380 research outputs found
Thalamic pathology and memory loss in early Alzheimer's disease: moving the focus from the medial temporal lobe to Papez circuit.
No full textIt is widely assumed that incipient protein pathology in the medial temporal lobe instigates the loss of episodic memory in Alzheimer’s disease, one of the earliest cognitive deficits in this type of dementia. Within this region, the hippocampus is seen as the most vital for episodic memory. Consequently, research into the causes of memory loss in Alzheimer’s disease continues to centre on hippocampal dysfunction and how disease-modifying therapies in this region can potentially alleviate memory symptomology. The present review questions this entrenched notion by bringing together findings from post-mortem studies, non-invasive imaging (including studies of presymptomatic, at-risk cases) and genetically modified animal models. The combined evidence indicates that the loss of episodic memory in early Alzheimer’s disease reflects much wider neurodegeneration in an extended mnemonic system (Papez circuit), which critically involves the limbic thalamus. Within this system, the anterior thalamic nuclei are prominent, both for their vital contributions to episodic memory and for how these same nuclei appear vulnerable in prodromal Alzheimer’s disease. As thalamic abnormalities occur in some of the earliest stages of the disease, the idea that such changes are merely secondary to medial temporal lobe dysfunctions is challenged. This alternate view is further strengthened by the interdependent relationship between the anterior thalamic nuclei and retrosplenial cortex, given how dysfunctions in the latter cortical area provide some of the earliest in vivo imaging evidence of prodromal Alzheimer’s disease. Appreciating the importance of the anterior thalamic nuclei for memory and attention provides a more balanced understanding of Alzheimer’s disease. Furthermore, this refocus on the limbic thalamus, as well as the rest of Papez circuit, would have significant implications for the diagnostics, modelling, and experimental treatment of cognitive symptoms in Alzheimer’s disease
The role of the Amygdala in the perception of reward
No full textThis study set out to examine the role of the amygdala in a number of appetitively motivated tasks. Experiment one was a position discrimination task with reversals, which in later reversals involved manipulation of some secondary reinforcers associated with a correct response, and the introduction of a magnitude of reward component. Rats with NMDA-induced amygdala lesions performed at a similar level to shams at the initial discrimination and first three reversals, proceeding to reverse faster than controls in the subsequent three reversals. Manipulation of secondary reinforcers led to an equal and significant decline in performance for both groups, with the lesioned animals retaining their significant superiority in reversal performance. Alteration of the task from a 2 vs 0 pellet discrimination to a 2 vs 1 led to a drastic increase in task difficulty, but both groups completed three reversals and did not differ significantly in performance. Experience of handling the lesioned animals led to the confirmation, in experiment two, that they were significantly more hostile/reactive to handling than shams (using die "blind" ratings of experienced animal handlers). Experiment three attempted to refine die picture of this behavioural change by measuring gross activity levels - no differences between groups were found. The finding of enhanced reversal performance and the absence of a magnitude of reward deficit amongst lesioned animals in experiment one were unanticipated, problematic and demand replication. No strong support was provided for either of the principal contemporary theories of amygdala involvement in secondary reinforcement. Increased reactivity to handling was found to be consistent with a minority of the past literature, and activity levels were as anticipated. It is argued that the notion of "stimulus-reward associations" as an amygdala function is incoherent and unhelpful, and that references to the functions of the amygdale as a whole rather than of subnuclei can be equally misleading
Differing time dependencies of object recognition memory impairments produced by nicotinic and muscarinic cholinergic antagonism in perirhinal cortex
No full textThe roles of muscarinic and nicotinic cholinergic receptors in perirhinal cortex in object recognition memory were compared. Rats' discrimination of a novel object preference test (NOP) test was measured after either systemic or local infusion into the perirhinal cortex of the nicotinic receptor antagonist methyllycaconitine (MLA), which targets alpha-7 (alpha 7) amongst other nicotinic receptors or the muscarinic receptor antagonists scopolamine, AFDX-384, and pirenzepine. Methyllycaconitine administered systemically or intraperirhinally before acquisition impaired recognition memory tested after a 24-h, but not a 20-min delay. In contrast, all three muscarinic antagonists produced a similar, unusual pattern of impairment with amnesia after a 20-min delay, but remembrance after a 24-h delay. Thus, the amnesic effects of nicotinic and muscarinic antagonism were doubly dissociated across the 20-min and 24-h delays. The same pattern of shorter-term but not longer-term memory impairment was found for scopolamine whether the object preference test was carried out in a square arena or a Y-maze and whether rats of the Dark Agouti or Lister-hooded strains were used. Coinfusion of MLA and either scopolamine or AFDX-384 produced an impairment profile matching that for MLA. Hence, the antagonists did not act additively when coadministered. These findings establish an important role in recognition memory for both nicotinic and muscarinic cholinergic receptors in perirhinal cortex, and provide a challenge to simple ideas about the role of cholinergic processes in recognition memory: The effects of muscarinic and nicotinic antagonism are neither independent nor additive.The roles of muscarinic and nicotinic cholinergic receptors in perirhinal cortex in object recognition memory were compared. Rats' discrimination of a novel object preference test (NOP) test was measured after either systemic or local infusion into the perirhinal cortex of the nicotinic receptor antagonist methyllycaconitine (MLA), which targets alpha-7 (alpha 7) amongst other nicotinic receptors or the muscarinic receptor antagonists scopolamine, AFDX-384, and pirenzepine. Methyllycaconitine administered systemically or intraperirhinally before acquisition impaired recognition memory tested after a 24-h, but not a 20-min delay. In contrast, all three muscarinic antagonists produced a similar, unusual pattern of impairment with amnesia after a 20-min delay, but remembrance after a 24-h delay. Thus, the amnesic effects of nicotinic and muscarinic antagonism were doubly dissociated across the 20-min and 24-h delays. The same pattern of shorter-term but not longer-term memory impairment was found for scopolamine whether the object preference test was carried out in a square arena or a Y-maze and whether rats of the Dark Agouti or Lister-hooded strains were used. Coinfusion of MLA and either scopolamine or AFDX-384 produced an impairment profile matching that for MLA. Hence, the antagonists did not act additively when coadministered. These findings establish an important role in recognition memory for both nicotinic and muscarinic cholinergic receptors in perirhinal cortex, and provide a challenge to simple ideas about the role of cholinergic processes in recognition memory: The effects of muscarinic and nicotinic antagonism are neither independent nor additive
Remembering and knowing in a patient with preserved recognition and impaired recall
No full textROB is a patient who has a severe deficit in recalling recently presented verbal material following rupture and repair of an anterior communicating artery aneurysm [Hanley JR, Davies ADM, Downes J, Mayes A. Cognitive Neuropsychology 1994;11:543-78; Hanley JR, Davies ADM. In: Parkin A, editor. Case Studies in the Neuropsychology of Memory. Hillsdale, NJ: Lawrence Erlbaum, 1997. p. 111-26]. Despite this, her performance on tests of recognition memory is comfortably within the normal range. In the present series of experiments, we investigated whether or not ROB's performance on tests of recognition memory might be associated with a disproportionately large number of correct decisions made on the basis of familiarity rather than contextual retrieval [e.g. Mandler G. Psychological Review 1980;87:252-71]. Contrary to this hypothesis, the results showed that ROB made a high proportion of remember decisions relative to know decisions in recognition [cf. Gardiner JM. Memory & Cognition 1988;16:309-13] and produced a high recollection score when conscious recollection and familiarity were placed in opposition to one another [cf. Jacoby LL, Woloshyn V, Kelley C. Journal of Experimental Psychology: General 1989;118:115-25.]. ROB's recognition memory performance therefore appears to be qualitatively as well as quantitatively similar to that found in the normal population. As ROB has suffered damage to both the fornix and the anterior thalamus, the results of the present study are consistent with the claim that damage to the extended hippocampal system has a much more severe effect on recall than on recognition [Aggleton JP, Shaw C. Neuropsychologia 1996;34:51-62; Aggleton JP, Saunders RC. Memory 1997;5:49-71]. The present results provide no support, however, for the additional suggestion [Aggleton JP, Brown MW. Behavioral and Brain Sciences 1999;22:425-56.] that the extended hippocampal system is necessary for recognition memory decisions that are based on contextual retrieval. Copyright © 2001 Elsevier Science Ltd
Disentangling the stigma of HIV/AIDS from the stigmas of drugs use, commercial sex and commercial blood donation – A factorial survey of medical students in China
No full textBackground: HIV/AIDS related stigma interferes with the provision of appropriate care and
support for people living with HIV/AIDS. Currently, programs to address the stigma approach it as
if it occurs in isolation, separate from the co-stigmas related to the various modes of disease
transmission including injection drug use (IDU) and commercial sex (CS). In order to develop
better programs to address HIV/AIDS related stigma, the inter-relationship (or 'layering') between
HIV/AIDS stigma and the co-stigmas needs to be better understood. This paper describes an
experimental study for disentangling the layering of HIV/AIDS related stigmas.
Methods: The study used a factorial survey design. 352 medical students from Guangzhou were
presented with four random vignettes each describing a hypothetical male. The vignettes were
identical except for the presence of a disease diagnosis (AIDS, leukaemia, or no disease) and a cocharacteristic
(IDU, CS, commercial blood donation (CBD), blood transfusion or no cocharacteristic).
After reading each vignette, participants completed a measure of social distance that
assessed the level of stigmatising attitudes.
Results: Bivariate and multivariable analyses revealed statistically significant levels of stigma associated with AIDS, IDU, CS and CBD. The layering of stigma was explored using a recently
developed technique. Strong interactions between the stigmas of AIDS and the co-characteristics
were also found. AIDS was significantly less stigmatising than IDU or CS. Critically, the stigma of
AIDS in combination with either the stigmas of IDU or CS was significantly less than the stigma of
IDU alone or CS alone.
Conclusion: The findings pose several surprising challenges to conventional beliefs about HIV/
AIDS related stigma and stigma interventions that have focused exclusively on the disease stigma.
Contrary to the belief that having a co-stigma would add to the intensity of stigma attached to
people with HIV/AIDS, the findings indicate the presence of an illness might have a moderating
effect on the stigma of certain co-characteristics like IDU. The strong interdependence between
the stigmas of HIV/AIDS and the co-stigmas of IDU and CS suggest that reducing the co-stigmas
should be an integral part of HIV/AIDS stigma intervention within this context
“What is the Use of a Book Without Pictures?” An Exploration of the Impact of Illustrations on Reading Experience in A Monster Calls
No full textThis article examines the effect of Jim Kay’s illustrations on the experience of reading A Monster Calls by Patrick Ness. The author compares the responses of six Key Stage Three children (11–14 years old), three of whom were given an illustrated version of the text, and three a non-illustrated version. The children with an illustrated copy engaged with the text more deeply and critically than the others. They were also more likely to relate the story to their own lives. The illustrations were found to work alongside the participants’ own visualisations rather than replacing them, and opened up further possible interpretations rather than limiting them. The illustrations did not appear to have influenced the participants’ overall enjoyment of the book, nor did they significantly alter the readers’ views on key themes and ideas of the text
Contrasting hippocampal and perirhinalcortex function using immediate early gene imaging
No full textThe perirhinal cortex and hippocampus have close anatomical links, and it might, therefore, be predicted that they have close, interlinked roles in memory. Lesion studies have, however, often failed to support this prediction, providing dissociations and double dissociations between the two regions on tests of object recognition and spatial memory. In a series of rat studies we have compared these two regions using the expression of the immediate early gene c-fosas a marker of neuronal activity. This gene imaging approach makes it possible to assess the relative involve-ment of different brain regions and avoids many of the limitations of the lesion approach. A very consistent pattern of results was found as the various hippocampal subfields but not the peri-rhinal cortex show increased c-fosactivity following tests of spatial learning. In contrast, the perirhinal cortex but none of the hippocampal subfields show increased c-fosactivity when presented with novel rather than familiar visual objects. When novel scenes are created by the spatial rearrangement of familiar objects it is the hippocampus and not the perirhinal cortex that shows c-foschanges. This double dissociation for gene expression accords with that found from lesion studies and highlights the different contributions of the perirhinal cortex and hippocampus to memory
Vestibular influence on water maze retention: transient whole body rotations improve the accuracy of the cue-based retention strategy
No full textSpatial learning in the water maze is thought to rely both on distal cues and vestibular information [Aggleton JP, Vann SD, Oswald CJP, Good M. Identifying cortical inputs to the rat hippocampus that subserves allocentric spatial processes: a simple problem with a complex answer. Hippocampus 2000;10:466–74; Pearce JM. Animal learning and cognition: an introduction. UK: Psychology Press; 1997]. Experiment 1 demonstrates that while water maze retention relies primarily on cue-platform based associations, this strategy is not precise, as animals tend to focus at the side of the pool. In experiment 2, we demonstrate that vestibular rotation eliminates this inaccuracy. These experiments highlight the importance of both cue and vestibular information for accurate retention of the water maze
Interleaving brain systems for episodic and recognition memory
No full textConflicting models persist over the nature of long-term memory. Crucial issues are whether episodic memory and recognition memory reflect the same underlying processes, and the extent to which various brain structures work as a single unit to support these processes. New findings that have resulted from improved resolution of functional brain imaging, together with recent studies of amnesia and developments in animal testing, reinforce the view that recognition memory comprises at least two independent processes: one recollective and the other using familiarity detection. Only recollective recognition appears to depend on episodic memory. Attempts to map brain areas supporting these two putative components of recognition memory indicate that they depend on separate, but interlinked, structures.Conflicting models persist over the nature of long-term memory. Crucial issues are whether episodic memory and recognition memory reflect the same underlying processes, and the extent to which various brain structures work as a single unit to support these processes. New findings that have resulted from improved resolution of functional brain imaging, together with recent studies of amnesia and developments in animal testing, reinforce the view that recognition memory comprises at least two independent processes: one recollective and the other using familiarity detection. Only recollective recognition appears to depend on episodic memory. Attempts to map brain areas supporting these two putative components of recognition memory indicate that they depend on separate, but interlinked, structures
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