The differentiation of semantic dementia and frontal lobe dementia (temporal and frontal variants of frontotemporal dementia) from early Alzheimer's disease: a comparative neuropsychological study

The authors compared age-matched groups of patients with the frontal and temporal lobe variants of frontotemporal dementia (FTD; dementia of frontal type [DFT] and semantic dementia), early Alzheimer's disease (AD), and normal controls (n = 9 per group) on a comprehensive neuropsychological battery. A distinct profile emerged for each group: Those with AD showed a severe deficit in episodic memory with more subtle, but significant, impairments in semantic memory and visuospatial skills; patients with semantic dementia showed the previously documented picture of isolated, but profound, semantic memory breakdown with anomia and surface dyslexia but were indistinguishable from the AD group on a test of story recall; and the DFT group were the least impaired and showed mild deficits in episodic memory and verbal fluency but normal semantic memory. The frontal and temporal presentations of FTD are clearly separable from each other and from early AD.     

Working memory and new learning following pediatric traumatic brain injury

Working memory (WM), the ability to monitor, process and maintain task relevant information on-line to respond to immediate environmental demands, is controlled by frontal systems (D'Esposito et al., 2006), which are particularly vulnerable to damage from a traumatic brain injury (TBI). This study employed the adult-based Working Memory model of Baddeley and Hitch (1974) to examine the relationship between working memory function and new verbal learning in children with TBI. A cross-sectional sample of 36 school-aged children with a moderate to severe TBI was compared to age-matched healthy Controls on a series of tasks assessing working memory subsystems: the Phonological Loop (PL) and Central Executive (CE). The TBI group performed significantly more poorly than Controls on the PL measure and the majority of CE tasks. On new learning tasks, the TBI group consistently produced fewer words than Controls across the learning and delayed recall phases. Results revealed impaired PL function related to poor encoding and acquisition on a new verbal learning task in the TBI group. CE retrieval deficits in the TBI group contributed to general memory dysfunction in acquisition, retrieval and recognition memory. These results suggest that the nature of learning and memory deficits in children with TBI is related to working memory impairment.     

Memory encoding and retrieval in frontotemporal dementia and Alzheimer's disease

Memory encoding and retrieval strategies were assessed in patients with behavior-executive variant frontotemporal dementia (FTD), language variant FTD, and Alzheimer's disease (AD) using verbal and visuospatial supraspan learning tests. FTD patients obtained higher free recall, cued recall, and recognition scores than AD patients. Comparison of free recall scores with cued recall and recognition scores was similar in the 3 dementia groups. Groups did not differ in semantic clustering strategies during learning, but serial-order recall was more common in FTD patients. These data do not support the idea that FTD patients' poor memory is due to a selective retrieval disorder, though FTD patients may fail to implement sophisticated organizational strategies during learning. FTD patients' retained capacity for encoding new information into long-term declarative memory is likely due to relatively spared medial temporal lobe involvement.     

Patterns of verbal long-term and working memory performance reveal deficits in strategic processing in children with frontal infarcts related to sickle cell disease

Frontal brain regions are thought to mediate strategic processes that facilitate memory. We hypothesized that children with frontal cerebral infarcts related to sickle cell disease (SCD) would exhibit impairments in long-term and working memory as a result of disruptions in strategic processing. Word-list learning and digit span tasks were used to assess verbal memory and strategic processing in 21 children with SCD without infarcts (controls) and in 10 children with SCD with frontal infarcts. On the word-list learning task, children with frontal infarcts performed more poorly in terms of learning and free recall, although recognition and cued recall were adequate; this pattern suggested intact encoding and storage with impaired retrieval. Children with frontal infarcts performed more poorly on backward digit span, although forward digit span was adequate; this pattern suggested intact maintenance with impaired manipulation of information in working memory. Overall, these findings support the notion that disruptions in strategic processing contribute to memory impairments in children with frontal infarcts.     

Recall and recognition memory deficits in depression.

The aim of the present study was to establish the nature of memory deficits of depressive subjects in word learning tests. A word learning test consisting of 1, 3 or 5 learning trials was used. We found that patients were characterized by inferior memory recall compared to controls when 5 learning trials were given. Patients performed significantly slower than controls on a recognition test but both patients and controls recognized the same number of words. This suggests that the memory deficits that are present in many depressive subjects may be restricted to impaired active retrieval from memory. A second experiment revealed that recognition memory and delayed recall as well as immediate recall were impaired in depressive patients after 1 learning trial. These short-comings vanished after 3 trials, except for immediate recall. These data suggest that not only retrieval but also encoding of information into memory may be impaired in depression, especially in the beginning of a task when demands on cognitive effort are high. The results are discussed in terms of resource allocation and demands on effort that may change in the course of a task.     

An investigation of visuospatial memory impairment in children with attention deficit hyperactivity disorder (ADHD), combined type

BACKGROUND: Memory impairment is not considered a core cognitive feature of attention deficit hyperactivity disorder, combined type (ADHD-CT), although it is associated with impairments in attentional and executive functions. This study investigates visuospatial memory impairment, in particular encoding and retrieval aspects, in children with ADHD-CT who are stimulant-medication naive and medicated with stimulant medication. METHOD: A cross-sectional study of visuospatial memory in 6- to 12-year-old children with stimulant-medication-naive ADHD-CT (n = 62) and medicated ADHD-CT (n = 58) compared to an age- and gender-matched healthy control group (n = 39) was completed. RESULTS: Both medication-naive and medicated ADHD-CT groups demonstrated subtle yet significant impairment in visuospatial memory. The memory impairment was delay-independent, which, along with other factors, suggest dysfunction of the encoding rather than retrieval phase of visuospatial memory. CONCLUSIONS: Careful study of large ADHD-CT samples does detect deficits in a visuospatial memory task, but these reflect attentional deficits rather than being specifically due to dysfunction of the medial temporal lobe explicit memory system. Children with ADHD-CT may benefit from cognitive and behavioural strategies focused on improving encoding of relevant information rather than retrieval strategies.     

Evidence for intact semantic representations in patients with frontal lobe lesions

Patients with frontal lobe lesions and control participants were assessed on 2 tests of semantic knowledge. In the triadic comparison task, participants were shown all possible triplets of 12 animal names and judged which 2 of each triplet were most alike. In the ordered similarity task, participants rank ordered animals in terms of their similarity to a target animal. For both tasks, semantic structure--derived from multidimensional scaling techniques--revealed similar representations in patients with frontal lobe lesions and control participants. Additional pathfinder analyses also produced networks that did not differ between groups. These patients exhibited intact semantic knowledge despite deficits on tests of free recall and verbal fluency that involved the same semantic category and exemplars. Thus, intact representation of semantic knowledge in frontal patients stands in contrast to their marked deficits in strategic retrieval of semantic knowledge.     

Recreational use of 3,4-methylenedioxymethamphetamine (MDMA) or 'ecstasy': evidence for cognitive impairment

BACKGROUND: It has recently been shown that 3,4-methylenedioxymethamphetamine (MDMA) or 'ecstasy' causes long-lasting alterations to brain structure and function in animals, and there is mounting evidence that recreational users of the drug show impairments in some aspects of cognitive functioning including memory for verbal information. The present study investigates possible effects on other cognitive functions and explores the temporal course of development and resolution of these impairments by comparing novice, regular and abstaining users with a matched group of non-users. METHODS: Eighty participants categorized as non-users, novice users, regular users or currently abstinent users of MDMA were assessed on tests of verbal IQ, reversed digit span, immediate and delayed recall of a prose passage and of a complex geometric figure and verbal fluency. RESULTS: The four groups were well-matched for verbal IQ and on demographic variables. They differed in frequency of cannabis use over the last month, but this did not correlate with any cognitive test scores. All three groups of MDMA users showed significantly poorer verbal fluency and immediate and delayed prose recall than non-users. Days since last use and total lifetime consumption of MDMA made separate contributions to the variance in recall scores, accounting jointly for almost half of the variance in delayed recall. By contrast, the groups did not differ on either visual recall or reversed digit span. CONCLUSIONS: The observed deficits provide further evidence of impairments of verbal but not visual memory in MDMA users, and indicate that the deficits are not attributable either to differences in general reasoning ability or to impairment of working memory. The data further suggest that the observed impairments may be attributable to a combination of reversible acute effects of MDMA resolving over a period of 2-3 weeks and more long-term changes associated with extent of lifetime consumption.     

Verbal memory tests in the differential diagnosis of depression and dementia: discriminative power of seven test variations.

The many tasks for the assessment of verbal memory differ widely in features of presentation and retrieval. In this study, seven common memory tasks (immediate and delayed free recall, randomized presentation, selective reminding, serial recall, recognition after short and long delay) were compared for their discriminative power between depressed, demented, and healthy elderly subjects. Tasks that require little cognitive capacity were hypothesized to be particularly useful to differentiate the patient groups. Demented and depressed patients demonstrated deficits on all tests, the demented being more severe. Only recognition after long and short delay, and delayed recall distinguished demented from depressed patients. Delayed retrieval tasks were more useful to discriminate patient groups than tasks that require little cognitive capacity.     

Impaired memory for faces and social scenes in autism: clinical implications of memory dysfunction.

A clinical memory test, the Wechsler Memory Scale-III (WMS-III), was used to study the auditory and visual memory of 29 high-functioning adults with autism and 34 group-matched normal controls. The individuals with autism performed as well as the controls on immediate and delayed memory for word pairs and stories and on a verbal working memory task. The autism group was impaired on immediate and delayed recall of faces and of family scenes and had impaired spatial working memory. The integrity of verbal working memory and impaired spatial working memory is consistent with the findings of other studies and may reflect the greater computational demands of the spatial task. Most importantly, the deficits in memory for faces and common social scenes, complex visual/spatial stimuli, demonstrate the contribution of memory dysfunction in autism to deficits in real life function.     

Schizophrenic syndromes, cognitive performance and neurological dysfunction

In a sample of chronic schizophrenic patients, a group of symptoms which included poverty of speech and lack of spontaneous movement was found to be associated with poor performance in tests of conceptual thinking, object naming and long-term memory, and also with cortical neurological signs. A second group of symptoms which included formal thought disorder and inappropriate affect was associated with poor performance in tests of concentration, immediate recall and word learning, and with cortical neurological signs. The findings suggest that these two syndromes are associated with dysfunction at two different sites within the frontal lobes. A third group of symptoms, comprising various delusions and hallucinations, was associated with poor figure-ground perception, and might reflect temporal lobe dysfunction.     

Dissociations in hippocampal and frontal contributions to episodic memory performance

The hippocampus and frontal lobes both contribute to episodic memory performance. In the present study, the authors evaluated the relative contributions of hippocampus, frontal lobes, anterior temporal cortex, and posterior cortex to memory performance in neurodegenerative patients and normal older controls. Subjects (n=42) were studied with structural MRI and a memory paradigm that measured delayed recall, semantic clustering during recall, recognition discriminability, and recognition response bias. Data were analyzed with multiple regression. Consistent with the authors' hypotheses, hippocampal volumes were the best predictor of delayed recall and recognition discriminability, whereas frontal volumes were the best predictor of semantic clustering and response bias. Smaller frontal volumes were associated with less semantic clustering during recall and a more liberal response bias. Results indicate that hippocampal and frontal contributions to episodic memory can be dissociated, with the hippocampus more important for memory accuracy, and frontal structures more important for strategic processing and decision making.     

Specificity of frontal dysfunctions in relapsing-remitting multiple sclerosis.

Various studies have reported deficits in frontal cognitive functions in patients with multiple sclerosis (MS). However, the frontal deficit is not uniform and is often very subtle. The aim of this study was to assess frontal functions in a broad sample of patients with relapsing-remitting multiple sclerosis at the mild-to-moderate stage. The sample included a series of 165 patients. We used a test battery covering the frontal functions that have been described as being altered in MS. Significant differences were found between the patient group and healthy controls on the WAIS Arithmetic subtest, the PASAT, category word recall and the number of trials required to reach the first category of the WCST. In conclusion, we observed significant differences with respect to the control group in terms of information processing speed and working memory. These functions involve connections between the frontal lobe and other brain regions.     

Arousal and cortisol interact in modulating memory consolidation in healthy young men

Animal studies indicate that adrenal glucocorticoids enhance memory consolidation while impairing memory retrieval. In humans, beneficial effects on consolidation have been observed infrequently. In the current double-blind study, subjects (N = 29) received placebo or cortisol (30 mg) 10 min before viewing emotionally arousing or neutral pictures. Cortisol treatment had no effects on immediate recall. In the 24-hr delayed recall condition, cortisol led to an enhanced emotional memory facilitation because of decreased neutral and increased emotional memory recall. No effects of cortisol treatment were observed for recognition memory or mood. Results support the notion that glucocorticoids specifically enhance the consolidation of emotional material.     

Neuropsychological functioning in HIV-positive African-American women with a history of drug use.

This preliminary investigation examined neuropsychological performance in a sample of human immunodeficiency virus (HIV)-positive and HIV-negative African-American women with a history of drug use. The study population was comprised of 10 HIV-negative, 9 asymptomatic HIV-positive, 13 symptomatic HIV-positive, and 10 acquired immunodeficiency virus (AIDS) patients. A neuropsychological battery designed to assess attention, psychomotor processing, verbal memory, and visual memory was administered to participants. No evidence of HIV-related cognitive impairment was found in patients in the early stages of HIV infection. Multivariate analyses of variance revealed significant deficits in psychomotor processing and verbal recall in persons with AIDS. These individuals showed greater difficulty in tasks requiring maintained attention and performed poorly on measures of immediate and delayed verbal recall. In contrast, HIV status was not related to visual memory, verbal recognition, or the number of errors made during a verbal recall task. The pattern of cognitive deficits observed in persons with AIDS resembles that commonly associated with subcortical pathology. The cognitive deficits observed were not related to depression or recentness of drug use.     

Consolidation of temporal order in episodic memories

Even though it is known that sleep benefits declarative memory consolidation, the role of sleep in the storage of temporal sequences has rarely been examined. Thus we explored the influence of sleep on temporal order in an episodic memory task followed by sleep or sleep deprivation. Thirty-four healthy subjects (17 men) aged between 19 and 28 years participated in the randomized, counterbalanced, between-subject design. Parameters of interests were NREM/REM cycles, spindle activity and spindle-related EEG power spectra. Participants of both groups (sleep group/sleep deprivation group) performed retrieval in the evening, morning and three days after the learning night. Results revealed that performance in temporal order memory significantly deteriorated over three days only in sleep deprived participants. Furthermore our data showed a positive relationship between the ratios of the (i) first NREM/REM cycle with more REM being associated with delayed temporal order recall. Most interestingly, data additionally indicated that (ii) memory enhancers in the sleep group show more fast spindle related alpha power at frontal electrode sites possibly indicating access to a yet to be consolidated memory trace. We suggest that distinct sleep mechanisms subserve different aspects of episodic memory and are jointly involved in sleep-dependent memory consolidation.     

Patterns of Verbal Long-Term and Working Memory Performance Reveal Deficits in Strategic Processing in Children With Frontal Infarcts Related to Sickle Cell Disease

Frontal brain regions are thought to mediate strategic processes that facilitate memory. We hypothesized that children with frontal cerebral infarcts related to sickle cell disease (SCD) would exhibit impairments in long-term and working memory as a result of disruptions in strategic processing. Word-list learning and digit span tasks were used to assess verbal memory and strategic processing in 21 children with SCD without infarcts (controls) and in 10 children with SCD with frontal infarcts. On the word-list learning task, children with frontal infarcts performed more poorly in terms of learning and free recall, although recognition and cued recall were adequate; this pattern suggested intact encoding and storage with impaired retrieval. Children with frontal infarcts performed more poorly on backward digit span, although forward digit span was adequate; this pattern suggested intact maintenance with impaired manipulation of information in working memory. Overall, these findings support the notion that disruptions in strategic processing contribute to memory impairments in children with frontal infarcts.     

A neuropsychological comparison of schizophrenia and schizophrenia-like psychosis of epilepsy

BACKGROUND: The schizophrenia-like psychoses of epilepsy (SLPE) might represent a secondary form of schizophrenia in which the pathology is relatively confined to the temporal lobe. To test this possibility we have compared the neuropsychological profile of schizophrenia and SLPE. Our main hypothesis was that both psychotic groups would show deficits of temporal lobe function but that prefrontal impairment, as measured by tests of executive function, would be found only in the primary schi ophrenic group. METHODS: Four groups were studied: (1) patients with SLPE (N = 25); (2) patients with epilepsy but not psychiatric history (N = 24); (3) patients with schizophrenia (N = 22); and (4) healthy volunteers (N = 24). Neuropsychological testing comprised measures of pre-morbid IQ, current verbal and performance IQ, information processing, digit span, motor speed, verbal and visual learning and memory, verbal fluency, the Wisconsin Card Sorting Task, the Stroop test and the trail making task. RESULTS: Patients with schizophrenia and those with SLPE had almost identical neuropsychological profiles, with impairments of attention, episodic memory (verbal > visual) and executive function. The epileptic controls showed similar though less severe impairments of memory and of some tests of executive function. CONCLUSIONS: Our results do not support the hypothesis that the pathophysiology of SLPE and schizophrenia are distinct. While our findings suggest an important role for dominant temporal lobe abnormality in schizophrenia, both in its primary form and in that occurring in patients with epilepsy, they also implicate generalized cognitive impairment, manifest in particular as attentional deficits, in both forms of the disorder.     

Neural correlates of dementia: regional brain metabolism (FDG-PET) and the CERAD neuropsychological battery.

The present Investigation examined the biological correlates of the cognitive deficits of Alzheimer's disease and related dementias using the neuropsychological assessment battery of the Consortium to Establish a Registry of Alzheimer's Disease (CERAD) and positron emission tomography (PET). Resting state cerebral glucose metabolism was measured using the labelled radiotracer, [18F] Fluoro-2-deoxyglucose (FDG), in a sample of patients with mild to moderate dementia (n = 66). Specific and predictable relationships were seen between regional brain metabolism (left and right, frontal, temporal, and parietal lobes) and the neuropsychological measures of verbal fluency, constructional praxis, and verbal list learning. On tests of naming and delayed verbal recall only diminished FDG uptake in the left frontal lobe and the left temporal lobe, respectively, approached significance. This study demonstrates the expected relationships between neuropsychological performance and regional cerebral metabolism, thereby providing support for the CERAD battery as a valid measure in the clinical evaluation of dementia and for the use of FDG-PET in brain-behavior studies of dementia.     

What does a patient with semantic dementia remember in verbal short-term memory? Order and sound but not words

In this study, we explored capacities for three different aspects of short-term verbal memory in patients with semantic dementia. As expected, the two patients had poor recall for lexico-semantic item information, as assessed by immediate serial recall of word lists. In contrast, their short-term memory for phonological information was preserved, as evidenced by normal performance for immediate serial recall of nonword lists, with normal or increased nonword phonotactic-frequency effects, and increased sensitivity to phonological lures in a delayed probe recognition task. Furthermore, the patients appeared to have excellent memory for the serial order of the words in a list. These data provide further support for the proposal that language knowledge is a major determining factor of verbal STM capacity, but they also highlight the necessary distinction of processes involved in item and order recall, as proposed by recent models of STM.