Salivary conditioning with antennal gustatory unconditioned stimulus in an insect

Classical conditioning of olfactory conditioning stimulus (CS) with gustatory unconditioned stimulus (US) in insects has been used as a pertinent model for elucidation of neural mechanisms underlying learning and memory. However, a conditioning system in which stable intracellular recordings from brain neurons are feasibly obtained while monitoring the conditioning effect has remained to be established. Recently, we found classical conditioning of salivation in cockroaches Periplaneta americana, in which an odor was associated with sucrose solution applied to the mouth, and this conditioning could be monitored by activities of salivary neurons. Application of gustatory US to the mouth, however, leads to feeding movement accompanying a movement of the brain that prevents stable recordings from brain neurons. Here we investigated whether a gustatory stimulus presented to an antenna could serve as an effective US for producing salivary conditioning. Presentation of sucrose or sodium chloride solution to an antenna induced salivation and also increased activities of salivary neurons. A single pairing trial of an odor with antennal presentation of sucrose or sodium chloride solution produced conditioning of salivation or of activities of salivary neurons. Five pairing trials led to a conditioning effect that lasted for one day. Water or tactile stimulus presented to an antenna was not effective for producing conditioning. The results demonstrate that gustatory US presented to an antenna is as effective as that presented to the mouth for producing salivary conditioning. This conditioning system provides a useful model for studying the neural basis of learning at the level of singly identifiable neurons.     

A marginal maximum likelihood method for the vector threshold model to analyze dichotomous choice data

Abstract: At least two types of models, the vector model and the unfolding model can be used for the analysis of dichotomous choice data taken from, for example, the pick any/ n method. The previous vector threshold models have a difficulty with estimation of the nuisance parameters such as the individual vectors and thresholds. This paper proposes a new probabilistic vector threshold model, where, unlike the former vector models, the angle that defines an individual vector is a random variable, and where the marginal maximum likelihood estimation method using the expectation-maximization algorithm is adopted to avoid incidental parameters. The paper also attempts to discuss which of the two models is more appropriate to account for dichotomous choice data. Two sets of dichotomous choice data are analyzed by the model.     

Implicit attitudes and executive control interact to regulate interest in extra-pair relationships

Do we actively maintain monogamous relationships by force of will, or does monogamy flow automatically? During functional magnetic resonance imaging (fMRI), male participants in a romantic relationship performed the Implicit Association Test (IAT) to evaluate implicit attitudes toward adultery and a go/no-go task to measure prefrontal activity implicated in explicit executive control. Subsequently, they were engaged in a date-rating task in which they rated how much they wanted to date unfamiliar females. We found that the individuals with higher prefrontal activity during go/no-go task could regulate the interest for dates with unattractive females; moreover, the individuals with both a stronger negative attitude toward adultery and higher prefrontal activity could regulate their interest for dates with attractive females, and such individuals tended to maintain longer romantic relationships with a particular partner. These results indicate that regulation of amorous temptation via monogamous relationship is affected by the combination of automatic and reflective processes.     

The bizarreness effect and individual differences in imaging ability

The bizarreness effect refers to the superior performance in recall of bizarre sentences as compared to common sentences. The subjects studied each target word and in Exp. 1 rated its congruity with its sentence frame. In Exp. 2 they rated the vividness of the image for each sentence frame in which it was included. Four types of sentence frames were provided: bizarre image sentences, bizarre nonimage sentences, common image sentences, and common nonimage sentences. Good imagers and poor imagers were assessed on the Questionnaire Upon Mental Imagery. Both experiments showed that good imagers recalled target words in bizarre image sentences better than target words in common image sentences. A difference between the two sentence types was not observed for poor imagers. The differences between bizarre nonimage sentences and common nonimage sentences were not found for both type of imagers. The results were interpreted as showing that a difference in imaging ability was critical for the occurrence of a bizarreness effect.     

Judgments of grammaticality of sentences violating the principle of full interpretation: a further exploration

54 Japanese speakers judged isolated simple bitransitive sentences involving an unnecessary extra argument in addition to three legitimate arguments. Two variables were manipulated, with one variable concerning the role the extra argument assumed in a sentence, subjective, dative, or objective and the other concerning the relation it bore with the legitimate argument. The sentences with the extra arguments were judged to be an average grammaticality of about 3 on a 7-point scale. This score, although still lower than that obtained for sentences involving only the legitimate arguments, suggests that speakers' judgments are not fully consistent with the judgments expected if they might possess and demonstrate the knowledge of the principle of Full Interpretation.     

Speakers' knowledge of word meanings: stable and perfect?

This study explored whether the actual state of speakers' knowledge of word meanings is as stable and perfect as Chomsky has claimed. 73 speakers of Japanese (11 men and 62 women, M age=20.6 yr.) each engaged in two tasks, one of defining the meanings of function words and content words and the other of creating a short sentence involving one of these words. Some speakers did a meaning-definition task first and then a sentence-creation task, while others did these tasks in reverse order. Use-dependent definition as an index of insufficient knowledge of word meanings was examined. Findings showed this type of definition occurred more often for the function words than for the content words and that it also occurred more often when the speakers performed the sentence-creation task before the meaning-definition task. The findings suggest that the actual state of speakers' knowledge of word meanings is not as stable nor as perfect as Chomsky has claimed.     

"Blaming the victim" under memory load

When presented with negative outcomes, people often engage in counterfactual thinking, imagining various ways that events might have been different. This appears to be a spontaneous behavior, with considerable adaptive value. Nevertheless, counterfactual thinking may also engender systematic biases in various judgment tasks, such as allocating blame for a mishap, or deciding on the appropriate compensation to a victim. Thus, counterfactuals sometimes require thought suppression or discounting, potentially resource-demanding tasks. In this study, participants made mock-jury decisions about control and counterfactual versions of simple stories. The judgments of two groups of participants, differing in their respective levels of working memory capacity, were compared. In addition, all participants held memory loads during various stages of the primary task. Lower-span individuals were especially susceptible to bias associated with the counterfactual manipulation, but only when holding memory loads during judgment. The results suggest that counterfactual thoughts arise automatically, and may later require effortful, capacity-demanding suppression.     

Response preparation and stimulus-response congruence to fractionating reaction time of upper and lower limbs

We measured the fractionating reaction time for upper and lower limbs of 18 young men, using an electromyogram to clarify the interaction of response preparation and stimulus-response congruence on premotor and motor time. The reaction time was divided into two periods with respect to the onset of the electromyogram, premotor and motor components. Manipulating the probability of the Go versus NoGo signals varied three different amounts of response preparation. Prior to the imperative stimulus, precue information about the position of a stimulus was presented. In the stimulus-response congruent task, subjects were required to release a key on the same side of the body using either an upper or lower limb in response to an imperative Go stimulus. In the stimulus-response incongruent task, subjects were required to act in a reverse manner. Subjects were not supposed to respond to the NoGo stimulus. The premotor time of the upper and lower limb responses was affected by the respective effects of response preparation and stimulus-response congruence. The motor time of the upper and lower limb responses increased as the probability of the Go signal decreased but not in relation to stimulus-response congruence. These results suggest that response preparation affects not only information processing time but also peripheral motor activity due to motor programming, and that the stimulus-response congruence effect on motor time disappears when information about the position of the imperative stimulus is precued.