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John S. Duncan - One of the best experts on this subject based on the ideXlab platform.
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Factors affecting reorganisation of Memory Encoding networks in temporal lobe epilepsy
Epilepsy research, 2014Co-Authors: Meneka K. Sidhu, Jason Stretton, Gavin P. Winston, Mark R. Symms, Pamela J. Thompson, Matthias J. Koepp, John S. DuncanAbstract:Summary Aims In temporal lobe epilepsy (TLE) due to hippocampal sclerosis reorganisation in the Memory Encoding network has been consistently described. Distinct areas of reorganisation have been shown to be efficient when associated with successful subsequent Memory formation or inefficient when not associated with successful subsequent Memory. We investigated the effect of clinical parameters that modulate Memory functions: age at onset of epilepsy, epilepsy duration and seizure frequency in a large cohort of patients. Methods We studied 53 patients with unilateral TLE and hippocampal sclerosis (29 left). All participants performed a functional magnetic resonance imaging Memory Encoding paradigm of faces and words. A continuous regression analysis was used to investigate the effects of age at onset of epilepsy, epilepsy duration and seizure frequency on the activation patterns in the Memory Encoding network. Results Earlier age at onset of epilepsy was associated with left posterior hippocampus activations that were involved in successful subsequent Memory formation in left hippocampal sclerosis patients. No association of age at onset of epilepsy was seen with face Encoding in right hippocampal sclerosis patients. In both left hippocampal sclerosis patients during word Encoding and right hippocampal sclerosis patients during face Encoding, shorter duration of epilepsy and lower seizure frequency were associated with medial temporal lobe activations that were involved in successful Memory formation. Longer epilepsy duration and higher seizure frequency were associated with contralateral extra-temporal activations that were not associated with successful Memory formation. Conclusion Age at onset of epilepsy influenced verbal Memory Encoding in patients with TLE due to hippocampal sclerosis in the speech-dominant hemisphere. Shorter duration of epilepsy and lower seizure frequency were associated with less disruption of the efficient Memory Encoding network whilst longer duration and higher seizure frequency were associated with greater, inefficient, extra-temporal reorganisation.
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MK EFFECT OF AGE AT ONSET AND DURATION OF EPILEPSY ON Memory Encoding IN TEMPORAL LOBE EPILEPSY
Journal of Neurology Neurosurgery & Psychiatry, 2012Co-Authors: A Sidhu, Jason Stretton, Mark R. Symms, Pamela J. Thompson, Matthias J. Koepp, Gp Winston, Silvia B. Bonelli, John S. DuncanAbstract:Rationale Earlier age at onset and longer duration of epilepsy is associated with more severe neuropsychological impairment in temporal lobe epilepsy (TLE). The prefrontal cortex (PFC) and medial temporal lobe (MTL) play a fundamental role in Memory Encoding demonstrating material specific fMRI activations with verbal and non-verbal Memory tasks on the left and right respectively. It has shown that patients with hippocampal sclerosis (HS) ipsilateral to the side of material Encoding additionally recruit the contralateral MTL and PFC. We therefore aimed to investigate the effect of age at onset of epilepsy on the Memory Encoding network in TLE patients. Methods 53 pre-surgical patients with unilateral HS (29 left) performed an fMRI Memory Encoding paradigm of faces and words. fMRI analysis was performed with SPM8. The effect of age at onset and duration of epilepsy was explored in an ANCOVA. Results: Age at onset In the left HS group, earlier age at onset was associated with bilateral posterior hippocampal and temporal activations whereas later onset correlated with increased left anterior temporal and frontal activations during word Encoding. There was no correlation between age at onset and face Encoding for either of the patient groups during face Encoding. Duration Shorter duration of epilepsy associated with left anterior hippocampal activations whilst longer duration associated with frontal activations in Left HS patients during word and face Encoding. No significant effect of duration of epilepsy was seen in right HS patients during face and word Encoding. Conclusions Earlier age at onset and longer duration of epilepsy in the dominant hemisphere is associated with posterior temporal and frontal reorganisation respectively during Encoding.
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1218 Frontal lobe activity during Memory Encoding in temporal lobe epilepsy
Journal of Neurology Neurosurgery & Psychiatry, 2012Co-Authors: Meneka K. Sidhu, Jason Stretton, Matthias J. Koepp, Gp Winston, Christian Vollmar, Silvia B. Bonelli, Paul M. Thompson, John S. DuncanAbstract:Purpose The contribution of the frontal lobes to Memory Encoding has been recently appreciated. Functional MRI (fMRI) studies have demonstrated material specific prefrontal cortex (PFC) activations with verbal and non-verbal Memory tasks on the left and right respectively in healthy individuals. We investigated the patterns of PFC activations in Memory Encoding for both verbal and non-verbal episodic Memory in Temporal Lobe Epilepsy (TLE) patients using fMRI. Methods 27 healthy controls and 42 patients with hippocampal sclerosis (21 Right) were scanned on a 3T MRI scanner. An fMRI paradigm of Memory Encoding of faces and words was employed. fMRI analysis was performed with SPM8. Results Word Encoding: controls and right HS patients activated the left PFC. Patients with left HS showed bilateral HC activations and significant additional right PFC activations greater than in controls and the right HS group p Conclusion We showed material specific PFC lateralisation in healthy controls as previously described. Patients with HS ipsilateral to side of material Encoding showed additional contralateral PFC activations, implying reorganisation of the underlying network to involve the contralateral frontal lobes.
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Material-specific lateralization of Memory Encoding in the medial temporal lobe: blocked versus event-related design.
NeuroImage, 2005Co-Authors: H W R Powell, Mark R. Symms, Pamela J. Thompson, Matthias J. Koepp, John S. Duncan, P A Boulby, Afraim Salek-haddadi, Mark P. RichardsonAbstract:Lesion-deficit studies have provided evidence for a functional dissociation between the left medial temporal lobe (MTL) mediating verbal Memory Encoding and right MTL mediating non-verbal Memory Encoding. While a small number of functional MRI studies have demonstrated similar findings, none has looked specifically for material-specific lateralization using subsequent Memory effects. In addition, in many fMRI studies, Encoding activity has been located in posterior MTL structures, at odds with lesion-deficit and positron emission tomography (PET) evidence. In this study, we used an event-related fMRI Memory Encoding paradigm to demonstrate a material-specific lateralization of Encoding in the medial temporal lobes of ten healthy control subjects. Activation was left-lateralized for word Encoding, bilateral for picture Encoding, and right-lateralized for face Encoding. Secondly, we demonstrated the locations of activations revealed using an event-related analysis to be more anterior than those revealed using a blocked analysis of the same data. This suggests that anterior MTL structures underlie Memory Encoding as judged by subsequent Memory effects, and that more posterior activity detected in other fMRI studies is related to deficiencies of blocked designs in the analysis of Memory Encoding.
Kevin S Labar - One of the best experts on this subject based on the ideXlab platform.
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Reprint of: fMRI studies of successful emotional Memory Encoding: a quantitative meta-analysis.
Neuropsychologia, 2011Co-Authors: Vishnu P. Murty, R. Alison Adcock, Maureen Ritchey, Kevin S LabarAbstract:Over the past decade, fMRI techniques have been increasingly used to interrogate the neural correlates of successful emotional Memory Encoding. These investigations have typically aimed to either characterize the contributions of the amygdala and medial temporal lobe (MTL) Memory system, replicating results in animals, or delineate the neural correlates of specific behavioral phenomena. It has remained difficult, however, to synthesize these findings into a systems neuroscience account of how networks across the whole-brain support the enhancing effects of emotion on Memory Encoding. To this end, the present study employed a meta-analytic approach using activation likelihood estimates to assess the anatomical specificity and reliability of event-related fMRI activations related to successful Memory Encoding for emotional versus neutral information. The meta-analysis revealed consistent clusters within bilateral amygdala, anterior hippocampus, anterior and posterior parahippocampal gyrus, the ventral visual stream, left lateral prefrontal cortex and right ventral parietal cortex. The results within the amygdala and MTL support a wealth of findings from the animal literature linking these regions to arousal-mediated Memory effects. The consistency of findings in cortical targets, including the visual, prefrontal, and parietal cortices, underscores the importance of generating hypotheses regarding their participation in emotional Memory formation. In particular, we propose that the amygdala interacts with these structures to promote enhancements in perceptual processing, semantic elaboration, and attention, which serve to benefit subsequent Memory for emotional material. These findings may motivate future research on emotional modulation of widespread neural systems and the implications of this modulation for cognition.
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fMRI studies of successful emotional Memory Encoding: A quantitative meta-analysis
Neuropsychologia, 2010Co-Authors: Vishnu P. Murty, R. Alison Adcock, Maureen Ritchey, Kevin S LabarAbstract:Over the past decade, fMRI techniques have been increasingly used to interrogate the neural correlates of successful emotional Memory Encoding. These investigations have typically aimed to either characterize the contributions of the amygdala and medial temporal lobe (MTL) Memory system, replicating results in animals, or delineate the neural correlates of specific behavioral phenomena. It has remained difficult, however, to synthesize these findings into a systems neuroscience account of how networks across the whole-brain support the enhancing effects of emotion on Memory Encoding. To this end, the present study employed a meta-analytic approach using activation likelihood estimates to assess the anatomical specificity and reliability of event-related fMRI activations related to successful Memory Encoding for emotional versus neutral information. The meta-analysis revealed consistent clusters within bilateral amygdala, anterior hippocampus, anterior and posterior parahippocampal gyrus, the ventral visual stream, left lateral prefrontal cortex and right ventral parietal cortex. The results within the amygdala and MTL support a wealth of findings from the animal literature linking these regions to arousal-mediated Memory effects. The consistency of findings in cortical targets, including the visual, prefrontal, and parietal cortices, underscores the importance of generating hypotheses regarding their participation in emotional Memory formation. In particular, we propose that the amygdala interacts with these structures to promote enhancements in perceptual processing, semantic elaboration, and attention, which serve to benefit subsequent Memory for emotional material. These findings may motivate future research on emotional modulation of widespread neural systems and the implications of this modulation for cognition.
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fMRI studies of successful emotional Memory Encoding: A quantitative
2010Co-Authors: Vishnu P. Murty, R. Alison Adcock, Maureen Ritchey, Kevin S LabarAbstract:Over the past decade, fMRI techniques have been increasingly used to interrogate the neural correlates of successful emotional Memory Encoding. These investigations have typically aimed to either characterize the contributions of the amygdala and medial temporal lobe (MTL) Memory system, replicating results in animals, or delineate the neural correlates of specific behavioral phenomena. It has remained difficult, however, to synthesize these findings into a systems neuroscience account of how networks across the whole-brain support the enhancing effects of emotion on Memory Encoding. To this end, the present study employed a meta-analytic approach using activation likelihood estimates to assess the anatomical specificity and reliability of event-related fMRI activations related to successful Memory Encoding for emotional versus neutral information. The meta-analysis revealed consistent clusters within bilateral amygdala, anterior hippocampus, anterior and posterior parahippocampal gyrus, the ventral visual stream, left lateral prefrontal cortex and right ventral parietal cortex. The results within the amygdala and MTL support a wealth of findings from the animal literature linking these regions to arousal-mediated Memory effects. The consistency of findings in cortical targets, including the visual, prefrontal, and parietal cortices, underscores the importance of generating hypotheses regarding their participation in emotional Memory formation. In particular, we propose that the amygdala interacts with these structures to promote enhancements in perceptual processing, semantic elaboration, and attention, which serve to benefit subsequent Memory for emotional material. These findings may motivate future research on emotional modulation of widespread neural systems and the implications of this modulation for cognition.
Christian E. Elger - One of the best experts on this subject based on the ideXlab platform.
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medial temporal theta alpha power enhancement precedes successful Memory Encoding evidence based on intracranial eeg
The Journal of Neuroscience, 2011Co-Authors: Juergen Fell, Christian E. Elger, Eva Ludowig, Bernhard P. Staresina, Tobias Wagner, Thorsten A. Kranz, Nikolai AxmacherAbstract:Not only poststimulus, but also prestimulus neural activity has been shown to be predictive for later successful Memory Encoding. However, it is still not clear which medial temporal lobe processes precede effective Memory formation. Here, our aim was to investigate whether such prestimulus markers for successful Memory Encoding can be specified based on intracranial recordings directly from the hippocampus and rhinal cortex. For this purpose, we analyzed subsequent Memory effects during a continuous word recognition paradigm in 31 presurgical epilepsy patients. We found that rhinal and hippocampal theta and successive alpha power enhancement before word presentation predicted successful Memory Encoding. Previous studies suggest that stimulus-triggered hippocampal theta activity is particularly related to Memory retrieval and activation of a mnemonic context, whereas the alpha rhythm reflects inhibitory top-down control of task processing and executive functioning. In line with these suggestions, we propose that the observed medial temporal theta and alpha power increases before stimulus presentation reflect activation of contextual information and inhibitory top-down control processes preparing for stimulus-triggered Memory processing.
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Medial Temporal Theta/Alpha Power Enhancement Precedes Successful Memory Encoding: Evidence Based on Intracranial EEG
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2011Co-Authors: Juergen Fell, Christian E. Elger, Eva Ludowig, Bernhard P. Staresina, Tobias Wagner, Thorsten A. Kranz, Nikolai AxmacherAbstract:Not only poststimulus, but also prestimulus neural activity has been shown to be predictive for later successful Memory Encoding. However, it is still not clear which medial temporal lobe processes precede effective Memory formation. Here, our aim was to investigate whether such prestimulus markers for successful Memory Encoding can be specified based on intracranial recordings directly from the hippocampus and rhinal cortex. For this purpose, we analyzed subsequent Memory effects during a continuous word recognition paradigm in 31 presurgical epilepsy patients. We found that rhinal and hippocampal theta and successive alpha power enhancement before word presentation predicted successful Memory Encoding. Previous studies suggest that stimulus-triggered hippocampal theta activity is particularly related to Memory retrieval and activation of a mnemonic context, whereas the alpha rhythm reflects inhibitory top-down control of task processing and executive functioning. In line with these suggestions, we propose that the observed medial temporal theta and alpha power increases before stimulus presentation reflect activation of contextual information and inhibitory top-down control processes preparing for stimulus-triggered Memory processing.
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Differential effects of semantic processing on Memory Encoding.
Human brain mapping, 2010Co-Authors: Klaus Fliessbach, Corinna Buerger, Peter Trautner, Christian E. Elger, Bernd WeberAbstract:Deeper semantic processing of words leads to enhanced Memory Encoding (depth of processing effect). The left inferior prefrontal cortex (LIPC) and the left hippocampus are known to be involved in this effect. We tested the hypothesis that different semantic Encoding processes contribute qualitatively differently to Memory Encoding. In a Memory experiment using functional magnetic resonance imaging, we compared three different Encoding tasks: a nonsemantic alphabetical, an animacy decision, and a size comparison tasks. Recognition Memory was tested subsequently. We hypothesized that the size comparison task would activate brain areas involved in the processing of object features and that this would be associated with successful Memory Encoding. Results showed that the size comparison task led to significantly better Memory Encoding than the two other tasks. As with the animacy decision task, it led to stronger activation of the LIPC and left hippocampus than the nonsemantic task. Both regions also had stronger activations for later remembered than for nonremembered words. The size comparison task additionally led to stronger activation in the left anterior fusiform gyrus, which was also associated with successful Memory Encoding. We conclude that different types of semantic processing affect Memory Encoding based on distinguishable brain processes.
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Comparison of implicit Memory Encoding paradigms for the activation of mediotemporal structures
Epilepsy & behavior : E&B, 2007Co-Authors: Bernd Weber, Frank Kügler, Christian E. ElgerAbstract:The medial temporal lobes (MTLs) are essential for both Encoding and retrieval processes in declarative Memory. In addition, they are a frequent seizure focus for medically refractory epilepsy. One of the major side effects of MTL resection is a decline in Memory functions. Most functional imaging paradigms have been developed to find preoperative measures that, to obtain a prognosis of postoperative Memory performance, employ explicit Memory Encoding strategies to elicit MTL activation, and require a great amount of cognitive effort. We applied three different implicit Encoding tasks, which require less effort and time, to a group of healthy subjects. We found left-lateralized activation for verbal stimuli, bilateral activation for pictures, and right-lateralized activation for faces. The present study shows that even with an implicit Memory-Encoding paradigm, a lateralized activation of MTL structures can be achieved. This may lead to paradigms for routine clinical application that require less cognitive effort and time on the part of patients.
Jerzy P. Szaflarski - One of the best experts on this subject based on the ideXlab platform.
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The effect of medial temporal lobe epilepsy on visual Memory Encoding.
Epilepsy & behavior : E&B, 2015Co-Authors: A.m. Gregory, Rodolphe Nenert, Jane B. Allendorfer, Roy C. Martin, Rajesh K. Kana, Jerzy P. SzaflarskiAbstract:Abstract Effective visual Memory Encoding, a function important for everyday functioning, relies on episodic and semantic Memory processes. In patients with medial temporal lobe epilepsy (MTLE), Memory deficits are common as the structures typically involved in seizure generation are also involved in acquisition, maintenance, and retrieval of episodic memories. In this study, we used group independent component analysis (GICA) combined with Granger causality analysis to investigate the neuronal networks involved in visual Memory Encoding during a complex fMRI scene-Encoding task in patients with left MTLE (LMTLE; N = 28) and in patients with right MTLE (RMTLE; N = 18). Additionally, we built models of Memory Encoding in LMTLE and RMTLE and compared them with a model of healthy Memory Encoding (Nenert et al., 2014). For those with LMTLE, we identified and retained for further analyses and model generation 7 ICA task-related components that were attributed to four different networks: the frontal and posterior components of the DMN, visual network, auditory-insular network, and an “other” network. For those with RMTLE, ICA produced 9 task-related components that were attributed to the somatosensory and cerebellar networks in addition to the same networks as in patients with LMTLE. Granger causality analysis revealed group differences in causality relations within the visual Memory network and MTLE-related deviations from normal network function. Our results demonstrate differences in the networks for visual Memory Encoding between those with LMTLE and those with RMTLE. Consistent with previous studies, the organization of Memory Encoding is dependent on laterality of seizure focus and may be mediated by functional reorganization in chronic epilepsy. These differences may underlie the observed differences in Memory abilities between patients with LMTLE and patients with RMTLE and highlight the modulating effects of epilepsy on the network for Memory Encoding.
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A model for visual Memory Encoding.
PloS one, 2014Co-Authors: Rodolphe Nenert, Jane B. Allendorfer, Jerzy P. SzaflarskiAbstract:Memory Encoding engages multiple concurrent and sequential processes. While the individual processes involved in successful Encoding have been examined in many studies, a sequence of events and the importance of modules associated with Memory Encoding has not been established. For this reason, we sought to perform a comprehensive examination of the network for Memory Encoding using data driven methods and to determine the directionality of the information flow in order to build a viable model of visual Memory Encoding. Forty healthy controls ages 19–59 performed a visual scene Encoding task. FMRI data were preprocessed using SPM8 and then processed using independent component analysis (ICA) with the reliability of the identified components confirmed using ICASSO as implemented in GIFT. The directionality of the information flow was examined using Granger causality analyses (GCA). All participants performed the fMRI task well above the chance level (>90% correct on both active and control conditions) and the post-fMRI testing recall revealed correct Memory Encoding at 86.33±5.83%. ICA identified involvement of components of five different networks in the process of Memory Encoding, and the GCA allowed for the directionality of the information flow to be assessed, from visual cortex via ventral stream to the attention network and then to the default mode network (DMN). Two additional networks involved in this process were the cerebellar and the auditory-insular network. This study provides evidence that successful visual Memory Encoding is dependent on multiple modules that are part of other networks that are only indirectly related to the main process. This model may help to identify the node(s) of the network that are affected by a specific disease processes and explain the presence of Memory Encoding difficulties in patients in whom focal or global network dysfunction exists.
Matthias J. Koepp - One of the best experts on this subject based on the ideXlab platform.
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Factors affecting reorganisation of Memory Encoding networks in temporal lobe epilepsy
Epilepsy research, 2014Co-Authors: Meneka K. Sidhu, Jason Stretton, Gavin P. Winston, Mark R. Symms, Pamela J. Thompson, Matthias J. Koepp, John S. DuncanAbstract:Summary Aims In temporal lobe epilepsy (TLE) due to hippocampal sclerosis reorganisation in the Memory Encoding network has been consistently described. Distinct areas of reorganisation have been shown to be efficient when associated with successful subsequent Memory formation or inefficient when not associated with successful subsequent Memory. We investigated the effect of clinical parameters that modulate Memory functions: age at onset of epilepsy, epilepsy duration and seizure frequency in a large cohort of patients. Methods We studied 53 patients with unilateral TLE and hippocampal sclerosis (29 left). All participants performed a functional magnetic resonance imaging Memory Encoding paradigm of faces and words. A continuous regression analysis was used to investigate the effects of age at onset of epilepsy, epilepsy duration and seizure frequency on the activation patterns in the Memory Encoding network. Results Earlier age at onset of epilepsy was associated with left posterior hippocampus activations that were involved in successful subsequent Memory formation in left hippocampal sclerosis patients. No association of age at onset of epilepsy was seen with face Encoding in right hippocampal sclerosis patients. In both left hippocampal sclerosis patients during word Encoding and right hippocampal sclerosis patients during face Encoding, shorter duration of epilepsy and lower seizure frequency were associated with medial temporal lobe activations that were involved in successful Memory formation. Longer epilepsy duration and higher seizure frequency were associated with contralateral extra-temporal activations that were not associated with successful Memory formation. Conclusion Age at onset of epilepsy influenced verbal Memory Encoding in patients with TLE due to hippocampal sclerosis in the speech-dominant hemisphere. Shorter duration of epilepsy and lower seizure frequency were associated with less disruption of the efficient Memory Encoding network whilst longer duration and higher seizure frequency were associated with greater, inefficient, extra-temporal reorganisation.
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MK EFFECT OF AGE AT ONSET AND DURATION OF EPILEPSY ON Memory Encoding IN TEMPORAL LOBE EPILEPSY
Journal of Neurology Neurosurgery & Psychiatry, 2012Co-Authors: A Sidhu, Jason Stretton, Mark R. Symms, Pamela J. Thompson, Matthias J. Koepp, Gp Winston, Silvia B. Bonelli, John S. DuncanAbstract:Rationale Earlier age at onset and longer duration of epilepsy is associated with more severe neuropsychological impairment in temporal lobe epilepsy (TLE). The prefrontal cortex (PFC) and medial temporal lobe (MTL) play a fundamental role in Memory Encoding demonstrating material specific fMRI activations with verbal and non-verbal Memory tasks on the left and right respectively. It has shown that patients with hippocampal sclerosis (HS) ipsilateral to the side of material Encoding additionally recruit the contralateral MTL and PFC. We therefore aimed to investigate the effect of age at onset of epilepsy on the Memory Encoding network in TLE patients. Methods 53 pre-surgical patients with unilateral HS (29 left) performed an fMRI Memory Encoding paradigm of faces and words. fMRI analysis was performed with SPM8. The effect of age at onset and duration of epilepsy was explored in an ANCOVA. Results: Age at onset In the left HS group, earlier age at onset was associated with bilateral posterior hippocampal and temporal activations whereas later onset correlated with increased left anterior temporal and frontal activations during word Encoding. There was no correlation between age at onset and face Encoding for either of the patient groups during face Encoding. Duration Shorter duration of epilepsy associated with left anterior hippocampal activations whilst longer duration associated with frontal activations in Left HS patients during word and face Encoding. No significant effect of duration of epilepsy was seen in right HS patients during face and word Encoding. Conclusions Earlier age at onset and longer duration of epilepsy in the dominant hemisphere is associated with posterior temporal and frontal reorganisation respectively during Encoding.
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1218 Frontal lobe activity during Memory Encoding in temporal lobe epilepsy
Journal of Neurology Neurosurgery & Psychiatry, 2012Co-Authors: Meneka K. Sidhu, Jason Stretton, Matthias J. Koepp, Gp Winston, Christian Vollmar, Silvia B. Bonelli, Paul M. Thompson, John S. DuncanAbstract:Purpose The contribution of the frontal lobes to Memory Encoding has been recently appreciated. Functional MRI (fMRI) studies have demonstrated material specific prefrontal cortex (PFC) activations with verbal and non-verbal Memory tasks on the left and right respectively in healthy individuals. We investigated the patterns of PFC activations in Memory Encoding for both verbal and non-verbal episodic Memory in Temporal Lobe Epilepsy (TLE) patients using fMRI. Methods 27 healthy controls and 42 patients with hippocampal sclerosis (21 Right) were scanned on a 3T MRI scanner. An fMRI paradigm of Memory Encoding of faces and words was employed. fMRI analysis was performed with SPM8. Results Word Encoding: controls and right HS patients activated the left PFC. Patients with left HS showed bilateral HC activations and significant additional right PFC activations greater than in controls and the right HS group p Conclusion We showed material specific PFC lateralisation in healthy controls as previously described. Patients with HS ipsilateral to side of material Encoding showed additional contralateral PFC activations, implying reorganisation of the underlying network to involve the contralateral frontal lobes.
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Material-specific lateralization of Memory Encoding in the medial temporal lobe: blocked versus event-related design.
NeuroImage, 2005Co-Authors: H W R Powell, Mark R. Symms, Pamela J. Thompson, Matthias J. Koepp, John S. Duncan, P A Boulby, Afraim Salek-haddadi, Mark P. RichardsonAbstract:Lesion-deficit studies have provided evidence for a functional dissociation between the left medial temporal lobe (MTL) mediating verbal Memory Encoding and right MTL mediating non-verbal Memory Encoding. While a small number of functional MRI studies have demonstrated similar findings, none has looked specifically for material-specific lateralization using subsequent Memory effects. In addition, in many fMRI studies, Encoding activity has been located in posterior MTL structures, at odds with lesion-deficit and positron emission tomography (PET) evidence. In this study, we used an event-related fMRI Memory Encoding paradigm to demonstrate a material-specific lateralization of Encoding in the medial temporal lobes of ten healthy control subjects. Activation was left-lateralized for word Encoding, bilateral for picture Encoding, and right-lateralized for face Encoding. Secondly, we demonstrated the locations of activations revealed using an event-related analysis to be more anterior than those revealed using a blocked analysis of the same data. This suggests that anterior MTL structures underlie Memory Encoding as judged by subsequent Memory effects, and that more posterior activity detected in other fMRI studies is related to deficiencies of blocked designs in the analysis of Memory Encoding.