Search results for "Amnesia"
showing 10 items of 54 documents
Pure Progressive Amnesia and the APPV717G Mutation
2009
We report an isolated, slowly progressive, pure amnestic phenotype in a 59-year-old member of a family affected by autosomal dominant familial Alzheimer disease. Early-onset Alzheimer disease in this family was associated with a V717G mutation in the amyloid precursor protein gene (APP). Subjective impairment of episodic memory began in our subject at the age of 44 years and subsequent, longitudinal neuropsychologic assessment confirmed progressive, severe, global impairment of memory functions over a period of 14 years with preservation of other cognitive domains. The mean annual hippocampal atrophy rate, determined by volumetric magnetic resonance imaging was intermediate between values p…
The role of the thalamus in amnesia: a tractography, high-resolution MRI and neuropsychological study.
2008
Although it is well established that thalamic lesions may lead to profound amnesia, the precise contribution of thalamic sub-regions to memory remains unclear. In an influential article Aggleton and Brown proposed that recognition memory depends on two processes supported by distinct thalamic and cortical structures. Familiarity is mediated by the mediodorsal (MD) thalamic nucleus and the entorhinal/ perirhinal cortex. Recollection ismediated by the anterior thalamic nucleus (AN), the mamillothalamic tract (MTT) and the hippocampus. The authors also suggested that the lateral dorsal nucleus (LD) may contribute to the thalamic/hippocampus system, thereby implying that the LD may play a role …
Confabulation: damage to a specific inferior medial prefrontal system
2008
Confabulation, the pathological production of false memories, occurs following a variety of aetiologies involving the frontal lobes, and is frequently held to be underpinned by combined memory and executive deficits. However, the critical frontal regions and specific cognitive deficits involved are unclear. Studies in amnesic patients have associated confabulation with damage to the orbital and ventromedial prefrontal cortices. However, neuroimaging studies have associated memory-control processes which are assumed to underlie confabulation with the right lateral prefrontal cortex. We used a confabulation battery to investigate the occurrence and localisation of confabulation in an unselect…
Recollection and familiarity in hippocampal amnesia
2008
Currently, there is a general agreement that two distinct cognitive operations, recollection and familiarity, contribute to performance on recognition memory tests. However, there is a controversy about whether recollection and familiarity reflect different memory processes, mediated by distinct neural substrates (dual-process models), or whether they are the expression of memory traces of different strength in the context of a unitary declarative memory system (unitary-strength models). Critical in this debate is the status of recognition memory in hippocampal amnesia and, in particular, whether the various structures in the medial temporal lobe (MTL) contribute differentially to the recol…
Integration of cognitive allocentric information in visuospatial short-term memory through the hippocampus
2005
Visuospatial short-term memory relies on a widely distributed neocortical network: some areas support the encoding process of the visually acquired spatial information, whereas other ares are more involved in the active maintenance of the encoded information. Recently, in a pointing to remembered targets task, it has been shown in healthy subjects that, for memory delays of 5 s, spatial errors are affected also by cognitive allocentric information, i.e., covert spatial information derived from a pure mental representation. We tested the effect of a lesion of the hippocampus on the accuracy of pointing movements toward remembered targets, with memory delays falling in the 0.5-30 s range. The…
The hippocampus is required for short-term topographical memory in humans.
2007
The hippocampus plays a crucial role within the neural systems for long-term memory, but little if any role in the short-term retention of some types of stimuli. Nonetheless, the hippocampus may be specialized for allocentric topographical processing, which impacts on short-term memory or even perception. To investigate this we developed performance-matched tests of perception (match-to-sample) and short-term memory (2 s delayed-match-to-sample) for the topography and for the nonspatial aspects of visual scenes. Four patients with focal hippocampal damage and one with more extensive damage, including right parahippocampal gyrus, were tested. All five patients showed impaired topographical m…
Recognition memory for single items and for associations in amnesic patients
2004
Recognition memory performance reflects two distinct processes or types of memory referred to as recollection and familiarity. According to theoretical claims about the two types of memory, single item and associative recognition tasks can be used as an experimental method to distinguish recollection and familiarity processes. Associative recognition decisions can be used as an index of recollection while memory for single items is mostly based on familiarity judgement. We employed this procedure to examine a possible dissociation in the memory performance of amnesic patients between spared single item and impaired associative recognition. Twelve amnesic patients, six with damage confined t…
Effects of magnetic seizure therapy on anterograde and retrograde amnesia in treatment‐resistant depression
2019
Background Electroconvulsive therapy (ECT) is the gold standard for treatment-resistant depression (TRD). However, cognitive side effects, mainly anterograde and retrograde amnesia, frequently occur. Magnetic seizure therapy (MST) is tested using more focal seizure induction. However, the suggestion MST may be more beneficial than ECT because it causes fewer amnesia have not yet been comprehensively investigated using common neuropsychological testing specifically for ECT. We aimed to examine whether MST causes anterograde and retrograde amnesia. Methods Ten patients with TRD were treated with MST (8.9 [2] treatments) at 100% machine output, a frequency of 100 Hz and 657.4 (62) pulses per t…
Selective erasure of a fear memory
2009
International audience; Memories are thought to be encoded by sparsely distributed groups of neurons. However, identifying the precise neurons supporting a given memory (the memory trace) has been a long-standing challenge. We have shown previously that lateral amygdala (LA) neurons with increased cyclic adenosine monophosphate response element-binding protein (CREB) are preferentially activated by fear memory expression, which suggests that they are selectively recruited into the memory trace. We used an inducible diphtheria-toxin strategy to specifically ablate these neurons. Selectively deleting neurons overexpressing CREB (but not a similar portion of random LA neurons) after learning b…
Dissociation between priming and recognition in the expression of sequential knowledge
2002
Exposure to a repeating sequence of target stimuli in a speeded localization task can support both priming of sequence-consistent responses and recognition of sequence components. Here, a task is introduced in which measures of priming and recognition are obtained concurrently, and it is demonstrated that priming of sequence-consistent responses occurs even when test stimuli are not recognized. The results show that sequence knowledge can be expressed in the absence of conscious recognition. However, we also show that this result is consistent with a simple model in which priming and recognition depend on exactly the same underlying memory strength variable.