ORCID Profile
0000-0002-5573-1308
Current Organisation
Cardiff University
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Publisher: Public Library of Science (PLoS)
Date: 28-03-2013
Publisher: American Psychological Association (APA)
Date: 2010
DOI: 10.1037/A0019287
Publisher: American Psychological Association (APA)
Date: 10-2012
DOI: 10.1037/A0029754
Publisher: Elsevier BV
Date: 2004
Publisher: Cold Spring Harbor Laboratory
Date: 08-2010
DOI: 10.1101/LM.1879610
Abstract: Animals often show an innate preference for novelty. This preference facilitates spontaneous exploration tasks of novelty discrimination (recognition memory). In response to limitations with standard spontaneous object recognition procedures for rodents, a new task (“bow-tie maze”) was devised. This task combines features of delayed nonmatching-to-s le with spontaneous exploration. The present study explored aspects of object recognition in the bow-tie maze not amenable to standard procedures. Two rat strains (Lister Hooded, Dark Agouti) displayed very reliable object recognition in both the light and dark, with the Lister Hooded strain showing superior performance (Experiment 1). These findings reveal the potential contribution of tactile and odor cues in object recognition. As the bow-tie maze task permits multiple trials within a session, it was possible to derive forgetting curves both within-session and between-sessions (Experiment 1). In Experiment 2, rats with hippoc al or fornix lesions performed at normal levels on the basic version of the recognition task, contrasting with the marked deficits previously seen after perirhinal cortex lesions. Next, the training protocol was adapted (Experiment 3), and this modified version was used successfully with mice (Experiment 4). The overall findings demonstrate the efficacy of this new behavioral task and advance our understanding of object recognition.
Publisher: Wiley
Date: 27-06-2011
Publisher: Elsevier BV
Date: 04-2016
Publisher: American Psychological Association (APA)
Date: 12-2009
DOI: 10.1037/A0017444
Publisher: SAGE Publications
Date: 2011
DOI: 10.1080/17470218.2010.495407
Abstract: Sequence learning and spatial alternation were examined in rats with anterior thalamic lesions or sham surgeries. There was a lesion-induced deficit in spatial alternation but not in sequence learning. During sequence learning, rats discriminated between six different sequentially presented compounds (e.g., reinforce A before B, but not B before A), composed of audio-visual elements. The solution required rats to learn both specific stimulus sequences and the reward contingencies associated with these specific temporal relationships. The failure of anterior thalamic lesions to affect the acquisition of this sequential configural task complements the recent finding that anterior thalamic lesions also spare the acquisition of a configural task involving specific stimulus pairings and their spatial relationships. These findings suggest that such “structural” learning is more reliant on cortico-hippoc al than thalamo-hippoc al interactions.
Publisher: Society for Neuroscience
Date: 14-09-2011
DOI: 10.1523/JNEUROSCI.2317-11.2011
Abstract: Human episodic memory is supported by networks of white matter tracts that connect frontal, temporal, and parietal regions. Degradation of white matter microstructure is increasingly recognized as a general mechanism of cognitive deterioration with aging. However, atrophy of gray matter regions also occurs and, to date, the potential role of specific white matter connections has been largely ignored. Changes to frontotemporal tracts may be important for the decline of episodic memory while frontotemporal cooperation is known to be critical, the precise pathways of interaction are unknown. Diffusion-weighted MRI tractography was used to reconstruct three candidate fasciculi known to link components of memory networks: the fornix, the parahippoc al cingulum, and the uncinate fasciculus. Age-related changes in the microstructure of these tracts were investigated in 40 healthy older adults between the ages of 53 and 93 years. The relationships between aging, microstructure, and episodic memory were assessed for each in idual tract. Age-related reductions of mean fractional anisotropy and/or increased mean diffusivity were found in all three tracts. However, age-related decline in recall was specifically associated with degradation of fornix microstructure, consistent with the view that this tract is important for episodic memory. In contrast, a decline in uncinate fasciculus microstructure was linked to impaired error monitoring in a visual object–location association task, echoing the effects of uncinate transection in monkeys. These results suggest that degradation of microstructure in the fornix and the uncinate fasciculus make critical but differential contributions to the mechanisms underlying age-related cognitive decline and subserve distinct components of memory.
Publisher: Springer Science and Business Media LLC
Date: 08-2003
DOI: 10.1007/S00221-003-1499-0
Abstract: Fos levels were measured in rats trained in one of two qualitatively different spatial memory tasks in a water maze. In one task, ( landmark condition) rats found a submerged platform that was always 25 cm south of a visible landmark, the absolute position of the platform and landmark changing after every trial. In the other task ( place condition), rats swam to a platform that remained in the same absolute position on every session, but changed session to session, with this task relying on the memory of allocentric cues. Despite matched swim times, the landmark condition resulted in higher levels of Fos in a wide range of cortical and subcortical sites, including the hippoc us and its connections. Structural equation modelling revealed two different patterns of hippoc al function. In the allocentric place task there was a significant association between Fos activity in the entorhinal cortices and the hippoc us proper, while in the non-allocentric landmark task this relationship was not present, but was replaced by a connection from the entorhinal cortices to the subiculum. Thus, the two different tasks engage two different modes of hippoc al activity as demonstrated by Fos expression.
Publisher: Wiley
Date: 30-11-2009
DOI: 10.1111/J.1460-9568.2009.07010.X
Abstract: Two forms of account have been proposed for how animals form integrated memories for patterns of stimulation: the elemental account holds that the elements that make up the pattern become directly linked to one another, whereas the configural account holds that these elements become bound together through their capacity to activate a separate, shared configural memory. The hippoc us and perirhinal cortex have been linked to both elemental and configural processes. Here, we assessed the role of the rat hippoc us and perirhinal cortex in these distinct ways of processing patterns of sensory stimulation involving auditory, visual context and temporal information. Using selective lesions and inactivation techniques we identified a specific role for the hippoc us in the retrieval of configural memories but not of those that could be encoded elementally we also identified a role for the rat perirhinal cortex in visual contextual learning. These results, using a novel combination of behavioural assays, provide clear support for the view that patterns of stimulation can be encoded either elementally or configurally, and that disruption of hippoc al function leaves rats reliant on elemental processes.
Publisher: Society for Neuroscience
Date: 05-12-2012
DOI: 10.1523/JNEUROSCI.3299-12.2012
Abstract: Cognitive control, an important facet of human cognition, provides flexibility in response to varying behavioral demands. Previous work has focused on the role of prefrontal cortex, notably the anterior cingulate cortex. However, it is now clear that this is one node of a distributed cognitive network. In this emerging network view, structural connections are inherent elements, but their role has not been emphasized. Furthermore, lesion and functional imaging studies have contributed little knowledge about anatomical segregation, functional specialization, and behavioral importance of white matter connections. The relationship between cognitive control and microstructure of connections within the cingulum, a major white matter tract and conduit of projections to prefrontal sites, was probed in vivo in humans with diffusion MRI. Twenty healthy controls and 25 in iduals with amnestic mild cognitive impairment (MCI), an early stage of age-associated cognitive deterioration, underwent cognitive testing, including several measures of cognitive control. For each in idual, the anterior, middle, posterior, and parahippoc al portions of the cingulum bundle were reconstructed separately using deterministic tractography and anatomical landmarks. Microstructural variation in the left anterior cingulum was closely related to interin idual control based on verbal or symbolic rules. Errors in a task that involved maintenance of spatial rules were largely restricted to patients with MCI and were related, additionally, to right anterior cingulum microstructure. Cognitive control in MCI was also independently related to posterior parahippoc al connections. These results show how specific subpopulations of connections are critical in cognitive control and illustrate fine-grained anatomical specializations in the white matter infrastructure of this network.
Publisher: Elsevier BV
Date: 2006
DOI: 10.1016/J.NEUROSCIENCE.2005.09.034
Abstract: Activity of the immediate early genes c-fos and zif268 was compared across hemispheres in rats with unilateral, excitotoxic lesions of the hippoc us (dentate gyrus and CA fields 1-4). Counts of the protein products of these genes were made shortly after rats performed a test of spatial working memory in the radial-arm maze, a task that is sensitive to bilateral lesions of the hippoc us. Unilateral hippoc al lesions produced evidence of widespread hypoactivity. Significant reductions in immediate early gene counts were observed within all three anterior thalamic nuclei, as well as the entorhinal, perirhinal, and postrhinal cortices, and much of the subicular complex. In contrast, no observable changes were detected in the anterior cingulate, infralimbic or prelimbic cortices, as well as several amygdala nuclei, even though many of these regions receive projections from the subiculum. Instead, the immediate early gene changes were closely linked to sites that are thought to be required for successful task performance, with both immediate early genes giving similar patterns of results. The findings support the notion that the anterior thalamic nuclei, hippoc us, and parahippoc al cortices form the key components of an interdependent neuronal network involved in spatial mnemonic processing.
Publisher: Wiley
Date: 06-2004
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 21-11-2012
Publisher: Cold Spring Harbor Laboratory
Date: 17-06-2011
DOI: 10.1101/LM.2132911
Abstract: Two different models (convergent and parallel) potentially describe how recognition memory, the ability to detect the re-occurrence of a stimulus, is organized across different senses. To contrast these two models, rats with or without perirhinal cortex lesions were compared across various conditions that controlled available information from specific sensory modalities. Intact rats not only showed visual, tactile, and olfactory recognition, but also overcame changes in the types of sensory information available between object s ling and subsequent object recognition, e.g., between s ling in the light and recognition in the dark, or vice versa. Perirhinal lesions severely impaired object recognition whenever visual cues were available, but spared olfactory recognition and tactile-based object recognition when tested in the dark. The perirhinal lesions also blocked the ability to recognize an object s led in the light and then tested for recognition in the dark, or vice versa. The findings reveal parallel recognition systems for different senses reliant on distinct brain areas, e.g., perirhinal cortex for vision, but also show that: (1) recognition memory for multisensory stimuli involves competition between sensory systems and (2) perirhinal cortex lesions produce a bias to rely on vision, despite the presence of intact recognition memory systems serving other senses.
Publisher: American Psychological Association (APA)
Date: 2003
Publisher: Wiley
Date: 10-2002
DOI: 10.1046/J.1460-9568.2002.02211.X
Abstract: Activity of the immediate early gene c-fos was compared across hemispheres in rats with unilateral anterior thalamic lesions. Fos protein was quantified after rats performed a spatial working memory test in the radial-arm maze, a task that is sensitive to bilateral lesions of the anterior thalamic nuclei. Unilateral anterior thalamic lesions produced evidence of a widespread hippoc al hypoactivity, as there were significant reductions in Fos counts in a range of regions within the ipsilateral hippoc al formation (rostral CA1, rostral dentate gyrus, 'dorsal' hippoc us, presubiculum and postsubiculum). A decrease in Fos levels was also found in the rostral and caudal retrosplenial cortex but not in the parahippoc al cortices or anterior cingulate cortices. The Fos changes seem most closely linked to sites that are also required for successful task performance, supporting the notion that the anterior thalamus, retrosplenial cortex and hippoc us form key components of an interdependent neuronal network involved in spatial mnemonic processing.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for John Aggleton.