Rémy Versace

The contents of long-term memory and the emergence of knowledge

Through a review of the literature, this paper proposes arguments in favour of a multimodal, dynamic, functional, and situational conception of memory. Memory is assumed to contain traces that reflect past experiences. The properties of these experiences are considered to be distributed across multiple neuronal systems, which are responsible, in particular, for sensorimotor and emotional processing. Memory is dynamic because knowledge emerges almost continuously from the activation and integration of these multimodal components. Memory is functional and situational because knowledge emerges from the subjects activity in a given situation, that is from a type of resonance between the properties of the past experiences that have shaped the neuronal networks and the properties of present experiences.

Word frequency effect on repetition priming as a function of prime duration and delay between the prime and the target.

Two experiments studied the necessary conditions for the occurrence of repetition priming and word frequency effect on priming in a lexical decision task. To examine the role of prime processing duration, the prime was presented either for 50 ms or for 700 ms, and an interfering task was introduced between the prime and the target in order to restrict the time during which the prime was effectively processed and to limit it to exactly 50 ms or 700 ms. The interstimulus interval (ISI) between the prime and the target was 1500 ms or 3000 ms in Expt 1, and 600 ms in Expt 2. With primes presented for 50 ms, repetition priming effects were not dependent on target frequency, decreased with an increase of the ISI, and were no longer significant with an ISI of 3000 ms. With primes presented for 700 ms, repetition priming was systematically larger for low-frequency words than for high-frequency words, and remained reliable even with an ISI of 3000 ms. Thus, a minimum of prime duration was required both for maintaining repetition priming effects over more than some hundreds of milliseconds and for the occurrence of frequency effect on repetition priming. Theoretical interpretations of these results are discussed.

The Sensory Nature of Episodic Memory: Sensory Priming Effects Due to Memory Trace Activation

The aim of this study was to provide evidence that memory and perceptual processing are underpinned by the same mechanisms. Specifically, the authors conducted 3 experiments that emphasized the sensory aspect of memory traces. They examined their predictions with a short-term priming paradigm based on 2 distinct phases: a learning phase consisting of the association between a geometrical shape and a white noise and a priming phase examining the priming effect of the geometrical shape, seen in the learning phase, on the processing of target tones. In the 3 experiments, the authors found that only the prime associated with the sound in the learning phase had an effect on the target processing. The perceptual nature of the auditory component reactivated by the prime was shown in Experiments 1 and 2 via manipulation of the white noise duration in the learning phase and the stimulus onset asynchrony in the priming phase. Moreover, Experiment 3 highlighted the importance of the simultaneous association of sensory components in the learning phase, which makes it possible to integrate these components in a memory trace.

Evidence for a selective deficit in automatic activation of positive information in patients with Alzheimer's disease in an affective priming paradigm

Using an affective priming paradigm, we studied the automatic and unconscious activation of emotional information in long-term memory. Participants had to judge target words preceded by various primes as positive or negative. The primes were masked and the SOA between the onset of primes and the onset of targets was 50 ms. Our results showed that in patients with dementia of the Alzheimer type (DAT), the negativity bias was preserved and the emotional priming effect was perturbed with positive targets. In control participants, this priming effect was restricted to negative targets. These findings are discussed in terms of preserved automatic activation of emotional information in Alzheimers disease (AD) and in terms of an early deficit of the left hemisphere in AD making positive information more vulnerable to disease.

Act-In: An integrated view of memory mechanisms

The present article proposes a new memory model called Act-In (Activation-Integration). Act-In extends the multiple trace memory models by placing them within the situated cognition perspective. Act-In considers that the activation and integration mechanisms play a key role in memory processes. These mechanisms are involved in both the construction of memory traces and the emergence of knowledge. The model is based on four main assumptions: (1) Memory traces reflect all the components of past experiences and, in particular, their sensory properties, actions performed on the objects in the environment and the emotional states of individuals. Memory traces are therefore distributed across multiple neuronal systems which code the multiple components of the experiences. (2) Knowledge is emergent and is the product of the coupling of the present experience with past experiences. (3) The brain is a categorisation system which develops by accumulating experiences and which, by default, produces categorical knowledge. (4) The emergence of specific knowledge (memories or episodic knowledge) requires very simple mechanisms which occur during learning and/or during retrieval. These assumptions are defended and discussed in the light of the work reported in the literature.

Visual memory and visual perception: when memory improves visual search

This study examined the relationship between memory and perception in order to identify the influence of a memory dimension in perceptual processing. Our aim was to determine whether the variation of typical size between items (i.e., the size in real life) affects visual search. In two experiments, the congruency between typical size difference and perceptual size difference was manipulated in a visual search task. We observed that congruency between the typical and perceptual size differences decreased reaction times in the visual search (Exp. 1), and noncongruency between these two differences increased reaction times in the visual search (Exp. 2). We argue that these results highlight that memory and perception share some resources and reveal the intervention of typical size difference on the computation of the perceptual size difference.

Impaired emotional memory enhancement on recognition of pictorial stimuli in Alzheimer's disease: No influence of the nature of encoding.

OBJECTIVES There is some discrepancy in the results regarding emotional enhancement of memory (EEM) in Alzheimers disease (AD). Some studies report better retrieval of emotional information, especially positive, than neutral information. This observation is similar to the positivity effect reported in healthy older adults. It was suggested that this effect is due to privileged, deeper and more controlled processing of positive information. One way of testing this is to control both the intention to encode the information and the cognitive resources involved during encoding. Studies investigating EEM in AD patients did not systematically control the nature of encoding. Consequently, the purpose of our study was to examine EEM in AD while manipulating the nature of encoding. METHODS Two experiments were conducted. In Experiment 1 the intention to encode stimuli was manipulated by giving or not giving instructions to participants about the subsequent retrieval. In Experiment 2 cognitive resources involved during encoding were varied (low vs high). In both experiments participants performed immediate recognition task of negative, positive and neutral pictures. 41 mild AD patients and 44 older healthy adults participated in Exp. 1, and 17 mild AD patients and 20 older healthy adults participated in Exp. 2. RESULTS AD patients did not present EEM. Positivity effect, better performance for positive than neutral and negative pictures was observed with older healthy adults. CONCLUSION The data suggest that EEM is disturbed in mild AD patients, with respect to both negative and positive stimuli, at least concerning laboratory, not real-life material. They also suggest there is a positivity effect in healthy older adults and lend support to the idea that this effect is due to preferential cognitive processing of positive information in this population.

The perceptual nature of audiovisual interactions for semantic knowledge in young and elderly adults.

Audiovisual interactions for familiar objects are at the core of perception. The nature of these interactions depends on the amodal--sensory abstracted--or modal--sensory-dependent--approach of knowledge. According to these approaches, the interactions should be respectively semantic and indirect or perceptual and direct. This issue is therefore a central question to memory and perception, yet the nature of these interactions remains unexplored in young and elderly adults. We used a cross-modal priming paradigm combined with a visual masking procedure of half of the auditory primes. The data demonstrated similar results in the young and elderly adult groups. The mask interfered with the priming effect in the semantically congruent condition, whereas the mask facilitated the processing of the visual target in the semantically incongruent condition. These findings indicate that audiovisual interactions are perceptual, and support the grounded cognition theory.

Does age worsen sleep‐dependent memory consolidation?

Slow wave sleep (SWS) is known to favour episodic memory consolidation. Given that ageing is associated with a reduction in SWS and episodic memory impairment, our aim was to investigate whether memory continues to benefit from sleep in older adults. Episodic memory consolidation was tested in 20 young (22.1 ± 1.7 years) and 20 older volunteers (68.9 ± 5.3 years) who performed a visuospatial two‐dimensional object‐location task. Retention capacities were evaluated after 12 h of wakefulness or 12 h of sleep. Performances before and after the interval allowed us to calculate a forgetting rate. Sleep architecture was measured by polysomnography (older adults = 410 min; young adults: 467 min). Our results showed that the beneficial effect of sleep on memory consolidation was reduced in older adults compared to young adults. In older adults, sleep did not enhance memory consolidation significantly compared to wakefulness. Sleep prevented young adults from forgetting (−0.10% ± 2.1), while the forgetting rate in older adults was still important after a period of sleep (16.60% ± 4.2; P = 0.05). The sleep architecture of older adults was characterized by a decrease in sleep efficiency (−12%; P < 0.05), in total cycle time (−137 min; P < 0.05), in percentage of total cycle time (−21%; P < 0.05) and in rapid eye movement time (−41 min; P < 0.05) compared to young adults. However, no difference in slow wave sleep was observed (−1%; not significant) and no correlation was found with performance. Age‐related changes in sleep parameters may have a negative impact on memory consolidation in older adults.

The disconnection syndrome in the Alzheimer's disease: The cross-modal priming example

Implicit memory is generally supposed to be preserved in Alzheimers disease (AD). Yet, some implicit priming effects are impaired and others are not. The preserved/impaired priming effects are often interpreted according to the perceptual/conceptual or identification/production distinctions. Perceptual-identification priming paradigms shall be preserved and conceptual-production priming paradigms impaired. A third interpretation is yet possible based on the disconnection syndrome hypothesis which states that patients with AD should fail tasks requiring relatively complex brain communications. In this case, patients with AD should not demonstrated a significant perceptual priming effect in an identification task if this one involved complex brain communications. The present study tests this latter hypothesis with two cross-modal priming experiments using a categorization task. A visual meaningless mask presented with half of the auditory primes tested the nature of the cross-modal priming effect. The control group exhibited significant priming effects for unmasked primes. The interference effect of the mask demonstrated that the priming effect was perceptually driven. Patients with AD did not present any priming effect nor mask interference. The present findings therefore showed that perceptual priming using an identification task could be impaired in AD supporting the disconnection syndrome hypothesis.