Memory rehabilitation: restorative, specific knowledge acquisition, compensatory, and holistic approaches.

Memory impairment following an acquired brain injury can negatively impact daily living and quality of life-but can be reduced by memory rehabilitation. Here, we review the literature on four approaches for memory rehabilitation and their associated strategies: (1) the restorative approach, aimed at a return to pre-morbid functioning, (2) the knowledge acquisition approach, involving training on specific information relevant to daily life, (3) the compensatory approach, targeted at improving daily functioning, and (4) the holistic approach, in which social, emotional, and behavioral deficits are addressed alongside cognitive consequences of acquired brain injury. Each memory rehabilitation approach includes specific strategies such as drill and practice (restorative), spaced retrieval (knowledge acquisition), memory aids (compensatory), or a combination of psychotherapy and cognitive strategies (holistic).

On the memory benefits of repeated study with variable tasks.

Encoding variability refers to the situation in which repeated items are processed in different ways on each presentation. Superior memory performance resulting from encoding variability is sometimes argued to underlie important phenomena in human memory such as the spacing effect. However, the memory benefits of encoding variability are often elusive.

On the sensitivity of event-related potentials to retrieval mode.

Event-related potential (ERP) signatures of preparation to retrieve episodic memories have been identified in several studies. A common finding is relatively more positive-going ERP activity over right-frontal sites when people prepare for episodic rather than semantic retrieval. This activity has been linked to the process of retrieval mode - a retrieval set that ensures subsequent events are treated as cues for episodic retrieval.

On the sensitivity of event-related fields to recollection and familiarity.

The sensitivity of event-related potentials (ERPs) to the processes of recollection and familiarity has been explored extensively, and ERPs have been used subsequently to infer the contributions these processes make to memory judgments under a range of different circumstances. It has also been shown that event-related fields (ERFs, the magnetic counterparts of ERPs) are sensitive to memory retrieval processes. The links between ERFs, recollection and familiarity are, however, established only weakly.

On the Antecedents of an Electrophysiological Signature of Retrieval Mode.

It has been proposed that people employ a common set of sustained operations (retrieval mode) when preparing to remember different kinds of episodic information. In two experiments, however, there was no evidence for the pattern of brain activity commonly assumed to index these operations. In both experiments event-related potentials (ERPs) were recorded time-locked to alternating preparatory cues signalling that participants should prepare for different retrieval tasks.

Separating content-specific retrieval from post-retrieval processing.

According to cortical reinstatement accounts, neural processes engaged at the time of encoding are re-engaged at the time of memory retrieval. The temporal precision of event-related potentials (ERPs) has been exploited to assess this possibility, and in this study ERPs were acquired while people made memory judgments to visually presented words encoded in two different ways. There were reliable differences between the scalp distributions of the signatures of successful retrieval of different contents from 300 to 1100 ms after stimulus presentation.

Electrophysiological evidence for flexible goal-directed cue processing during episodic retrieval.

A widely held assumption is that memory retrieval is aided by cognitive control processes that are engaged flexibly in service of memory retrieval and memory decisions. While there is some empirical support for this view, a notable exception is the absence of evidence for the flexible use of retrieval control in functional neuroimaging experiments requiring frequent switches between tasks with different cognitive demands. This absence is troublesome in so far as frequent switches between tasks mimic some of the challenges that are typically placed on memory outside the laboratory.

Direct real-time neural evidence for task-set inertia.

One influential explanation for the costs incurred when switching between tasks is that they reflect interference arising from completing the previous task-known as task-set inertia. We report a novel approach for assessing task-set inertia in a memory experiment using event-related potentials (ERPs). After a study phase, participants completed a test block in which they switched between a memory task (retrieving information from the study phase) and a perceptual task.

Electrophysiological evidence for retrieval mode immediately after a task switch.

It has been suggested that retrieving episodic information can involve adopting a cognitive state or set: retrieval mode. In a series of studies, an event-related potential (ERP) index of retrieval mode has been identified in designs which cue participants on a trial-by-trial basis to switch between preparing for and then completing an episodic or non-episodic retrieval task. However, a confound in these studies is that along with task type the content of what is to be retrieved has varied.

The role of working memory capacity in the control of recollection.

The links between control over recollection and working memory capacity (WMC) were investigated using event-related potentials (ERPs) and behavioural assays. Electrophysiological evidence for a relationship between greater control over recollection and higher scores on a measure of WMC was obtained. In addition, people with high WMC who first completed a task requiring cognitive control showed no electrophysiological evidence for control over recollection on a subsequent task.

Electrophysiological correlates of memory processes.

Abstract In this commentary we highlight what are to our minds conflicting findings that have been employed to argue for different functional accounts of the mid-frontal event-related potential (ERP) old/new effect. We also offer our views on the difficulties associated with measuring conceptual priming as well as familiarity, and reemphasise that these issues are only a sub-set of those to consider when assessing the ERP literature that is germane to the question of the proceses that the mid-frontal ERP old/new effect indexes.

Immediate judgments of learning predict subsequent recollection: evidence from event-related potentials.

Judgments of learning (JOLs) are assessments of how well materials have been learned. Although a wide body of literature has demonstrated a reliable correlation between memory performance and JOLs, relatively little is known about the nature of this link. Here, we investigate the relationship between JOLs and the memory retrieval processes engaged on a subsequent memory test.

Recollection and familiarity make independent contributions to memory judgments.

Recognition memory can be supported by the processes of recollection and familiarity. Recollection is recovery of qualitative information about a prior event. Familiarity is a scalar strength signal that permits judgments of prior occurrence.

A role for perirhinal cortex in memory for novel object-context associations.

It is debated whether functional divisions between structures in the medial temporal lobe (MTL), in particular the perirhinal cortex (PrC) and hippocampus (HC), are best conceptualized according to memory process (Diana et al., 2007; Ranganath, 2010; Wixted et al., 2010) or stimulus category (Graham et al.

Functional specialisation in the hippocampus and perirhinal cortex during the encoding of verbal associations.

Functional magnetic resonance imaging (fMRI) was employed to investigate the contributions of medial temporal lobe (MTL) regions to encoding operations underpinning recollection and familiarity. Participants first studied word pairs. Words in pairs were either weakly or strongly semantically related.

Temporally and functionally dissociable retrieval processing operations revealed by event-related potentials.

In a pair of recent studies, frontally distributed event-related potential (ERP) indices of two distinct post-retrieval processes were identified. It has been proposed that one of these processes operates over any kinds of task relevant information in service of task demands, while the other operates selectively over recovered contextual (episodic) information. The experiment described here was designed to test this account, by requiring retrieval of different kinds of contextual information to that required in previous relevant studies.

Requirements at retrieval modulate subsequent memory effects: An event-related potential study.

Neural indices of memory formation can be acquired by contrasting activity during study for items that are remembered or forgotten on a subsequent memory test. These "subsequent memory" effects vary with the stimulus types that are encoded, how they are encoded, the correspondences between study and test materials, and the time intervals between study and test phases. We investigated whether event-related potential (ERP) subsequent memory effects also vary with the content people must retrieve.

Variational Bayes for spatiotemporal identification of event-related potential subcomponents.

We propose a novel method for detection and tracking of event-related potential (ERP) subcomponents. The ERP subcomponent sources are assumed to be electric current dipoles (ECDs), and their locations and parameters (amplitude, latency, and width) are estimated and tracked from trial to trial. Variational Bayes implies that the parameters can be estimated separately using the likelihood function of each parameter.

Functional neuroanatomy supporting judgments of when events occurred.

The neural substrates of memory for when events occurred are not well described. One reason for this is that the paradigms used to date have permitted isolation of only some of the relevant memory processes. In this experiment, functional magnetic resonance imaging was used to identify for the first time brain regions that support two distinct bases upon which "when" judgments can be made.

Judgments of learning do not reduce to memory encoding operations: event-related potential evidence for distinct metacognitive processes.

To examine how judgments of learning (JOLs) are made, we used event-related potentials (ERPs) to compare neural correlates of JOLs and successful memory encoding. Participants saw word pairs, and for each made a JOL indicating how confident they were that they would remember the pairing on a later cued recall task. ERPs were recorded while JOLs were made and were separated according to whether items were: (i) remembered or forgotten on the subsequent test, and (ii) rated likely or unlikely to be remembered.

The application of particle filters in single trial event-related potential estimation.

In this paper, an approach for the estimation of single trial event-related potentials (ST-ERPs) using particle filters (PFs) is presented. The method is based on recursive Bayesian mean square estimation of ERP wavelet coefficients using their previous estimates as prior information. To enable a performance evaluation of the approach in the Gaussian and non-Gaussian distributed noise conditions, we added Gaussian white noise (GWN) and real electroencephalogram (EEG) signals recorded during rest to the simulated ERPs.

Neural correlates of individual differences in strategic retrieval processing.

Processes engaged when information is encoded into memory are an important determinant of whether that information will be recovered subsequently. Also influential, however, are processes engaged at the time of retrieval, and these were investigated here by using event-related potentials (ERPs) to measure a specific class of retrieval operations. These operations were revealed by contrasts between ERPs elicited by new (unstudied) test items in distinct tasks, the assumption being that these contrasts index operations that are engaged in service of retrieval and that vary according to the demands of different retrieval tasks.

Prefrontal cortex contributions to episodic retrieval monitoring and evaluation.

Although the prefrontal cortex (PFC) plays roles in episodic memory judgments, the specific processes it supports are not understood fully. Event-related potential (ERP) studies of episodic retrieval have revealed an electrophysiological modulation - the right-frontal ERP old/new effect - which is thought to reflect activity in PFC. The functional significance of this old/new effect remains a matter of debate, and this study was designed to test two accounts: (i) that the effect indexes processes linked to the monitoring or evaluation of the products of retrieval in service of task demands, or (ii) that it indexes the number of internal decisions required for a task judgment.

Material-specific neural correlates of memory retrieval.

It is well established that the neural activity engaged during memory retrieval varies with the kinds of information that are recovered. Less well established is whether this activity reflects online recovery of information, or processes operating downstream of successful recovery. We used event-related potentials (ERPs) to adjudicate between these alternatives, emphasizing that an online recovery account would be supported if material-specific indices of successful retrieval occurred no later than a material-independent index of recollection, the left-parietal ERP old/new effect.

Retrieval processes supporting judgments of recency.

The circumstances under which different retrieval processes can support judgments about how long ago events occurred remain a matter of debate, as do the ways in which retrieved information can be employed in support of such judgments. In order to contribute to an understanding of the nature and number of distinct retrieval processes that support time judgments, event-related potentials (ERPs) were acquired during a continuous verbal memory task, where the lag between presentation and re-presentation of words was varied. Participants made judgments of recency (JORs), indicating the number of words that had intervened between presentation and re-presentation.