6,489 research outputs found

    Hippocampal Infusion of Zeta Inhibitory Peptide Impairs Recent, but Not Remote, Recognition Memory in Rats.

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    Spatial memory in rodents can be erased following the infusion of zeta inhibitory peptide (ZIP) into the dorsal hippocampus via indwelling guide cannulas. It is believed that ZIP impairs spatial memory by reversing established late-phase long-term potentiation (LTP). However, it is unclear whether other forms of hippocampus-dependent memory, such as recognition memory, are also supported by hippocampal LTP. In the current study, we tested recognition memory in rats following hippocampal ZIP infusion. In order to combat the limited targeting of infusions via cannula, we implemented a stereotaxic approach for infusing ZIP throughout the dorsal, intermediate, and ventral hippocampus. Rats infused with ZIP 3-7 days after training on the novel object recognition task exhibited impaired object recognition memory compared to control rats (those infused with aCSF). In contrast, rats infused with ZIP 1 month after training performed similar to control rats. The ability to form new memories after ZIP infusions remained intact. We suggest that enhanced recognition memory for recent events is supported by hippocampal LTP, which can be reversed by hippocampal ZIP infusion

    The contribution of episodic long-term memory to working memory for bindings

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    The present experiments support two conclusions about the capacity limit of working memory (WM). First, they provide evidence for the Binding Hypothesis, WM capacity is limited by interference between bindings but not items. Second, they show that episodic LTM contributes substantially to binding memory when the capacity of WM is stretched to the limit by larger set sizes. We tested immediate memory for sets of word-picture pairs. With increasing set size, memory for bindings declined more precipitously than memory for items, as predicted from the binding hypothesis. Yet, at higher set sizes performance was more stable than expected from a capacity limited memory, suggesting a contribution of episodic long-term memory (LTM) to circumvent the WM capacity limit. In support of that hypothesis, we show a double dissociation of contributions of WM and episodic LTM to binding memory: Performance at set sizes larger than 3 was specifically affected by proactive interference - but were immune to influences from a distractor-filled delay. In contrast, performance at set size 2 was unaffected by proactive interference but harmed by a distractor-filled delay

    Contributions of cortical feedback to sensory processing in primary visual cortex

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    Closing the structure-function divide is more challenging in the brain than in any other organ (Lichtman and Denk, 2011). For example, in early visual cortex, feedback projections to V1 can be quantified (e.g., Budd, 1998) but the understanding of feedback function is comparatively rudimentary (Muckli and Petro, 2013). Focusing on the function of feedback, we discuss how textbook descriptions mask the complexity of V1 responses, and how feedback and local activity reflects not only sensory processing but internal brain states

    Age and distraction are determinants of performance on a novel visual search task in aged Beagle dogs

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    Aging has been shown to disrupt performance on tasks that require intact visual search and discrimination abilities in human studies. The goal of the present study was to determine if canines show age-related decline in their ability to perform a novel simultaneous visual search task. Three groups of canines were included: a young group (N = 10; 3 to 4.5 years), an old group (N = 10; 8 to 9.5 years), and a senior group (N = 8; 11 to 15.3 years). Subjects were first tested for their ability to learn a simple two-choice discrimination task, followed by the visual search task. Attentional demands in the task were manipulated by varying the number of distracter items; dogs received an equal number of trials with either zero, one, two, or three distracters. Performance on the two-choice discrimination task varied with age, with senior canines making significantly more errors than the young. Performance accuracy on the visual search task also varied with age; senior animals were significantly impaired compared to both the young and old, and old canines were intermediate in performance between young and senior. Accuracy decreased significantly with added distracters in all age groups. These results suggest that aging impairs the ability of canines to discriminate between task-relevant and -irrelevant stimuli. This is likely to be derived from impairments in cognitive domains such as visual memory and learning and selective attention

    The hippocampus and visual perception

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    In this review, we will discuss the idea that the hippocampus may be involved in both memory and perception, contrary to theories that posit functional and neuroanatomical segregation of these processes. This suggestion is based on a number of recent neuropsychological and functional neuroimaging studies that have demonstrated that the hippocampus is involved in the visual discrimination of complex spatial scene stimuli. We argue that these findings cannot be explained by long-term memory or working memory processing or, in the case of patient findings, dysfunction beyond the medial temporal lobe (MTL). Instead, these studies point toward a role for the hippocampus in higher-order spatial perception. We suggest that the hippocampus processes complex conjunctions of spatial features, and that it may be more appropriate to consider the representations for which this structure is critical, rather than the cognitive processes that it mediates

    A cognitive examination of compulsive checkers' working memory and inhibitory performance

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    Checking is one of the most common symptoms observed in Obsessive Compulsive Disorder (OCD) with 50-80% of patients (Antony, Downie, & Swinson, 1998; Henderson & Pollard, 1988; Rasmussen & Eisen, 1988) and an additional ~15% of the general population demonstrating subclinical checking compulsions (Stein et al., 1997). A common finding is that checking actually impairs the memory of those items checked (van den Hout & Kindt, 2003a, 2003b), even though the mechanism underlying checking-related memory impairment has remained elusive. This is a shortcoming that we presently address in a series of short-term memory experiments and attentional tasks comparing high and low checkers (see VOCI; Thordarson et al., 2004). Generally, our memory tasks required stimuli to be remembered in their locations, which was designed to engage the episodic buffer (EB) of working memory (WM) (Baddeley, 2000). The key manipulation was to present an intermediate probe (between encoding and recall) in the form of a resolvable or misleading challenge which questioned an aspect of the encoding set; this was either present or absent, respectively. As expected, misleading probes specifically (Exp. 1, 2, extreme meta-comparison 3 & 9; Harkin & Kessler, 2009; 2011a; Harkin, Rutherford, & Kessler, 2011) and intermediate probes generally (Exp. 4; Harkin & Kessler, 2011a) tap into the inhibitory impairments of high (not low) checkers, which hampers EB functionality and impairs their memory. Indeed, it was only during misleading trials that high checkers made more unnecessary eye movements specifically to empty locations (Exp. 5; Harkin & Kessler, subm). Furthermore, for ecologically valid stimuli high checkers were impaired in inhibiting attention to threatening ‘ON’ states (Tasks 6 & 7; Harkin & Kessler, in press) and in their ability to recall if an appliance was ‘ON’ or ‘OFF’ (Exp. 8; Harkin, Rutherford, & Kessler, 2011). High checkers’ intact performance on baseline no-probe-1 trials excludes a capacity-based explanation of their WM impairments. Overall, confidence measures revealed a general task-independent impairment which was attenuated by an intermediate probe. These findings were then used to create a classification system based upon Executive-Functioning, Binding Complexity and Memory Load (EBL) to explain otherwise discrepant findings from 58 memory studies (Harkin & Kessler, 2011b). Thus, the contribution of this research is not only to (Exp. 1-9) indicate an actual mechanism (i.e., episodic buffer of WM) of memory impairment in checking/OCD but it also provides a new research platform on which to base where we will and will not observe memory impairments in OCD participants. The conclusion summarizes the main findings with respect to the development and maintenance of OCD symptoms, highlights limitations and provides solutions to these through future research

    Acetylcholine neuromodulation in normal and abnormal learning and memory: vigilance control in waking, sleep, autism, amnesia, and Alzheimer's disease

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    This article provides a unified mechanistic neural explanation of how learning, recognition, and cognition break down during Alzheimer's disease, medial temporal amnesia, and autism. It also clarifies whey there are often sleep disturbances during these disorders. A key mechanism is how acetylcholine modules vigilance control in cortical layer

    One-shot Learning for iEEG Seizure Detection Using End-to-end Binary Operations: Local Binary Patterns with Hyperdimensional Computing

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    This paper presents an efficient binarized algorithm for both learning and classification of human epileptic seizures from intracranial electroencephalography (iEEG). The algorithm combines local binary patterns with brain-inspired hyperdimensional computing to enable end-to-end learning and inference with binary operations. The algorithm first transforms iEEG time series from each electrode into local binary pattern codes. Then atomic high-dimensional binary vectors are used to construct composite representations of seizures across all electrodes. For the majority of our patients (10 out of 16), the algorithm quickly learns from one or two seizures (i.e., one-/few-shot learning) and perfectly generalizes on 27 further seizures. For other patients, the algorithm requires three to six seizures for learning. Overall, our algorithm surpasses the state-of-the-art methods for detecting 65 novel seizures with higher specificity and sensitivity, and lower memory footprint.Comment: Published as a conference paper at the IEEE BioCAS 201

    Lost in Time and Space: States of High Arousal Disrupt Implicit Acquisition of Spatial and Sequential Context Information

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    Biased cognition during high arousal states is a relevant phenomenon in a variety of topics: from the development of post-traumatic stress disorders or stress-triggered addictive behaviors to forensic considerations regarding crimes of passion. Recent evidence indicates that arousal modulates the engagement of a hippocampus-based “cognitive” system in favor of a striatum-based “habit” system in learning and memory, promoting a switch from flexible, contextualized to more rigid, reflexive responses. Existing findings appear inconsistent, therefore it is unclear whether and which type of context processing is disrupted by enhanced arousal. In this behavioral study, we investigated such arousal-triggered cognitive-state shifts in human subjects. We validated an arousal induction procedure (three experimental conditions: violent scene, erotic scene, neutral control scene) using pupillometry (Preliminary Experiment, n = 13) and randomly administered this method to healthy young adults to examine whether high arousal states affect performance in two core domains of contextual processing, the acquisition of spatial (spatial discrimination paradigm; Experiment 1, n = 66) and sequence information (learned irrelevance paradigm; Experiment 2, n = 84). In both paradigms, spatial location and sequences were encoded incidentally and both displacements when retrieving spatial position as well as the predictability of the target by a cue in sequence learning changed stepwise. Results showed that both implicit spatial and sequence learning were disrupted during high arousal states, regardless of valence. Compared to the control group, participants in the arousal conditions showed impaired discrimination of spatial positions and abolished learning of associative sequences. Furthermore, Bayesian analyses revealed evidence against the null models. In line with recent models of stress effects on cognition, both experiments provide evidence for decreased engagement of flexible, cognitive systems supporting encoding of context information in active cognition during acute arousal, promoting reduced sensitivity for contextual details. We argue that arousal fosters cognitive adaptation towards less demanding, more present-oriented information processing, which prioritizes a current behavioral response set at the cost of contextual cues. This transient state of behavioral perseverance might reduce reliance on context information in unpredictable environments and thus represent an adaptive response in certain situations

    Plasticity mechanisms of memory consolidation and reconsolidation in the perirhinal cortex

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    In this review we explore the role of the perirhinal cortex (Prh) in memory, focusing on the cellular and molecular mechanisms that have been described to happen in this structure. The Prh is part of the medial temporal lobe, but the evidences show that it has a different function than that of the hippocampus. In particular, the Prh is known to be important for object recognition memory, although it could have a role in other types of memory. However, despite the fact that object recognition tasks are widely used, information regarding the molecular and cellular mechanisms underlying this type of memory in Prh is lacking. We discuss a series of studies of memory and plasticity in this region and how they might relate. In addition, we propose that Prh could play a role as a “pattern separator” for object memories, similar to the function of the dentate gyrus of the hippocampus in the spatial domain.Fil: Miranda, Magdalena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; ArgentinaFil: Bekinschtein, Pedro Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; Argentin
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