The hippocampus and prefrontal cortex are differentially involved in serial memory retrieval in non-stress and stress conditions

We previously showed that 24 h after learning, mice significantly remembered the first (D1) but not the second (D2) discrimination in a serial spatial task and that an acute stress delivered 5 min before the test phase reversed this memory retrieval pattern.A first experiment evaluated the effects of dorsal hippocampus (HPC) or prefrontal cortex (PFC) lesions, these two brain areas being well-known for their involvement in serial and spatial memory processes. For this purpose, six independent groups of mice were used: non-lesioned (controls), PFC or HPC-lesioned animals, submitted or not to an acute stress (electric footshocks; 0.9 mA). Results show that (i) non-stressed controls as well as PFC-lesioned mice (stressed or not) remembered D1 but not D2; (ii) stressed controls and HPC-lesioned mice (stressed or not) remembered D2 but not D1; (iii) stress significantly increased plasma corticosterone in controls and PFC-lesioned mice, but not in HPC-lesioned mice which already showed a significant plasma corticosterone increase in non-stressed condition.Since data from this first experiment showed that stress inhibited the hippocampal-dependent D1 memory retrieval, a second experiment evaluated the behavioral effect of intrahippocampal corticosterone injection in non-stressed mice. Results show that intrahippocampal corticosterone injection induced a reversal of serial memory retrieval pattern similar to that induced by acute stress.Overall, our study shows that (i) in non-stress condition, the emergence of D1 is HPC-dependent; (ii) in stress condition, the emergence of D2 requires the PFC integrity; moreover, intrahippocampal corticosterone injection mimicked the effects of stress in the CSD task.     

Locus of control and cerebral asymmetry.

Data about the lack of synchronism of flexor carpi ulnaris peak EMG values of bimanual reactions during a semantic and during a visuospatial discrimination reaction time task are reported. The effects of type of task as well as the presence or absence of an unexpected stimulus preceding the reaction stimulus on lack of synchronism clearly depend upon the locus of control of the subjects, as measured on Rotter's I-E scale. On the basis of several arguments it is proposed that the measure of lack of synchronism reflects in an opposite sense the amount of dopaminergic activation or motor readiness in the sense in which Pribram and McGuinness in 1975 and Tucker and Williamson in 1984 have defined these concepts. The results for 15 women and 18 men show that more internally oriented subjects are more activated by a semantic task and by an unexpected preparatory stimulus in this type of task than more externally oriented subjects. The opposite appears to hold on the visuospatial task and unexpected preparatory stimuli therein. Together with earlier findings about reaction times and a number of relevant findings in the literature, the results are interpreted as indicative of basic differences in asymmetric tonic activation of the cerebral hemispheres between more internally and more externally oriented subjects. A model is proposed to explain phasic activating effects which ensue when tonically more left- or right-activated subjects perform left- or right-hemisphere tasks and when supplementary irrelevant stimuli are received.     

A System for Relational Reasoning in Human Prefrontal Cortex

The integration of multiple relations between mental representations is critical for higher level cognition. For both deductive- and inductive-reasoning tasks, patients with prefrontal damage exhibited a selective and catastrophic deficit in the integration of relations, whereas patients with anterior temporal lobe damage, matched for overall IQ but with intact prefrontal cortex, exhibited normal relational integration. In contrast, prefrontal patients performed more accurately than temporal patients on tests of both episodic memory and semantic knowledge. These double dissociations suggest that integration of relations is a specific source of cognitive complexity for which intact prefrontal cortex is essential. The integration of relations may be the fundamental common factor linking the diverse abilities that depend on prefrontal function, such as planning, problem solving, and fluid intelligence.     

Contribution of ankle, knee, and hip joints to the perception threshold for support surface rotation

The purpose of the present experiment was to investigate the extent to which subjects can perceive, at very slow velocities, an angular rotation of the support surface about the medio-lateral axis of the ankle, knee, hip, or neck joint when visual cues are not available. Subjects were passively displaced on a slowly rotating platform at .01, .03, and .05 deg/sec. The subjects’ task was to detect movements of the platform in four different postural conditions allowing body oscillations about the ankle, knee, hip, or neck joint. In Experiment 1, subjects had to detect backward and forward rotation (pitching). In Experiment 2, they had to detect left and right rotations of the platform (rolling). In Experiment 3, subjects had to detect both backward/forward and left/right rotations of the platform, with the body fixed and the head either fixed or free to move. Overall, when the body was free to oscillate about the ankle, knee, or hip joints, a similar threshold for movement perception was observed. This threshold was lower for rolling than for pitching. Interestingly, in these postural conditions, an unconscious compensation in the direction opposite to the platform rotation was observed on most trials. The threshold for movement perception was much higher when the head was the only segment free to oscillate about the neck joint. These results suggest that, in static conditions, the otoliths are poor detectors of the direction of gravity forces. They also suggest that accurate perception of body orientation is improved when proprioceptive information can be dynamically integrated.     

Reexamining the word length effect in visual word recognition: New evidence from the English Lexicon Project

In the present study, we reexamined the effect of word length (number of letters in a word) on lexical decision. Using the English Lexicon Project, which is based on a large data set of over 40,481 words (Balota et al., 2002), we performed simultaneous multiple regression analyses on a selection of 33,006 English words (ranging from 3 to 13 letters in length). Our analyses revealed an unexpected pattern of results taking the form of a U-shaped curve. The effect of number of letters was facilitatory for words of 3–5 letters, null for words of 5–8 letters, and inhibitory for words of 8–13 letters. We also showed that printed frequency, number of syllables, and number of orthographic neighbors all made independent contributions. The length effects were replicated in a new analysis of a subset of 3,833 monomorphemic nouns (ranging from 3 to 10 letters), and also in another analysis based on 12,987 bisyllabic items (ranging from 3 to 9 letters). These effects were independent of printed frequency, number of syllables, and number of orthographic neighbors. Furthermore, we also observed robust linear inhibitory effects of number of syllables. Implications for models of visual word recognition are discussed.     

How Does the Bible Refer to Christ? Interacting with Augustine the Allegorist

Abstract: Traditional Christianity teaches that the Bible's primary referent is Jesus Christ, the Messiah, and Christians have long looked for ways to connect every passage in the Bible to the Christ. One venerable strategy is the allegorical or figurative approach of creatively interpreting any unit of biblical meaning, sometimes down to the individual words, as referencing Christ. Alternatively, we might take the biblical narrative itself as referencing Christ and find the connection of smaller units of meaning to Christ through their place in that narrative. My article clarifies this topic through interaction with an exemplary practitioner of the strategy of figurative reading, the Church Father Augustine. I will first explain Augustine's reasons for his hermeneutics, which stem largely from his focus on smaller units of reference such as the word and the sentence. Then I will argue that his reasons are not persuasive if indeed the Bible does refer to Christ at a broader level, the level of narrative.     

No Place to Hide: When Shame Causes Proselfs to Cooperate

Shame is considered a social emotion with action tendencies that elicit socially beneficial behavior. Yet, unlike other social emotions, prior experimental studies do not indicate that incidental shame boosts prosocial behavior. Based on the affect as information theory, we hypothesize that incidental feelings of shame can increase cooperation, but only for self-interested individuals, and only in a context where shame is relevant with regards to its action tendency. To test this hypothesis, cooperation levels are compared between a simultaneous prisoner's dilemma (where “defect” may result from multiple motives) and a sequential prisoner's dilemma (where “second player defect” is the result of intentional greediness). As hypothesized, shame positively affected proselfs in a sequential prisoner's dilemma. Hence ashamed proselfs become inclined to cooperate when they believe they have no way to hide their greediness, and not necessarily because they want to make up for earlier wrong-doing.     

The Necklace of Numbers

The necklace of numbers is a symbol that came in one of my dreams at the end of 2006, at the time when I was about to leave France, my native country, and come to the United States. As I was going through the process of becoming an American citizen, I felt compelled to reconnect to my French roots. The result was this personal account which tells the most important dreams that led me to this country. It is also a tale of a mid-life transformation, a tale of an immigrant viewed from inside, and a tale of individuation by following the path of love.