Biomedical subjects

Amélie M Achim

Publications and source records attributed to Amélie M Achim.

8 recordsLinked to original sources

PubMed2006

Associative memory encoding and recognition in schizophrenia: an event-related fMRI study.

BACKGROUND: We used an event-related functional Magnetic Resonance Imaging (fMRI) approach to examine the neural basis of the selective associative memory deficit in schizophrenia. METHODS: Fifteen people with schizophrenia and 18 controls were scanned during a pair and item memory encoding and recognition task. During encoding, subjects studied items and pairs of visual objects. In a subsequent retrieval task, participants performed an item recognition memory test (old/new decisions) and an associative recognition test (intact/rearranged decisions). The fMRI analysis of the recognition data was restricted to correct items only and a random effects model was used. RESULTS: At the behavioral level, both groups performed equally well on item recognition, whereas people with schizophrenia demonstrated lower performance on associative recognition relative to the control group. At the brain level, the comparison between associative and item encoding revealed greater activity in the control group in the left prefrontal cortex and cingulate gyrus relative to the schizophrenia group. During recognition, greater left dorsolateral prefrontal and right inferior prefrontal activations were observed in the control group relative to the schizophrenia group. CONCLUSION: This fMRI study implicates the prefrontal cortex among other brain regions as the basis for the selective associative memory encoding and recognition deficit seen in schizophrenia.

Adult↗

PubMed2005

Associative interference does not affect recognition memory in schizophrenia.

Studies of schizophrenia suggest a specific impairment in binding different parts of a memory event into a cohesive whole, a finding that may account for the reported preferential deficits in associative recognition memory relative to item recognition. As a further test of this hypothesis and to exert greater control over task differences, we used a recognition memory interference test in which participants encoded landscape pictures that had each been divided into three segments. During encoding, subjects were presented with one segment from each of the landscapes. Then, an interference generating task followed consisting of the presentation of the second segment from half of the landscapes. Finally, a forced-choice recognition memory test consisted of the presentation of each encoding picture stimulus concurrently with the related third segment that had never been presented before. Thus, for half of the stimuli, additional related information was encoded and this is known to interfere with recognition memory. However, an impaired ability to bind this related information should reduce the interfering effect of associated stimuli. Thirty-five schizophrenia patients and 37 healthy controls were administered this memory interference task. A significant interaction between groups and recognition conditions was found with a significant interference effect observed for controls (performance dropping from 76% to 62%) but not for patients (performance remaining unchanged from 66% to 68%). These results provide further support for faulty associative memory processing in schizophrenia.

Adult↗

PubMed2005

Cognitive and clinical moderators of recognition memory in schizophrenia: a meta-analysis.

Recognition memory performance in schizophrenia has been shown to vary greatly across studies. To identify the conditions under which recognition memory is significantly impaired, we used a meta-analytic strategy to quantify the moderating effects of several cognitive and clinical variables. Eighty-four studies (from 1965 to July 2003) provided recognition memory data for both a schizophrenia and control group. The overall group comparison for recognition memory yielded a significant mean weighted effect size of d=0.76. Material specificity was the most significant cognitive variable found, with patients exhibiting greater impairment for figural than verbal recognition. A yes-no recognition format and auditory encoding also led to significantly greater effect sizes for recognition memory relative to forced-choice recognition tests and visual encoding, respectively. Furthermore, the effect size for recognition memory as measured by false alarm was smaller than the effect size as measured by hit rate or by d-prime and its related measures. Among clinical variables that were associated with higher effect sizes, chronicity was the most significant, but different trends linking poor performance to negative symptoms and general symptomatology were also observed. Thus, a recognition memory deficit moderated by both cognitive and clinical variables is clearly present in schizophrenia.

Cognition Disorders↗

PubMed2005

Neural correlates of memory for items and for associations: an event-related functional magnetic resonance imaging study.

Although results from cognitive psychology, neuropsychology, and behavioral neuroscience clearly suggest that item and associative information in memory rely on partly different brain regions, little is known concerning the differences and similarities that exist between these two types of information as a function of memory stage (i.e., encoding and retrieval). We used event-related functional magnetic resonance imaging to assess neural correlates of item and associative encoding and retrieval of simple images in 18 healthy subjects. During encoding, subjects memorized items and pairs. During retrieval, subjects made item recognition judgments (old vs. new) and associative recognition judgments (intact vs. rearranged). Relative to baseline, item and associative trials activated bilateral medial temporal and prefrontal regions during both encoding and retrieval. Direct contrasts were then performed between item and associative trials for each memory stage. During en- coding, greater prefrontal, hippocampal, and parietal activation was observed for associations, but no significant activation was observed for items at the selected threshold. During recognition, greater activation was observed for associative trials in the left dorsolateral prefrontal cortex and superior parietal lobules bilaterally, whereas item recognition trials showed greater activation of bilateral frontal regions, bilateral anterior medial temporal areas, and the right temporo-parietal junction. Post hoc analyses suggested that the anterior medial temporal activation observed during item recognition was driven mainly by new items, confirming a role for this structure in novelty detection. These results suggest that although some structures such as the medial temporal and prefrontal cortex play a general role in memory, the pattern of activation in these regions can be modulated by the type of information (items or associations) interacting with memory stages.

Adult↗

PubMed2005

Episodic memory-related activation in schizophrenia: meta-analysis.

BACKGROUND: Numerous studies have examined the neural correlates of episodic memory deficits in schizophrenia, yielding both consistencies and discrepancies in the reported patterns of results. AIMS: To identify in schizophrenia the brain regions in which activity is consistently abnormal across imaging studies of memory. METHOD: Data from 18 studies meeting the inclusion criteria were combined using a recently developed quantitative meta-analytic approach. RESULTS: Regions of consistent differential activation between groups were observed in the left inferior prefrontal cortex, medial temporal cortex bilaterally, left cerebellum, and in other prefrontal and temporal lobe regions. Subsequent analyses explored memory encoding and retrieval separately and identified between-group differences in specific prefrontal and medial temporal lobe regions. CONCLUSIONS: Beneath the apparent heterogeneity of published findings on schizophrenia and memory, a consistent and robust pattern of group differences is observed as a function of memory processes.

Brain↗

PubMed2004

Dorsolateral prefrontal cortex involvement in memory post-retrieval monitoring revealed in both item and associative recognition tests.

Post-retrieval monitoring is a process that contributes to episodic memory retrieval by allowing people to evaluate the relevance of retrieved information in relation to the task requirements. Previous studies have suggested that post-retrieval monitoring is supported by the dorsolateral prefrontal cortex (DLPFC). In this study, we used functional magnetic resonance imaging (fMRI) to evaluate involvement of the DLPFC in post-retrieval monitoring in two different recognition tests (item recognition and associative recognition). The item recognition memory test required subjects to make old/new judgments and the associative recognition memory test required them to make intact/rearranged judgments. Because the post-retrieval monitoring demand increases during old (hits) relative to new (correct rejections) item recognition trials, and also during rearranged (correct rejections) relative to intact (hits) associative recognition trials, we evaluated the brain activation associated with the interaction of Memory test (item versus associative) by Recognition trial (hit versus correct rejection). As expected, the DLPFC was activated in this interaction as well as for both old relative to new item recognition trials and rearranged relative to intact associative recognition trials. This study provides strong evidence that DLPFC activation supports post-retrieval monitoring across different types of recognition tasks.

Adult↗

PubMed2004

The interfering effect of related events on recognition memory discriminability: a functional magnetic resonance imaging study.

Retrieval of information from memory often involves the selection of an event among competing related events, a process that frequently gives rise to interference effects. The present study used a forced-choice recognition test to identify neural correlates of the interfering effect of related events on recognition memory discriminability. Participants encoded landscape pictures divided into three segments. One segment was presented during encoding, and a forced-choice recognition task contrasted a studied and a nonstudied segment for each landscape. For half of the landscapes, the third segment was presented between encoding and recognition tasks to induce associative interference by reducing recognition discriminability. A behavioral study with 40 subjects yielded a significant difference in the correct recognition rate between control and interference trials (76% and 64%, respectively, p<0.001). A subsequent event-related fMRI study with 16 subjects yielded significant activations for correct interference recognition trials relative to control trials in left superior parietal regions, which suggests that these regions play a role in the representation of stimuli and associated information. The opposite contrast yielded significant activations in inferior prefrontal regions bilaterally, right dorsolateral prefrontal cortex and right parahippocampal cortex. Since this contrast was conducted using only correctly recognized trials, these findings could reflect an index of memory discriminability or saliency which could influence conscious recollection.

Adult↗

PubMed2003

Is associative recognition more impaired than item recognition memory in Schizophrenia? A meta-analysis.

Item recognition memory judgment can be based on two processes: item familiarity and/or the conscious recollection of the initial event. On the other hand, associative recognition relies preferably on conscious recollection. Since evidence points to a specific deficit of conscious recollection in schizophrenia, these patients could show greater impairment during associative recognition tasks relative to item recognition tasks. A meta-analysis of 23 studies of recognition memory in schizophrenia was conducted to test this hypothesis. The impairment is indeed 20% greater (p=0.04) for associative recognition relative to item recognition. This study supports the hypothesis of a specific conscious recollection deficit underlying episodic memory impairment in schizophrenia.

Association↗