Biomedical subjects

Michael Seidenberg

Publications and source records attributed to Michael Seidenberg.

At least 19 recordsLinked to original sources

PubMed2007

Structural and functional neuroimaging correlates of depression in temporal lobe epilepsy.

Depression is commonly experienced among persons with temporal lobe epilepsy (TLE). Although evidence exists implicating dysfunction of distributed neural structure and circuitry among depressed persons without epilepsy, little is known regarding the neural correlates of depression in TLE. We examined the relationship between self-reported depression severity and both structural MRI volumetry and [(18)F]fluorodeoxyglucose positron emission tomography (PET)-measured resting metabolism of the amygdala and hippocampus of 18 patients with TLE. Significant positive relationships were noted between right and left amygdala volumes and depression. No other significant relationships were observed between amygdala PET measures, hippocampal volumes, or hippocampal PET measures and degree of depressive symptomatology. These findings indicate that both right and left amygdala volumes are associated with depression severity among persons with TLE. Future studies examining the potential role of extended neural regions may clarify the observed structural relationship between depressive symptoms and the amygdala.

Adolescent↗

PubMed2007

Cognitive phenotypes in temporal lobe epilepsy.

The objective of this study is to determine if distinct cognitive phenotypes could be identified in temporal lobe epilepsy. Epilepsy patients (n = 96) and healthy controls (n = 82) underwent comprehensive neuropsychological assessment. Adjusted (age, gender, and education) test scores for epilepsy subjects were grouped into cognitive domains (intelligence, language, visuoperception, immediate and delayed memory, executive function, and cognitive/psychomotor speed). Cluster analysis revealed three distinct cognitive profiles types: (1) minimally impaired (47% of subjects); (2) memory impaired (24%); and (3) memory, executive, and speed impaired (29%). The three cluster groups exhibited different patterns of results on demographic, clinical epilepsy, brain volumetrics, and cognitive course over a 4-year interval. The specific profile characteristics of the identified cognitive phenotypes are presented and their implications for the investigation of the neurobehavioral complications of epilepsy are discussed.

Adolescent↗

PubMed2006

Quality of life and comorbid medical and psychiatric conditions in temporal lobe epilepsy.

Patients with epilepsy frequently report dissatisfaction with their quality of life (QOL), and there is considerable interest in understanding the factors and mechanisms associated with this perception. To date, investigation has focused on the potential contribution of seizure variables (e.g., seizure control) and psychiatric conditions to QOL, but there has not been an examination of the potential role of comorbid medical conditions. Information was gathered concerning current medical and psychiatric conditions for 93 patients with temporal lobe epilepsy, and their relationship with QOL was examined. The numbers of medical and psychiatric conditions were distinct and significant predictors of QOL satisfaction, and both were stronger correlates than seizure-related factors and demographic variables. The implications of these findings for the treatment and management of patients with epilepsy are discussed.

Adult↗

PubMed2006

Children with new-onset epilepsy: neuropsychological status and brain structure.

Abnormalities in cognition, academic performance and brain volumetrics have been reported in children with chronic epilepsy. The nature and degree to which these problems may be present at epilepsy onset or may instead become more evident over time remains to be determined. This study characterizes neuropsychological status, brain structure and their interrelationship in children with recent-onset epilepsy compared with healthy controls. Children (age: 8-18 years) with recent-onset idiopathic epilepsy (n = 53) and healthy controls (n = 50) underwent comprehensive neuropsychological assessment and quantitative volumetric measurement of segmented (grey and white matter) volumes of total cerebrum and lobar regions. Compared with controls, children with recent-onset epilepsy exhibit a pattern of mild diffuse cognitive impairment, regardless of epilepsy syndrome, as well as academic underachievement that in a subset of children antedates the first recognized seizure. There are no overall differences in MR morphometric analyses of total cerebral or lobar tissue volumes. Controls show a strong association between cognitive development and increasing cerebral tissue volume (especially white matter volume), an association that is absent in children with epilepsy. Children with a history of academic achievement problems exhibit the most abnormal cognitive function and have significant volumetric reductions in left occipital and parietal lobe grey matter. Patients with idiopathic epilepsy exhibit cognitive dysfunction and academic underachievement at the onset of the disorder, irrespective of epilepsy syndrome, and indications of antecedent neurocognitive impairment are present in a subset of children. Volumetric abnormalities are not yet apparent in the epilepsy group as a whole, but there are indications of an altered structure-function relationship in epilepsy, and the subset of children with prior history of academic problems have abnormal volume of posterior left hemisphere grey matter. These early abnormalities need to be integrated into lifespan models of the neuropsychology of epilepsy.

Adolescent↗

PubMed2006

Cognitive prognosis in chronic temporal lobe epilepsy.

OBJECTIVE: First, to determine whether patients with chronic temporal lobe epilepsy have a different cognitive trajectory compared to control subjects over a prospective 4-year interval; second, to determine the proportion of patients who exhibit abnormal cognitive change and their profile of demographic, clinical epilepsy, and baseline quantitative magnetic resonance imaging characteristics; and third, to determine the most vulnerable cognitive domains. METHODS: Participants with chronic temporal lobe epilepsy (n = 46) attending a tertiary referral clinic and healthy control subjects (n = 65) underwent neuropsychological assessment and reevaluation 4 years later. Analysis of test-retest patterns identified individual patients with adverse cognition outcomes. RESULTS: The prospective cognitive trajectory of patients with chronic temporal lobe epilepsy differs from age- and sex-matched healthy control subjects. Lack of practice effects is common, but frank adverse cognitive outcomes are observed in a subset of patients (20-25%), particularly in vulnerable cognitive domains that include memory. Cognitive declines are associated with a profile of abnormalities in baseline quantitative magnetic resonance volumetrics, lower baseline intellectual capacity, as well as longer duration of epilepsy and older chronological age. INTERPRETATION: Cognitive prognosis is poor for a subset of patients characterized by chronicity of epilepsy, older age, lower intellectual ability, and more baseline abnormalities in quantitative magnetic resonance volumetrics.

Adolescent↗

PubMed2006

Memory for famous faces and the temporal pole: functional imaging findings in temporal lobe epilepsy.

The ability to recognize, name, and provide information about famous persons is deficient in patients with temporal lobe epilepsy (TLE), although the neural basis for these deficits is not well understood. We examined the relationship of resting metabolism of the temporal poles, as determined by [18F] fluorodeoxyglucose positron emission tomography, to performance on a task of famous face recognition, naming, and generation of semantic information in 12 patients with TLE. Correlations between metabolic measures of the temporal poles and performance on the Famous Faces Task revealed strong relationships between all aspects of the Famous Faces Task and the left temporal pole, whereas Famous Faces Task correlations with the right temporal pole were not significant. These findings indicate that the left temporal pole is associated with lexical and semantic retrieval of knowledge of famous persons in patients with TLE. Further study appears warranted to elucidate the networks involved in semantic knowledge for famous faces.

Adolescent↗

PubMed2006

Quantitative MRI biomarkers of cognitive morbidity in temporal lobe epilepsy.

PURPOSE: To determine the relation between neuropsychological morbidity, quantitative magnetic resonance imaging (MRI) measures of whole brain structure, and clinical seizure factors reflecting epilepsy cause, course, and treatment. METHODS: Quantitative MRI measurements of total (whole brain) cerebrospinal fluid (CSF) and gray- and white-matter volumes and clinical seizure features were examined in relation to summary indices of cognitive morbidity in 96 patients with temporal lobe epilepsy. MRI volumes were adjusted for intracranial volume (ICV), and cognitive scores were adjusted for age, education, and gender, based on a sample of 82 healthy controls. RESULTS: Whole-brain volumes (gray, white, and CSF) were abnormal in chronic temporal lobe epilepsy patients compared with controls and were related significantly to neuropsychological morbidity, especially total CSF. Statistical modeling demonstrated that markers of total atrophy (CSF) was the primary mediator of the relation between clinical seizure variables and neuropsychological morbidity. CONCLUSIONS: Quantitative measurements of overall brain abnormality (atrophy) in temporal lobe epilepsy are clinically meaningful markers that are associated with increased cognitive morbidity. These biomarkers appear to mediate the adverse effects of some clinical seizure variables on cognition.

Adolescent↗

PubMed2005

Age-related functional recruitment for famous name recognition: an event-related fMRI study.

Recent neuroimaging research shows that older adults exhibit recruitment, or increased activation on various cognitive tasks. The current study evaluated whether a similar pattern also occurs in semantic memory by evaluating age-related differences during recognition of Recent (since the 1990s) and Enduring (1950s to present) famous names. Fifteen healthy older and 15 healthy younger adults performed the name recognition task with a high and comparable degree of accuracy, although older adults had slower reaction time in response to Recent famous names. Event-related functional MRI showed extensive networks of activation in the two groups including posterior cingulate, right hippocampus, temporal lobe and left prefrontal regions. The Recent condition produced more extensive activation than the Enduring condition. Older adults had more extensive and greater magnitude of activation in 15 of 20 regions, particularly for the Recent condition (15 of 15; 7 of 15 also differed for Enduring); young adults did not show greater activation magnitude in any region. There were no group differences for non-famous names, indicating that age differences are task-specific. The results support and extend the existing literature to semantic memory tasks, indicating that older adult brains use functional recruitment to support task performance, even when task performance accuracy is high.

Age Factors↗

PubMed2005

Medial temporal lobe activity for recognition of recent and remote famous names: an event-related fMRI study.

Previous neuroimaging studies examining recognition of famous faces have identified activation of an extensive bilateral neural network [Gorno Tempini, M. L., Price, C. J., Josephs, O., Vandenberghe, R., Cappa, S. F., Kapur, N. et al. (1998). The neural systems sustaining face and proper-name processing. Brain, 121, 2103-2118], including the medial temporal lobe (MTL) and specifically the hippocampal complex [Haist, F., Bowden, G. J., & Mao, H. (2001). Consolidation of human memory over decades revealed by functional magnetic resonance imaging. Nature Neuroscience, 4, 1139-1145; Leveroni, C. L., Seidenberg, M., Mayer, A. R., Mead, L. A., Binder, J. R., & Rao, S. M. (2000). Neural systems underlying the recognition of familiar and newly learned faces. Journal of Neuroscience, 20, 878-886]. One model of hippocampal functioning in autobiographical, episodic memory retrieval argues that the hippocampal complex remains active in retrieval tasks regardless of time or age of memory (multiple trace theory, MTT), whereas another proposal posits that the hippocampal complex plays a time-limited role in retrieval of autobiographical memories. The current event-related fMRI study focused on the medial temporal lobe and its response to recognition judgments of famous names from two distinct time epochs (1990s and 1950s) in 15 right-handed healthy older adults (mean age=70 years). A pilot study with an independent sample of young and older subjects ensured that the stimuli were representative of a recent and remote time period. Increased MR signal activity was observed on a bilateral basis for both the hippocampus and parahippocampal gyrus (PHG) during recognition of familiar names from both the recent and remote time periods when compared to non-famous names. However, the impulse response functions in the right hippocampus and right PHG demonstrated a differential response to stimuli from different time epochs, with the 1990s names showing the greatest MR signal intensity change, followed by the 1950s names, followed by foils. The finding that recognition of famous names produced significant bilateral MTL activation regardless of time epoch relative to foils provides support for the MTT model. However, the finding of a temporal gradient in the right MTL also provides support for the HC model, given the greater MTL response associated with recently famous names relative to remotely famous names.

Adult↗

PubMed2005

Cerebellar atrophy in temporal lobe epilepsy.

PURPOSE: The goal of this work was to determine the presence and degree of cerebellar atrophy in chronic temporal lobe epilepsy, its clinical seizure correlates, and its association with general cortical atrophy. METHODS: Study participants were 78 persons with temporal lobe epilepsy and 63 age- and gender-matched healthy controls. All subjects underwent high-resolution MRI with manual tracing of the cerebellum. Clinical seizure features and history were obtained by structured interview and review of medical records. RESULTS: The epilepsy group exhibited significant abnormality in cerebellar volume, with mean reductions ranging from 4 to 6.6% depending on adjustments. Significantly more individual subjects with epilepsy exhibited cerebellar atrophy compared with controls across all operational definitions or thresholds of abnormality including z < or = -2.0 (13% TLE, 3.4% controls) and z < or = 1.5 (22% TLE, 3.4% controls). Clinical seizure features reflecting both neurodevelopmental (history of initial precipitating injuries) and severity of course (longer duration, increased number of lifetime generalized tonic-clonic seizures) factors were associated with cerebellar atrophy. Atrophy of the cerebellum could be observed independent of more general (cerebral) atrophic processes. CONCLUSIONS: The presence of cerebellar atrophy is a reflection of the extratemporal abnormalities that can be observed in localization-related temporal lobe epilepsy, which may be due, at least in part, to factors associated with epilepsy chronicity.

Adult↗

PubMed2005

The acquisition of face and person identity information following anterior temporal lobectomy.

Thirty unilateral anterior temporal lobectomy (ATL) subjects (15 right and 15 left) and 15 controls were presented a multitrial learning task in which unfamiliar faces were paired with biographical information (occupation, city location, and a person's name). Face recognition hits were similar between groups, but the right ATL group committed more false-positive errors to face foils. Both left and right ATL groups were impaired relative to controls in acquiring biographical information, but the deficit was more pronounced for the left ATL group. Recall levels also varied for the different types of biographical information; occupation was most commonly recalled followed by city name and person name. In addition, city and person name recall was more likely when occupation was also recalled. Overall, recall of biographical information was positively correlated with clinical measures of anterograde episodic memory. Findings are discussed in terms of the role of the temporal lobe and associative learning ability in the successful acquisition of new face semantic (biographical) representations.

Adult↗

PubMed2005

Temporal lobe epilepsy and the selective reminding test: the conventional 30-minute delay suffices.

Conventional memory assessment may fail to identify memory dysfunction characterized by intact recall for a relatively brief period but rapid forgetting thereafter. This study assessed learning and retention after 30-min and 24-hr delays on auditory and visual selective reminding tests (SRTs) in right (n=20) and left (n=22) temporal lobe epilepsy (TLE) patients and controls (n=49). The left TLE group performed significantly worse than controls on all 3 trials of both tests. The right TLE group differed from the controls on all 3 visual SRT trials and on learning for the auditory SRT. There were no between-groups differences in rate of information lost at the 30-min versus the 24-hr delay. At the individual level, there was no difference in the percentage of patients versus controls who demonstrated isolated memory impairment at the 24-hr delay. Accelerated forgetting over 24 hr is uncommon in TLE patients.

Adolescent↗

PubMed2005

Ipsilateral and contralateral MRI volumetric abnormalities in chronic unilateral temporal lobe epilepsy and their clinical correlates.

PURPOSE: To assess the presence, extent, and clinical correlates of quantitative MR volumetric abnormalities in ipsilateral and contralateral hippocampus, and temporal and extratemporal lobe regions in unilateral temporal lobe epilepsy (TLE). METHODS: In total, 34 subjects with unilateral left (n = 15) or right (n = 19) TLE were compared with 65 healthy controls. Regions of interest included the ipsilateral and contralateral hippocampus as well as temporal, frontal, parietal, and occipital lobe gray and white matter. Clinical markers of neurodevelopmental insult (initial precipitating insult, early age of recurrent seizures) and chronicity of epilepsy (epilepsy duration, estimated number of lifetime generalized seizures) were related to magnetic resonance (MR) volume abnormalities. RESULTS: Quantitative MR abnormalities extend beyond the ipsilateral hippocampus and temporal lobe with extratemporal (frontal and parietal lobe) reductions in cerebral white matter, especially ipsilateral but also contralateral to the side of seizure onset. Volumetric abnormalities in ipsilateral hippocampus and bilateral cerebral white matter are associated with factors related to both the onset and the chronicity of the patients' epilepsy. CONCLUSIONS: These cross-sectional findings support the view that volumetric abnormalities in chronic TLE are associated with a combination of neurodevelopmental and progressive effects, characterized by a prominent disruption in ipsilateral hippocampus and neural connectivity (i.e., white matter volume loss) that extends beyond the temporal lobe, affecting both ipsilateral and contralateral hemispheres.

Adolescent↗

PubMed2005

Investigating temporal lobe contribution to confrontation naming using MRI quantitative volumetrics.

Confrontation naming ability entails the operation of distinct cognitive operations and the integrity of a distributed neural network. Previous research has indicated a critical role for the left temporal lobe region in naming ability, but there is less agreement about the relative role of distinct temporal lobe regions. In the current paper, we used quantitative MR volumetrics to investigate the relative contribution of the hippocampus and extrahippocampal temporal lobe (segmented gray and white matter) volumes to confrontation naming performance in 53 patients with temporal lobe epilepsy. Findings showed (1) a stronger relationship for left temporal lobe volume than right temporal lobe volume in predicting naming performance; (2) both left temporal lobe white matter volume and left hippocampus volume contributed a significant amount of unique variance to spontaneous naming performance; and (3) left temporal lobe white matter volume but not left hippocampus volume predicted recognition naming performance.

Adolescent↗

PubMed2004

Voxel-based morphometry of unilateral temporal lobe epilepsy reveals abnormalities in cerebral white matter.

Voxel-based morphometric (VBM) investigations of temporal lobe epilepsy have focused on the presence and distribution of gray matter abnormalities. VBM studies to date have identified the expected abnormalities in hippocampus and extrahippocampal temporal lobe, as well as more diffuse abnormalities in the thalamus, cerebellum, and extratemporal neocortical areas. To date, there has not been a comprehensive VBM investigation of cerebral white matter in nonlesional temporal lobe epilepsy. This study examined 25 lateralized temporal lobe epilepsy patients (13 left, 12 right) and 62 healthy controls in regard to both temporal and extratemporal lobe gray and white matter. Consistent with prior reports, gray matter abnormalities were evident in ipsilateral hippocampus and ipsilateral thalamus. Temporal and extratemporal white matter was affected ipsilateral to the side of seizure onset, in both left and right temporal lobe epilepsy groups. These findings indicate that chronic temporal lobe epilepsy is associated not only with abnormalities in gray matter, but also with concomitant abnormalities in cerebral white matter regions that may affect connectivity both within and between the cerebral hemispheres.

Adolescent↗

PubMed2004

Neural networks underlying endogenous and exogenous visual-spatial orienting.

The orienting of visual-spatial attention is fundamental to most organisms and is controlled through external (exogenous) or internal (endogenous) processes. Exogenous orienting is considered to be reflexive and automatic, whereas endogenous orienting refers to the purposeful allocation of attentional resources to a predetermined location in space. Although behavioral, electrophysiological and lesion research in both primates and humans suggests that separate neural systems control these different modes of orienting, previous human neuroimaging studies have largely reported common neuronal substrates. Therefore, event-related FMRI (ER-FMRI) was used to independently examine different components of the orienting response including endogenous facilitation, exogenous facilitation and inhibition of return (IOR). In contrast to previous studies, endogenous versus exogenous facilitation resulted in widespread cortical activation including bilateral temporoparietal junction, bilateral superior temporal gyrus, right middle temporal gyrus, right frontal eye field and left intraparietal sulcus. Conversely, IOR compared to endogenous facilitation resulted in only a single focus of activation in the left superior temporal gyrus. These findings suggest that endogenous orienting activates a large cortical network to achieve internally generated shifts of attentional resources versus the automatic orienting that occurs with exogenous cues. However, similar networks may mediate endogenous orienting and IOR. The activation of the temporoparietal junction suggests that it is involved in more effortful processes, such as endogenous orienting, as well as in attentional reorienting and locating targets. Current results are discussed in terms of the functional development of the visual-spatial attentional system.

Adult↗

PubMed2004

Memory relationships between MRI volumes and resting PET metabolism of medial temporal lobe structures.

Prior studies of temporal lobe epilepsy (TLE) patients showed that MRI volumes and resting PET scan measures of temporal lobe structures were related to memory. Weintrob and colleagues [Ann. Neurol. 2002;51:442-7] reported that PET glucose uptake in the left perirhinal cortex predicted verbal paired associate (PA) learning, whereas MRI volume of the left hippocampus did not. We investigated whether MRI volumes could account for memory functioning if both PET and volumes were from the same region in 18 TLE patients. Volumes and glucose uptake of the hippocampus and parahippocampal gyrus (PHG) were compared with WMS-III performance. Significant correlations were observed between hippocampal volumes and PA and Logical Memory (LM) Percent Retention, but not between memory and PHG volumes or any PET measures. Multiple regression revealed that hippocampal volumes, but not PHG volumes or PET, significantly predicted PA and LM retention scores. These findings suggest that hippocampal volumes provide unique information regarding memory.

Adolescent↗

PubMed2004

Relationship between information processing speed in temporal lobe epilepsy and white matter volume.

Abnormalities in white matter have been linked to processing speed impairment in clinical populations (e.g., multiple sclerosis, closed head injury). Recent studies indicate the presence of significant reduction in cerebral white matter volume in some patients with chronic temporal lobe epilepsy (TLE). The objective of this study was to examine the relationship between white matter volume and processing speed and performance efficiency on the Sternberg Memory Scanning Test (SMST). The study groups included TLE subjects with white matter volume reduction (n=13), TLE subjects with normal white matter volume (n=14), and healthy controls (n=18). The groups did not differ in total cerebral gray matter volume. Compared with the controls, the reduced white matter volume TLE group exhibited a significantly steeper slope on the SMST. This was characterized by a disproportionate increase in reaction time with increased processing demands (set size), particularly for negative probe trials. In contrast, no significant differences on the SMST were evident between controls and the normal white matter volume TLE group. These findings suggest the presence of information processing speed and efficiency impairment in TLE and its relationship with white matter volume integrity.

Adolescent↗