Location of the epileptic zone and its physiopathological effects on memory-related activity of the temporal lobe structures: a study with intracranial event-related potentials

PURPOSE: Neuropsychological research with epileptic patients has suggested that the location of seizure focus may be an important variable determining the nature and severity of memory impairments. According to this assumption, this study was designed to investigate the effects of the location of the epileptic zone on the memory-related activity recorded directly from different temporal lobe structures. METHODS: Intracranial event-related potentials (ERPs) were recorded during a continuous recognition memory task, which is known to elicit the modulation of N400 and P600 components (i.e., the ERP old/new effect). The patients were separated into three groups according to the location of their epileptic zone: unilateral temporal (UTE), temporal plus extratemporal (TEE), and bitemporal (BTE). Recordings were obtained from three temporal lobe structures: hippocampus, amygdala, and lateral temporal cortex. RESULTS: The results showed that in the hippocampus, the ERP old/new effect was abolished in the TEE group only. In the amygdala, although largely unaffected, the ERP modulation appeared to be more impaired in UTE patients. Contrasting with these data is the observation that the magnitude and reliability of the ERP old/new effect recorded at the neocortical level increases as the epileptic zone extends to the temporal lobes (i.e., BTE>TEE>UTE). CONCLUSIONS: It is concluded that the memory-related activity modulation of memory ERPs recorded from different temporal lobe structures is affected differently by the presence of an epileptic zone as a function of its location. The possible clinical implications of these findings in surgery planning are also discussed.     

Increased intrusions during verbal recall in traumatic and nontraumatic lesions of the temporal lobe.

The mesial temporal and lateral frontal lobes were the most common sites of parenchymal abnormality on magnetic resonance imaging (MRI) scans for 12 patients with chronic traumatic brain injury (TBI). Ventricular widening was also common, and 3 patients showed increased size of the upper third ventricle. Of 10 right-handed TBI patients with no evidence of learning disability, 6 showed dominant temporal lesions and 3 showed an increase in the size of the upper third ventricle. Only patients with dominant temporal lesions (4 of 6) exceeded the normal confidence interval (based on 20 non-TBI controls) for intrusion errors on delay trials of the California Verbal Learning Test (CVLT), though other patients also demonstrated impaired recall. The pattern of increased intrusions during CVLT delay trials was confirmed in non-TBI patients who had undergone dominant temporal surgery or had dominant or bilateral temporal lesions, even when frontal changes could be ruled out. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Event-related potentials during memorization of spatial locations in the auditory and visual modalities

Event-related potential (ERP) studies of working memory have used delayed S1-S2 match-to-sample tasks in which S1 is held in memory for comparison with S2. ERP negativities in the S1-S2 interval have been interpreted either in terms of working memory operations, or in terms of general preparatory motor processing. Two experiments (N = 20 each) were carried out to explore the nature of ERP negativities in a visuospatial memory task and in an auditory spatial memory task, respectively. In the experimental condition, subjects had to memorize the location of S1 (S1-memorize) so as to respond whether S2 appeared in the same spatial location (S2-memorize). In the control condition, subjects were requested to ignore S1 (S1-passive), and to respond whether S2 matched or not a target location predetermined at the beginning of the trial block (S2-pressing). Results support the two main conclusions of Martin-Loeches et al. (Electroenceph. clin. Neurophysiol., 1994, 91: 363-373). Firstly, that the encoding into memory of spatial location is associated with an ERP negative wave over the brain areas putatively associated with the processing of sensory information (i.e. right parieto-occipital for the visual task; fronto-central and left temporal areas for the auditory task). Secondly, the P300 does not seem to be an important ERP feature related to spatial location encoding and retaining into memory. Despite the distinct scalp distribution of these memory-related, modality-specific ERP negativities, they also showed a considerable degree of temporal synchronicity across modalities.     

Word priming and recognition memory are both affected by mesial temporal lobe damage.

Amnesic patients with mesial temporal lobe pathology often produce normal priming effects despite severely impaired memory. This is generally interpreted to mean that whereas limbic structures are involved in conscious memory, other structures, comprising a separate memory system, mediate priming effects. Priming and recognition memory measures were correlated with magnetic resonance imaging (MRI) measures of damage to specific brain structures in a sample of 30 Ss. The results provide evidence that both priming and recognition memory may be adversely affected by mesial temporal lobe damage. Furthermore, the results suggest that striatal damage is associated with lexical or perceptual deficits and larger measured priming effects. Thus, co-existing striatal and limbic damage may lead to normal priming performance in some memory-impaired patients. In these instances, normal priming performance may not be mediated by a separate (implicit) memory processing system in the brain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cortical-hippocampal auditory processing identified by magnetoencephalography

We recorded magnetic and electrical responses simultaneously in an auditory detection task to elucidate the brain areas involved in auditory processing. Target stimuli evoked magnetic fields peaking at approximately the same latency of around about 400 msec (M400) over the anterior temporal, superior temporal, and parietal regions on each hemisphere. Equivalent current dipoles (ECDs) were analyzed with a time-varying multidipole model and superimposed on each subject's magnetic resonance image (MRI). Multiple independent dipoles located in the superior temporal plane, inferior parietal lobe, and mesial temporal region best accounted for the recorded M400 fields. These findings suggest that distributed activity in multiple structures including the mesial temporal, superior temporal, and inferior parietal regions on both hemispheres is engaged during auditory attention and memory updating.     

Surgical treatment of epilepsy due to cortical dysplasia: clinical and EEG findings

Seventeen patients with cortical dysplasia who had surgical resection for medically intractable partial epilepsy were studied. Compared with two groups of surgically treated patients with intractable epilepsy due to tumour (n = 20) and mesial temporal sclerosis (n = 40), patients with cortical dysplasia showed significantly more frequent extratemporal lesions, more frequent non-epileptiform EEG abnormalities and less favourable surgical outcome for seizure control. Patients with cortical dysplasia were younger at onset of seizures and had a lower detection rate of CT abnormalities compared with the tumour group, and lower IQ compared with the mesial temporal sclerosis group. MRI was abnormal in five of seven patients. Six patients became seizure-free or almost seizure-free but eight did not experience relief of seizures. Surgical outcome related to the extent of pathology but not to the histological abnormality. Lesions outside the temporal and frontal lobes were correlated with poor surgical outcome, as were generalised interictal EEG abnormalities, which may reflect extensive or multiple lesions. Ictal intracranial recordings were not useful for presurgical evaluation of cortical dysplasia.     

Temporal and spatial context memory in patients with focal frontal, temporal lobe, and diencephalic lesions

Patients with focal frontal, temporal lobe, or diencephalic lesions were investigated on measures of temporal (recency) and spatial (position) context memory, after manipulating exposure times to match recognition memory for targets (pictorial stimuli) as closely as possible. Patients with diencephalic lesions from an alcoholic Korsakoff syndrome showed significant impairment on the temporal context (recency) task, as did patients with frontal lesions penetrating the dorsolateral frontal cortex, according to MRI (and PET) evidence. Patients with temporal lobe lesions showed only a moderate (non-significant) impairment on this task, and patients with medial frontal lesions, or large frontal lesions not penetrating the dorsolateral cortical margins, performed as well as healthy controls at this task. On the spatial context memory task, patients with lesions in the temporal lobes showed significant impairment, and patients with right temporal lesions performed significantly worse than patients with left temporal lesions. Patients with diencephalic lesions showed only a modest (non-significant) impairment on this task, and the frontal lobe group performed normally. When a group of patients with temporal lobe lesions resulting from herpes encephalitis were examined separately, an identical pattern of results was obtained, the herpes group being significantly impaired on spatial memory and showing a trend towards impairment for temporal context memory. There were strong correlations between anterograde memory quotients and context memory performance (despite the use of an exposure time titration procedure) and a weak association in the frontal group with one frontal/executive task [corrected] (card-sorting perservations). It is predicted that correlations between temporal context memory and frontal/executive tasks will be greater in samples of patients all of whom have frontal lesions invading the dorsolateral cortical margin.     

Nutrition in infancy: implications for practice

The aim of the present study was to assess selective atrophy of the temporal lobe and amygdala in the early stages of Alzheimer dementia (AD). Magnetic resonance imaging (MRI) measurements and the presence of highsignal lesions (HSL) were analysed in 31 patients with mild to moderate probable AD and 22 controls. In the AD group, MRI findings were compared with cognitive variables and specific features of memory functions. Alzheimer patients showed a significant reduction in volumetric measurement compared with controls in the total volume (P < 0.01), temporal lobe (P < 0.01) and amygdala (P < 0.05). The temporal lobe/brain volume ratio was also significantly reduced in AD subjects (P < 0.05). Atrophy of temporal structures was significantly related to the degree of episodic and semantic memory impairment according to a material-specific effect. No significant correlations between amygdala and cognitive variables were found. The results of our study confirm the usefulness of measures of temporal lobe atrophy assessed with MRI in the diagnosis of AD. In contrast, HSL are relatively common in AD patients (12/31 cases) and were not related to volumetric findings, severity of dementia or functional disability.     

P3-like brain waves in normal monkeys and in monkeys with medial temporal lesions.

The human brain produces a characteristic electrical response to relevant events that occur unexpectedly. Recent reports have suggested that a prominent part of this event-related brain potential—the P3 wave—may be related to memory functions and may arise from activity within the medial temporal lobe, especially the hippocampus. The latter idea was tested by means of epidural recordings of brain waves in monkeys. Responses to deviant auditory stimuli bore a close resemblance to P3 waves recorded from human subjects under comparable conditions. Monkeys with bilateral lesions of the medial temporal lobe still produced P3-like brain waves, which indicates that medial temporal brain structures are not critical for their generation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amygdala-hippocampal atrophy and memory performance in dementia of Alzheimer type

The aim of the present study was to examine the involvement of brain structures, especially the amygdala-hippocampal complex, in dementia of Alzheimer type (DAT), and to assess the relation of amygdala-hippocampal atrophy with memory dysfunction. 14 patients with DAT and 10 healthy age-matched controls were examined with different neuropsychologic tests including the UCLA-Auditory Verbal Learning Test. MRI was performed with a conventional 1.5-tesla scanner. Atrophy was found in many brain structures of demented subjects in comparison with healthy age-matched controls. The volumes of amygdala-hippocampal complexes and of the temporal lobes of demented subjects were more reduced than the total brain volume and other structures. Memory dysfunction was highly correlated with atrophy of the amygdala-hippocampal complexes and of the temporal lobes. Consequently, DAT seems to affect the amygdala-hippocampal complex and their related function (i.e. memory) more than other cerebral structures, but cerebral degeneration in DAT is not restricted to these structures.     

A case of neuro-Beh?et's encephalitis with pleds as distinct from herpes simplex encephalitis: a differential diagnosis

We report a male patient with neuro-Beh?et's disease who had somnolence, mild motor aphasia and periodic lateralized epileptiform discharge. SPECT study showed decreased cerebral blood flow in the left frontal and temporal lobes. An MRI scan of the head showed only mild brain stem atrophy. His clinical signs were markedly improved after administration of prednisolone. We propose that some cases of neuro-Beh,cet's disease may have very similar clinical features to herpes simplex encephalitis and that SPECT and MRI examinations can be very useful in distinguishing the ischemic lesion of neuro-Beh?et's from the inflammatory lesion of herpes simplex encephalitis.     

Improved peripheral nerve conduction, EEG and verbal IQ after bone marrow transplantation for adult metachromatic leukodystrophy

A 28-year-old woman with a 4 year history of slowly progressing 'frontal dementia' was diagnosed as having adult metachromatic leukodystrophy and was followed for 4 years after bone marrow transplantation (BMT). MRI, neurophysiological tests (EEG, ENeG, VEP, SEP and BAEP) and neuropsychological assessment were performed before, and repeatedly after BMT. MRI showed symmetrical white matter lesions in the frontal and parieto-occipital lobes and in the corpus callosum. EEG showed frontal and temporal slow wave abnormalities and nerve conduction was slow. Neuropsychological tests showed cognitive impairment in executive functions, decline in visuospatial-constructive and spatial memory tasks and disorganized thinking. IQ was low (52), with slightly better values for verbal IQ than for performance IQ. After BMT, the patient was followed for 4 years. Clear improvements were seen in EEG, in peripheral nerve conduction and in neuropsychological tests (especially in verbal IQ). MRI findings were unchanged. We believe that the improvement in our patient resulted from the bone marrow transplantation.     

Neuropsychological examinations in childhood

Three groups of children aged 8-12 years have been investigated by a test battery to gain insight into the problems surrounding the relationship between cerebral and behavioral development. One group was of children with circumscribed cortical lesions, one was a group of dyslexics with neurologic anomalies, and the third was a control group of children without brain lesions. General test intelligence did not differ significantly in the three groups. Marked differences between the various lesion groups are observable in some tests but not in others. For example, the results of children with left temporal lesions in the verbal part of the intelligence test and in fresh language memory were inferior to those of all other lesion groups and the controls, while the dyslexics showed a similar if less marked deficit. Non-linguistic (figural) memory did not differ as between groups. On the other hand, children with right frontal lesions were notable for inferior results in a visual learning test and a classification test. In a linguistic-dichotic test all the groups of brain lesions and the dyslexics differed from the control group, a fact which suggests retarded development of hemispheric dominance for speech functions. From these provisional results it can be concluded that the brain areas do not all specialize simultaneously, and that compensation of cerebral lesions in relation to different functions probably results in retardation of overall brain development and anatomico-functional specialization.     

Auditory event-related potentials in Parkinson's disease

We studied 49 patients with Parkinson's disease (PD) by a neuropsychological battery examining the temporo-spatial orientation, short-term memory, comprehension, non-verbal intelligence, long-term memory and anomia and the Auditory Event-Related Potentials. In the patients the latencies of the N100 and N200 waves were prolonged and the amplitude of the P300 wave was reduced compared with controls. No difference was found in the ERP of patients with and without cognitive deficits. Equally, no correlation was found between the ERP, the cognitive impairment, the length or the severity of the disease evaluated by Hoehn-Yahr's and Webster's scales.     

Sex differences in the relationship between visual memory and MRI hippocampal volumes.

This study investigated sex differences in the relationships between visual memory and MRI-determined hippocampal volume data before and after right and left temporal lobectomy (TL). Preoperative visual memory and postoperative visual memory change were evaluated by the Wechsler Memory Scale-Revised, and MRI hippocampal volumes were obtained in 54 right (28 men and 26 women) and 75 left (33 men, 42 women) TL patients. Preoperative visual memory and postoperative visual memory change were significantly related to the difference between hippocampal volumes (DHV) in right TL women but not right TL men. That is, extirpation of a large right hippocampus was significantly associated with a visual memory decline, but only in women. These findings support the presence of sexually dimorphic brain function and suggest that visual memory ability in women may be less plastic after a developmentally early right mesial temporal insult. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verb generation in patients with focal frontal lesions: a neuropsychological test of neuroimaging findings

What are the neural bases of semantic memory? Traditional beliefs that the temporal lobes subserve the retrieval of semantic knowledge, arising from lesion studies, have been recently called into question by functional neuroimaging studies finding correlations between semantic retrieval and activity in left prefrontal cortex. Has neuroimaging taught us something new about the neural bases of cognition that older methods could not reveal or has it merely identified brain activity that is correlated with but not causally related to the process of semantic retrieval? We examined the ability of patients with focal frontal lesions to perform a task commonly used in neuroimaging experiments, the generation of semantically appropriate action words for concrete nouns, and found evidence of the necessity of the left inferior frontal gyrus for certain components of the verb generation task. Notably, these components did not include semantic retrieval per se.     

Brain potentials implicate temporal lobe abnormalities in criminal psychopaths.

Psychopathy is associated with abnormalities in attention and orienting. However, few studies have examined the neural systems underlying these processes. To address this issue, the authors recorded event-related potentials (ERPs) while 80 incarcerated men, classified as psychopathic or nonpsychopathic via the Hare Psychopathy Checklist-Revised (R. D. Hare, 1991, 2003), completed an auditory oddball task. Consistent with hypotheses, processing of targets elicited larger frontocentral negativities (N550) in psychopaths than in nonpsychopaths. Psychopaths also showed an enlarged N2 and reduced P3 during target detection. Similar ERP modulations have been reported in patients with amygdala and temporal lobe damage. The data are interpreted as supporting the hypothesis that psychopathy may be related to dysfunction of the paralimbic system--a system that includes parts of the temporal and frontal lobes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Regional cerebral volume loss associated with verbal learning and memory in dementia of the Alzheimer type.

Twenty-seven research participants with dementia of the Alzheimer type were studied with the California Verbal Learning Test (D. C. Delis, J. H. Kramer, E. Kaplan, & B. A. Ober, 1987) and standardized volume measures of the mesial temporal cortical gray matter, neocortical gray matter, thalamus, and caudate nuclei, from magnetic resonance imaging. A pattern of atrophic brain changes in the mesial temporal lobes (MTL) and the thalamus, with relatively less severe atrophy in the neocortical gray matter, was associated with poorer learning of the word list. Similar patterns of brain atrophy were observed for measures of delayed recall and recognition hits. However, for delayed recall, neither contribution was statistically significant, and for recognition hits, MTL was only at the trend level for significance. These results provide evidence that the verbal memory deficit of Alzheimer's disease (AD) is associated not only with the mesial temporal limbic cortex, thought to be the site of earliest and most severe pathology in AD, but also with damage in the thalamus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Leptomeningeal angiomatosis accompanied by hair follicle nevus

A 5-day-old male infant with leptomeningeal angiomatosis accompanied by hair follicle nevus and congenital alopecia is reported. Admitted for frequent left hemiconvulsions, he had three small papular lesions around his right eye and ipsilateral alopecia from the frontal to parietal areas. Histopathological examination of the papular lesions revealed crowding of hair follicles. There were no other skin lesions and no ophthalmic abnormalities. Ictal EEG showed a theta burst in the right parietal area. Computed tomography of the brain revealed cerebral atrophy and a slightly high intensity lesion in the right parietal and occipital lobes with calcification. Gyriform enhancement was demonstrated by contrast MRI in these areas. The pathogenesis is discussed. This case may represent a previously unknown neurocutaneous syndrome.     

High-density recording and topographic analysis of the auditory oddball event-related potential in patients with schizophrenia

BACKGROUND: Prior research has shown reductions of the N1, N2, and P300 auditory event-related potential (ERP) components in schizophrenic patients. Most studies have shown a greater P300 reduction in left versus right temporal leads in schizophrenic patients. These studies were done with sparse electrode arrays, covering restricted areas of the head, thus providing an incomplete representation of the topographic field distribution. METHODS: We used a 64-channel montage to acquire auditory oddball ERPs from 24 schizophrenic patients and 24 controls subjects. The N1, P2, N2, P300, and N2 difference (N2d) amplitudes and latencies were tested for group and laterality differences. Component topographies were mapped onto a three-dimensional head model to display the group differences. RESULTS: The schizophrenic group showed reduction of the N1 component, perhaps reflecting reduced arousal or vigilance, but no N1 topographic difference. An N2d was not apparent in the schizophrenic patients, perhaps reflecting severe disruption in neural systems of stimulus categorization. In the patients, the P300 was smaller over the left temporal lobe sites than the right. CONCLUSIONS: The increased ERP spatial sampling allowed a more complete representation of the dipolar nature of the P300, which showed field contours consistent with neural sources in the posterior superior temporal plane.