Parallel processing of stimulus features during RSVP: evidence from the second response

When observers are asked to report a feature of a single target displayed in rapid serial visual presentation, they frequently make errors. Most frequently, a feature from the to-be-reported dimension pertaining to a stimulus presented near the target is reported. These migrations are so-called illusory conjunctions in the time domain. From parallel models, it is proposed that during the presentation of the series, the response features of the stimuli are extracted. If a high rate of presentation does not enable proper binding processes, the system could base its response on sophisticated guessing on the basis of the relative levels of activation of the available response features. However, the multiple extractions assumption has not received direct empirical support. We report two experiments in which the observers had to report their first and second response candidates. This double response paradigm makes it possible to test the assumption that more than one response feature is available for making a response. Furthermore, the application of the constant ratio rule (following Botella, Barriopedro, & Suero's, 2001, model) to the first responses allows predictions for the ratios between choices of the items for the second responses. The correlations between the observed and the predicted response proportions were .887 and .956 in the two experiments. This high predictive capacity indicates, first, that the observers have more than one response available, among which to choose, and second, that the choice among responses is determined largely in the same way for both, first and second responses. Nevertheless, the small errors in prediction are further reduced if a proportion of pure guesses is assumed in the second responses. These are probably due to memory losses, misidentifications of the features, and other factors impairing performance in second responses in comparison with first responses.     

Definition of compassion-evoking images in a Mexican sample

To assemble a calibrated set of compassion-eliciting visual stimuli, 60 clinically healthy Mexican volunteers (36 women, 24 men; M age = 27.5 yr., SD = 2.4) assessed 84 pictures selected from the International Affective Picture System catalogue using the dimensions of Valence, Arousal, and Dominance included in the Self-assessment Manikin scale and an additional dimension of Compassion. Pictures showing suffering in social contexts and expressions of sadness elicited similar responses of compassion. The highest compassion response was reported for pictures showing illness and pain. Men and women differed in the intensity but not the quality of the compassionate responses. Compassion included attributes of negative emotions such as displeasure. The quality of the emotional response was not different from that previously reported for samples in the U.S.A., Spain, and Brazil. A set of 28 pictures was selected as high-compassion-evoking images and 28 as null-compassion controls suitable for studies designed to ascertain the neural substrates of this moral emotion.     

‘Comparisons of traumatic and positive memories in people with and without PTSD profile’

According to most post‐traumatic stress disorder (PTSD) theories, memory mechanisms are involved in its development and maintenance. However, the specific memory characteristics responsible for this disorder are still not well known. In the present study, 210 participants having reported at least one traumatic experience were assigned to a PTSD or to a non‐PTSD symptom profile group. Both groups rated their memories for their most traumatic and intense positive life events. We observed that the traumatic memories of PTSD profile participants were more clear, detailed and judged as significant compared with those of the non‐PTSD profile group. However, participants in the first group acknowledged having more difficulties putting their traumatic memories into words and controlling these remembrances. These differences were absent in their positive memories. Additionally, clear relationships emerged between memory ratings and PTSD symptoms measures. Results are discussed according to fragmentation and superiority views of traumatic memories in PTSD. Copyright © 2006 John Wiley & Sons, Ltd.     

Morningness in German and Spanish students: a comparative study

Humans show pronounced individual differences in circadian orientation. Transcultural comparisons are interesting since biological (or environmental) factors together with cultural ones may contribute to differences in morningness–eveningness. We compared Spanish and German undergraduates using the Composite Scale of Morningness (CSM) to assess circadian preferences. Confirmatory and multiple groups confirmatory factor analysis were used to assess factor structure and structural invariance across countries. The results showed that a three‐factor model of morningness best characterises the CSM structure of both samples. Partial factorial invariance (factor loadings) across countries was demonstrated for the factors ‘morningness’ and ‘morning alertness’. Scores of both factors were higher in German students. Potential cultural and biological explanations for the differences are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Modulation of stress consequences by hippocampal monoaminergic, glutamatergic and nitrergic neurotransmitter systems

Several findings relate the hippocampal formation to the behavioural consequences of stress. It contains a high concentration of corticoid receptors and undergoes plastic modifications, including decreased neurogenesis and cellular remodelling, following stress exposure. Various major neurotransmitter systems in the hippocampus are involved in these effects. Serotonin (5-HT) seems to exert a protective role in the hippocampus and attenuates the behavioural consequences of stress by activating 5-HT1A receptors in this structure. These effects may mediate the therapeutic actions of several antidepressants. The role of noradrenaline is less clear and possibly depends on the specific hippocampal region (dorsal vs. ventral). The deleterious modifications induced in the hippocampus by stress might involve a decrease in neurotrophic factors such as brain derived neurotrophic factor (BDNF) following glutamate N-methyl-D-aspartate (NMDA) receptor activation. In addition to glutamate, nitric oxide (NO) could also be related to these effects. Systemic and intra-hippocampal administration of nitric oxide synthase (NOS) inhibitors attenuates stress-induced behavioural consequences. The challenge for the future will be to integrate results related to these different neurotransmitter systems in a unifying theory about the role of the hippocampus in mood regulation, depressive disorder and antidepressant effects.     

The role of the frequency of constituents in compound words: Evidence from Basque and Spanish

Recent data from compound word processing suggests that compounds are recognized via their constituent lexemes (Juhasz, Starr, Inhoff, & Placke, 2003). The present lexical decision experiment manipulated orthogonally the frequency of the constituents of compound words in two languages: Basque and Spanish. Basque and Spanish diverge widely in their morphological properties and in the number of existing compound words. Furthermore, the head lexeme (i.e., the most meaningful lexeme related to the whole-word meaning) in Spanish tends to be the second lexeme, whereas in Basque the percentage is more distributed. Results showed a facilitative effect of the frequency of the second lexeme, in both Basque and Spanish compounds. Thus, both Basque and Spanish readers decompose compounds into their constituents for lexical access, and this decomposition is carried out in a language-independent and blind-to-semantics manner. We examine the implications of these results for models of lexical access.     

A response rule for positive and negative stimulus interaction in associative learning and performance

The present article presents a response rule developed to account for both positive and negative stimulus interaction. In the response rule proposed here, positive interaction phenomena (e.g., second-order conditioning) and negative interaction phenomena (e.g., Pavlovian conditioned inhibition) are presumed to occur during performance and acquisition, respectively. Also, in this rule the novelty of the test stimulus determines the expression of positive interaction on responding. As the stimulus loses its novelty over training, positive interaction effects will wane, which will allow negative interaction effects to emerge in responding elicited by the stimulus. It is proposed that this response rule can be adopted by acquisition-focused associative models (e.g., Rescorla & Wagner, 1972) in order to account for contrary associative phenomena in the literature. The simulation program used in this study is available for download from the author’s website and from the Psychonomic Society website at www.psychonomic.org/archive.     

Differential effects of muscarinic receptor blockade in prelimbic cortex on acquisition and memory formation of an odor-reward task

The present experiments determined the consequences of blocking muscarinic cholinergic receptors of the prelimbic (PL) cortex in the acquisition and retention of an odor-reward associative task. Rats underwent a training test (five trials) and a 24-h retention test (two retention trials and two relearning trials). In the first experiment, rats were bilaterally infused with scopolamine (20 or 5 microg/site) prior to training. Although scopolamine rats showed acquisition equivalent to PBS-injected controls, they exhibited weakened performance in the 24-h retention test measured by number of errors. In the second experiment, rats were injected with scopolamine (20 microg/site) immediately or 1 h after training and tested 24 h later. Scopolamine rats injected immediately showed severe amnesia detected in two performance measures (errors and latencies), demonstrating deficits in retention and relearning, whereas those injected 1 h later showed good 24-h test performance, similar to controls. These results suggest that muscarinic transmission in the PL cortex is essential for early memory formation, but not for acquisition, of a rapidly learned odor discrimination task. Findings corroborate the role of acetylcholine in consolidation processes and the participation of muscarinic receptors in olfactory associative tasks.     

Reinstatement of episodic-like memory in rats by neurokinin-1 receptor antagonism

We previously showed that a systemic administration of the selective non-peptide neurokinin-1-receptor (NK-1-R) antagonist SR140333 increases hippocampal acetylcholine levels and facilitates long term memory. In the present study, we investigated whether systemic SR140333 has beneficial effects on episodic-like memory for unique experiences. Rats received either no injection, a vehicle injection or SR140333 at doses of 1, 3 and 9 mg/kg (i.p.) prior to the acquisition of an object memory for what, where and when. In line with previous results, untreated rats showed episodic-like memory, while vehicle-injected rats were impaired. A low dose of 1mg/kg SR140333 reinstated episodic-like memory. This result might be related to the effects of SR140333 on hippocampal cholinergic transmission and/or on the stress-response elicited by the injection procedure. Higher doses of SR140333 (3 and 9 mg/kg) induced psychomotor effects, including stereotypic behaviors and arched posture. Since NK-1-R antagonists have anxiolytic and promestic properties and induce hippocampal acetylcholine release at lower doses, they might be effective in the alleviation of the cognitive deficits and increased anxiety seen in early stages of Alzheimer's disease.