The dependence of the rate of learning on the probability of the random performance of an acquired reaction under different regimens of aversive reinforcement in rats

Learning of rats in the process of elaboration of instrumental conditioned reflex takes place much faster at the probability of random fulfillment of correct reaction (PRCR) equal to 0.25 and 0.125 than at PRCR 0.5 and 0.05. Decrease of the frequency of positive reinforcements of correct reactions from 100 to 25% does not influence the speed of learning at PRCR 0.25 and 0.125, however significantly retards the process of learning at PRCR 0.05. There exist optimum and pessimum for learning PRCR values at different regimes of reinforcement.     

Direct measurement of the concentration- and time-dependent open probability of the nicotinic acetylcholine receptor channel.

Using the outside-out patch clamp recording technique together with a rapid solution exchange system, we measured ionic currents through nicotinic acetylcholine (ACh) receptor channels from BC3H-1 cells in response to rapid applications of 0.3-1,000 microM ACh. We used nonstationary fluctuation analysis of ensembles of responses to deduce the number of channels in the patch, the maximum open channel probability as a function of ACh concentration and the time course of a fast desensitization process. We found that: (a) Excised patches from BC3H-1 cells typically contain between 50 and 150 functional ACh receptor ion channels. (b) The open channel probability is proportional to [ACh]1.95 at low concentrations of ACh, is half-maximal at 20 microM ACh and saturates above 100 microM ACh. (c) ACh is a very efficacious agonist; 100 microM ACh opens at least 90% of the available channels. This estimate of efficacy is model-independent. (d) The rate of decay of the agonist-induced current is concentration-dependent. In the presence of 100 microM ACh the current decays with a time constant of 50-100 ms. It decays more slowly in the presence of lower concentrations of agonist but is relatively insensitive to voltage.     

Within-trial contrast: The effect of probability of reinforcement in training

There is evidence that pigeons prefer conditioned reinforcers that are preceded by greater effort over those that are preceded by less effort (an effect that has been attributed to within-trial contrast). In past research the probability of reinforcement for correct choice of the conditioned reinforcer has been 100%, however, the high level of reinforcement for both alternatives in training may result in a performance ceiling when choice between those alternatives is provided on test trials. In the present study we tested this hypothesis by including a group for which the probability of reinforcement in training was only 50%. Pigeons were trained on two simultaneous discriminations, one that was preceded by a 30 peck requirement the other by a single peck requirement. On test trials, we found a significant preference for the S+ that required the greater effort in training for pigeons trained with 100% and a small but nonsignificant effect for pigeons trained with 50% reinforcement. Although the hypothesis that the within-trial contrast effect was constrained by a performance ceiling was not confirmed, we did find a reliable within-trial contrast effect with 100% reinforcement.     

Weighting coefficients for the estimation of sensory threshold

This paper discusses the determ-nation of difference thresholds(ED50) by least squares procedures. A table of weights (W) tocorrect ED50 for chance probability was constructed for pairedand triangle designs. The probability (P) of a correct judgmentabove chance for the paired design is P = 2p^*–1, wherep^* is the actual proportion of correct responses. For the triangledesign, P = (3p^*–l)/2. In both designs, P was weightedby W = y²/p^*q^*, where y² is the squared ordinate of the normalcurve based on P, and q^* = 1–p^*. An example of the useof the table of weights is provided.     

An experimental study on the self-reference effect

Self-reference at encoding increases the probability of recollective experience in recognition memory. Self-reference effect (SRE) in memory is observed when the degree of self-reference of to-be-remembered materials is varied. Usually items encoded in terms of self-reference are associated with significantly higher recall performance relative to items encoded in other ways, including semantic encoding. In our three experiments, four orientating tasks formed four levels in a between-subjects design. The conditions were rating personality traits with reference to self, mother, Lu Xun (a famous Chinese writer) or rating the traits on a negative-positive dimension. In a recognition test, subjects first identified old items and then indicated which of these were accompanied by recollective experience ('remember' responses) and which were recognized on some other basis ('know' responses). Our results showed that both the self-reference condition and mother condition were associated with the same highest propo     

An experimental study on the self-reference effect

Self-reference at encoding increases the probability of recollective experience in recognition memory. Self-reference effect (SRE) in memory is observed when the degree of self-reference of to-be-remembered materials is varied. Usually items encoded in terms of self-reference are associated with significantly higher recall performance relative to items encoded in other ways, including semantic encoding. In our three experiments, four orientating tasks formed four levels in a between-subjects design. The conditions were rating personality traits with reference to self, mother, Lu Xun (a famous Chinese writer) or rating the traits on a negative-positive dimension. In a recognition test, subjects first identified old items and then indicated which of these were accompanied by recollective experience (‘remember’ responses) and which were recognized on some other basis (‘know’ responses). Our results showed that both the self-reference condition and mother condition were associated with the same highest proportion of correct remember responses and the same lowest proportion of correct know responses. In contrast, for Western subjects, the self-reference condition, relative to the mother condition, was associated with a higher proportion of correct remember responses and a lower proportion of correct know responses. We discussed the results with reference to the HERA model (hemispheric encoding/retrieval asymmetry).     

Zygosity diagnosis in the absence of genotypic data: an approach using latent class analysis.

For zygosity diagnosis in the absence of genotypic data, or in the recruitment phase of a twin study where only single twins from same-sex pairs are being screened, or to provide a test for sample duplication leading to the false identification of a dizygotic pair as monozygotic, the appropriate analysis of respondents' answers to questions about zygosity is critical. Using data from a young adult Australian twin cohort (N = 2094 complete pairs and 519 singleton twins from same-sex pairs with complete responses to all zygosity items), we show that application of latent class analysis (LCA), fitting a 2-class model, yields results that show good concordance with traditional methods of zygosity diagnosis, but with certain important advantages. These include the ability, in many cases, to assign zygosity with specified probability on the basis of responses of a single informant (advantageous when one zygosity type is being oversampled); and the ability to quantify the probability of misassignment of zygosity, allowing prioritization of cases for genotyping as well as identification of cases of probable laboratory error. Out of 242 twins (from 121 like-sex pairs) where genotypic data were available for zygosity confirmation, only a single case was identified of incorrect zygosity assignment by the latent class algorithm. Zygosity assignment for that single case was identified by the LCA as uncertain (probability of being a monozygotic twin only 76%), and the co-twin's responses clearly identified the pair as dizygotic (probability of being dizygotic 100%). In the absence of genotypic data, or as a safeguard against sample duplication, application of LCA for zygosity assignment or confirmation is strongly recommended.     

Factors affecting the landing and feeding responses of the tsetse fly Glossina pallidipes to a stationary ox

In Zimbabwe, studies were made of the landing and feeding responses of Glossina pallidipes on an ox. Of the tsetse approaching an ox, ≈ 70% fed. Increasing densities of tsetse increased the grooming responses of the ox but had no significant effect on the percentage of tsetse that engorged. The landing site of tsetse on the ox varied with density, with ≈ 50% landing on the legs at low densities (< 20 flies per ox), compared to ≈ 80% at densities > 40 flies per ox. For male G. pallidipes , the mean bloodmeal size was 37 mg. The probability of feeding was negatively correlated with fat content, declining from 91% for flies with < 1 mg fat to < 50% for flies with > 4 mg fat. Bloodmeal size was also negatively correlated with fat content; the regression equation relating bloodmeal size and fat content indicated that the mean wet weight declined from 42 mg for flies with 1 mg of fat to 31 mg for flies with 5 mg of fat. For females, the probability of feeding was not significantly affected by age as determined by ovarian category but there was a paucity of young (ovarian category 0) flies attracted to the ox. Pregnancy status had no significant effect on the probability of feeding, but samples of flies attracted to the ox showed a relative dearth of females approaching larviposition and a preponderance just after.     

Population variability complicates the accurate detection of climate change responses

The rush to assess species’ responses to anthropogenic climate change (CC) has underestimated the importance of interannual population variability (PV). Researchers assume sampling rigor alone will lead to an accurate detection of response regardless of the underlying population fluctuations of the species under consideration. Using population simulations across a realistic, empirically based gradient in PV, we show that moderate to high PV can lead to opposite and biased conclusions about CC responses. Between pre‐ and post‐CC sampling bouts of modeled populations as in resurvey studies, there is: (i) A 50% probability of erroneously detecting the opposite trend in population abundance change and nearly zero probability of detecting no change. (ii) Across multiple years of sampling, it is nearly impossible to accurately detect any directional shift in population sizes with even moderate PV. (iii) There is up to 50% probability of detecting a population extirpation when the species is present, but in very low natural abundances. (iv) Under scenarios of moderate to high PV across a species’ range or at the range edges, there is a bias toward erroneous detection of range shifts or contractions. Essentially, the frequency and magnitude of population peaks and troughs greatly impact the accuracy of our CC response measurements. Species with moderate to high PV (many small vertebrates, invertebrates, and annual plants) may be inaccurate ‘canaries in the coal mine’ for CC without pertinent demographic analyses and additional repeat sampling. Variation in PV may explain some idiosyncrasies in CC responses detected so far and urgently needs more careful consideration in design and analysis of CC responses.     

Short term memory may be the depletion of the readily releasable pool of presynaptic neurotransmitter vesicles of a metastable long term memory trace pattern

The Tagging/Retagging model of short term memory was introduced earlier (Tarnow in Cogn Neurodyn 2(4):347–353, 2008) to explain the linear relationship between response time and correct response probability for word recall and recognition: At the initial stimulus presentation the words displayed tag the corresponding long term memory locations. The tagging process is linear in time and takes about one second to reach a tagging level of 100%. After stimulus presentation the tagging level decays logarithmically with time to 50% after 14 s and to 20% after 220 s. If a probe word is reintroduced the tagging level has to return to 100% for the word to be properly identified, which leads to a delay in response time. This delay is proportional to the tagging loss. The tagging level is directly related to the probability of correct word recall and recognition. Evidence presented suggests that the tagging level is the level of depletion of the Readily Releasable Pool (RRP) of neurotransmitter vesicles at presynaptic terminals. The evidence includes the initial linear relationship between tagging level and time as well as the subsequent logarithmic decay of the tagging level. The activation of a short term memory may thus be the depletion of RRP (exocytosis) and short term memory decay may be the ensuing recycling of the neurotransmitter vesicles (endocytosis). The pattern of depleted presynaptic terminals corresponds to the long term memory trace.

Influence of elongated refractoriness on forward masking of tone bursts in single units of the mouse inferior colliculus

The responses of single units located in the inferior colliculus of albino mice narcotized by barbital were registered. Pairs of low-intensity tone bursts were used as stimuli. The probability of the response to the second burst in the pair was obtained under two conditions: the presence and absence of spike activity in the reaction to the first burst. With a 50-ms interval between the bursts in the majority of units, the probability of response was lower in the presence of spike activity in response to the first burst. In a few number of units, the opposite tendency was observed. As the interburst interval increased up to 100 and 200 ms, the dependence of the response probability to the second burst on the presence of the firing to the first one gradually weakened. The suppression of inhibitory inputs by bicuculline emphasized the effect of the afterspike decrease in excitability rather than weakened it. Possible mechanisms of interdependence of spike responses to two consecutive signals are discussed.     

Host plant volatiles serve to increase the response of male European grape berry moths, <Emphasis Type="Italic">Eupoecilia ambiguella,</Emphasis> to their sex pheromone

The European grape berry moth is an important pest in vineyards. Males respond to the female-produced sex pheromone released from a piezo nebulizer in a dose-dependent manner in a wind tunnel: <50% arrive at the source at 5–50 pg/min (underdosed), 80% arrive at 100 pg/min to 10 ng/min (optimal) and <20% arrive at 100 ng/min (overdosed). Males responding to overdosed pheromone show in flight arrestment at 80 cm from the source. Host plant chemostimuli for Eupoecilia ambiguella increase the responses of males to underdosed and overdosed pheromone. (Z)-3-hexen-1-ol, (+)-terpinen-4-ol, (E)-β-caryophyllene and methyl salicylate released with the underdosed pheromone cause a significant increase in male E. ambiguella flying to the source. Time–event analysis indicates a positive correlation between faster activation and probability of source contact by the responding males. The four host plant compounds added to the overdosed pheromone permitted males to take off faster and with a higher probability of flying to the source. This suggests that perception of host plant products with the sex pheromone facilitates male E. ambiguella to locate females on host plants, lending credence to the hypothesis that plant products can signal rendezvous sites suitable for mating. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Characteristics of the response of sensomotor cortex neurons of the cat during performance of rapid purposeful movements

Neuronal activity of cat sensorimotor cortical area was studied during performance of movements of grasping a visual goal appearing for a short time. Characteristics and the pattern of neuronal discharge became stabilized in the process of animal training and did not depend on the time of goal presentation, absence or presence of the reinforcement under preservation of animal's motor reaction. Changes in responses were observed in situations of uncertainty: at 50% of reinforcement probability and (or) at successful performance of the motor reaction in half of cases.     

Characterization of radiation-induced emesis in the ferret

Forty-eight ferrets (Mustela putorius furo) were individually head-shielded and radiated with bilateral 60Co gamma radiation at 100 cGy min-1 at doses ranging between 49 and 601 cGy. The emetic threshold was observed at 69 cGy, the ED50 was calculated at 77 cGy, and 100% incidence of emesis occurred at 201 cGy. With increasing doses of radiation, the latency to first emesis after radiation decreased dramatically, whereas the duration of the prodromal period increased. Two other sets of experiments suggest that dopaminergic mechanisms play a minor role in radiation-induced emesis in the ferret. Twenty-two animals were injected either intravenously or subcutaneously with 30 to 300 micrograms/kg of apomorphine. Fewer than 50% of the animals vomited to 300 micrograms/kg apomorphine; central dopaminergic receptor activation was apparent at all doses. Another eight animals received 1 mg/kg domperidone prior to either 201 (n = 4) or 401 (n = 4) cGy radiation and their emetic responses were compared with NaCl-injected-irradiated controls (n = 8). At 201 cGy, domperidone significantly reduced only the total time in emetic behavior. At 401 cGy, domperidone had no salutary effect on radiation-induced emesis. The emetic responses of the ferret to radiation and apomorphine are compared with these responses in other vomiting species.     

Neurophysiological and behavioural evidence for an olfactory function for the dorsal organ and a gustatory one for the terminal organ in Drosophila melanogaster larvae

Multicellular electrophysiological responses from the dorsal organ on the cephalic lobes of third instar Drosophila melanogaster larvae (wild-type Canton S) stimulated with a cold-trapped banana volatile extract showed that this structure has an olfactory function in the fruit fly. Responses of the dorsal organ were also recorded to constituents of the banana volatile extract as they eluted from a gas chromatographic column (GC-coupled dorsal organ electrophysiology). The active chemostimulants were identified as 2-heptanone, isoamyl alcohol, hexyl acetate, hexanol and hexyl butyrate by gas chromatography-coupled mass spectrometry. Applying the same recording system to the terminal organ sensilla, no responses were obtained to either the banana volatile bouquet or its constituents. By contrast, high frequency multicellular responses were recorded in response to touching the terminal organ with the gustatory stimuli KCl and grapefruit juice; responses were absent on similar stimulation of the dorsal organ with either NaCl or KCl. This suggests a role for olfaction by the dorsal organ and for gustation by the terminal organ in Drosophila larvae.In a 7-mm high wind tunnel with a thin 1.2% agar floor, the Drosophila larvae showed odour-conditioned upwind responses in an air stream of 0.1 m/s bearing banana volatiles. Drosophila larvae responded best to the odour of cut bananas. A 1:1 mixture of the banana odour constituents 2-heptanone and hexanol (at either 50 or 100 &mgr;g source dose each) proved as attractive as the known larval attractants propionic acid and isoamyl acetate on their own at 100 &mgr;g, whereas hexanol and 2-heptanone on their own at a 100 &mgr;g source dose were less attractive. The stronger behavioural response to the banana volatile bouquet and to the binary mixture serves to underline the multireceptor nature of the dorsal organ response to food odour in Drosophila.     

Duration discrimination in the mouse (<Emphasis Type="Italic">Mus musculus</Emphasis>)

Detection thresholds for an increment in duration of a 10-kHz pure tone were determined in the NMRI mouse using a Go/NoGo-procedure and the method of constant stimuli. Thresholds for reference durations of 50, 100 and 200 ms were obtained presenting the signals at a fixed level or at a level varying by ±3 dB. Thresholds were determined using signal-detection theory (d=1.0 or d=1.8) and the criterion of 50% correct responses. For a fixed level, the average Weber fraction T/T (criterion of d=1.8) significantly decreased from 1.18 or 1.23 at reference durations of 50 or 100 ms, respectively, to 0.97 at a reference duration of 200 ms. Thresholds were on average reduced by 46.8 or 55.4% for the threshold criteria d=1 or 50% correct responses, respectively. There was no effect of randomizing the level on the discrimination threshold. Duration discrimination in the NMRI mouse does not follow Webers law. The results are consistent with a mechanism summing up neural impulses over the duration of the stimulus. The psychoacoustic data are compared with results obtained by Brand et al. (J Acoust Soc Am 51:1291–1223, 2000) on the representation of acoustic signal duration in the mouse inferior colliculus.     

Testing the reliability of noninvasive genetic sampling by comparing analyses of blood and fecal samples in Barbary macaques (Macaca sylvanus).

Genetic studies of wild animal populations are often hindered by difficulties in obtaining blood samples. Recent advances in molecular biology have allowed the use of noninvasive samples as sources of DNA (e.g., hair or feces), but such samples may provide low-quality DNA and prevent the determination of true genotypes in subsequent DNA analysis. We present a preliminary study aimed at assessing the reliability of using fecal samples for genotyping in Barbary macaques (Macaca sylvanus). The test was performed on samples of blood and feces from 11 captive animals, using three dinucleotide microsatellites. The CTAB DNA extraction method was found to be the most relevant for Barbary macaque feces, yielding successful amplification at all loci for 70% of PCRs. All the fecal samples tested gave correct genotypes at least once for each locus when referenced against blood-derived genotypes. An average of 18.3% of PCRs displayed spurious genotypes (false homozygous or false allele). The minimum theoretical probability required to obtain a 100% accurate genotype is 0.74, based on the criterion that a correct genotype is assessed only if it was observed at least twice. The observed probability of obtaining a correct genotype from three PCRs, based on our genotyping results, was greater (0.81 on average) than the minimum threshold. In conclusion, our comparison of blood and fecal samples showed that fecal sampling is a reliable tool for the further study of wild Barbary macaque populations.     

Changes in the heart rate and electromyogram beyond the limit time of an isotonic isometric contraction

Nine men [24.6 (SEM 1.1) years] carried out isometric contractions (IC) of the right elbow flexors at 50% and 100% of the maximal voluntary contraction (MVC). At 50% MVC they had to maintain IC until the limit time (isotonic IC: IIC₅₀ and beyond for as long as possible (anisotonic IC: AIC₅₀). At 100% MVC, IC was anisotonic since the decrease in force was immediate (AIC₁₀₀). Measurements of the force, the integrated electromyogram (iEMG) and the heart rate (f _c) were made during the entire period of contraction. There was a linear relationship between the iEMG increase and thef _c increase for IIC₅₀ and AIC₁₀₀. This relationship was not found for AIC₅₀. The role played by the peripheral information would seem to have become more important inf _c regulation when the isotonic IC preceding the anisotonic IC was sufficiently long (submaximal IIC). It would seem that the idea of muscle exhaustion at the limit time was only relative, and depended greatly on the subject's motivation and his capacity to endure a certain degree of pain.     

Changes in breathing pattern at loads near perceptual threshold at different work levels

Five subjects were tested to determine the threshold for detection of an added resistance to inspiration in three tests, one at rest and two with exercise (mild = 50 W; moderate = 100 W) on a cycle ergometer. Changes in the breathing pattern were examined at added resistances near the perceptual threshold. Added inspiratory resistances with a 50% probability of detection were very variable at rest; they decreased significantly from rest (250 Pa.l-1.s-1) to moderate exercise (98 Pa.l-1.s-1) in four subjects. It is suggested that physical exercise may cause discomfort even when workers wearing a respirator do not have any abnormal sensation during sedentary work. Breathing patterns were compared between resistance loaded and unloaded breathing during each test. Decreases in inspiratory peak flow and acceleration of flow early in inspiration were found in resistance loaded breathing in almost all tests and a tendency for tidal volume to decrease was found during moderate exercise only. The ratios of resistance loaded to unloaded breathing for inspiratory time (ti) and total time (tt) tended to be greater in the detected than in the undetected responses at rest and during mild exercise but not during moderate exercise. This would imply that further prolongation of ti and tt in the detected responses was attributable to conscious or subconscious aspects of the resistance leading responses: however, these adjustments in breathing, which reduce frequency, would be less likely to occur as the work rate increases.     

Demographic parameters of a free-ranging deep-diving cetacean,the long-finned pilot whale

Demographic parameters provide baselines to estimate future population trajectories which can then be used in management decisions. The aim here was to estimate demographic parameters of long-finned pilot whale (Globicephala melas) from the Strait of Gibraltar by fitting mark-recapture models to photo-identification data of primary and secondary marked individuals. These parameters were used to forecast the future population trajectories in a population viability analysis (PVA) given different scenarios of demographic rates. Survival rate increased with age from 0.629, 95% CI [0.409, 0.805] for calves, 0.869, 95% CI [0.758, 0.934] for juveniles, to 0.972, 95% CI [0.953, 0.983] for adults. A preliminary mean observed interval of viable calves was 4.5 years. The PVA estimated the population would persist over 100 years with a 100% probability for all scenarios except those with lower 95% CI survival values, for which the probability of extinction reached 100%. Population growth rate was negative in all scenarios except those with 95% CI upper survival values. Interbirth interval and juvenile survival were found most influential and depended on the correct identification of secondary marked (e.g., calves and juveniles) individuals on a long-term basis. This population was found in a precarious state prior to a morbillivirus outbreak that might even more endanger its long-term viability.