"Artificial grammar learning depends on implicit acquisition of both abstract and exemplar-specific information": Correction.

Reports an error in the original article by B. J. Knowlton and L. R. Squire (Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol 22[1], 169–181). The Appendix on page 181 contains several errors. The corrected Appendix is provided. (The following abstract of this article originally appeared in record 1996-02680-010). The contributions of exemplar-specific and abstract knowledge to artificial grammar learning were examined in amnesic patients and controls. In Experiment 1, grammatical rule adherence and chunk strength exerted separate effects in grammaticality judgments. Amnesic patients exhibited intact classification performance, demonstrating the same pattern of results as controls. In Experiment 2, amnesic patients exhibited impaired declarative memory for chunks. In Experiment 3, both amnesic patients and controls exhibited transfer when tested with a letter set different than the one used for training, although performance was better when the same letter sets were used at the training and test. The results suggest that individuals learn both abstract information about training items and exemplar-specific information about chunk strength and that both types of learning occur independently of declarative memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the acquisition of new declarative knowledge in amnesia.

In 2 experiments, the acquisition of new declarative knowledge was examined in amnesic patients and in 7 groups of controls, with a study-only procedure that delayed testing until the conclusion of training. The study-only procedure was compared with a standard procedure in which study and test trials alternated (study-test). The amnesic patients acquired new factual (declarative) knowledge at an abnormally slow rate, learning more with the study-only procedure than with the study-test procedure. Controls exhibited the opposite pattern. The advantage of the study-only procedure for amnesic patients was related to the presence of frontal lobe dysfunction. The 2 groups exhibited a similar ability to use their knowledge flexibly, suggesting that the information acquired by amnesic patients was based on their residual capacity for declarative memory. In addition, the capacity for factual learning in amnesia was proportional to the capacity to recollect specific events in the learning session. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual Feature Learning in Artificial Grammar Classification.

The Artificial Grammar Learning task has been used extensively to assess individuals' implicit learning capabilities. Previous work suggests that participants implicitly acquire rule-based knowledge as well as exemplar-specific knowledge in this task. This study investigated whether exemplar-specific knowledge acquired in this task is based on the visual features of the exemplars. When a change in the font and case occurred between study and test, there was no effect on sensitivity to grammatical rules in classification judgments. However, such a change did virtually eliminate sensitivity to training frequencies of letter bigrams and trigrams (chunk strength) in classification judgments. Performance of a secondary task during study eliminated this font sensitivity and generally reduced the contribution of chunk strength knowledge. The results are consistent with the idea that perceptual fluency makes a contribution to artificial grammar judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociable properties of memory systems: Differences in the flexibility of declarative and nondeclarative knowledge.

Amnesic patients (n?=?8), who have severely impaired declarative memory, learned a probabilistic classification task at the same rate as normal subjects (n?=?16); but subsequently were impaired on transfer tests that required flexible use of their task knowledge. A second group of controls (n?=?20) rated the questions on the transfer tests according to whether the questions simply reinstated the training conditions or required flexible use of task knowledge. The amnesic patients tended to be impaired on the same items that were rated as requiring indirect or flexible use of knowledge. Thus, control subjects acquired declarative knowledge about the task that could be applied flexibly to the transfer tests. The nondeclarative memory available to amnesic patients was relatively inflexible and available only in conditions that reinstated the conditions of training. These findings show that declarative memory has different operating characteristics than nondeclarative memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

When amnesic patients perform well on recognition memory tests.

Extended exposure to study material can markedly improve subsequent recognition memory performance in amnesic patients, even the densely amnesic patient H.M. To understand this phenomenon, the severely amnesic patient E.P., 3 other amnesic patients, and controls studied pictorial material and then were given either a yes–no (Experiment 1) or a 2-alternative, forced-choice (Experiment 2) recognition test. The amnesic patients and controls benefited substantially from extended exposure, but patient E.P. consistently performed at chance. Furthermore, confidence ratings corresponded to recognition accuracy. The results do not support the idea that the benefit of extended study time is due to some kind of familiarity process made available through nondeclarative memory. It is likely that amnesic patients benefit from extended study time to the extent that they have residual capacity for declarative memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the relationship between recall and recognition memory.

The relationship between recall and recognition has been a central topic for the study of memory. A test of alternative views about recall and recognition was arranged by studying amnesic patients. In amnesia, damage has occurred to a brain system important for declarative (conscious) memory, but skill learning, priming, and other forms of nonconscious memory are intact. Recall and recognition were found to be proportionately impaired in amnesic patients, and confidence ratings for the recognition judgments were commensurate with the level of impaired performance. The results are contrary to views that either recognition memory or associated confidence judgments are ordinarily supported significantly by nonconscious memory. The results favor the view that recall and recognition are related functions of declarative memory and equivalently dependent on the brain system damaged in amnesia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the development of declarative memory.

In the visual paired-comparison task, which has been used to demonstrate memory abilities in human infants, Ss view pairs of pictures and then view new pictures paired with old ones. Memory is demonstrated when Ss spend more time looking at new pictures than at old ones. In a series of studies involving amnesic patients and normal Ss, the authors evaluated what kind of memory is exhibited in this task. The results suggest that performance ordinarily depends on the brain structures essential for declarative memory. These and other findings suggest that the visual paired-comparison test also depends on declarative memory when the task is given to human infants. Thus, successful performance on this task by infants probably reflects an early capacity for declarative memory. The relevance of these findings to the phenomenon of infantile amnesia is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Learning and generalization deficits in patients with memory impairments due to anterior communicating artery aneurysm rupture or hypoxic brain injury": Correction.

Reports an error in "Learning and generalization deficits in patients with memory impairments due to anterior communicating artery aneurysm rupture or hypoxic brain injury" by Catherine E. Myers, Ramona O. Hopkins, John DeLuca, Nancy B. Moore, Leo J. Wolansky, Jennifer M. Sumner and Mark A. Gluck (Neuropsychology, 2008[Sep], Vol 22[5], 681-686). Author Ramona O. Hopkins's name was misspelled as Romona O. Hopkins. (The following abstract of the original article appeared in record 2008-11707-013.) Human anterograde amnesia can result from a variety of etiologies, including hypoxic brain injury and anterior communicating artery (ACoA) aneurysm rupture. Although each etiology can cause a similarly severe disruption in declarative memory for verbal and visual material, there may be differences in incrementally acquired, feedback-based learning, as well as generalization. Here, 6 individuals who survived hypoxic brain injury, 7 individuals who survived ACoA aneurysm rupture, and 13 matched controls were tested on 2 tasks that included a feedback-based learning phase followed by a transfer phase in which familiar information is presented in new ways. In both tasks, the ACoA group was slow on initial learning, but those patients who completed the learning phase went on to transfer as well as controls. In the hypoxic group, 1 patient failed to complete either task; the remaining hypoxic group did not differ from controls during learning of either task, but was impaired on transfer. These results highlight a difference in feedback-based learning in 2 amnesic etiologies, despite similar levels of declarative memory impairment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired transverse patterning in human amnesia is a special case of impaired memory for two-choice discrimination tasks.

Three amnesic patients with damage limited to the hippocampal formation, a severely amnesic patient with extensive medial temporal lobe damage, and 9 controls were tested on the transverse patterning problem (A?+?B–, B?+?C–, and C?+?A–) and also on 2 control problems. One of the control problems was matched to the transverse patterning problem with respect to the number of pairwise decisions that were required. The 2nd control problem was matched to the transverse patterning problem with respect to the number of trials needed by controls to learn the task. The amnesic patients were impaired at solving both the transverse patterning problem and the control problems. The findings suggest that impaired learning of the transverse patterning problem by amnesic patients derives from their general impairment in declarative memory, which affects performance on most 2-choice discrimination tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relationship between recall and recognition in amnesia: Effects of matching recognition between patients with amnesia and controls.

To examine the relationship between recall and recognition memory in amnesia, the authors conducted 2 experiments in which recognition memory was equated between patients with amnesia and control participants. It was then determined whether recall was also similar across groups. In Experiment 1, recognition was equated by providing amnesic patients with additional study exposures; in Experiment 2, recognition was equated by testing controls following a longer delay. These different methods of equating recognition across groups led to divergent results because amnesic patients' recall performance was lower than controls' recall performance in Experiment 1 but not in Experiment 2. These findings are accounted for by considering the differential contribution of recollection and familiarity to the performance of amnesic patients and controls in the 2 experiments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning and generalization deficits in patients with memory impairments due to anterior communicating artery aneurysm rupture or hypoxic brain injury.

[Correction Notice: An erratum for this article was reported in Vol 22(6) of Neuropsychology (see record 2008-15268-012). Author Ramona O. Hopkins's name was misspelled as Romona O. Hopkins.] Human anterograde amnesia can result from a variety of etiologies, including hypoxic brain injury and anterior communicating artery (ACoA) aneurysm rupture. Although each etiology can cause a similarly severe disruption in declarative memory for verbal and visual material, there may be differences in incrementally acquired, feedback-based learning, as well as generalization. Here, 6 individuals who survived hypoxic brain injury, 7 individuals who survived ACoA aneurysm rupture, and 13 matched controls were tested on 2 tasks that included a feedback-based learning phase followed by a transfer phase in which familiar information is presented in new ways. In both tasks, the ACoA group was slow on initial learning, but those patients who completed the learning phase went on to transfer as well as controls. In the hypoxic group, 1 patient failed to complete either task; the remaining hypoxic group did not differ from controls during learning of either task, but was impaired on transfer. These results highlight a difference in feedback-based learning in 2 amnesic etiologies, despite similar levels of declarative memory impairment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two mechanisms in implicit artificial grammar learning? Comment on Meulemans and Van der Linden (1997).

T. Meulemans and M. Van der Linden (see record 1997-05320-013) presented evidence for 2 distinct mechanisms involved in artificial grammar learning. They suggested that after training on 32 letter strings (Experiment 2A), participants classify test strings using knowledge of the distributional statistics of letter chunks, whereas after training on 125 letter strings (Experiment 2B) they classify on the basis of knowledge of the rules of the grammar. This article offers an alternative unitary account of Meulemans and Van der Linden's findings. The authors show that information about grammatical rules and chunk locations was confounded in the test strings used in Experiment 2B and then present evidence that all of the data can be explained in terms of distributional knowledge, provided this includes knowledge of the positional constraints on chunks. Finally, the authors question the utility of traditional finite-state grammars for investigating abstraction processes, and suggest alternative methods. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The information acquired during artificial grammar learning.

In an artificial grammar learning task, amnesic patients classified test items as well as normal Ss did. Item similarity did not affect grammaticality judgments when similar and nonsimilar test items were balanced for the frequency with which bigrams and trigrams (chunks) that appeared in the training set also appeared in the test items. Amnesic Ss performed like normal Ss. Results suggest that concrete information about letter chunks can influence grammaticality judgments and that this information is acquired implicitly. The similarity of whole test items to training items does not appear to affect grammaticality judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Paired-associate learning and priming effects in amnesia: A neuropsychological study.

Conducted 4 experiments investigating the role of priming effects in paired-associate learning. Ss for all 4 experiments were 5 male and 3 female alcoholics (mean age 53.8 yrs; WAIS—R IQs 85–203) with Korsakoff syndrome. Control Ss were 26 male alcoholics (mean age 47.6 yrs). Exp I illustrated the distinction between the memory impairment of amnesic (Korsakoff) Ss and their intact priming ability. In Exp II, amnesic Ss showed good paired-associate learning for related word pairs but controls performed significantly better. Exp II also showed that the forgetting of related word pairs by amnesic Ss followed the same time course as the decay of word priming. Exp III showed that amnesic Ss were as good as controls at learning related word pairs when word-association tests were used. Exp IV showed that amnesic Ss exhibited normal priming when they were asked to free associate to words that were semantically related to previously presented words. Results indicate that both priming effects and paired-associate learning of related words depended on activation, a process that is preserved in amnesia. Activation is a transient phenomenon presumed to operate on and facilitate access to preexisting representations. (67 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Level-of-processing effects in word-completion priming: A neuropsychological study.

Recent reviews (A. S. Brown & D. B. Mitchell, see record 82:16176; B. Challis & D. R. Brodbeck, see record 79:30007) concluded that level-of-processing (LOP) manipulations affect priming in perceptual tasks, contrary to earlier suggestions that such tasks are insensitive to LOP. In 3 experiments with amnesic patients and control Ss, the authors examined the effect of LOP manipulations on priming in word-stem and word-fragment completion and on recognition memory. Amnesic patients exhibited reduced or near-zero LOP effects in word-completion priming compared with controls. LOP affected recognition memory for both amnesic patients and control Ss, confirming that the LOP manipulation affected explicit memory. When the effect of explicit retrieval on control performance was reduced by using a low-level encoding task, priming was the same for amnesic patients and controls. The authors suggest that LOP effects in word-completion priming tasks reflect the influence of explicit retrieval, which can be used usefully by control Ss but much less so by amnesic patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Word memory test performance in amnesic patients with hippocampal damage.

Many symptom validity tests (SVTs) assess performance validity via declarative memory paradigms. One widely used SVT, the Word Memory Test (WMT), uses a variety of memory tests to assess performance. It is well known that declarative memory requires the hippocampus and related medial temporal lobe structures. In the present study, WMT performance was examined in nonlitigating amnesic subjects (n = 3) with well-documented focal bilateral hippocampal atrophy who were nondemented and otherwise cognitively unimpaired compared with matched controls. The amnesic subjects had no external incentives. Amnesic subjects performed significantly below the level of matched comparison subjects but above established cutoff scores on the immediate recognition and delay recognition subtests and consistency component. In contrast, the amnesic subjects were impaired relative to our comparison subjects on the multiple-choice, paired associate, free-recall, and long delay free-recall subtests and had extremely low performance on these measures. Thus, there was a differential effect of hippocampal damage on WMT performance where the recognition subtests were performed within the normal range, yet the free recall was profoundly impaired in amnesic subjects. Such an approach where SVT performance is assessed in populations with well-known cognitive impairments adds breadth to SVT clinical interpretations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of the striatum, cerebellum and frontal lobes in the automatization of a repeated visuomotor sequence of movements

Recently, Doyon et al. [20] demonstrated that lesions to both the striatum and to the cerebellum in humans produce a similar deficit in the learning of a repeated visuomotor sequence, which occurs late in the acquisition process. We now report the results of two experiments that were designed to examine whether this impairment was due to a lack of automatization of the repeating sequence of finger movements by using a dual-task paradigm and by testing for long-term retention of this skill. In Experiment 1, the performance of groups of patients with Parkinson's disease, or with damage to the cerebellum or to the frontal lobes, was compared to that of matched control subjects on the Repeated Sequence Test (primary task) and the Brooks' Matrices Test (secondary task). These two tests were administered concomitantly in both early and late learning phases of the visuomotor sequence. Overall, the groups did not differ in their ability to execute the primary task. By contrast, in accordance with the predictions, patients in Stages 2-3 of Parkinson's disease or with a cerebellar lesion failed to reveal the expected increase in performance on the secondary task seen with learning, suggesting that the latter groups of patients did not have access to the same level of residual cognitive resources to complete the matrices compared to controls. In Experiment 2, the same groups of patients and control subjects were retested again 10-18 months later. They were given four blocks of 100 trials each of the repeating sequence task, followed by a questionnaire and a self-generation task that measured their declarative knowledge of that sequence. The results revealed a long-term retention impairment only in patients who changed from Stage I to Stage II of the disease (suggesting further striatal degeneration) during the one-year interval, or who had a cerebellar lesion. By contrast, performance of the three clinical groups did not differ from controls on declarative memory tests. These findings suggest that both the striatum and the cerebellum participate to the automatization process during the late (slow) learning stage of a sequence of finger movements and that these structures also play a role in the neuronal mechanism subserving long-term retention of such a motor sequence behavior.     

Images of medial temporal lobe functions in human learning and memory

Investigations of the neural basis of mammalian memory have focused more often on the medial temporal lobe (MTL) than on any other brain region. In humans, the amnesic syndrome revealed the essential importance of the multiple structures located in the MTL system for declarative memory (the remembrance of events and facts). Other neural systems mediate procedural forms of memory, including delay eyeblink conditioning, which depends on the cerebellum, and cognitive skill learning, which depends on the striatum. We review three functional imaging studies that reveal different patterns of MTL activation associated with declarative and procedural memory tasks. One study shows separate MTL activations during the encoding or retrieval of declarative memories. A second study shows MTL activation that occurs in parallel with cerebellum-dependent delay eyeblink conditioning, but does not appear to influence that form of procedural memory. A third study reveals suppression of the MTL during striatum-dependent cognitive skill learning. These studies provide images of MTL activations that are correlated with, independent from, or antagonistic to memory performance.     

Probabilistic contingency learning with limbic or prefrontal damage.

A fundamental capacity of the human brain is to learn relations (contingencies) between environmental stimuli and the consequences of their occurrence. Some contingencies are probabilistic; that is, they predict an event in some situations but not in all. Animal studies suggest that damage to limbic structures or the prefrontal cortex may disturb probabilistic learning. The authors studied the learning of probabilistic contingencies in amnesic patients with limbic lesions, patients with prefrontal cortex damage, and healthy controls. Across 120 trials, participants learned contingent relations between spatial sequences and a button press. Amnesic patients had learning comparable to that of control subjects but failed to indicate what they had learned. Across the last 60 trials, amnesic patients and control subjects learned to avoid a noncontingent choice better than frontal patients. These results indicate that probabilistic learning does not depend on the brain structures supporting declarative memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)