Are there distinct forms of accelerated forgetting and, if so, why?

Whether accelerated long-term forgetting (ALF) and classic organic amnesia, particularly hippocampal-amnesia, differ qualitatively or merely quantitatively is disputed. Qualitative difference accounts postulate that ALF patients show normal recall memory for at least minutes, during which hippocampal-amnesics already show accelerated forgetting and impaired recall but, thereafter, ALF patients show accelerated forgetting and impaired delayed recall. These delayed impairments may be more severe than those shown by hippocampal-amnesics. In contrast, quantitative difference accounts postulate that ALF patients merely have mild hippocampal-amnesia, so their later forgetting rates and recall levels are sub-normal but always better than those of hippocampal-amnesics with worse initial recall levels (i.e., there is no cross-over in forgetting rates at longer delays). Many ALF studies in people with epilepsy have demonstrated evidence of a single dissociation-with accelerated delayed forgetting relative to healthy controls. Even when initial recall seems genuinely normal, uncompromised by patients needing more learning trials or showing below-average performance on more demanding recall tests, without further evidence, a quantitative interpretation remains possible. Resolution of the dispute requires evidence of a double dissociation between ALF patients and hippocampal-amnesics with more impaired initial recall in a comparison also involving matched controls. The only two studies that have made this comparison found that there was a cross-over interaction between initial and delayed recall in the ALF and amnesic patients, inconsistent with quantitative difference accounts. The functional and pathological conditions underlying this cross-over effect need to be systematically explored, controlling for potential methodological confounds, in temporal lobe epilepsy and transient epileptic amnesia as well as non-epileptic conditions. Future research must also explore under what conditions, if any, milder hippocampal-amnesics show relatively normal delayed forgetting of recall, and for how long, if at all, ALF patients show completely normal recall. Relatedly, the functional and pathological heterogeneity of ALF needs systematic exploration.

Memory for between-list and within-list information in amnesic patients with temporal lobe and diencephalic lesions.

Patients with medial temporal lobe damage and diencephalic damage were compared on two tests of verbal temporal order memory: between-list discrimination and within-list discrimination. Both patient groups were impaired relative to a group of healthy control participants. In addition, despite comparable levels of item recognition, the diencephalic group was impaired relative to the medial temporal lobe group on both within-list and between-list discrimination. Temporal order memory for between-list information showed a significant correlation with a composite measure of recognition memory, and the results are discussed in terms of the patients' reliance on familiarity and distance-based processes to make temporal order judgments.

Novelty-related activation within the medial temporal lobes.

Functional magnetic resonance imaging (fMRI) was used to examine whether (1) verbal associative encoding activates the medial temporal lobes (MTL) and related regions more than non-associative encoding, (2) verbal associative novelty is related to enhanced MTL activation, and (3) verbal item novelty is related to enhanced MTL activation and, if so, whether these activations are in different or overlapping sites. No increase in MTL activation was found during verbal associative encoding relative to non-associative encoding, although associative encoding was related to a relative increase in activation in the posterior cingulate cortex. In contrast, verbal associative novelty was found to activate the MTL and posterior cingulate cortex. Verbal item novelty did not significantly activate any brain region. The verbal associative novelty-related effect occurred despite subjects having little awareness of associative novelty. The verbal associative novelty-related activation in the MTL may be related either to unconscious novelty detection or to a priming effect at encoding. We argue that if the priming explanation is correct then this may account for our failure to observe an associative encoding MTL activation.

British memory research: A journey through the 20th century.

A century of research in memory has generated a wealth of knowledge encompassing theoretical developments within a number of distinct domains of memory. The aim of this article is to explore the progress made in memory research during the 20th century, to indicate critical influences on the direction of research, and to illustrate the important contribution made by British researchers. This article is confined to human memory research, and reviews research findings from the various psychological disciplines studied over the past 100 years.

Storage of verbal associations is sufficient to activate the left medial temporal lobe.

Neuroimaging studies have shown that memory encoding activates the medial temporal lobe (MTL). Many believe that these activations are related to novelty but it remains unproven which is critical - novelty detection or the rich associative encoding it triggers. We examined MTL activation during verbal associative encoding using functional magnetic resonance imaging. First, associative encoding activated left posterior MTL more than single word encoding even though novelty detection was matched, indicating not only that associative encoding activates the MTL particularly strongly, but also that activation does not require novelty detection. Moreover, it remains to be convincingly shown that novelty detection alone does produce such activation. Second, repetitive associative encoding produced less MTL activation than initial associative encoding, indicating that priming of associative information reduces MTL activation. Third, re-encoding familiar associations in a well-established way had a minimal effect on both memory and MTL activation, indicating that MTL activation reflects storage of associations, not merely their initial representation.

UNLEARNING JOHN MAJOR: THE USE OF ERRORLESS LEARNING IN THE REACQUISITION OF PROPER NAMES FOLLOWING HERPES SIMPLEX ENCEPHALITIS.

In this study we examined the value of errorless learning as a means of restoring memory for proper names in an individual who had becomedysnomic following herpes simplex encephalitis. In Experiment 1 the errorless learning technique was used to teach the subject (PM) the names of eightpoliticians thathe had forgotten. In evaluating thetechnique, we also examined whether there was any generalisation to the naming of untrained politicians' names that he had also forgotten and whether the technique had any effect on politicians' names he was able to produce at the outset of training. Training was successful in that PM reached criterion on naming the trained faces but there was no recovery of untrained names. Moreover, we also observed inhibition of politicians' name he was able to produce at the outset of the study. Experiment 2 used a similar procedure to teach PM the names of personal friends that he could not remember. However, the technique was modified so as to include a "refresh" trial at the end of each training session for those friends' names he was already able to produce. Errorless learning again facilitated the reacquisition of names but there was no inhibition of names available at the outset. These data illustrate that errorless learning can be used as a means of restoring lost vocabulary but demonstrate how retrieval inhibition is an important element in evaluating overall effectiveness. In addition, the data are discussed in relation to recent theories of memory restoration.