Global Familiarity of Visual Stimuli Affects Repetition-Related Neural Plasticity but Not Repetition Priming

In this study, we tested the prediction of the component process model of priming [Henson, R.N. (2003). Neuroimaging studies of priming. Prog Neurobiol, 70 (1), 53-81] that repetition priming of familiar and unfamiliar objects produces qualitatively different neural repetition effects. In an fMRI study, subjects viewed four repetitions of familiar objects and globally unfamiliar objects with familiar components. Reliable behavioral priming occurred for both item types across the four presentations and was of a similar magnitude for both stimulus types. The imaging data were analyzed using multivariate linear modeling, which permits explicit testing of the hypothesis that the repetition effects for familiar and unfamiliar objects are qualitatively different (i.e., non-scaled versions of one another). The results showed the presence of two qualitatively different latent spatial patterns of repetition effects from presentation 1 to presentation 4 for familiar and unfamiliar objects, indicating that familiarity with an object's global structural, semantic, or lexical features is an important factor in priming-related neural plasticity. The first latent spatial pattern strongly weighted regions with a similar repetition effect for both item types. The second pattern strongly weighted regions contributing a repetition suppression effect for the familiar objects and repetition enhancement for the unfamiliar objects, particularly the posterior insula, superior temporal gyrus, precentral gyrus, and cingulate cortex. This differential repetition effect might reflect the formation of novel memory representations for the unfamiliar items, which already exist for the familiar objects, consistent with the component process model of priming

Repetition Priming and Anomia: An Investigation of Stimulus Dosage

In a recent review of anomia management, Maher & Raymer reported that 30% of aphasia intervention research from 1946 to 2001 focused on naming; however, despite this proliferation of case reports and small group studies, there is still no clear agreement on how best to manage these deficits (Maher & Raymer, 2004, p. 13). The inconsistency of acquisition, maintenance, and generalization effects observed across participants and types of treatment protocols is likely to stem from an inadequate knowledge base about how subject and treatment variables influence learning. One treatment variable that has received increasing attention over the past two or three years is treatment intensity. Principles of neurobiological learning across both animal and human research suggest that the intensity of treatment is a significant factor for learning. Additional research exploring experience-dependent neural plasticity involved in memory and learning indicates that a large number of trials per session are required to elicit behavioral and/or neural change. Despite a considerable amount of literature examining overall treatment intensity, data are not available regarding the frequency (i.e., stimulus dosage) of treatment at which individuals with aphasia will maximally benefit. A single-subject A-B design with replication across four individuals with aphasia and one healthy non-brain injured gender-matched control participant was used to assess the influence of repeated attempts at picture-naming, coupled with repeated exposure to hearing and reading target words, on the acquisition and maintenance of trained stimuli, and generalization to untrained stimuli. Individuals with chronic aphasia participated in a multi-week repetition priming protocol designed to investigate the influence of stimulus dosage on naming accuracy and latency. Results revealed positive repetition priming effects for trained items across both acquisition and maintenance phases; such positive effects were not observed for untrained stimuli or alternate exemplars. Stimulus dosage manipulations did not consistently influence naming performance for individuals with aphasia

Inhibition in the dynamics of selective attention: an integrative model for negative priming

We introduce a computational model of the negative priming (NP) effect that includes perception, memory, attention, decision making, and action. The model is designed to provide a coherent picture across competing theories of NP. The model is formulated in terms of abstract dynamics for the activations of features, their binding into object entities, their semantic categorization as well as related memories and appropriate reactions. The dynamic variables interact in a connectionist network which is shown to be adaptable to a variety of experimental paradigms. We find that selective attention can be modeled by means of inhibitory processes and by a threshold dynamics. From the necessity of quantifying the experimental paradigms, we conclude that the specificity of the experimental paradigm must be taken into account when predicting the nature of the NP effect

Neural Correlates of Repetition Priming: A Coordinate-Based Meta-Analysis of fMRI Studies.

Repetition priming is a form of implicit memory, whereby classification or identification of a stimulus is improved by prior presentation of the same stimulus. Repetition priming is accompanied with a deceased fMRI signal for primed vs. unprimed stimuli in various brain regions, often called "repetition suppression," or RS. Previous studies proposed that RS in posterior regions is associated with priming of perceptual processes, whereas RS in more anterior (prefrontal) regions is associated with priming of conceptual processes. To clarify which regions exhibit reliable RS associated with perceptual and conceptual priming, we conducted a quantitative meta-analysis using coordinate-based activation likelihood estimation. This analysis included 65 fMRI studies that (i) employed visual repetition priming during either perceptual or conceptual tasks, (ii) demonstrated behavioral priming, and (iii) reported the results from whole-brain analyses. Our results showed that repetition priming was mainly associated with RS in left inferior frontal gyrus and fusiform gyrus. Importantly, RS in these regions was found for both perceptual and conceptual tasks, and no regions show RS that was selective to one of these tasks. These results question the simple distinction between conceptual and perceptual priming, and suggest consideration of other factors such as stimulus-response bindings

Location-independent and location-linked representations of sound objects.

For the recognition of sounds to benefit perception and action, their neural representations should also encode their current spatial position and their changes in position over time. The dual-stream model of auditory processing postulates separate (albeit interacting) processing streams for sound meaning and for sound location. Using a repetition priming paradigm in conjunction with distributed source modeling of auditory evoked potentials, we determined how individual sound objects are represented within these streams. Changes in perceived location were induced by interaural intensity differences, and sound location was either held constant or shifted across initial and repeated presentations (from one hemispace to the other in the main experiment or between locations within the right hemispace in a follow-up experiment). Location-linked representations were characterized by differences in priming effects between pairs presented to the same vs. different simulated lateralizations. These effects were significant at 20-39 ms post-stimulus onset within a cluster on the posterior part of the left superior and middle temporal gyri; and at 143-162 ms within a cluster on the left inferior and middle frontal gyri. Location-independent representations were characterized by a difference between initial and repeated presentations, independently of whether or not their simulated lateralization was held constant across repetitions. This effect was significant at 42-63 ms within three clusters on the right temporo-frontal region; and at 165-215 ms in a large cluster on the left temporo-parietal convexity. Our results reveal two varieties of representations of sound objects within the ventral/What stream: one location-independent, as initially postulated in the dual-stream model, and the other location-linked

Attractors, memory and perception

In this Thesis, the first three introductory chapters are devoted to the review of literature on contextual perception, its neural basis and network modeling of memory. In chapter 4, the first two sections give the definition of our model; and the next two sections, 4.3 and 4.4, report the original work of mine on retrieval properties of different network structures and network dynamics underlying the response to ambiguous patterns, respectively. The reported work in chapter 5 has been done in collaboration with Prof Bharathi Jagadeesh in University of Washington, and is already published in the journal \u201dCerebral Cortex\u201d. In this collaboration, Yan Liu, from the group in Seattle, carried out the recording experiments and I did the data analysis and network simulations. Chapter 6, which represents a network model for \u201dpriming\u201d and \u201dadaptation aftereffect\u201d is done by me. The works reported in 4.3, 4.5, and the whole chapter 6 are in preparation for publication

Cognitive function in normal aging and in older adults with mild cognitive impairment

Antecedentes: en este estudio investigamos los efectos del envejecimiento sano y patológico (déficit cognitivo leve, DCL) en varias funciones cognitivas (control ejecutivo, velocidad de procesamiento y memoria implícita). Método: veinte adultos jóvenes, 20 mayores sanos y 20 mayores DCL realizaron una serie de tareas cognitivas bajo condiciones controladas. Estas tareas fueron tiempo de reacción simple y de elección, el Test Wisconsin y una tarea de memoria implícita para objetos atendidos y no atendidos durante la codificación. Resultados: el grupo DCL mostró declives pronunciados en las tareas de velocidad de procesamiento y de control ejecutivo. Además, los jóvenes y los mayores sanos mostraron priming para los objetos atendidos durante la codificación estimular, pero no los mayores con DCL. Conclusiones: en este último grupo, la falta de priming de repetición para objetos atendidos en la tarea de memoria implícita fueron similares a los de los enfermos de Alzheimer (EA) y sugieren la existencia de un déficit temprano de la atención selectiva en mayores DCL, lo que podría ser un marcador del envejecimiento patológico

Priming of Familiar and Unfamiliar Visual Objects over Delays in Young and Older Adults

Although priming of familiar stimuli is usually age invariant, little is known about how aging affects priming of preexperimentally unfamiliar stimuli. Therefore, this study investigated the effects of aging and encoding-to-test delays (0 min, 20 min, 90 min, and 1 week) on priming of unfamiliar objects in block-based priming paradigms. During the encoding phase, participants viewed pictures of novel objects (Experiments 1 and 2) or novel and familiar objects (Experiment 3) and judged their left-right orientation. In the test block, priming was measured using the possible-impossible object-decision test (Experiment 1), symmetric-asymmetric object-decision test (Experiment 2), and real-nonreal object-decision test (Experiment 3). In Experiments 1 and 2, young adults showed priming for unfamiliar objects at all delays, whereas older adults whose baseline task performance was similar to that of young adults did not show any priming. Experiment 3 found no effects of age or delay on priming of familiar objects; however, priming of unfamiliar objects was only observed in the young participants. This suggests that when older adults cannot rely on preexisting memory representations, age-related deficits in priming can emerge

EMOTIONAL ENHANCEMENT AND REPETITION EFFECTS DURING WORKING MEMORY IN PERSONS WITH MILD COGNITIVE IMPAIRMENT

This dissertation introduces a framework for understanding differences in how emotional enhancement effects might influence memory in aging adults and then summarizes the findings of three studies of how repetition effects and emotional enhancement effects influence working memory in older adults without cognitive impairment (NC), older adults with amnestic mild cognitive impairment (MCI), and older adults with mild Alzheimer’s disease (AD). In these experiments, individuals with AD showed cognitive impairment in terms of accuracy and reaction time, but individuals with MCI showed milder behavioral impairment that was confined to manipulations of working memory. Individuals with AD showed relative sparing of repetition effects in behavioral performance, and this sparing was linked to an altered cortical repetition effect using event-related potentials (ERPs). Repetition effects in MCI appear absent in emotional tasks that lack a working memory component, but are present in a neural repetition mechanism that is evoked in the presence of working memory. Finally, persons with MCI showed working memory processing similar to persons without impairment when working with stimuli of low arousal and positive hedonic valence, but when working with stimuli of high arousal and negative hedonic valence, their working memory processing more resembled the AD phenotype