Left Medial Temporal Lobe Research Articles

Brain structure and symptom dimensions in borderline personality disorder.

Borderline personality disorder (BPD) presents with symptoms across different domains, whose neurobiology is poorly understood. We applied voxel-based morphometry on high-resolution magnetic resonance imaging scans of 19 female BPD patients and 50 matched female controls. Group comparison showed bilateral orbitofrontal gray matter loss in patients, but no significant changes in the hippocampus. Voxel-wise correlation of gray matter with symptom severity scores from the Borderline Symptom List (BSL-95) showed overall negative correlation in bilateral prefrontal, right inferior temporal/fusiform and occipital cortices, and left thalamus. Significant (negative) correlations with BSL-95 subscores within the patient cohort linked autoaggression to left lateral prefrontal and insular cortices, right inferior temporal/temporal pole, and right orbital cortex; dysthymia/dysphoria to right orbitofrontal cortex; self-perception to left postcentral, bilateral inferior/middle temporal, right orbitofrontal, and occipital cortices. Schema therapy-based Young Schema Questionnaire (YSQ-S2) scores of early maladaptive schemas on emotional deprivation were linked to left medial temporal lobe gray matter reductions. Our results confirm orbitofrontal structural deficits in BPD, while providing a framework and preliminary findings on identifying structural correlates of symptom dimensions in BPD, especially with dorsolateral and orbitofrontal cortices.

Complex partial seizures as sole presentation of acute stroke - Rare learning case

68 years old gentleman presented to ER with three days history of sudden onset of frequent spells of confusion and memory disturbance. These last for thirty to forty seconds at a time leaving him feeling very tired. His wife noted that he becomes unresponsive and stares in vague without jerks. He also described feeling as if he goes in a short dream repeatedly. He is diabetic, hypertensive and had CABG previously. Also suffered with long standing depression using SSRI’s on and off. No past history of similar symptoms, TIA or stroke. He admitted to have low mood. Clinically was fully alert, orientated but was unable to read or write nor to perform simple calculation without other focal signs. HisECG and basic blood tests were within normal limits. An MRI scan of the brain revealed a subacute infarction in the left medial temporal lobe with spots of minor bleeds. An EEG showed active seizure discharges from the same area. He was managed as inpatient with Aspirin and clopidogrel, atorvastatin and levetiracetam. He did well and all his symptoms resolved. He remained stable on follow up in the out patient three weeks later. Although it is well known, but very rare for a stroke to present with complex partial seizures without classical focal neurological signs, presenting with only seizures is even rarer. The back ground of depressive illness and vagueness of symptoms delayed his reporting to emergency department. Acute onset of neurological symptoms in a patient of such age with vascular risks should lead to imaging early.

Longitudinal Effects of Bumetanide on Neuro-Cognitive Functioning in Drug-Resistant Epilepsy.

Antiepileptic drugs (AEDs) have repeatedly shown inconsistent and almost contradictory effects on the neurocognitive system, from substantial impairments in processing speed to the noticeable improvement in working memory and executive functioning. Previous studies have provided a novel insight into the cognitive improvement by bumetanide as a potential antiepileptic drug. Through the current investigation, we evaluated the longitudinal effects of bumetanide, an NKCC1 co-transporter antagonist, on the brain microstructural organization as a probable underlying component for cognitive performance. Microstructure assessment was completed using SPM for the whole brain assay and Freesurfer/TRACULA for the automatic probabilistic tractography analysis. Primary cognitive operations including selective attention and processing speed, working memory capacity and spatial memory were evaluated in 12 patients with a confirmed diagnosis of refractory epilepsy. Participants treated with bumetanide (2 mg/ day) in two divided doses as an adjuvant therapy to their regular AEDs for 6 months, which followed by the re-assessment of their cognitive functions and microstructural organizations. Seizure frequency reduced in eight patients which accompanied by white matter reconstruction; fractional anisotropy (FA) increased in the cingulum-cingulate gyrus (CCG), anterior thalamic radiation (ATR), and temporal part of the superior longitudinal fasciculus (SLFt) in correlation with the clinical response. The voxel-based analysis in responder patients revealed increased FA in the left hippocampus, right cerebellum, and right medial temporal lobe, while mean diffusivity (MD) values reduced in the right occipital lobe and cerebellum. Microstructural changes in SLFt and ATR accompanied by a reduction in the error rate in the spatial memory test. These primary results have provided preliminary evidence for the effect of bumetanide on cognitive functioning through microstructural changes in patients with drug-resistant epilepsy.

Gray matter predictors of treatment outcomes in semantic variant primary progressive aphasia

Gray matter predictors of treatment outcomes in semantic variant primary progressive aphasia

Specific lexico-semantic predictions are associated with unique spatial and temporal patterns of neural activity.

We used Magnetoencephalography (MEG) in combination with Representational Similarity Analysis to probe neural activity associated with distinct, item-specific lexico-semantic predictions during language comprehension. MEG activity was measured as participants read highly constraining sentences in which the final words could be predicted. Before the onset of the predicted words, both the spatial and temporal patterns of brain activity were more similar when the same words were predicted than when different words were predicted. The temporal patterns localized to the left inferior and medial temporal lobe. These findings provide evidence that unique spatial and temporal patterns of neural activity are associated with item-specific lexico-semantic predictions. We suggest that the unique spatial patterns reflected the prediction of spatially distributed semantic features associated with the predicted word, and that the left inferior/medial temporal lobe played a role in temporally 'binding' these features, giving rise to unique lexico-semantic predictions.

Absence of an early hippocampal encoding signal after medial temporal lesions: No consequence for the spacing effect.

Immediately repeated meaningful pictures in a continuous recognition task induce a positive frontal potential at about 200-300 ms, which appears to emanate from the medial temporal lobe (MTL) centered on the hippocampus, as concluded from inverse solutions, coherence measurements, and depth electrode recordings in humans. In this study, we tested patients with unilateral MTL lesions due to stroke to verify the provenance of this signal and its association with the spacing effect (SE)-the improved learning of material encountered in spaced rather than massed presentation. We found that unilateral left or right MTL lesions abolished the early frontal MTL-mediated signal but not the spacing effect. We conclude that the SE does not depend on MTL integrity. We suggest that the early frontal signal at 200-300 ms after immediate picture repetition may serve as a direct biomarker of MTL integrity that may be useful in the early stages of diseases like Alzheimer's.

Functional Connectivity of Paired Default Mode Network Subregions in Retinal Detachment.

PurposeTo explore the difference of the default mode network (DMN) in patients with retinal detachment (RD) by the study of the resting state functional connectivity (rs-FC).MethodsA total of 30 patients with RD (16 men, 14 women) and 30 similarly matched normal controls (NCs) were examined and recorded with rs-fMRI. The DMN was divided into eight core regions, and each rs-FC map of each subregion was obtained. The receiver operating characteristic (ROC) curve was performed to classify the mean FC values of RD patients from NCs, and the interrelationships between the FC and each region were evaluated with Pearson's correlation analysis.ResultsCompared with NCs, there were significantly increased FC in the left medial temporal lobe (MTL.L) and posterior cingulate cortex (PCC), MTL.L and left hippocampus formation (HF.L), MTL.L and HF.R, MTL.L and left inferior parietal cortices (IPC.L), MTL.L and IPC.R in the RD group (P < 0.05). Nevertheless, no correlation between the FC values of each paired region and the manifestations was found in the RD group. ROC curve analysis showed that the accuracy of the area under the curve was excellent in MTL.L-HF.R and MTL.L-IPC.R and less reliable in MTL.L-PCC, MTL.L-HF.L, and MTL.L-IPC.L.ConclusionsThe visual function impairments of RD patients were closely related to the DMN functional connections, which provided insight into the neural variation in RD patients and assisted in revealing the potential mechanisms of RD.Translational RelevanceThis study provided insight into the neural variation in RD patients and assisted in revealing the potential mechanisms of RD.

Smaller medial temporal lobe volumes in individuals with subjective cognitive decline and biomarker evidence of Alzheimer's disease—Data from three memory clinic studies

IntroductionPrevious studies showed associations of brain volume differences and biomarker evidence for Alzheimer's disease (AD) in subjective cognitive decline (SCD). The consistency of this finding across SCD studies has not been investigated. MethodsWe studied gray matter volume differences between SCD subjects with and without cerebrospinal fluid biomarker evidence for AD across three European memory clinic samples (German Center for Neurodegenerative Diseases Longitudinal Cognitive Impairment and Dementia study, Amsterdam, Barcelona). Analysis of covariance models with samples and cerebrospinal fluid biomarkers as between-subject factors were calculated. ResultsA significant main effect for AD biomarker (Aβ42− > Aβ42+) in the left medial temporal lobe (MTL) was found, with the absence of main effects for sample or interaction effects between AD biomarker and sample. This indicates consistent lower left MTL volume across three samples in SCD subjects with abnormal Aβ42 levels. DiscussionOur results support the model that in the presence of AD pathology, SCD corresponds to the late preclinical stage (stage 2 of AD) with smaller MTL volumes.

Epigastric Paresthesia: Can It Be This Serious?

Intoduction: Paresthesia is an abnormal sensation caused by an altered sensory pathway anywhere from the peripheral nervous system up to the sensory cortex. Epigastric paresthesia is an unusual presentation that sometimes warrants an extensive workup to rule out any gastrointestinal pathology. In our patient the result of the workup was unexpected. Case Summary: A 58-year-old male with a history of hypertension and diabetes presented to the hospital with epigastric numbness and warmth sensation of 2 weeks duration. His numbness episodes were sudden, lasting 2-3 minutes, starting in the epigastric area, then spreading to the whole abdomen and extremities. These episodes were associated with nausea and vomiting but no abdominal pain, diarrhea or constipation. A Computed Tomography (CT) scans of the head, abdomen and pelvis were negative. Esophagogastroduodenoscopy (EGD) was negative for any pathology. Due to the suspicion of seizures, an Electroencephalogram (EEG) was done and showed spikes consistent with seizure tendency. A Magnetic Resonance Imaging (MRI) of the brain showed focal asymmetric enlargement of the left posterior medial temporal lobe with inhomogeneous mass enhancement concerning for a neoplasm (Figure 1-A, 2-A). A multi-disciplinary discussion including neurology, neurosurgery, and oncology thought that the MRI findings were secondary to enhancement from seizures, but the neoplastic process was not excluded. Patient was discharged on Levetiracetam 750 mg BID, with a scheduled MRI in 4 weeks. The repeat MRI showed increasing size and enhancement of the lesion concerning for a primary brain tumor (Figure 1-B, 2-B). As a result, a stereotactic needle biopsy and laser interstitial thermotherapy were performed, and the pathology showed high-grade glioma. His post-operative course was unremarkable, and he was discharged to follow up with neuro-oncology and neurosurgery. Conclusion: Epigastric paresthesia is a rare presentation, and when it is associated with GI upset it warrants a workup to rule out any GI pathology. Given the seriousness of the diagnosis in our patient, primary brain tumor should be considered with patients presenting with abdominal paresthesia.2477_A Figure 1. A: Brain mass at first presentation B: Brain mass 4 weeks later2477_B Figure 2. A: Brain mass at first presentation B: Brain mass 4 weeks later

Dynamic Causal Modeling of Preclinical Autosomal-Dominant Alzheimer's Disease.

Dynamic causal modeling (DCM) is a framework for making inferences about changes in brain connectivity using neuroimaging data. We fitted DCMs to high-density EEG data from subjects performing a semantic picture matching task. The subjects are carriers of the PSEN1 mutation, which leads to early onset Alzheimer’s disease, but at the time of EEG acquisition in 1999, these subjects were cognitively unimpaired. We asked 1) what is the optimal model architecture for explaining the event-related potentials in this population, 2) which connections are different between this Presymptomatic Carrier (PreC) group and a Non-Carrier (NonC) group performing the same task, and 3) which network connections are predictive of subsequent Mini-Mental State Exam (MMSE) trajectories. We found 1) a model with hierarchical rather than lateral connections between hemispheres to be optimal, 2) that a pathway from right inferotemporal cortex (IT) to left medial temporal lobe (MTL) was preferentially activated by incongruent items for subjects in the PreC group but not the NonC group, and 3) that increased effective connectivity among left MTL, right IT, and right MTL was predictive of subsequent MMSE scores.

A Rare Case of Paraneoplastic Encephalitis in Association With Breast Cancer

We present a case of a 47-year-old female who presented with diffuse dysesthetic pain in both legs for past 3 months. She described the sensation as of pins and needles. She also had balance difficulty and developed progressively worsening back pain and spasms. Relatives reported that the patient had memory difficulties. The patient would repeat questions even after the questions had already been answered. Magnetic resonance imaging (MRI) of cervical, thoracic and lumbosacral spine with and without contrast showed mild multilevel degenerative changes in cervical spine and minimal disc bulges from L1 to S1 levels with no areas of significant spinal canal or neural foraminal stenosis. MRI of brain was performed which showed abnormal T2/FLAIR hyperintensity along the left medial temporal lobe and additional small foci in the right centrum semiovale/corona radiate and bilateral periventricular white matter. Based on the MRI findings, a diagnosis of limbic encephalitis was made. A lumbar puncture was also done. Cerebrospinal fluid (CSF) showed 14 oligoclonal bands with elevated IgG synthesis. Paraneoplastic antibody panel showed high titers of amphiphysin antibody (1:15,360). Since this is a paraneoplastic antibody, computed tomography of chest, abdomen and pelvis was performed. It showed several enlarged right axillary lymph nodes. Ultrasound of right breast showed 4 mm hypoechoic nodule at 2 o’clock axis (upper inner quadrant). The biopsy of this lesion and axillary lymph node showed invasive ductal carcinoma of the breast. For further evaluation, MRI of bilateral breast was performed. It revealed additional areas of enhancements in upper outer and lower outer quadrants of right breast. Biopsy of the upper outer area of enhancement revealed invasive ductal carcinoma and ductal carcinoma in situ (DCIS). Biopsy of the lower outer aspect showed infiltrating lobular carcinoma and lobular carcinoma in situ (LCIS). Our report highlights a rare patient presenting with paraneoplastic limbic encephalitis with underlying breast cancer. When encountering a patient with unexplained neurologic symptoms, paraneoplastic neurological syndromes (PNSs) should be considered as part of the differential. And a thorough search of autoantibodies associated with PNS should be considered. If such autoantibodies are present, search for an underlying malignancy should be undertaken. J Med Cases. 2018;9(9):296-302 doi: https://doi.org/10.14740/jmc3120w

Regional Cerebral Blood Flow in Mania: Assessment Using 320-Slice Computed Tomography

Objectives: While evidence that episodes of mania in bipolar I are associated with changes in bioenergetic and regional cerebral blood flow (rCBF) and cerebral blood flow velocity (rCBFV), both the regions and the extent of these changes have not yet been defined. Therefore, we determined the pattern of regional cerebral perfusion mania patients and using patients with major depressive disorder (MDD) as positive controls and healthy participants as negative controls.Methods: Twenty participants with mania, together with 22 MDD patients and 24 healthy volunteers, were recruited for this study. On all participants, Transcranial Doppler (TCD) was conducted to measure rCBFV parameters, 320-slice CT was conducted to measure rCBF in the different cerebral artery regions, and hematological parameters were assessed. ANOVA and Pearson's tests were used for the statistical analysis.Results: Our data indicated that rCBF in the medial temporal lobe and hippocampus, especially in the left medial temporal lobe and the right hippocampus, was increased in the mania group compared with the control and MDD groups (p < 0.01). In contrast, rCBF in the medial temporal lobe and hippocampus was decreased in the depression group (p < 0.01) compared with healthy controls. In addition, values of rCBFV in the bilateral internal carotid arteries (ICAs) and middle cerebral arteries (MCA) were increased in mania (p < 0.01) in comparison to the MDD group. Whole blood viscosity and hematocrit as well as red blood cell sedimentation rate remained unchanged in all group (p > 0.05).Conclusions: In mania, rCBF is increased in the medial temporal lobe and hippocampus, with a corresponding increase in rCBFV in the same regions.

Intractable epilepsy associated with angiographic obliteration of a medial temporal arteriovenous malformation following stereotactic radiosurgery

Abstract We present a case with recurrence of intractable complex partial epilepsy, despite angiographic obliteration of a cerebral arteriovenous malformation in the left medial temporal lobe following gamma knife radiosurgery. Preoperative memory function was normal, with no evidence of hippocampal atrophy by magnetic resonance imaging. Intraoperative electrocorticography demonstrated two independent foci of paroxysmal activity in the lateral and medial temporal lobes. As preoperative magnetic resonance imaging demonstrated subcortical hyperintensity, the lateral temporal lobe was resected. Histologically, there was evidence of subcortical myelin pallor, likely resulting from ischemic damage associated with hemodynamic changes following radiosurgery. As there was a decrease in the frequency of paroxysmal discharges in the hippocampus following arteriovenous malformation nidus removal, the hippocampus was preserved. Histological examination of the nidus revealed that some of the vessels had patent lumina, while ischemia affecting the neighboring hippocampus was considered to show improvement. A good seizure outcome was obtained. In summary, perioperative multimodal examinations, including intraoperative electrocorticography, revealed various epileptogenic mechanisms, probably related to myelin pallor in the lateral temporal lobe and focal ischemia secondary to patent AVM in the medial temporal lobe, of this patient.

Interactive effects of seizure frequency and lateralization on intratemporal effective connectivity in temporal lobe epilepsy.

Patients with temporal lobe epilepsy (TLE) show brain connectivity changes in association with cognitive impairment. Seizure frequency and lateralization are 2 important clinical factors that characterize epileptic seizures. In this study, we sought to examine an interactive effect of the 2 seizure factors on intratemporal effective connectivity based on resting-state functional magnetic resonance imaging (rsfMRI) in patients with TLE. For rsfMRI data acquired from 48 TLE patients and 45 healthy controls, we applied stochastic dynamical causal modeling to infer effective connectivity between 3 medial temporal lobe (MTL) regions, including the hippocampus (Hipp), parahippocampal gyrus (PHG), and amygdala (Amyg), ipsilateral to the seizure focus. We searched for the effect of the 2 seizure factors, seizure frequency (good vs poor seizure control) and lateralization (left vs right TLE), on connection strengths and their relationship with the level of verbal memory and language impairment. Impairment of verbal memory and language function was mainly affected by seizure lateralization, consistent with preferential involvement of the left MTL in verbal mnemonic processing. For the fully connected model, which was selected as the effective connectivity structure that best explained the observed rsfMRI time series, alterations in connection strengths were primarily influenced by seizure frequency; there was an increase in the strength of the Hipp to PHG connection in TLE patients with poor seizure control, whereas the strength of the Amyg to PHG connection increased in those with good seizure control. Furthermore, the association between connection strength alterations and cognitive impairment was interactively affected by both seizure frequency and lateralization. These findings suggest an interactive effect as well as an individual effect of seizure frequency and lateralization on neuroimaging features and cognitive function. This potential interaction needs to be evaluated in the consideration of multiple seizure factors.

Severe episodic memory impairment after strategic infarct: A case report

ABSTRACT.Brain infarcts located in strategic regions often result in cognitive impairment. Based on a case study, this paper describes unusual and specific clinical and neuropsychological features of a strategic ischemic lesion in the left medial temporal lobe (MTL) structures. Taken together with the literature data, the case illustrates that a unilateral strategic infarct in MTL structures may result in severe impairment of episodic memory (EM), which refers to the ability to encode and retrieve personal experiences, including information about the time and place of an event and detailed description of the event itself. The preservation of other cognitive functions, the severe functional impairment, and the type of visual-verbal deficit in a left-sided lesion were identified as singular features of the case. The current case supports the critical role of the MTL structures in EM formation.

Effects of Combined Physical and Cognitive Exercises on Cognition and Mobility in Patients With Mild Cognitive Impairment: A Randomized Clinical Trial

ImportanceAlthough participation in physical and cognitive activities is encouraged to reduce the risk of dementia, the preventive efficacy of these activities for patients with mild cognitive impairment is unestablished. ObjectiveTo compare the cognitive and mobility effects of a 40-week program of combined cognitive and physical activity with those of a health education program. DesignA randomized, parallel, single-blind controlled trial. SettingA population-based study of participants recruited from Obu, a residential suburb of Nagoya, Japan. ParticipantsBetween August 2011 and February 2012, we evaluated 945 adults 65 years or older with mild cognitive impairment, enrolled 308, and randomly assigned them to the combined activity group (n = 154) or the health education control group (n = 154). InterventionsThe combined activity program involved weekly 90-minute sessions for 40 weeks focused on physical and cognitive activities. The control group attended 90-minute health promotion classes thrice during the 40-week trial period. MeasurementThe outcome measures were assessed at the study's beginning and end by personnel blinded to mild cognitive impairment subtype and group. The primary endpoints were postintervention changes in scores on (1) the Mini-Mental State Examination as a measure of general cognitive status and memory, (2) the Wechsler Memory Scale-Revised–Logical Memory II, and (3) the Rey Auditory Verbal Learning Test. We applied mobility assessments and assessed brain atrophy with magnetic resonance imaging. ResultsCompared with the control group, the combined activity group showed significantly greater scores on the Mini-Mental State Examination (difference = 0.8 points, P = .012) and Wechsler Memory Scale-Revised–Logical Memory II (difference = 1.0, P = .004), significant improvements in mobility and the nonmemory domains and reduced left medial temporal lobe atrophy in amnestic mild cognitive impairment (Z-score difference = −31.3, P < .05). ConclusionCombined physical and cognitive activity improves or maintains cognitive and physical performance in older adults with mild cognitive impairment, especially the amnestic type.

Automated diagnosis of temporal lobe epilepsy in the absence of interictal spikes.

ObjectiveTo diagnose and lateralise temporal lobe epilepsy (TLE) by building a classification system that uses directed functional connectivity patterns estimated during EEG periods without visible pathological activity.MethodsResting-state high-density EEG recording data from 20 left TLE patients, 20 right TLE patients and 35 healthy controls was used. Epochs without interictal spikes were selected. The cortical source activity was obtained for 82 regions of interest and whole-brain directed functional connectivity was estimated in the theta, alpha and beta frequency bands. These connectivity values were then used to build a classification system based on two two-class Random Forests classifiers: TLE vs healthy controls and left vs right TLE. Feature selection and classifier training were done in a leave-one-out procedure to compute the mean classification accuracy.ResultsThe diagnosis and lateralization classifiers achieved a high accuracy (90.7% and 90.0% respectively), sensitivity (95.0% and 90.0% respectively) and specificity (85.7% and 90.0% respectively). The most important features for diagnosis were the outflows from left and right medial temporal lobe, and for lateralization the right anterior cingulate cortex. The interaction between features was important to achieve correct classification.SignificanceThis is the first study to automatically diagnose and lateralise TLE based on EEG. The high accuracy achieved demonstrates the potential of directed functional connectivity estimated from EEG periods without visible pathological activity for helping in the diagnosis and lateralization of TLE.

Brain reactivity to visual food stimuli after moderate-intensity exercise in children.

Exercise may play a role in moderating eating behaviors. The purpose of this study was to examine the effect of an acute bout of exercise on neural responses to visual food stimuli in children ages 8-11years. We hypothesized that acute exercise would result in reduced activity in reward areas of the brain. Using a randomized cross-over design, 26 healthy weight children completed two separate laboratory conditions (exercise; sedentary). During the exercise condition, each participant completed a 30-min bout of exercise at moderate-intensity (~ 67% HR maximum) on a motor-driven treadmill. During the sedentary session, participants sat continuously for 30min. Neural responses to high- and low-calorie pictures of food were determined immediately following each condition using functional magnetic resonance imaging. There was a significant exercise condition*stimulus-type (high- vs. low-calorie pictures) interaction in the left hippocampus and right medial temporal lobe (p < 0.05). Main effects of exercise condition were observed in the left posterior central gyrus (reduced activation after exercise) (p < 0.05) and the right anterior insula (greater activation after exercise) (p < 0.05). The left hippocampus, right medial temporal lobe, left posterior central gyrus, and right anterior insula appear to be activated by visual food stimuli differently following an acute bout of exercise compared to a non-exercise sedentary session in 8-11year-old children. Specifically, an acute bout of exercise results in greater activation to high-calorie and reduced activation to low-calorie pictures of food in both the left hippocampus and right medial temporal lobe. This study shows that response to external food cues can be altered by exercise and understanding this mechanism will inform the development of future interventions aimed at altering energy intake in children.

Cortical Metabolic and Cognitive Correlates of Disorientation in Alzheimer's Disease.

Orientation to time, date, and place is commonly utilized in clinical settings to aid in diagnosis, staging, and monitoring of Alzheimer's disease (AD). This study aimed to identify the cerebral metabolic correlates of orientation in patients with AD, and the degree to which regions associated with orientation overlap with memory-related structures. Eighty-five patients with a diagnosis of probable AD underwent fluorodeoxyglucose positron emission tomography (FDG-PET) and neuropsychological testing. Orientation items from the Dementia Rating Scale and recognition performance from the Consortium to Establish a Registry for AD (CERAD) Word List Learning test were correlated with cerebral glucose metabolism. Post-hoc analyses examined neuropsychological predictors of orientation. Better orientation performance related to greater cerebral metabolism in the bilateral middle-inferior temporal lobes, bilateral middle-posterior cingulate, left angular gyrus, and left middle occipital gyrus. In comparison, higher CERAD recognition discriminability score was associated with greater metabolic activity in left medial temporal lobe regions including the hippocampal and parahippocampal gyri, and the left fusiform gyrus. Post-hoc behavioral analyses revealed multiple cognitive functions to be related to orientation, including list learning, recognition memory, visuospatial functioning, attention, and language. Findings from the present study suggest that disorientation in AD results from dysfunction of a network of structures and cognitive abilities commonly found to be implicated in AD. The study supports the notion that memory is necessary but not sufficient for successful orientation.

P362 Automated diagnosis of temporal lobe epilepsy in the absence of interictal spikes

Objective To diagnose and lateralise Temporal Lobe Epilepsy (TLE) by building a classification system that uses directed functional connectivity patterns estimated during EEG periods without visible pathological activity. Methods Resting-state high-density EEG recording data from 20 left TLE patients, 20 right TLE patients and 35 healthy controls was used. Epochs without interictal spikes were selected. The cortical source activity was obtained for 82 regions of interest and whole-brain directed functional connectivity was estimated in the theta, alpha and beta frequency bands. These connectivity values were then used to build a classification system based on two two-class Random Forests classifiers: TLE vs healthy controls and left vs right TLE. Feature selection and classifier training were done in a leave-one-out procedure to compute the mean classification accuracy. Results The diagnosis and lateralization classifiers achieved a high accuracy (90.7% and 90.0% respectively), sensitivity (95.0% and 90.0% respectively) and specificity (85.7% and 90.0% respectively). The most important features for diagnosis were the outflows from left and right medial temporal lobe, and for lateralization the right anterior cingulate cortex. The interaction between features was important to achieve correct classification. Conclusions This is the first study to automatically diagnose and lateralise TLE based on EEG. The high accuracy achieved demonstrates the potential of directed functional connectivity estimated from EEG periods without visible pathological activity for helping in the diagnosis and lateralization of TLE.