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PubMed1997

CD4+ CD7- T cells: a separate subpopulation of memory T cells?

The CD7 molecule is apparently involved in T cell activation but is absent in a substantial subpopulation of human T cells under physiological and certain pathological conditions. The majority of CD7- T cells expresses TCR alpha/beta and is of CD4+ helper and CD45R0+CD45RA- memory phenotype. After birth, percentages and absolute numbers of circulating CD7- T cells increase significantly during aging. A number of molecules thought to be involved in organ-specific T cell homing are preferentially expressed within the subset of CD4+CD7- T cells. Specific absence of CD7 antigen expression on T cells is observed in a variety of pathologic conditions such as cutaneous T cell lymphoma, HIV infection, rheumatoid arthritis, and kidney transplantation. Current in vitro results suggest that specific downregulation of CD7 antigen expression in T cells reflects a separate and stable differentiation state occurring late in the immune response. Expansion of CD7- T cells in vivo has been found in certain diseases associated with chronically repeated T cell stimulation. The potential pathophysiological significance of this T cell subset in certain human diseases is discussed.

Animals↗
PubMed1982

Auditory and visual sequential memory of Down syndrome and nonretarded children.

The study was designed to investigate auditory and visual sequential memory of mentally retarded individuals. Experiment 1, conducted with Down syndrome children and adolescents, replicated previous findings of poor auditory sequential memory on the Illinois Test of Psycholinguistic Abilities. In Experiment 2, nonretarded kindergarteners showed superior recall of auditory items on a more comparable set of auditory and visual tasks. These same tasks, administered to the Down syndrome sample in Experiment 3, supported the earlier finding that retarded individuals have difficulty recalling auditorially presented verbal material. Their difficulty, however, did not appear to be linked to the sequential nature of recall. We suggested that the auditory-visual recall difference evidenced by nonretarded but not by retarded subjects may have been due to the differential use of information in echoic memory.

Adolescent↗
PubMedDate not supplied

Inhibition of the endothelial isoform of nitric oxide synthase impairs long-term memory formation in the chick.

Previous studies with general inhibitors of nitric oxide synthase have yielded variable and contradictory results with respect to their effects on memory. This may have been due to differential effects of blocking the various isoforms of this enzyme. We show that day-old chicks trained on a single-trial passive-avoidance task suffered significant memory loss from approximately 40 min post-training following post-training intracranial administration of a potent inhibitor of eNOS. Administration of a specific nNOS or iNOS inhibitor at the same time had no effect on retention, although a role for either of these isoforms when administered at a different time after learning has yet to be fully investigated. The onset of memory loss following eNOS inhibition is the same as observed following general NOS inhibition, which suggests that amnestic effects observed in previous studies using nonspecific inhibitors may be attributable to blocking the function of eNOS. The findings indicate that eNOS may play a role in memory formation for this task, which is at least distinct from any role that may be played by nNOS.

Animals↗
PubMed1992

Muscimol injections into the nucleus basalis magnocellularis of rats: selective impairment of working memory in the double Y-maze.

Anatomical and neurochemical results suggest that the cortico- and amygdalopetal cholinergic neurons of the nucleus basalis magnocellularis (NBM) may receive GABAergic inputs. The present experiments were undertaken to evaluate the possible influence of intra-NBM injections of the GABAA agonist, muscimol, on memory. In two experiments, rats were chronically implanted with guide cannulae placed bilaterally into the NBM. Rats were trained to a criterion of at least 83% correct on each component in a double Y-maze task that allowed a dissociation of working and reference memory. The task began with placement into one of the two end arms of the first Y-maze and the reference memory task was to go to the stem for food. Access to the second Y was then given and the working memory task was to go to the goal arm opposite the arm in the first maze from which that trial began. In experiment 1, pre-trained rats (n = 7) received muscimol (0.5 microliter) in doses of 0, 0.01, 0.1 and 1.0 microgram in a counterbalanced order with re-training to criterion between injections. In experiment 2, pre-trained rats (n = 8) received saline, muscimol (0.1 microgram), the GABAA antagonist, bicuculline (0.01 microgram), and muscimol + bicuculline. Results of experiment 1 revealed that intra-NBM muscimol produced a dose-dependent and differential impairment of working and reference memory. A dose of 0.1 microgram impaired working memory without significantly affecting reference memory; doses of 0.01 microgram and 1.0 microgram affected neither and both types of memory, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

[Differential diagnosis of schizophrenic symptoms complicated with brain anomalies including bilateral temporal arachnoid cysts by eye mark recorder and PET: a case study].

Bilateral temporal arachnoid cysts and other intracranial congenital lesions including a moderately large left temporal arachnoid cyst accompanied by remarkable dysplasia of the temporal lobe in particular were discovered by chance during computerized axial tomography of a 26-year-old Japanese male who had been diagnosed as schizophrenia approximately 10 years earlier. A detailed re-assessment revealed no other organic symptoms or signs. His symptoms and clinical course met the DSM-IV criteria for schizophrenia, disorganized type. Based on his symptoms, positron emission tomography (PET) and the eye-movement recording test developed by Kojima et al. were performed. In addition, psychological tests including WAIS, Rorschach Test, and Wechsler's Memory Test were administered for further differential diagnosis. PET using continuous inhalation of oxygen 15-gas revealed a regional decrease in CBF and CMRO2 in the superior medial frontal lobe including the anterior cingulate gylus, findings sometimes associated with schizophrenia. However, no abnormal findings were noted around the arachnoid cysts. In the eye-movement recording test, several parameters including the responsive search score (RSS) were about the same level as that commonly observed in schizophrenics and are classified as schizophrenia by discrimination analysis. The psychological tests offered no reason to doubt the diagnosis of schizophrenia. Thus, the patient was diagnosed as schizophrenia with arachnoid cysts and other intracranial lesions. The way of diagnosis we used here might bring forth a breakthrough in schizophrenia research by differentiating schizophrenia from the other organic brain diseases.

Adult↗
PubMed1996

Recency effect in anterograde amnesia: evidence for distinct memory stores underlying enhanced retrieval of terminal items in immediate and delayed recall paradigms.

This study was devised to investigate immediate and delayed recency effects in anterograde amnesic patients. For this purpose, a word-list immediate recall paradigm and a modified version of the procedure devised by Baddeley and Hitch [Attention and Performance, Erlbaum, NJ, 1977] for eliciting the recency effect in delayed recall conditions was administered to a sample of amnesic patients and to a group of age-matched healthy subjects. Amnesics disclosed a fully normal recency effect in the immediate recall paradigm and a deficient recency effect in the delayed recall condition. These data, taken together with experimental evidence from a patient affected by a pure form of phonological short-term memory impairment [35], draw a double neuropsychological dissociation suggesting a differential origin for the two kinds of recency effects: a short-term memory output underlying enhanced recall of terminal items in immediate recall paradigms, and an ordinal retrieval strategy applied to long-term memory stored units at the root of the delayed recency effect.

Adult↗
PubMed1998

Right hemisphere involvement in imprinting memory revealed by glutamate treatment.

The lateralized use of the forebrain hemispheres during recall of imprinting memory was investigated using unilateral intrahemispheric injections of glutamate. Administration of glutamate to the right hemisphere 1.3, or 6 h after exposure to the imprinting stimulus disrupted recall 8 h after the end of training, whereas the same treatment of the left hemisphere had no effect. Imprinted chicks treated with glutamate injected into the right hemisphere did not approach the imprinting stimulus in preference to an alternative, unfamiliar stimulus during a simultaneous choice test, whereas imprinted chicks treated with glutamate injected into the left hemisphere showed a preference for the imprinting stimulus. Thus, the left and right hemispheres are involved differentially in the recall of imprinting memory. Fear behavior or activity levels were not altered by glutamate treatment of either the right or left hemisphere, indicating that the effects of glutamate were specific to recall of imprinting memory. However, the amnestic effect of treatment of the right hemisphere with glutamate was transient: it was no longer evident by 48 h after the end of training. Also, glutamate had no effect when the chicks were treated 9 h after the end of training. These results suggest that regions in right hemisphere of the chick brain are involved in early (0-8 h after training) recall of imprinting memory.

Animals↗
PubMed2003

Mini-review CD4 T cells are required for CD8 T cell memory generation.

Whereas the role of CD4 T cells in B cell memory generation is well established and unequivocal, the role that CD4 T cells play in CD8 responses was until recently far more elusive and controversial. A series of recent reports, however, have re-assessed the role of CD4 help on CD8 responses and have given rise to surprisingly unambiguous conclusions. While studying very different systems, they demonstrated that CD4 T cells are absolutely required for the generation of bona fide CD8 memory cells; the reports allow, for the first time, strong analogies to be made between B and CD8 memory cell generation. These data invite us to drastically change our idea of CD4 help on CD8 responses because they show that the old dichotomy - Th-dependent versus Th-independent CD8 responses - is no longer accurate.

Animals↗
PubMedDate not supplied

Auditory memory and age-related differences in two-tone frequency discrimination: trace decay and interference.

We investigated age-related differences in the time course of two-tone frequency discrimination. Healthy young and elderly adults with normal hearing acuity in the 500-2000 Hz range performed a two-alternative forced choice frequency discrimination task. The stimuli were short tones separated by either a 250-ms (short), 850-ms (medium), or 3000-ms (long) silent inter-interstimulus interval (ISI). Frequency discrimination thresholds were estimated using an adaptive staircase procedure. Although young listeners performed better than the elderly at all ISIs, the latter showed a dramatic elevation of discrimination thresholds at 250 ms, while the thresholds of the young subjects increased significantly at 3000 ms. These results suggest that the elderly may be especially vulnerable to the effects of masking produced by the second tone at the short interval, whereas the young listeners tend to be differentially affected by the trace decay at long ISI. The results are discussed in the framework of stimulus persistence hypothesis.

Acoustic Stimulation↗
PubMed1995

Effects of ACTH and ACTH 4-10 on aversive memory retrieval in rats.

The aim of the study was to examine whether ACTH and ACTH-fragment 4-10, given before the test would produce a selectively enhanced retrieval of aversive memories, in the same way as preexposure to inescapable footshocks, in rats. For this purpose animals conditioned in a T-maze with appetitive (10% sucrose) and aversive (2.0 mA footshock) events were administered (s.c.) a single dose of 10, 20 or 40 ug/rat of ACTH or 5, 10 or 20 ug/rat of ACTH-fragment 4-10, 20-min before testing. The retention test conducted in the same training apparatus 72-hrs after conditioning showed a dose-dependent increase in latencies to enter the previously shocked goalarm with the absence of such a difference in responding to the nonshocked goalarm, in ACTH and ACTH 4-10 treated groups. This differential response was not observed in saline treated rats. This effect of peptides on memory retrieval was similar to that seen following inescapable footshock in rats. The results suggest the possible involvement of ACTH in the differential enhancement of memory of helplessness condition.

Adrenocorticotropic Hormone↗
PubMed1991

A follow-up study of auditory sequential memory abilities in children with histories of preschool language impairment.

Auditory sequential memory abilities of 15 subjects with histories of preschool language impairment were compared to 15 non-language impaired matched controls on an auditory processing screening battery. The battery included assessment of symbols, syllables, words, sentences and commands in auditory sequential memory tasks. All five subtests significantly differentiated the subjects from their matched controls at the 1% level. Information from teacher and parent questionnaires revealed that many of the subjects presented with some areas of academic difficulty. These subjects seem predisposed to develop persistent communication difficulties. A dynamic continuum of language-learning disabilities is proposed. Clinical and theoretical implications and directions for research are discussed.

Achievement↗
PubMed2005

Brain activation in offspring of AD cases corresponds to 10q linkage.

Previously, we reported evidence of genetic heterogeneity in late-onset familial Alzheimer's disease, based on sex of affected parent, demonstrating linkage to chromosome 10q, a region identified by other groups and implicated as a quantitative trait loci for Abeta levels, in families with an affected mother. Using functional magnetic resonance imaging and a memory encoding task, we now show differential brain activation patterns among asymptomatic offspring which correspond to the previous linkage finding. These results suggest the possibility that activation patterns may prove useful as a preclinical quantitative trait related to the putative familial late-onset AD gene in this chromosome 10 region.

Alzheimer Disease↗
PubMed1996

Memory performance among women with parental abuse histories: enhanced directed forgetting or directed remembering?

Performance on a directed forgetting task was assessed in 24 individuals with borderline personality disorder and early life parental abuse, 24 borderline individuals with no history of abuse, and 24 healthy nonclinical controls under conditions of explicit and implicit memory. In the explicit memory condition, individuals with abuse histories showed greater differential recall of "to-be-remembered" versus "to-be-forgotten" material compared to the 2 comparison groups. Implicit memory performance was equivalent for all 3 groups. The enhanced selective memory in the abused group was the result of better recall for "remember" and not poorer recall for "forget" information, indicating that abused individuals have an enhanced ability to sustain attention to designated "remember" information. Because most people with childhood abuse recall their abuse, enhanced remembering of designated events (e.g., information not associated with abuse) may be a coping strategy.

Adult↗
PubMedDate not supplied

Mapping of olfactory memory circuits: region-specific c-fos activation after odor-reward associative learning or after its retrieval.

Although there is growing knowledge about intracellular mechanisms underlying neuronal plasticity and memory consolidation and reconsolidation after retrieval, information concerning the interaction among brain areas during formation and retrieval of memory is relatively sparse and fragmented. Addressing this question requires simultaneous monitoring of activity in multiple brain regions during learning, the post-acquisition consolidation period, and retrieval and subsequent reconsolidation. Immunoreaction to the immediate early gene c-fos is a powerful tool to mark neuronal activation of specific populations of neurons. Using this method, we are able to report, for the first time, post-training activation of a network of closely related brain regions, particularly in the frontal cortex and the basolateral amygdala (BLA), that is specific to the learning of an odor-reward association. On the other hand, retrieval of a well-established associative memory trace does not seem to differentially activate the same regions. The amygdala, in particular, is not engaged after retrieval, whereas the lateral habenula (LHab) shows strong activation that is restricted to animals having previously learned the association. Although intracellular mechanisms may be similar during consolidation and reconsolidation, this study indicates that different brain circuits are involved in the two processes, at least with respect to a rapidly learned olfactory task.

Amygdala↗
PubMed1995

Effects of central administration of arginine-vasopressin on aversive memory retrieval.

This study examined whether arginine-vasopressin (A-VP), given before the test would produce an improved retrieval of aversive memory, in the same way as pre-exposure to inescapable footshocks, in rats. For this purpose animals conditioned in a T-maze with appetitive (10% sucrose) and aversive (2.0 mA footshock) events were administered (intracerebroventricular) a single dose of 2.5, 5, 10 or 20 ng/rat of A-VP, 20-min before testing. In the retention test conducted with the same training apparatus 72 h after conditioning, the peptide treated rats showed a dose-dependent increase in latencies to enter the previously shocked goalarm, with the absence of such a difference in responding to the non-shocked goalarm. This differential response was not observed in saline treated rats. This effect of peptide on memory retrieval was similar to that seen following inescapable footshock in rats. These results suggest the possible involvement of central vasopressinergic mechanisms in the differential enhancement of memory of helplessness condition.

Animals↗
PubMed1992

Maturation and dispersal of B-cell clones during T cell-dependent antibody responses.

Germinal centers develop in follicles during TD antibody responses in the first 3 wk following each immunization. In primary responses to protein-based antigens, T-cell help is limiting, follicles develop towards the end of the 1st wk from immunization and the size of the follicular response in relatively small. When T-cell help is provided the primary B-cell response in follicles is much larger, B cells start to proliferate in follicles within a few hours of immunization and reach peak size 3-4 d later. Available evidence suggests that virgin B cells that colonize follicles to form germinal centers must first be activated by antigen outside follicles, probably in T zones. Memory B cells also proliferate in follicles and they can do so without first being activated outside follicles. Germinal center formation consists of an initial phase of exponential proliferation of B cells within the follicular dendritic cell network. After a single immunization the follicular response is oligoclonal and on average only 3 cells colonize each follicle. In responses to hapten-protein in rats primed previously with the carrier protein these 3 cells increase to around 10(4) cells in 3 d with a cell cycle time of about 6 h. At the end of the period of exponential growth of B blasts, the classical structure of germinal centers emerges. The B blasts become centroblasts in the dark zone of the germinal center which develops at that pole of the FDC network nearer the T zones. The centroblasts are still in rapid cell cycle but do not more than sustain their numbers. The rest of their progeny move to the heart of the FDC network where they come out of cell cycle as centrocytes. Evidence is cited which indicates that somatic mutation occurs in the Ig V-region genes of centroblasts and that centrocytes are selected on the basis of their ability to respond to antigen held on FDC. Centrocytes not receiving this antigen-dependent signal kill themselves by apoptosis. Centrocytes positively selected by interaction with antigen on FDC receive further signals which induce the cells to differentiate to become either plasma cells or memory B cells. The nature of some of these differentiation signals is described. It is shown that proliferation, selection and differentiation occur within germinal centers in distinct micro-environments.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗