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Dive into the research topics where Dimitris Tsivilis is active.

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Featured researches published by Dimitris Tsivilis.


Nature Neuroscience | 2008

A disproportionate role for the fornix and mammillary bodies in recall versus recognition memory

Dimitris Tsivilis; Seralynne Denise Vann; Christine Denby; Neil Roberts; Andrew R. Mayes; Daniela Montaldi; John Patrick Aggleton

Uncovering the functional relationship between temporal lobe amnesia and diencephalic amnesia depends on determining the role of the fornix, the major interlinking fiber tract. In this study relating fornix volume with memory, we made magnetic resonance imaging–based volume estimates of 13 brain structures in 38 individuals with surgically removed colloid cysts. Fornix status was assessed directly by overall volume and indirectly by mammillary body volume (which atrophies after fornix damage). Mammillary body volume significantly correlated with 13 out of 14 tests of episodic memory recall, but correlated poorly with recognition memory. Furthermore, as the volumes of the left fornix and the left mammillary bodies decreased, the difference between recall and recognition scores increased. No other structure was consistently associated with memory. These findings support models of diencephalic memory mechanisms that require hippocampal inputs for recall, but not for key elements of recognition.


Journal of Cognitive Neuroscience | 2008

Induced electroencephalogram oscillations during source memory: Familiarity is reflected in the gamma band, recollection in the theta band

Thomas Gruber; Dimitris Tsivilis; Claire Marie Giabbiconi; Matthias M. Müller

Modulations of oscillatory electroencephalogram (EEG) activity in the induced gamma and theta frequency ranges (induced gamma and theta band responses; iGBRs: >30 Hz; iTBRs: 6 Hz) have been associated with retrieval of information from long-term memory. However, the specific functional role of these two forms of oscillatory activity remains unclear. The present study examines theta- and gamma-oscillations within a dual-process framework, which defines familiarity and recollection as the two component processes of recognition memory. During encoding, participants were instructed to make bigger/smaller than a shoebox or living/nonliving decisions for different object pictures. During retrieval old/new recognition was followed (for items judged old) by a source discrimination task regarding the decision made for each item at encoding. iGBRs (3580 Hz; 210330 msec) were higher for correctly identified old relative to new objects. Importantly, they did not distinguish between successful and unsuccessful source judgments. In contrast, iTBRs (47.5 Hz; 6001200 msec) were sensitive to source discrimination. We propose that iGBRs mirror early associative processes linked to familiarity-related retrieval processes, whereas iTBRs reflect later onsetting, episodic, recollection-related mechanisms.


American Journal of Neuroradiology | 2009

The Frequency and Extent of Mammillary Body Atrophy Associated with Surgical Removal of a Colloid Cyst

Christine Denby; Seralynne Denise Vann; Dimitris Tsivilis; John Patrick Aggleton; Daniela Montaldi; Neil Roberts; Andrew R. Mayes

BACKGROUND AND PURPOSE: Patients who have had a colloid cyst removed from the third ventricle sometimes experience some difficulty with day-to-day memory. This study provided quantitative MR imaging volume measures of 1 structure potentially responsible for mnemonic problems, the mammillary bodies. Additional volume estimates in structures connected to the mammillary bodies sought to determine the specificity of any atrophy. MATERIALS AND METHODS: Volume estimates of the mammillary bodies were performed on 38 patients after surgical removal of colloid cysts and 20 control subjects by the application of stereologic volume-estimation techniques. For the mammillary body measures, 2 groups of MR images were assessed (0.8- and 1.0-mm section thickness) to compare the sensitivity of each imaging sequence for detecting any atrophy. Other structures associated with memory processes, such as the hippocampus and fornix, were also assessed quantitatively to determine whether there was a correlation between mammillary body damage and atrophy in connecting structures. RESULTS: Our investigations established the superiority of 0.8-mm-volume scans over standard isotropic 1.0-mm-thick-volume scans for mammillary body assessments. Comparisons with 20 age-matched controls revealed that patients with colloid cysts frequently showed significant mammillary body atrophy (mean volume of colloid cysts, 0.037 cm3 right and 0.038 cm3 left; control subjects, 0.069 cm3 right and 0.067 cm3 left). In fact, every patient had a mammillary body volume below the control mean, and the majority of patients had a volume decrease of >1 SD (82% right, 74% left). Mammillary body volumes correlated with fornix volumes in the same patient group. CONCLUSIONS: Our results reveal the frequent presence of mammillary body atrophy in patients with surgical removal of colloid cysts and indicate that this atrophy is partly due to a loss of temporal lobe projections in the fornix.


PLOS ONE | 2013

Explicit Mentalizing Mechanisms and Their Adaptive Role in Memory Conformity

Rebecca Wheeler; Kevin Allan; Dimitris Tsivilis; Douglas Martin; Fiona Gabbert

Memory conformity occurs when an individual endorses what other individuals remember about past events. Research on memory conformity is currently dominated by a ‘forensic’ perspective, which views the phenomenon as inherently undesirable. This is because conformity not only distorts the accuracy of an individuals memory, but also produces false corroboration between individuals, effects that act to undermine criminal justice systems. There is growing awareness, however, that memory conformity may be interpreted more generally as an adaptive social behavior regulated by explicit mentalizing mechanisms. Here, we provide novel evidence in support of this emerging alternative theoretical perspective. We carried out a memory conformity experiment which revealed that explicit belief-simulation (i.e. using ones own beliefs to model what other people believe) systematically biases conformity towards like-minded individuals, even when there is no objective evidence that they have a more accurate memory than dissimilar individuals. We suggest that this bias is functional, i.e. adaptive, to the extent that it fosters trust, and hence cooperation, between in-group versus out-group individuals. We conclude that memory conformity is, in more fundamental terms, a highly desirable product of explicit mentalizing mechanisms that promote adaptive forms of social learning and cooperation.


Proceedings of the National Academy of Sciences of the United States of America | 2009

Impaired recollection but spared familiarity in patients with extended hippocampal system damage revealed by 3 convergent methods

Seralynne Denise Vann; Dimitris Tsivilis; Christine Denby; Joel R. Quamme; Andrew P. Yonelinas; John Patrick Aggleton; Daniela Montaldi; Andrew R. Mayes


Neuroreport | 2004

Induced gamma band responses: An early marker of memory encoding and retrieval

Thomas Gruber; Dimitris Tsivilis; Daniela Montaldi; Matthias M. Müller


Neuroscience Imaging. 2008;2. | 2008

MRI Measurement of Fornix Pathology: Evidence of extensive fornix damage following surgical removal of colloid cysts in the third ventricle

Christine Denby; Seralynne Denise Vann; Dimitris Tsivilis; John Patrick Aggleton; Andrew R. Mayes; V Slumming; Neil Roberts; Daniela Montaldi


Brain and Cognition | 2001

Prefrontal cortical activation during word associative, face associative, and word-face associative encoding.

John Joseph Downes; Clare E. Mackay; Dimitris Tsivilis; Andrew R. Mayes; Daniela Montaldi; N M Hunkin; K D Singh; Neil Roberts


PLOS ONE | 2013

Explicit Mentalizing Mechanisms and Their Adaptive Role

Rebecca Wheeler; Kevin Allan; Dimitris Tsivilis; Douglas S. Martin; Fiona Gabbert


Neuroscience Imaging. 2008;2. | 2008

Neuroimaging of the Fornix: present and future.

Christine Denby; Seralynne Denise Vann; Dimitris Tsivilis; Andrew R. Mayes; Daniela Montaldi; John Patrick Aggleton

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Neil Roberts

University of Edinburgh

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N M Hunkin

Royal Hallamshire Hospital

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Thomas Gruber

University of Osnabrück

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