Anatomy of verbal memory: a functional MRI study

Reduced Enhancement of Memory for Faces Encoded by Semantic and Socioemotional Processes in Patients with Parkinson's Disease

OBJECTIVES

Patients with Parkinson's disease (PD) exhibit impaired semantic and socioemotional processes, which are thought to be related to dysfunctions in the fronto-striatal circuit. However, little is known about how the memory enhancement by these processes was reduced in PD. The present study investigated this issue.

METHODS

The retrieval performance of face memories encoded by semantic and socioemotional processes was compared between 24 PD patients and 24 age-matched healthy controls (HC). During encoding, participants were presented with unfamiliar faces and made judgment about them in three encoding conditions of semantic judgment (Semantics), attractiveness judgment (Attractiveness), and form judgment (Form). In Semantics, participants rated to what degree each face looked like an office worker, whereas in Attractiveness, participants rated how attractive each face was. The Form condition as a control required participants to judge the shape of each face. During retrieval after encoding, participants made old or new judgment for target and distracter faces.

RESULTS

In HC, the retrieval of faces encoded by Semantics and Attractiveness was significantly more accurate than that encoded by Form, whereas this memory enhancement was not identified in PD. In addition, individual scores in frontal lobe function and long-term memory correlated with the retrieval performance of memories encoded in Semantics and Attractiveness but not Form.

CONCLUSIONS

These findings suggest that the processing of semantic and socioemotional signals conveyed from faces could be impaired in PD and that the impairment of these processes could decrease the enhancement of face memories by semantic and socioemotional elaborations.

Effects of supratentorial and infratentorial tumor location on cognitive functioning of children with brain tumor

PURPOSE

Effects of tumor location on cognitive performance of patients with brain tumor are controversial: some studies reported higher risks related to supratentorial locations, some to infratentorial locations, and still others did not find any differences. We aimed to address this issue by comparing school-aged children with supratentorial or infratentorial tumor with respect not only to cognitive outcomes but also to the associations between core cognitive domains and academic abilities.

METHODS

32 children with infratentorial tumor and 22 with supratentorial tumor participated in the study. To detect relationships among cognitive domains, we tested which neuropsychological variable(s) predicted academic skills, controlling for the effects of radiotherapy and time since diagnosis.

RESULTS

Radiotherapy and time since diagnosis, but not tumor location, predicted cognitive outcomes. Radiotherapy negatively influenced attention and executive functioning, as well as reading speed and arithmetic operations accuracy. Unexpectedly, longer time since diagnosis was associated with improvement in attention and reading speed. Tumor location showed an effect on the relationships between core cognitive domains and academic skills: verbal and visual-spatial memory influenced reading and mathematical performance in supratentorial patients; in infratentorial patients, an only effect of visual-spatial memory on mathematical performance was detected.

CONCLUSIONS

Tumor location seems not to influence cognitive performance, while radiotherapy constitutes a key risk factor for cognitive impairment. Attentional and reading abilities may improve over time, possibly due to the weakening of cancer care effects. Different patterns of cognitive associations seem to characterize supratentorial and infratentorial patients, probably associated with different neuroplastic reorganization processes after tumor occurrence.

Transcranial Direct Current Stimulation Improves Audioverbal Memory in Stroke Patients

OBJECTIVE

The aim of this study was to investigate whether anodal transcranial direct current stimulation over the left temporoparietal area improved audioverbal memory performance in stroke patients.

DESIGN

Twelve stroke patients with audioverbal memory impairment participated in a single-masked, crossover, and sham-controlled experiment. The anodal or sham transcranial direct current stimulation was applied during the Rey Auditory Verbal Learning Test, which evaluates the ability to recall a list of 15 heard words over five trials. The number of correctly recalled words was compared between the anodal and sham conditions and the influence of transcranial direct current stimulation on serial position effect of the 15 words was also examined.

RESULTS

The increase in the number of correctly recalled words from the first to the fifth trial was significantly greater in the anodal condition than in the sham condition (P < 0.01). There was a significant difference (P < 0.01) between the anodal and sham conditions in the number of correctly recalled words within the first five words (primacy region) over the second to fifth trial trials, but not in the middle (next five words) or recency (last five words) regions.

CONCLUSIONS

Anodal transcranial direct current stimulation over the left temporoparietal area improved audioverbal memory performance and induced the primacy effect in stroke patients.

A new semantic list learning task to probe functioning of the Papez circuit

INTRODUCTION

List learning tasks are powerful clinical tools for studying memory, yet have been relatively underutilized within the functional imaging literature. This limits understanding of regions such as the Papez circuit that support memory performance in healthy, nondemented adults.

METHOD

The current study characterized list learning performance in 40 adults who completed a semantic list learning task (SLLT) with a Brown-Peterson manipulation during functional magnetic resonance imaging (fMRI). Cued recall with semantic cues and recognition memory were assessed after imaging. Internal reliability, convergent, and discriminant validity were evaluated.

RESULTS

Subjects averaged 38% accuracy in recall (62% for recognition), with primacy but no recency effects observed. Validity and reliability were demonstrated by showing that the SLLT was correlated with the California Verbal Learning Test (CVLT), but not with executive functioning tests, and by high intraclass correlation coefficient across lists for recall (.91). fMRI measurements during encoding (vs. silent rehearsal) revealed significant activation in bilateral hippocampus, parahippocampus, and bilateral anterior and posterior cingulate cortex. Post hoc analyses showed increased activation in anterior and middle hippocampus, subgenual cingulate, and mammillary bodies specific to encoding. In addition, increasing age was positively associated with increased activation in a diffuse network, particularly frontal cortex and specific Papez regions for correctly recalled words. Gender differences were specific to left inferior and superior frontal cortex.

CONCLUSIONS

This is a clinically relevant list learning task that can be used in studies of groups for which the Papez circuit is damaged or disrupted, in mixed or crossover studies at imaging and clinical sites.

Neurocognition in individuals at high familial risk of mood disorders with or without subsequent onset of depression

BACKGROUND

Neurocognitive performance deficits have been observed in mood disorder patients and their unaffected relatives and may therefore qualify as endophenotypes. However, the precise time course of neurocognitive deficits has not been studied so that it is unknown whether neurocognitive abnormalities reflect the early effects of familial vulnerability to mood disorders or if they emerge at illness onset.

METHOD

A neuropsychological test battery was administered at baseline and after a 2-year follow-up interval in 111 initially unaffected young adults at high familial risk of mood disorders and 93 healthy controls (HC). During the follow-up period, 20 high-risk subjects developed major depressive disorder (HR-MDD), with the remainder remaining well (HR-well). Linear mixed-effects models were used to investigate differences and longitudinal changes in the domains of attentional processing, working memory, verbal learning and memory, and cognitive flexibility.

RESULTS

Reduced long delay verbal memory and extradimensional set-shifting performance across both time points were found in the HR-well group relative to controls. The HR-MDD group displayed decreased extradimensional set-shifting abilities across both time points as compared with the HC group only. There were no significant performance differences between the two high-risk groups.

CONCLUSIONS

Reduced verbal memory and cognitive flexibility are familial trait markers for vulnerability to mood disorders in individuals with a close family history of bipolar disorder. Both neurocognitive performance deficits appear to be relatively stable over a 2-year time period and do not appear to be linked to the onset of MDD. These findings support their use as stable quantitative endophenotypes for mood disorders.

Segregating cognitive functions within hippocampal formation: a quantitative meta-analysis on spatial navigation and episodic memory

The most important cognitive domains where hippocampal formation is crucially involved are navigation and memory. Some evidence suggests that different hippocampal subregions mediate these domains. However, a quantitative meta-analysis on neuroimaging studies of spatial navigation versus memory is lacking. By means of activation likelihood estimation (ALE), we investigate concurrence of brain regions activated during spatial navigation encoding and retrieval as well as during episodic memory encoding and retrieval tasks in humans. During encoding in spatial navigation, activity was located in more posterior regions of the hippocampal formation, whereas episodic memory encoding was located in more anterior regions. Retrieval in spatial navigation was more strongly lateralized to the right compared to episodic memory retrieval. Within studies on spatial navigation retrieval, immediate recall was located more posterior and delayed recall more anterior. Overlap between concurrence of activation in spatial navigation and episodic memory was rather limited in comparison to uniquely involved regions. This argues in favor of two distinct networks, one for spatial navigation the other for episodic memory within the hippocampal formation.

MDMA intoxication and verbal memory performance: a placebo-controlled pharmaco-MRI study

The aim of the present study was to identify the neural substrate underlying memory impairment due to a single dose of MDMA (3,4-methylenedioxymethamphetamine) by means of pharmaco-MRI. Based on previous behavioral results it was hypothesized that this deficit could be attributed to a specific influence of MDMA on encoding. Fourteen Ecstasy users participated in this double-blind, placebo-controlled, within-subject study with two treatment conditions: MDMA (75 mg) and placebo. Memory performance was tested by means of a word learning task including two words lists, one addressing reading processes (control task, CWL) and a second (experimental task, EWL) addressing encoding and reading processes. Behavioral data showed that under the influence of MDMA, EWL performance was worse than placebo. Imaging data showed that Encoding was situated mainly in (pre)frontal, temporal and parietal areas. MDMA by Encoding interaction was situated in three areas: the left middle frontal gyrus (BA10), the right fusiform gyrus (BA19), and the left cuneus (BA18). Behavioral and functional data only correlated in BA10. It appeared that EWL performance caused BOLD signal change in BA10 during placebo treatment but not during MDMA intoxication. It is concluded that MDMA influences middle frontal gyrus processes resulting in impoverished memory encoding.

Enhancement of declarative memory performance following a daytime nap is contingent on strength of initial task acquisition

STUDY OBJECTIVES

In this study we examined the benefit of a daytime nap containing only NREM sleep on the performance of three declarative memory tasks: unrelated paired associates, maze learning, and the Rey-Osterrieth complex figure. Additionally, we explored the impact of factors related to task acquisition on sleep-related memory processing. To this end, we examined whether testing of paired associates during training leads to sleep-related enhancement of memory compared to simply learning the word pairs without test. We also examined whether strength of task acquisition modulates sleep-related processing for each of the three tasks. SUBJECTS AND PROCEDURE: Subjects (11 male, 22 female) arrived at 11:30, were trained on each of the declarative memory tasks at 12:15, and at 13:00 either took a nap or remained awake in the sleep lab. After the nap period, all subjects remained in the lab until retest at 16:00.

RESULTS

Compared to subjects who stayed awake during the training-retest interval, subjects who took a NREM nap demonstrated enhanced performance for word pairs that were tested during training, but not for untested word pairs. For each of the three declarative memory tasks, we observed a sleep-dependent performance benefit only for subjects that most strongly acquired the tasks during the training session.

CONCLUSIONS

NREM sleep obtained during a daytime nap benefits declarative memory performance, with these benefits being intimately tied to how well subjects acquire the tasks and the way in which the information is acquired.

Electrophysiological correlates of deficient encoding in a case of post-anoxic amnesia

Little is known about the initial stages of information processing in amnesia as compared to normal memory. In this study, we used electrical spatiotemporal mapping to compare cortical activation during encoding and recognition in a 56-year-old patient with severe, chronic post-anoxic amnesia and an age-matched control group. Event-related potentials were recorded as the subjects performed a continuous recognition task composed of meaningful designs. Activation in the control group rapidly progressed through eight different electrocortical configurations over 700 ms after onset of new stimuli. In contrast, activation in the amnesic patient was highly monotonous: it showed varying electrocortical patterns only during the first 150 ms but then remained abnormally stable for the remainder of the analysed time window. Electrical source localisation revealed that the patient failed to activate distributed cortical networks and that his processing was confined to visual areas. The present study suggests that the rapid activation of distributed cortical networks is critical for efficient encoding.

Age does not increase rate of forgetting over weeks--neuroanatomical volumes and visual memory across the adult life-span

The aim of the study was to investigate whether age affects visual memory retention across extended time intervals. In addition, we wanted to study how memory capabilities across different time intervals are related to the volume of different neuroanatomical structures (right hippocampus, right cortex, right white matter). One test of recognition (CVMT) and one test of recall (Rey-Osterrieth Complex Figure Test) were administered, giving measures of immediate recognition/recall, 20-30 min recognition/recall, and recognition/recall at a mean of 75 days. Volumetric measures of right hemisphere hippocampus, cortex, and white matter were obtained through an automated labelling procedure of MRI recordings. Results did not demonstrate a steeper rate of forgetting for older participants when the retention intervals were increased, indicating that older people have spared ability to retain information in the long-term store. Differences in neuroanatomical volumes could explain up to 36% of the variance in memory performance, but were not significantly related to rates of forgetting. Cortical volume and hippocampal volume were in some cases independent as predictors of memory function. Generally, cortical volume was a better predictor of recognition memory than hippocampal volume, while the 2 structures did not differ in their predictive power of recall abilities. While neuroanatomical volumetric differences can explain some of the differences in memory functioning between younger and older persons, the hippocampus does not seem to be unique in this respect.