Consolidation and long-term retention of an implanted behavioral memory

Hypothesized circuitry enabling information storage can be tested by attempting to implant memory directly in the brain in the absence of normal experience. Previously, we found that tone paired with activation of the cholinergic nucleus basalis (NB) does induce behavioral memory that shares cardinal features with natural memory; it is associative, highly specific, rapidly formed, consolidates and shows intermediate retention. Here we determine if implanted memory also exhibits long-term consolidation and retention. Adult male rats were first tested for behavioral responses (disruption of ongoing respiration) to tones (1-15 kHz), yielding pre-training behavioral frequency generalization gradients. They next received 3 days of training with a conditioned stimulus (CS) tone (8.0 kHz, 70 dB, 2s) either paired (n=7) or unpaired (n=6) with moderate electrical stimulation of the nucleus basalis (～ 65 μA, 100 Hz, 0.2s, co-terminating with CS offset). Testing for long-term retention was performed by obtaining post-training behavioral frequency generalization gradients 24h and 2 weeks after training. At 24h post-training, the Paired group exhibited specific associative behavioral memory, manifested by larger responses to the CS frequency band than the Unpaired group. This memory was retained 2 weeks post-training. Moreover, 2 weeks later, the specificity and magnitude of memory had become greater, indicating that the implanted memory had undergone consolidation. Overall, the results demonstrate the validity of NB-implanted memory for understanding natural memory and that activation of the cholinergic nucleus basalis is sufficient to form natural associative memory.     

Monkeys represent others' knowledge but not their beliefs

The capacity to reason about the false beliefs of others is classically considered the benchmark for a fully fledged understanding of the mental lives of others. Although much is known about the developmental origins of our understanding of others' beliefs, we still know much less about the evolutionary origins of this capacity. Here, we examine whether non-human primates - specifically, rhesus macaques (Macaca mulatta) - share this developmental achievement. We presented macaques with a looking-time measure of false belief understanding, one that had recently been developed for use with 15-month-old human infants. Like human infants, monkeys look longer when a human experimenter fails to search in the correct location when she has accurate knowledge. In contrast to infants, however, monkeys appear to make no prediction about how a human experimenter will act when she has a false belief. Across three studies, macaques' pattern of results is consistent with the view that monkeys can represent the knowledge and ignorance of others, but not their beliefs. The capacity to represent beliefs may therefore be a unique hallmark of human cognition.     

Inferring social attributes from different face regions: evidence for holistic processing

Two experiments investigated the role that different face regions play in a variety of social judgements that are commonly made from facial appearance (sex, age, distinctiveness, attractiveness, approachability, trustworthiness, and intelligence). These judgements lie along a continuum from those with a clear physical basis and high consequent accuracy (sex, age) to judgements that can achieve a degree of consensus between observers despite having little known validity (intelligence, trustworthiness). Results from Experiment 1 indicated that the face's internal features (eyes, nose, and mouth) provide information that is more useful for social inferences than the external features (hair, face shape, ears, and chin), especially when judging traits such as approachability and trustworthiness. Experiment 2 investigated how judgement agreement was affected when the upper head, eye, nose, or mouth regions were presented in isolation or when these regions were obscured. A different pattern of results emerged for different characteristics, indicating that different types of facial information are used in the various judgements. Moreover, the informativeness of a particular region/feature depends on whether it is presented alone or in the context of the whole face. These findings provide evidence for the importance of holistic processing in making social attributions from facial appearance.     

Questioning implicit motor learning as instantiated by the pursuit-tracking task

The effect of concurrent visual feedback on the implicit learning of repeated segments in a task of pursuit tracking has been tested. Although this feedback makes it possible to regulate the positional error during the movement, it could also induce negative guidance effects. To test this hypothesis, a first set of participants (N=42) were assigned to two groups, which performed either the standard pursuit-tracking task based on the experimental paradigm of Pew ( 1974 ; group F-ST), or a task called "movement reproduction" in which the feedback was suppressed (group noF-ST). A second set of participants (N=26) performed in the same feedback condition groups but in a dual-task situation (F-DT and noF-DT; Experiment 2). The results appear to confirm our predictions since the participants in groups without feedback, contrary to those in groups with feedback, succeeded with practice in differentiating their performances as a function of the nature of the segments (repeated or nonrepeated) both in simple (Experiment 1) and in dual-task (Experiment 2) situations. These experiments indicate that the feedback in the pursuit-tracking task induces a guidance function potentially resulting in an easiness tracking that prevents the participants from learning the repetition.     

Death Anxiety and Symbolic Immortality in Relatives at Risk for Familial Amyloid Polyneuropathy Type I (FAP I,ATTR V30M)

This study is an investigation of the impact of familial amyloid polyneuropathy type I (FAP I, ATTR V30M) on death anxiety and symbolic immortality. Templer and Drolet’s scales were administered to 524 individuals: (1) 84 relatives at risk, (2) 92 relatives not at risk for FAP I; and (3) a control group (n = 348) with no known hereditary disease in their families. At-risk relatives had, on average, a higher score for death anxiety and a lower score for symbolic immortality, than either those not-at-risk or controls. There were no significant differences in scores on either measure for those not-at-risk versus controls. Being at risk increases death anxiety and threatens the sense of symbolic immortality and psychosocial wellbeing. This may be true for other serious hereditary disorders as well. Genetic counsellors should become familiar with these concepts, feel comfortable initiating discussions about death with their patients, and be able to identify and reinforce their patients’ and family members’ sense of symbolic immortality.     

Clock drawing performance and brain morphology in mild cognitive impairment and Alzheimer's disease

The Clock Drawing Test (CDT) is a widely used instrument in the neuropsychological assessment of Alzheimer's disease (AD). As CDT performance necessitates several cognitive functions (e.g., visuospatial and constructional abilities, executive functioning), an interaction of multiple brain regions is likely. Fifty-one subjects with mild cognitive impairment, 23 with AD and 15 healthy controls underwent high-resolution magnetic resonance imaging. Optimized voxel-based morphometry (VBM) was performed to investigate the putative association between CDT performance and gray matter (GM) density throughout the entire brain. In the first step of analysis (p<.001, uncorrected), VBM revealed a reduced GM density in numerous cortical (temporal lobe, frontal lobe, parietal lobe, cerebellum) and subcortical (thalamus, basal ganglia) brain regions to be associated with poorer CDT performance. When corrected for multiple comparisons (p<.01), the associations remained significant predominantly in the left temporal and--less pronounced--the right temporal lobe. VBM demonstrated CDT performance to depend on the integrity of widely distributed cortical and subcortical areas in both brain hemispheres with accentuation in the left-sided temporal lobe region.     

Parametric induction of animacy experience

Graphical displays of simple moving geometrical figures have been repeatedly used to study the attribution of animacy in human observers. Yet little is known about the relevant movement characteristics responsible for this experience. The present study introduces a novel parametric research paradigm, which allows for the experimental control of specific motion parameters and a predictable influence on the attribution of animacy. Two experiments were conducted using 3D computer animations of one or two objects systematically introducing variations in the following aspects of motion: directionality, discontinuity and responsiveness. Both experiments further varied temporal kinematics. Results showed that animacy experience increased with the time a moving object paused in the vicinity of a second object and with increasing complexity of interaction between the objects (approach and responsiveness). The experience of animacy could be successfully modulated in a parametric fashion by the systematic variation of comparably simple differential movement characteristics.     

The origins of cognitive dissonance: evidence from children and monkeys

In a study exploring the origins of cognitive dissonance, preschoolers and capuchins were given a choice between two equally preferred alternatives (two different stickers and two differently colored M&M's, respectively). On the basis of previous research with adults, this choice was thought to cause dissonance because it conflicted with subjects' belief that the two options were equally valuable. We therefore expected subjects to change their attitude toward the unchosen alternative, deeming it less valuable. We then presented subjects with a choice between the unchosen option and an option that was originally as attractive as both options in the first choice. Both groups preferred the novel over the unchosen option in this experimental condition, but not in a control condition in which they did not take part in the first decision. These results provide the first evidence of decision rationalization in children and nonhuman primates. They suggest that the mechanisms underlying cognitive-dissonance reduction in human adults may have originated both developmentally and evolutionarily earlier than previously thought.     

‘Unwilling’ versus ‘unable’: capuchin monkeys’ (Cebus apella) understanding of human intentional action

A sensitivity to the intentions behind human action is a crucial developmental achievement in infants. Is this intention reading ability a unique and relatively recent product of human evolution and culture, or does this capacity instead have roots in our non‐human primate ancestors? Recent work by Call and colleagues (2004) lends credence to the latter hypothesis, providing evidence that chimpanzees are also sensitive to human intentions. Specifically, chimpanzees remained in a testing area longer and exhibited fewer frustration behaviors when an experimenter behaved as if he intended to give food but was unable to do so, than when the experimenter behaved as if he had no intention of giving food. The present research builds on and extends this paradigm, providing some of the first evidence of intention reading in a more distant primate relative, the capuchin monkey (Cebus apella). Like chimpanzees, capuchin monkeys distinguish between different goal‐directed acts, vacating an enclosure sooner when an experimenter acts unwilling to give food than when she acts unable to give food. Additionally, we found that this pattern is specific to animate action, and does not obtain when the same actions are performed by inanimate rods instead of human hands (for a similar logic, see Woodward, 1998 ). Taken together with the previous evidence, the present research suggests that our own intention reading is not a wholly unique aspect of the human species, but rather is shared broadly across the primate order.     

Formal Schooling Influences Two- but Not Three-Dimensional Naming Skills

The modulatory influence of literacy on the cognitive system of the human brain has been indicated in behavioral, neuroanatomic, and functional neuroimaging studies. In this study we explored the functional consequences of formal education and the acquisition of an alphabetic written language on two- and three-dimensional visual naming. The results show that illiterate subjects perform significantly worse on immediate naming of two-dimensional representations of common everyday objects compared to literate subjects, both in terms of accuracy and reaction times. In contrast, there was no significant difference when the subjects named the corresponding real objects. The results suggest that formal education and learning to read and to write modulate the cognitive process involved in processing two- but not three-dimensional representations of common everyday objects. Both the results of the reaction time and the error pattern analyses can be interpreted as indicating that the major influence of literacy affects the visual system or the interaction between the visual and the language systems. We suggest that the visual system in a wide sense and/or the interface between the visual and the language system are differently formatted in literate and illiterate subjects. In other words, we hypothesize that the pattern of interactions in the functional-anatomical networks subserving visual naming, that is, the interactions within and between the visual and language processing networks, differ in literate and illiterate subjects.