Lexico-semantic structure and the word-frequency effect in recognition memory

Integrating word-form representations with global similarity computation in recognition memory

In recognition memory, retrieval is thought to occur by computing the global similarity of the probe to each of the studied items. However, to date, very few global similarity models have employed perceptual representations of words despite the fact that false recognition errors for perceptually similar words have consistently been observed. In this work, we integrate representations of letter strings from the reading literature with global similarity models. Specifically, we employed models of absolute letter position (slot codes and overlap models) and relative letter position (closed and open bigrams). Each of the representations was used to construct a global similarity model that made contact with responses and RTs at the individual word level using the linear ballistic accumulator (LBA) model (Brown & Heathcote Cognitive Psychology, 57 , 153-178, 2008). Relative position models were favored in three of the four datasets and parameter estimates suggested additional influence of the initial letters in the words. When semantic representations from the word2vec model were incorporated into the models, results indicated that orthographic representations were almost equally consequential as semantic representations in determining inter-item similarity and false recognition errors, which undermines previous suggestions that long-term memory is primarily driven by semantic representations. The model was able to modestly capture individual word variability in the false alarm rates, but there were limitations in capturing variability in the hit rates that suggest that the underlying representations require extension.

Neurodynamical Computing at the Information Boundaries of Intelligent Systems

Artificial intelligence has not achieved defining features of biological intelligence despite models boasting more parameters than neurons in the human brain. In this perspective article, we synthesize historical approaches to understanding intelligent systems and argue that methodological and epistemic biases in these fields can be resolved by shifting away from cognitivist brain-as-computer theories and recognizing that brains exist within large, interdependent living systems. Integrating the dynamical systems view of cognition with the massive distributed feedback of perceptual control theory highlights a theoretical gap in our understanding of nonreductive neural mechanisms. Cell assemblies-properly conceived as reentrant dynamical flows and not merely as identified groups of neurons-may fill that gap by providing a minimal supraneuronal level of organization that establishes a neurodynamical base layer for computation. By considering information streams from physical embodiment and situational embedding, we discuss this computational base layer in terms of conserved oscillatory and structural properties of cortical-hippocampal networks. Our synthesis of embodied cognition, based in dynamical systems and perceptual control, aims to bypass the neurosymbolic stalemates that have arisen in artificial intelligence, cognitive science, and computational neuroscience.

Oscillatory brain responses in spoken word production reflect lexical frequency and sentential constraint

Two fundamental factors affecting the speed of spoken word production are lexical frequency and sentential constraint, but little is known about their timing and electrophysiological basis. In the present study, we investigated event-related potentials (ERPs) and oscillatory brain responses induced by these factors, using a task in which participants named pictures after reading sentences. Sentence contexts were either constraining or nonconstraining towards the final word, which was presented as a picture. Picture names varied in their frequency of occurrence in the language. Naming latencies and electrophysiological responses were examined as a function of context and lexical frequency. Lexical frequency is an index of our cumulative learning experience with words, so lexical-frequency effects most likely reflect access to memory representations for words. Pictures were named faster with constraining than nonconstraining contexts. Associated with this effect, starting around 400 ms pre-picture presentation, oscillatory power between 8 and 30 Hz was lower for constraining relative to nonconstraining contexts. Furthermore, pictures were named faster with high-frequency than low-frequency names, but only for nonconstraining contexts, suggesting differential ease of memory access as a function of sentential context. Associated with the lexical-frequency effect, starting around 500 ms pre-picture presentation, oscillatory power between 4 and 10 Hz was higher for high-frequency than for low-frequency names, but only for constraining contexts. Our results characterise electrophysiological responses associated with lexical frequency and sentential constraint in spoken word production, and point to new avenues for studying these fundamental factors in language production.

Attractor dynamics of spatially correlated neural activity in the limbic system

Attractor networks are a popular computational construct used to model different brain systems. These networks allow elegant computations that are thought to represent a number of aspects of brain function. Although there is good reason to believe that the brain displays attractor dynamics, it has proven difficult to test experimentally whether any particular attractor architecture resides in any particular brain circuit. We review models and experimental evidence for three systems in the rat brain that are presumed to be components of the rat's navigational and memory system. Head-direction cells have been modeled as a ring attractor, grid cells as a plane attractor, and place cells both as a plane attractor and as a point attractor. Whereas the models have proven to be extremely useful conceptual tools, the experimental evidence in their favor, although intriguing, is still mostly circumstantial.

Sensory feedback, error correction, and remapping in a multiple oscillator model of place-cell activity

Mammals navigate by integrating self-motion signals ("path integration") and occasionally fixing on familiar environmental landmarks. The rat hippocampus is a model system of spatial representation in which place cells are thought to integrate both sensory and spatial information from entorhinal cortex. The localized firing fields of hippocampal place cells and entorhinal grid-cells demonstrate a phase relationship with the local theta (6-10 Hz) rhythm that may be a temporal signature of path integration. However, encoding self-motion in the phase of theta oscillations requires high temporal precision and is susceptible to idiothetic noise, neuronal variability, and a changing environment. We present a model based on oscillatory interference theory, previously studied in the context of grid cells, in which transient temporal synchronization among a pool of path-integrating theta oscillators produces hippocampal-like place fields. We hypothesize that a spatiotemporally extended sensory interaction with external cues modulates feedback to the theta oscillators. We implement a form of this cue-driven feedback and show that it can retrieve fixed points in the phase code of position. A single cue can smoothly reset oscillator phases to correct for both systematic errors and continuous noise in path integration. Further, simulations in which local and global cues are rotated against each other reveal a phase-code mechanism in which conflicting cue arrangements can reproduce experimentally observed distributions of "partial remapping" responses. This abstract model demonstrates that phase-code feedback can provide stability to the temporal coding of position during navigation and may contribute to the context-dependence of hippocampal spatial representations. While the anatomical substrates of these processes have not been fully characterized, our findings suggest several signatures that can be evaluated in future experiments.

Why are some people's names easier to learn than others? The effects of face similarity on memory for face-name associations

Using synthetic faces that varied along four perceptual dimensions (Wilson, Loffler, & Wilkinson, 2002), we examined the effects of face similarity on memory for face-name associations. The nature of these stimuli allowed us to go beyond the categorical similarity manipulations used in previous verbal associative memory studies to trace out the parametric relation between similarity and various performance measures. In Experiment 1, we found that recall performance diminished as a function of how many studied faces were in the vicinity of the cue face in similarity space. Also, incorrect recalls were more likely to come from nearby positions in face space. Experiments 2 and 3, respectively, demonstrated analogous effects with a set of more distinguishable, photorealistic faces, and in an associative recognition task. These results highlight the similarity between associative recall and associative recognition, and between face-name association and other domains of associative memory.

‘My five moments for hand hygiene’: a user-centred design approach to understand, train, monitor and report hand hygiene

Hand hygiene is a core element of patient safety for the prevention of healthcare-associated infections and the spread of antimicrobial resistance. Its promotion represents a challenge that requires a multi-modal strategy using a clear, robust and simple conceptual framework. The World Health Organization First Global Patient Safety Challenge 'Clean Care is Safer Care' has expanded educational and promotional tools developed initially for the Swiss national hand hygiene campaign for worldwide use. Development methodology involved a user-centred design approach incorporating strategies of human factors engineering, cognitive behaviour science and elements of social marketing, followed by an iterative prototype test phase within the target population. This research resulted in a concept called 'My five moments for hand hygiene'. It describes the fundamental reference points for healthcare workers (HCWs) in a time-space framework and designates the moments when hand hygiene is required to effectively interrupt microbial transmission during the care sequence. The concept applies to a wide range of patient care activities and healthcare settings. It proposes a unified vision for trainers, observers and HCWs that should facilitate education, minimize inter-individual variation and resource use, and increase adherence. 'My five moments for hand hygiene' bridges the gap between scientific evidence and daily health practice and provides a solid basis to understand, teach, monitor and report hand hygiene practices.