanced). Each condition comprised acquisition and extinction sessions. The contingent negative variation (CNV) was elicited in anticipation of forewarned slides (fear relevant: small animals; fear irrelevant: landscapes). In acquisition, reinforced conditioned stimulus (CS+) (but not nonreinforced conditioned stimulus [CS-]) slides were followed by white noise as an unconditioned stimulus (UCS). In extinction, the UCS was omitted. In the fear-relevant condition, CNV amplitude was significantly larger for CS+ than CS- in both acquisition and extinction. In the fear-relevant condition, CNV amplitude was significantly larger for CS+ than CS- in both acquisition and extinction. In the fear-irrelevant condition, CNV differentiation between CS+ and CS- was weak in both sessions. CNV was significantly larger in the fear-relevant than in the fear-irrelevant condition, for CS+ but not CS-. The findings are consistent with a preparedness interpretation and suggest that CNV under such circumstances may represent an automatic affective response to fear-relevant stimuli. Electrocortical measures could be particularly useful in examining information processing mechanisms in phobia and cognition-affect relationships generally.

Adolescent↗
PubMed2006

Fear conditioning is impaired in systemic kainic acid and amygdala-stimulation models of epilepsy.

PURPOSE: The lateral nucleus of the amygdala is critical for fear conditioning, a paradigm of emotional learning, which requires recognition of an unconditioned stimulus as aversive and association of conditioned stimuli with an unconditioned stimulus. Some patients with temporal lobe epilepsy have amygdaloid damage associated with impaired emotional learning. Fear conditioning also is impaired at least in some animal models of epilepsy. We studied whether contextual or tone-cued fear conditioning is impaired in two status epilepticus models of epilepsy and whether impairment correlates with the extent of damage in the lateral nucleus of the amygdala. METHODS: We induced epilepsy in rats by either systemic kainic acid administration or electrical amygdala stimulation. Behavioral reactions in all phases of fear conditioning were analyzed from videotapes. Damage to the lateral nucleus of the amygdala was analyzed from thionin-stained sections both histologically and by volumetry. RESULTS: Immediate reflexive responses to unconditioned and conditioned stimuli were preserved, whereas the freezing response to an unconditioned stimulus was reduced. Contextual conditioning was severely impaired, whereas tone-cued conditioning was better preserved. The lateral nucleus pathology did not correlate with impaired fear conditioning. CONCLUSIONS: These data suggest that processing of complex contextual stimuli is severely affected in experimental epilepsy, whereas conditioning to simple cues is better preserved.

Acoustic Stimulation↗
PubMedDate not supplied

Effect of conditioned media from chicken and turkey intestinal cell cultures on invasion by sporozoites of three species of avian coccidia.

The effect of conditioned media from cultures of turkey and chicken intestinal cells on cellular invasion by sporozoites of avian Eimeria species was examined in vitro. Media conditioned by the growth of cells from the ceca, mid-intestine (area of the yolk stalk diverticulum), and duodenal loop were examined for their ability to enhance invasion. Conditioned medium from cultures of turkey cecal cells significantly enhanced invasion by the turkey coccidia Eimeria adenoeides, by 2.4-fold, and E. meleagrimitis, by 2.2-fold, as compared with invasion in the presence of control medium. Conditioned medium from mid-intestinal cell cultures enhanced invasion by the two coccidial species by 2.0- and 2.1-fold, respectively. The enhancement occurred with conditioned media from early (1) as well as later (11) passages of cells. This suggests that the enhancing factor was produced by fibroblast-like cells, the predominant cell type at both early and late passages, and not by epithelial-like cells that had disappeared by the first or second passage. Additionally, conditioned media from cultures of chicken cecal and duodenal loop cells significantly enhanced invasion by the turkey cecal coccidium, E. adenoeides, (1.7- and 1.6-fold, respectively). This was less enhancement than was caused by the turkey cell conditioned media. Heat treatment (56 degrees C for 45 min) of conditioned media failed to alter the effect on invasion. Neither the turkey or chicken cecal cell media nor conditioned media from any other chicken intestinal cell cultures enhanced invasion by E. tenella, the chicken cecal coccidium. Although morphologically dissimilar when they were first plated, the gross appearance and growth of the turkey and chicken cells when conditioned media was collected was comparable.

Animals↗
PubMed2003

L-type voltage-gated calcium channels are involved in the in vivo and in vitro expression of fear conditioning.

Fear conditioning, a behavioral model of fear learning and cue-related anxiety, causes enhanced neuronal transmission in the thalamic to lateral amygdala pathway.(1,2) In the expression phase of learned fear, this increased transmission recorded in vitro is revealed in increased amplitudes of excitatory postsynaptic currents (EPSCs) and occlusion of paired-pulse facilitation (PPF) implicating a presynaptic increase in transmitter release. Here we examined the contribution of L-type calcium channels in fear conditioning. We measured the effect of nimodipine (Nim, 1.5-20 mg/kg), an L-type calcium channel antagonist, on fear-potentiated startle in which startle was assessed in animals receiving paired or unpaired tone and foot shock. Nim administered intraperitoneally blocked fear-potentiated startle but not baseline startle in a dose-dependent manner. We also analyzed the effect of Nim (10 micro M) in vitro on synaptic facilitation of EPSCs and PPF in slices from naïve control, unpaired control, and fear-conditioned animals. In neurons from naïve control animals, Nim had no effect on EPSC amplitude or PPF, but in slices from fear-conditioned rats, Nim reduced EPSC amplitude, suggesting the recruitment of L-type calcium channels within the fear-conditioning pathway. Nim increased PPF in slices from fear-conditioned animals, suggesting that L-type calcium channels may contribute to increased probability of release in fear conditioning. In slices from unpaired animals, Nim decreased synaptic transmission but had little effect on PPF, suggesting that stress or contextual fear learning may induce L-type channel activity in fear-conditioned and unpaired control animal groups. We also analyzed protein expression of the alpha(1C) and alpha(1D) L-type calcium channel subunits isolated from the amygdala and found that alpha(1C) protein was significantly increased in fear-conditioned animals. These findings suggest that L-type calcium channels play a role in the amygdala in cued fear conditioning and have important implications in the treatment of anxiety and in emotional learning and plasticity.

Animals↗
PubMed2001

A two-locus model for experience-conditioned direction of paw usage in the mouse is suggested by dominant and recessive constitutive paw usage behaviours.

Left-right direction of paw usage in the mouse depends on the genotype and the directional nature of the test. There are two phenotypic classes; in some strains, direction of paw usage is learned or conditioned by the direction of the initial test chamber and the experience of reaching and, in other strains, paw usage is a constitutive behaviour not affected by previous experience. We report the evidence for locus heterogeneity in the cause of constitutive versus experience-conditioned paw usage from a phenotypic analysis of F1 hybrid generations from the experience-conditioned C57BL/6J, C3H/HeHa, and SWV strains and the constitutive CDS/Lay and DBA/2J strains. The F1 hybrids between strains of different phenotypic classes provide evidence of locus heterogeneity. Constitutive paw usage in CDS/Lay is phenotypically dominant to experience-conditioned behaviour in both C57BL/6J and SWV. However, constitutive paw usage in DBA/2J is phenotypically recessive to experience-conditioned behaviour in C57BL/6J and dominant to experience-conditioned behaviour in SWV. Among the experience-conditioned strains, C57BL/6J is highly lateralized but SWV is only weakly lateralized. Our data suggest a model in which C57BL/6J may have a "strong" allele that identifies a functional difference between the constitutive paw usage of CDS/Lay and DBA/2J. DBA/2J may have a loss-of-function mutation at the same locus that is recessive to the strong C57BL/6J allele. SWV may have a "weak" allele and the (SWV x D2)F1 compound heterozygote may be below a threshold for detectability of experience-conditioned behaviour, making the constitutive behaviour of DBA/2J appear to be dominant to the experience-conditioned behaviour of SWV. CDS/Lay may have a dominant allele at a second locus that suppresses experience-conditioned behaviour in all F1 hybrids.

Animals↗
PubMed2006

In vitro odor-aversion conditioning in a terrestrial mollusk.

We developed an in vitro odor-aversion conditioning system in the terrestrial mollusk, Limax, and found a behavioral correlate of network oscillation in the olfactory CNS. We first examined the odor-induced behavior of Limax, after odor-aversion conditioning in vivo. Shortening of mantle muscles was specifically observed in response to aversively conditioned odors. We previously identified that parietal nerves, which project to the mantle muscle in Limax, regulate shortening of the mantle muscle. We therefore isolated whole brains containing noses (sensory organs) and parietal nerves (motor output), and applied an odor-aversion conditioning paradigm to these in vitro preparations. Before the in vitro conditioning, application of attractive odors to the noses did not elicit any discharge in the parietal nerves. However, after odor-aversion conditioning, discharges in the parietal nerves were observed in response to the natively attractive but aversively conditioned odors. We also found that network oscillation frequency in the procerebrum (PC), the olfactory CNS of Limax, increased specifically in response to the aversively conditioned odors that elicited avoidance behavior. In naive (nonconditioned) preparations, increases in the PC oscillation frequency were observed specifically in response to innately aversive odors. These results indicate that the isolated brains have an ability of odor learning. They also suggest that changes in PC network oscillation are associated with aversively conditioned and innately aversive odors, both of which elicit avoidance behavior. This in vitro conditioning system would be an effective approach for exploring the neural mechanism to determine the aversion to odors.

Action Potentials↗
PubMed2003

Activity profiles of single neurons in caudal anterior cingulate cortex during trace eyeblink conditioning in the rabbit.

Acquisition of trace eyeblink conditioning involves the association of a conditioned stimulus (CS) with an unconditioned stimulus (US) separated by a stimulus-free trace interval. This form of conditioning is dependent upon the hippocampus and the caudal anterior cingulate cortex (AC), in addition to brain stem and cerebellar circuitry. Hippocampal involvement in trace eyeblink conditioning has been studied extensively, but the involvement of caudal AC is less well understood. In the present study, we compared neuronal responses from rabbits given either paired (trace conditioning) or unpaired (pseudoconditioning) presentations of the CS and US. Presentation of the CS elicited significant increases in neuronal activity at the onset of both trace conditioning and pseudoconditioning. A robust CS-elicited neuronal response persisted throughout the first 2 days of trace conditioning, declining gradually across subsequent training sessions. In contrast, the magnitude of the CS-elicited excitatory response during pseudoconditioning began to decline within the first 10 trials. Neurons exhibiting excitatory responses to the CS during trace conditioning also exhibited excitatory responses to the US that were significantly greater in magnitude than US-elicited responses during pseudoconditioning. CS-elicited decreases in neuronal activity became more robust over the course of trace conditioning compared to pseudoconditioning. Reductions in activity during the CS interval consistently preceded excitation in both training groups, suggesting that the CS-elicited decreases in neuronal activity may serve to increase the signal-to-noise ratio of the excitatory response to the tone. Taken together, these data suggest that the caudal AC is involved early in trace eyeblink conditioning and that maintenance of the CS-elicited excitatory response may serve to signal the salience of the tone.

Animals↗
PubMed1997

Dorsal column but not lateral column transection prevents down-conditioning of H reflex in rats.

Operant conditioning of the H reflex, the electrical analogue of the spinal stretch reflex, in freely moving rats is a relatively simple model for studying long-term supraspinal control over spinal cord function. Motivated by food reward, rats can gradually increase or decrease the soleus H reflex. This study is the first effort to determine which spinal cord pathways convey the descending influence from supraspinal structures that changes the H reflex. In anesthetized Sprague-Dawley rats, the entire dorsal column (DC), which includes the main corticospinal tract, or the right lateral column (LC) was transected by electrocautery. Animals recovered quickly and the minimal transient effects of transection on the right soleus H reflex disappeared within 16 days. Beginning at least 18 days after transection, 12 rats were exposed to the HRdown-conditioning mode, in which reward was given when the H reflex of the right soleus muscle was below a criterion value. In seven LC rats exposed to the HRdown mode, the H reflex fell to 71 +/- 8% (mean +/- SE) of its initial value. In six of the seven, conditioning was successful (i.e., decrease to < or = 80%). These results were comparable with those previously obtained from normal rats. In contrast, in five DC rats exposed to the HRdown mode, the H reflex at the end of exposure was 106 +/- 12% of its initial value. In none of these rats was HRdown-conditioning successful. DC rats differed significantly from normal and LC rats in both final H reflex values and number successful. In five DC and three LC rats that continued under control conditions over 30-78 days, the H reflex at the end of the period was 98 +/- 4% and 100 +/- 8%, respectively, of its initial value, indicating that DC or LC transection itself did not lead to gradual increase or decrease in the H reflex. The results indicate that the DC, containing the main corticospinal tract, is essential for HRdown-conditioning, whereas the ipsilateral LC, containing the main rubrospinal, vestibulospinal, and reticulospinal tracts, is not essential. Combined with the known muscular specificity of conditioning, these results suggest that the main corticospinal tract is essential for HRdown-conditioning. The DC ascending tract might also be necessary. The respective roles of the DC descending and ascending tracts, and transection effects on HRup-conditioning and on the maintenance of both HRup- and HRdown-conditioning after they have occurred, remain to be defined.

Animals↗
PubMed1997

Time-dependent changes in excitability after one-trial conditioning of Hermissenda.

The visual system of Hermissenda has been studied extensively as a site of cellular plasticity produced by classical conditioning. A one-trial conditioning procedure consisting of light paired with the application of serotonin (5-HT) to the exposed, but otherwise intact, nervous system produces suppression of phototactic behavior tested 24 h after conditioning. Short- and long-term enhancement (STE and LTE) of excitability in identified type B photoreceptors is a cellular correlate of one-trial conditioning. LTE can be expressed in the absence of STE suggesting that STE and LTE may be parallel processes. To examine the development of enhancement, we studied its time-dependent alterations after one-trial conditioning. Intracellular recordings from identified type B photoreceptors of independent groups collected at different times after conditioning revealed that enhanced excitability follows a biphasic pattern in its development. The analysis of spikes elicited by 2 and 30 s extrinsic current pulses at different levels of depolarization showed that enhancement reached a peak 3 h after conditioning. From its peak, excitability decreased toward baseline control levels 5-6 h after conditioning followed by an increase to a stable plateau at 16 to 24 h postconditioning. Excitability changes measured in cells from unpaired control groups showed maximal changes 1 h posttreatment that rapidly decremented within 2 h. The conditioned stimulus (CS) elicited significantly more spikes 24 h postconditioning for the conditioned group as compared with the unpaired control group. The analysis of the time-dependent development of enhancement may reveal the processes underlying different stages of memory for this associative experience.

Analysis of Variance↗
PubMed2003

Cerebellar and hippocampal activation during eyeblink conditioning depends on the experimental paradigm: a MEG study.

The cerebellum and the hippocampus are key structures for the acquisition of conditioned eyeblink responses. Whereas the cerebellum seems to be crucial for all types of eyeblink conditioning, the hippocampus appears to be involved only in complex types of learning. We conducted a differential conditioning study to explore the suitability of the design for magnetencephalography (MEG). In addition, we compared cerebellar and hippocampal activation during differential delay and trace conditioning. Comparable conditioning effects were seen in both conditions, but a greater resistance to extinction for trace conditioning. Brain activation differed between paradigms: delay conditioning provoked activation only in the cerebellum and trace conditioning only in the hippocampus. The results reflect differential brain activation patterns during the two types of eyeblink conditioning.

Adult↗
PubMed2006

Dorsal hippocampal contributions to unimodal contextual conditioning.

Although there is general consensus that the hippocampus is not critically involved in the acquisition of fear conditioned to an explicit conditioned stimulus (CS), the extent to which the hippocampus participates in contextual fear conditioning remains unclear. To further characterize the potential role of the hippocampus in contextual fear conditioning, the present experiments examined the effect of excitotoxic lesions of dorsal hippocampus on the acquisition of a novel contextual fear conditioning paradigm in which a unimodal (olfactory) cue served to disambiguate discrete "contexts" within a single behavioral training chamber. Selective lesions of dorsal hippocampus severely attenuated olfactory contextual conditioning without affecting conditioning to an explicit auditory or olfactory CS. Additional experiments indicate that these contextual conditioning deficits cannot be attributed to a lesion-induced decrement in olfactory perception, a preferential impairment of "weak" forms of conditioning, or hyperactivity. Thus, the hippocampus appears to contribute importantly to the acquisition of fear conditioned to explicitly nonspatial, unimodal, temporally, and spatially diffuse contextual stimuli.

Acoustic Stimulation↗
PubMed2004

Conditioned medium increases the polyploid cell composition of bovine somatic cell nuclear-transferred blastocysts.

The effects of bovine cumulus cell-conditioned medium on cloned bovine embryonic development and subsequent chromosome complement were examined using an air-dry procedure. Conditioned media were prepared using CR1aa supplemented with either fetal bovine serum (FBS) or bovine serum albumin (BSA). Nuclear-transferred embryos were reconstructed with nuclei from cumulus cells. Similar cleavage, morula, and blastocyst development was observed in conditioned media groups compared with the co-culture group. No differences (P > 0.05) were observed in the composition of blastocyst chromosomes after co-culture in different media, either with or without starvation of donor cells. The overall diploid blastocyst rate ranged from 75% to 84%. Chromosomal complement of blastocysts, however, was very different between conditioned medium and co-culture treatments. Overall incidence of chromosomal anomalies was 40% in conditioned medium, which was significantly higher (P < 0.001) than the co-culture group (20%). Moreover, a higher incidence (P < 0.05) of chromosomally abnormal blastocysts (41.5%) was observed after culture with FBS-containing conditioned medium than those cultured in BSA-containing conditioned medium (31.4%). No diploid improvement was observed after exchange of the culture system from conditioned medium to co-culture, or from co-culture to conditioned medium after the first 72 h of culture. The results of this study also indicated that the overall cell number was much lower (P < 0.01) in blastocysts with chromosomal abnormalities than those with a normal diploid state. We have concluded that medium conditioned with bovine cumulus cells increases the incidence of chromosomal anomalies in nuclear reconstructed embryos.

Animals↗
PubMed1982

Conditional discrimination vs. matching to sample: an expansion of the testing paradigm.

A subject's performance under a conditional-discrimination procedure defines conditional relations between stimuli: "If Al, then Bl; if A2, then B2." The procedure may also generate matching to sample. If so, the stimuli will be related not only by conditionality, but by equivalence: Al and Bl will become equivalent members of one stimulus class, A2 and B2 of another. One paradigm for testing whether a conditional-discrimination procedure has generated equivalence relations uses three sets of stimuli, A, B, and C, three stimuli per set. Subjects learn to select Set-B and Set-C comparisons conditionally upon Set-A samples. Having been explicitly taught six sample-comparison relations, A1B1, A1C1, A2B2, A2C2, A3B3,and A3C3, subjects prove immediately capable of matching the B- and C-stimuli; six new relations emerge (B1C1, B2C2, B3C3, C1B1, C2B2, C3B3). The 12 stimulus relations, six taught and six emergent, define the existence of three three-member stimulus classes, A1B1C1, A2B2C2 and A3B3C3. This paradigm was expanded by introducing three more stimuli (Set D), and teaching eight children not only the AB and AC relations but DC relations also-selecting Set-C comparisons conditionally upon Set-D samples. Six of the children proved immediately capable of matching the B- and D-stimuli to each other. By selecting appropriate Set-B comparisons conditionally upon Set-D samples, and Set-D comparisons conditionally upon Set-B samples, they demonstrated the existence of three four-member stimulus classes, A1B1C1D1, A2B2C2D2, and A3B3C3D3. These larger classes were confirmed by the subjects' success with the prerequisite lower-level conditional relations; they were also able to select Set-D comparisons conditionally upon samples from Sets A and C, and to do the BC and CB matching that defined the original three-member classes. Adding the three DC relations therefore generated 12 more, three each in BD, DB, AD, and CD. Enlarging each class by one member brought about a disproportionate increase in the number of emergent relations. Ancillary oral naming tests suggested that the subject's application of the same name to each stimulus was neither necessary nor sufficient to establish classes of equivalent stimuli.

Child↗