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PubMed2004

Impaired working memory for location but not for colour or shape in visual neglect: a comparison of parietal and non-parietal lesions.

Patients with spatial neglect due to right hemisphere pathology may show 'revisiting' behaviour during visual search and cancellation tasks, such that previously encountered targets are treated as if they are new discoveries. Revisiting behaviour is particularly evident when no visible trace is left to inform patients that a particular target has already been detected (Husain et al., 2001; Wojciulik et al., 2001), implying that spatial working memory may be impaired in neglect. To test whether working memory for location is selectively impaired relative to memory for colour and shape, we compared performances of right hemisphere neglect patients with parietal (n = 4) and non-parietal (n = 4) lesions on a change detection task. Patients were presented with a matrix containing four objects in different positions, and required to detect a change in the location, colour or shape of one of the objects following presentation of a brief visual mask. Parietal patients were selectively impaired in detecting location changes, regardless of the horizontal position of the object in the matrix, relative to colour and shape changes. This deficit of spatial working memory was not apparent for neglect patients with lesions that spared the parietal cortex. We conclude that the human parietal cortex is crucially involved in the updating and maintenance of spatial representations across saccades, and that neglect arising from parietal damage causes impairment in these re-mapping mechanisms.

Adult↗
PubMed2005

Potential therapeutic targets in the NF-kappaB pathway for Alzheimer's disease.

One characteristic of Alzheimer's disease is a deficit in new memory formation. Numerous studies and reviews have investigated targeting the CREB pathway for enhancing memory in diseases such as Alzheimer's. In addition, the possibility of targeting the nuclear factor kappaB (NF-kappaB) pathway for inflammatory conditions, which also play a role in Alzheimer's disease, has been investigated. Interestingly, recent data concerning NF-kappaB functioning indicates that the development of drugs targeting NF-kappaB regulation may prove beneficial for memory disorders. However, given the complexity of NF-kappaB functioning, the most important challenge remaining is whether to enhance or inhibit the activation NF-kappaB. Future studies undoubtedly will focus on selected targets and "optimal activation" levels during critical stages of specific disease pathologies. This short review summarizes past studies with CREB, describes NF-kappaB functioning and highlights new data on the potential role of NF-kappaB in new memory formation and Alzheimer's disease.

Alzheimer Disease↗
PubMed1989

Neuropsychological follow-up of patients operated for aneurysms of anterior communicating artery.

The neuropsychological outcome of 43 patients operated for ACoA aneurysms was assessed with a battery of 15 tests, tapping a wide spectrum of cognitive abilities. As a group ACoA aneurysms patients were impaired on 8 tests, including the three assessing memory. When however, patients falling below the cut-off point determined in normal controls were considered, 42% of the sample was unimpaired and only 35% fell on two or more tests. The analysis of single cases showed that memory was often affected, but short-term memory even more than long-term memory. In addition to the well known memory disorder, the patients showed a wide range of neuropsychological defects, including language and space functions. The hypotheses that could account for this broad-based neuropsychological impairment are discussed.

Follow-Up Studies↗
PubMed2005

Emotional autobiographical memories in amnesic patients with medial temporal lobe damage.

The recollection of emotional autobiographical memories has received little attention in patients with memory disorders. Here, we addressed this topic in amnesic patients with damage to the hippocampus (HC group; n = 8) or the hippocampus, amygdala, and surrounding cortices (HC+ group; n = 2). These patients were asked to recollect emotional events from their lives. HC patients produced recollections that were strikingly similar to those of brain-damaged (n = 10) and healthy (n = 25) comparison participants, in terms of both quantity and quality. In contrast, HC+ patients produced a lower proportion of unpleasant memories compared with the other participants. Specifically, the ratings and words used to describe recollections in the HC+ patients were more affectively positive. All groups produced more memories from between 10 and 30 years of age (the so-called autobiographical memory "bump") compared with other time periods in their lives. These results suggest that structures surrounding the hippocampus, but not the hippocampus itself, may be necessary for the recollection of highly emotional, unpleasant autobiographical memories. The amygdala and surrounding cortices of the medial temporal lobe may be a necessary component in the neural circuitry necessary for vivid recollection of unpleasant emotional events.

Adult↗
PubMed1998

Olfaction in persons with Alzheimer's disease.

The need for low cost, noninvasive procedures for aiding in the diagnosis and understanding of Alzheimer's Disease (AD) has led to theories and procedures examining the role of olfactory disorders because of the finding that the brains of AD patients invariably exhibit neuropathology in the hippocampus and entorhinal cortex. This loss correlates with the increase in the number of plaques and tangles and with the severity of dementia. Considered together, these findings suggest that brain structures closely related to the olfactory system demonstrate significant histopathology in AD. A comprehensive review of the literature pertaining to olfaction in persons with AD revealed that the olfactory identification ability of patients with memory disorders is impaired relative to controls. Consistency is lacking, however, when olfactory detection thresholds are investigated. Also, there is inconsistency in regards to severity of illness and olfactory function. In addition to differentiating AD patients from normals, the olfactory paradigm has shown some limited usefulness in differentiating AD patients from some other demented patients.

Aged↗
PubMed1998

The emergence of spatial rotation deficits in dementia and normal aging.

The mental rotation required in the Road Map Test of Direction Sense (the "Road Map Test"; J. Money, 1976; J. Money, D. Alexander, & H. T. Walker, 1965) has been thought to be impaired as a function of age, but not dementia. However, spatial rotation in dementia has not been investigated in reference to spatial coordinate systems. Patients with dementia (Alzheimer's and ischemic vascular dementias) and elderly control participants were administered the Road Map Test. The authors analyzed whether the geocentric or egocentric coordinate system determined rotation of Road Map Test turns and predicted impairment in dementia patients. They found equivalent impairment in both types of dementia, greater angulation effect in the geocentric system in patients relative to normal controls, and no egocentric effect. Results also suggest early emergence of spatial rotation deficit in dementia. Spatial rotation is most often associated with working memory, which predicts the correlations found.

Age Factors↗
PubMed2000

Verbal short-term memory deficits in Down syndrome: a consequence of problems in rehearsal?

Individuals with Down syndrome suffer from relatively poor verbal short-term memory. Previous explanations of this deficit have been framed in terms of inefficient or absent rehearsal of verbal material in Down syndrome within the phonological loop component of Baddeley and Hitch's (1974) working memory model. Two experiments are presented which test this explanation by looking for the markers of rehearsal in children with Down syndrome and verbal mental age matched controls. Both experiments confirm that individuals with Down syndrome show poorer verbal short-term memory performance than controls. However, they rule out rehearsal as an explanation of these deficits because the evidence suggests that neither individuals with Down syndrome nor matched controls are engaging in spontaneous subvocal rehearsal. Other explanations of poor verbal short-term memory performance in Down syndrome, in terms of impairments both within and outside of the phonological loop system, are discussed. Practical implications for intervention strategies aimed at improving verbal short-term memory skills in Down syndrome are also outlined.

Child↗
PubMed2005

Spatial working memory capacity in unilateral neglect.

It has been proposed recently that a deficit in keeping track of spatial locations may contribute to the severity of unilateral neglect in some right hemisphere stroke patients. However, performance on traditional spatial working memory (SWM) tasks (e.g. Corsi blocks) might be confounded by failure to encode leftward locations, rather than a true deficit of maintaining locations in SWM. Here we introduced new procedures for circumventing this to measure SWM capacity in neglect. In a first experiment, 20 right hemisphere stroke patients (10 with and 10 without neglect) were tested on a computerized vertical variant of the Corsi task. Sequences of spatial locations in a vertical column were displayed and participants had to tap out the remembered sequence on a touchscreen. Patients with left neglect were impaired on this vertical SWM task compared with all control groups. However, poor performance on this task (as for Corsi blocks) might involve impaired memory for stimulus sequence, or poor visuomotor control of manual responding, rather than reduced SWM capacity per se. A second experiment therefore employed a purer measure of vertical SWM. After the displayed sequence, a single location was now probed visually, with observers judging verbally (yes/no) if it had been in the preceding sequence. Hence order no longer mattered, and no spatial motor response was required. Again, the neglect group was impaired relative to all others, now with very little overlap between the performances of individual neglect patients versus individuals in control groups. Poor performance on the second task, which provides a purer measure of SWM capacity, correlated with severity of left neglect on cancellation tasks (but not on line bisection), consistent with recent proposals that SWM deficits can exacerbate left neglect on visual search tasks when present conjointly. Lesion anatomy indicated that neglect patients with a SWM deficit were most likely to have damage to parietal white matter, plus, in the second experiment, to the insula also. These findings demonstrate that an impairment in SWM capacity can contribute to the neglect syndrome in patients with stroke involving regions within the right parietal lobe and insula.

Adult↗
PubMedDate not supplied

[The effect of protein synthesis inhibition in the central nervous system on long-term memory formation in some behavioral tasks].

The effect of the maximum protein synthesis inhibition in brain and spinal cord on long-term memory formation in extreme situations was studied in various new behavioral tasks in rats. Cycloheximide injected bilaterally into the lateral ventricles three hours before learning suppressed protein synthesis in the central nervous system by 96% during one hour after learning. Forty-four hours after learning in a standard Morris water maze, the information about the platform position was not retained, whereas no memory disorder was observed in case of learning in a simplified Morris maze or a new test learned jump-out-of-water task. A more prolonged suppression of protein synthesis (76%, ten hours after learning) elicited amnesia in five out of eight rats learned in a simplified Morris maze but not disturbed information storage after 48 h and 14 days in the learned jump-out-of-water task. It was concluded that protein synthesis inhibitors are not a universal tool for disrupting formation of long-term memory. It was assumed that under extreme conditions, sometimes procedural long-term (to two weeks) memory is formed without de novo protein synthesis.

Animals↗
PubMed2006

Dissociable mechanisms for memory impairment in bipolar disorder and schizophrenia.

BACKGROUND: Although memory deficits are consistently reported in schizophrenia and bipolar disorder, the mechanisms underlying these impairments are poorly understood. Clarifying the nature and degree of overlap in memory deficits between the two illnesses could help to distinguish brain systems disrupted in these illnesses, and indicate cognitive remediation strategies to improve patient outcomes. METHOD: We examined performance on a non-verbal memory task in clinically stable out-patients with bipolar disorder (n=40), schizophrenia (n=40), and healthy comparison subjects (n=40). This task includes conditions in which distinct mnemonic strategies -- namely, using context to organize familiar stimuli or using holistic representation of novel stimuli -- facilitate performance. RESULT: When compared to a reference condition, bipolar patients had deficits consistent with organizational dysfunction and poor detection of novel information. Although patients with schizophrenia performed worse than the other groups, they were only differentially impaired when organizational demands were significant. Task performance was not correlated with severity of clinical symptomatology. CONCLUSIONS: This pattern of distinct memory impairments implies disturbances in partially overlapping neural systems in bipolar disorder and schizophrenia. Evidence of impairment in detection of novel stimuli that is unique to bipolar disorder suggests that, while the absolute level of cognitive dysfunction is less severe in bipolar disorder as compared to schizophrenia, subtle disruptions in memory are present. These findings can be used to plan targeted cognitive remediation programs by helping patients to capitalize on intact functions and to learn new strategies that they do not employ without training.

Adult↗
PubMedDate not supplied

[Comparative study of the effect of 3 M-cholinergic blockaders on memory and motor activity in rats].

Experiments on rats were made to study and compare pharmacologically three central antimuscarinic drugs, namely scopolamine, N-methyl-4-piperidinol benzylate and tropine phenylcyclopentylglycolate. A study was made of the effects of the compounds on rat motor activity by the Animex system and on short-term memory by passive avoidance behavior. Logit analysis was employed to define the ED50 of the compounds that inhibit the arecoline-induced tremor. Definite differences were discovered in the effects of the antimuscarinic drugs on CNS functions. For example, M-methyl-4-piperidinol benzylate applied in a wide dosage range induced motor hyperactivity without affecting the short-term memory, whereas tropine phenylcyclopentylglycolate provoked motor hyperactivity and memory disorders at equal doses. As regards the doses producing both the effects, scopolamine occupied the intermediate position. No correlation was found between central antimuscarinic activity of the compounds under study and their influences on motor hyperactivity and formation of passive avoidance behavior.

Animals↗
PubMed2005

Memory-guided saccades in Parkinson's disease: long delays can improve performance.

A recent study in control subjects suggested the existence of separate pathways for oculomotor spatial working memory tasks depending on whether the delay before movement execution is either short or long (>20 s). The long delay pathway might bypass brain areas commonly affected by Parkinson's disease (PD). This study aimed to assess spatial working memory in Parkinson's disease using short (3 s) and long (30 s) delays in a memory-guided saccade task. Fifteen mild-moderately affected PD subjects off-medication, and 15 age and sex-matched controls were tested (PD mean age 65.3; control 65.9). Subjects were tested in a darkened room using a horizontal LED bar to generate eye movements which were recorded using an infrared limbus tracker. Percentage error in amplitude of the primary saccade was analysed by repeated measures ANOVA. There was a significant interaction between the groups and their response to the short and long delay periods (P<0.02). PD subjects were more strongly impaired in the short delay than the long delay trials when compared with controls. Analysis of the percentage error in amplitude of the final eye position showed the same pattern but only in female subjects. This study provides the first evidence that the proposed parallel spatial memory pathway utilised in longer delay periods is relatively unimpaired in PD. In a broader sense, our results suggest there might be other alternative pathways to overcome deficits in functions impaired by PD.

Aged↗
PubMed1997

Validity of a recall and recognition condition to assess visual memory in the CERAD battery.

This study assessed the validity of a measure of visual recall and recognition memory using a modified administration of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Constructional Praxis task to extend the capacity of the CERAD neuropsychological battery's ability to assess nonverbal free and recognition recall. The sample consisted of consecutive university hospital memory disorders clinic patients (n = 77). To test the measures' ability to discriminate dementia severity based on an independently derived clinical dementia rating, scores on Free Visual Recall showed expected group differences as a function of dementia severity (ANOVA, F = 12.7, p = .0001), but exhibited a floor effect in the moderately severe dementia range. Recognition Visual Recall was also able to discriminate dementia severity based on an independently derived clinical dementia rating (ANOVA, F = 10.6, p = .0001). Both Free Visual Recall and Recognition Visual Recall measures were found to have strong concurrent validity based on intercorrelations with the Wechsler Memory Scale-Revised (WMS-R; Wechsler, 1987) Visual Reproduction I and II. In addition, moderate to strong discriminant validity for Free Visual Recall was demonstrated based on correlations with a family member self-report of memory problems in everyday life.

Journal Article↗