Frontal lobe structure and executive function in migraine patients

Neuroimaging studies have identified frontal lobe brain abnormalities in migraineurs. Neuropsychological investigations highlighted frontal lobe related cognitive impairments in migraineurs, including working memory and executive function deficits. The relationship between brain anatomy and cognitive function in migraine, however, is unclear. The aim of this study was to simultaneously investigated cortex structure and executive function (EF) in patients with migraine and control subjects. Thus, we assessed grey matter (GM) density in 25 adult patients with migraine, compared to age and sex-matched control subjects, using magnetic resonance imaging (MRI) and voxel-based-morphometry (VBM), and we measured EF in the same population, employing three EF tasks of the Maudsley attention and response suppression (MARS) battery. Migraineurs, compared to control subjects, showed decreased frontal and parietal lobe GM density and slower response time to task set-shifting and, the delayed response time correlated significantly with reduced GM density of the frontal lobes in migraineurs. Frontal and parietal lobe abnormalities in migraineurs could be an underlying cause of significantly slower response time during cognitive set-shifting.     

Evidence for intact semantic representations in patients with frontal lobe lesions

Patients with frontal lobe lesions and control participants were assessed on 2 tests of semantic knowledge. In the triadic comparison task, participants were shown all possible triplets of 12 animal names and judged which 2 of each triplet were most alike. In the ordered similarity task, participants rank ordered animals in terms of their similarity to a target animal. For both tasks, semantic structure--derived from multidimensional scaling techniques--revealed similar representations in patients with frontal lobe lesions and control participants. Additional pathfinder analyses also produced networks that did not differ between groups. These patients exhibited intact semantic knowledge despite deficits on tests of free recall and verbal fluency that involved the same semantic category and exemplars. Thus, intact representation of semantic knowledge in frontal patients stands in contrast to their marked deficits in strategic retrieval of semantic knowledge.     

Cognitive deficits in patients with unilateral war-related frontal lobe lesions.

The findings of this study may be summarized as follows: (1) No significant general cognitive impairment occurred in S samples with unilateral frontal lobe lesions; (2) Impairment of cognitive performance was greater in Ss with lesions posterior to the Fissure of Rolondo than in well-matched Ss with frontal lobe lesions; (3) Specific cognitive deficits are infrequent in Ss with frontal lobe lesions; (4) No significant differential impairment of cognitive performance was associated with hemispheric lateralization of frontal lesions; and (5) No significant differential impairment of verbal and nonverbal performance was associated with hemispheric lateralization of frontal lesions.     

Effects of divided attention on temporal processing in patients with lesions of the cerebellum or frontal lobe

Prefrontal cortex and cerebellum have both been implicated in temporal processing tasks although the exact contribution of each system remains unclear. To investigate this issue, control participants and patients with either prefrontal or cerebellar lesions were tested on temporal and nontemporal perceptual tasks under 2 levels of attentional load. Each trial involved a comparison between a standard tone and a subsequent comparison tone that varied in frequency, duration, or both. When participants had to make concurrent judgments on both dimensions, patients with frontal lobe lesions were significantly impaired on both tasks whereas the variability of cerebellar patients increased in the duration task only. This dissociation suggests that deficits on temporal processing tasks observed in frontal patients can be related to the attention demands of such tasks; cerebellar patients have a more specific problem related to timing.     

Frontal lobe function and executive skills in children with turner's syndrome

Children with Turner's syndrome (TS), a sex chromosome abnormality in which the second X chromosome is abnormal or deleted, were given a series of tasks that investigated executive skills traditionally considered to be subserved by the frontal lobes. The children with TS showed significant deficits in comparison to controls but the effects were task specific. They were impaired on the Stroop, Verbal Fluency and the abstract version of the Self‐Ordered Pointing task. However, performance was entirely normal on the Wisconsin Card Sorting Test, the Tower of London and the concrete version of the Self‐Ordered Pointing task. These results support the fraction‐ability of executive control processes in development, thereby contradicting Fodor's (1983) conception of the absence of modularity in such systems. The phenotype‐genotype relation for 45,XO TS differed significantly from that of other karyotypes on the Self‐Ordered Pointing task, confirming the distinctive nature of aspects of the cognitive development of children with TS associated with differing etiological genotypes.     

Figural fluency: differential impairment in patients with left versus right frontal lobe lesions.

Based on an experimental study, Jones-Gotman and Milner demonstrated that patients with right frontal lobe lesions were impaired on design fluency. We sought a clinical adaptation and developed a psychometrically sound technique for design fluency. The present study explores the validity of the Ruff Figural Fluency Test (RFFT) in discriminating patients with either right frontal or nonright frontal lobe lesions. In the first of two studies, six subjects with circumscribed focal lesions were given the RFFT and the Jones-Gotman and Milner figural fluency task. In the second study, we identified a larger sample of 30 patients with focal lesions in the right frontal, left frontal, right posterior, or left posterior cortex. The results from both studies support the validity of the RFFT as a measure which is sensitive to right anterior dysfunction.     

Movement disorders and psychological tests of frontal lobe function in schizophrenic patients.

Neuropsychological tests of frontal lobe functions were undertaken in 46 chronic schizophrenic patients who were also rated for movement disorders. Tardive dyskinesia was found to have significant associations with most of these psychological tests. The possible mechanisms are discussed within the context of known neostriatal psychological functions.     

Contribution of frontal and temporal lobe function to memory interference from divided attention at retrieval

On the basis of their scores on composite measures of frontal and temporal lobe function, derived from neuropsychological testing, seniors were divided preexperimentally into 4 groups. Participants studied a list of unrelated words under full attention and recalled them while concurrently performing an animacy decision task to words, an odd-digit identification task to numbers, or no distracting task. Large interference effects on memory were produced by the animacy but not by the odd-digit distracting task, and this pattern was not influenced by level of frontal or temporal lobe function. Results show associative retrieval is largely disrupted by competition for common representations, and it is not affected by a reduction in general processing resources, attentional capacity, or competition for memory structures in the temporal lobe.     

Working memory performance in typically developing children and adolescents: behavioral evidence of protracted frontal lobe development

Post-mortem histological and in vivo neuroimaging findings both reveal frontal lobe development that extends beyond the adolescent years. Few studies have examined whether this protracted neurodevelopment coincides with improvements in adolescent performance on putative frontal lobe tasks. An instrumental function supported by the frontal lobes is working memory, the ability to maintain and manipulate information online. This study investigated the performance of typically developing children and adolescents on a battery of working memory tasks. Findings revealed an improvement in performance on most working memory tasks across the adolescent years. In contrast, no improvement was observed on tasks largely supported by more posterior neural substrates. Current findings indicate a similar unfolding of the executive aspects of verbal working memory as previously demonstrated with spatial working memory. Factor analysis revealed a grouping of working memory tasks based largely on task demands, irrespective of working memory domain, adding support for process-specific models of prefrontal organization. Important implications for typical and atypical frontal lobe development are discussed.     

Hippocampal function and spatial memory: evidence from functional neuroimaging in healthy participants and performance of patients with medial temporal lobe resections

Several strategies can be used to find a destination in the environment. Using a virtual environment, the authors identified 2 strategies dependent on 2 different memory systems. A spatial strategy involved the use of multiple landmarks available in the environment, and a response strategy involved right and left turns from a given start position. Although a probe trial provided an objective measure of the strategy used, classification that was based on verbal reports was used in small groups to avoid risks of misclassification. The authors first demonstrated that the spatial strategy led to a significant activity of the hippocampus, whereas the response strategy led to a sustained activity in the caudate nucleus. Then, the authors administered the task to 15 patients with lesions to the medial temporal lobe, showing an impaired ability using the spatial strategy. Imaging and neuropsychological results are discussed to shed light on the human navigation system.     

Integration of diverse information in working memory within the frontal lobe

Ability to integrate diverse forms of information in current thought, or working memory, is essential for human reasoning and problem solving. We used functional imaging to identify brain regions preferentially involved in maintaining integrated versus unintegrated information in working memory. For equal amounts of verbal and spatial information, activation of prefrontal cortex was greater for maintaining integrated rather than unintegrated representations. Posterior brain regions showed the opposite pattern. These results demonstrate frontal-lobe specialization in maintaining working-memory representations that integrate verbal and spatial information. The role of prefrontal cortex in integrating multiple forms of information in working memory may underlie its unique contribution to high-level cognition that demands flexible mental representations.     

Microtubuloreticular structures in the cerebral vasculature of a patient with herpes simplex encephalitis

In this report we will document the presence of microtubuloreticular structure (MTRS) in the cerebral vasculature of a patient who had contracted herpes simplex (HSV) encephalitis. Twenty of twenty-one blood vessels (capillaries, arterioles, venules) contained MTRS within the cytoplasm of endothelial and/or associated cells. The use of this evidence to support a diagnosis of HSV encephalitis is discussed.     

The timing of associative memory formation: frontal lobe and anterior medial temporal lobe activity at associative binding predicts memory

The process of associating items encountered over time and across variable time delays is fundamental for creating memories in daily life, such as for stories and episodes. Forming associative memory for temporally discontiguous items involves medial temporal lobe structures and additional neocortical processing regions, including prefrontal cortex, parietal lobe, and lateral occipital regions. However, most prior memory studies, using concurrently presented stimuli, have failed to examine the temporal aspect of successful associative memory formation to identify when activity in these brain regions is predictive of associative memory formation. In the current study, functional MRI data were acquired while subjects were shown pairs of sequentially presented visual images with a fixed interitem delay within pairs. This design allowed the entire time course of the trial to be analyzed, starting from onset of the first item, across the 5.5-s delay period, and through offset of the second item. Subjects then completed a postscan recognition test for the items and associations they encoded during the scan and their confidence for each. After controlling for item-memory strength, we isolated brain regions selectively involved in associative encoding. Consistent with prior findings, increased regional activity predicting subsequent associative memory success was found in anterior medial temporal lobe regions of left perirhinal and entorhinal cortices and in left prefrontal cortex and lateral occipital regions. The temporal separation within each pair, however, allowed extension of these findings by isolating the timing of regional involvement, showing that increased response in these regions occurs during binding but not during maintenance.     

额叶癫癎患者的临床特点及脑电分析

目的：观察额叶癫痫患者的临床特点、EEG表现、治疗方法及效果。方法：回顾性分析62例额叶癫痫患者的临床表现、发作期及发作间期EEG改变和抗癫痫药物的治疗效果。结果：额叶癫痫常见的发作形式为复杂部分性发作（82％），主要表现为假自主运动，发声及重复语言，姿势性强直，并伴有发作持续时间短、频繁发作、发作后神志恢复快等特点。发作期EEG痫样放电检出率100％，但能定位额区仅占74％，发作新时期EEG8例无阳性发现。经抗癫痫药物治疗，有效率达93％，其中50％完全控制发作，主要用药为卡马西平。随访2-5年，仍有效者占88％。结论：额叶癫痫为一组以运动症状为主要表现的特征性癫痫综合征，卡马西平治疗效果满意。     

耐药性颞叶癫痫患者记忆功能损害的多因素分析

目的：观察耐药性颞叶癫痫患者记忆功能的损害并分析其影响因素。方法：采用韦氏记忆量表对32例耐药性颞叶癫痫患者记忆功能进行评估,并与32例普通癫痫患者进行比较,同时对可能的影响因素如发病年龄、发作频度、海马体积、脑电图异常放电范围、病程持续时间等进行相关性分析。结果：与普通癫痫患者比较,耐药性颞叶癫痫患者记忆功能普遍降低,尤其以短时记忆为明显。在其各种可能因素中,起病年龄、发作频度、抗癫痫药的种类和海马痫样放电的范围对记忆商（MQ）具有显著影响。结论：耐药性颞叶癫痫患者有明显记忆损害,起病年龄、发作频度、服用抗癫痫药的种类和海马痢样放电的范围是影响记忆功能的主要因素。     

Effects of regional striatal lesions on motor, motivational, and executive aspects of progressive-ratio performance in rats.

The striatum is implicated in response selection and performance, the dorsal striatum in sensorimotor control and habit learning, and the ventral striatum in motivation and rewarded behaviors. Ventral striatal lesions produce performance changes on food-reinforced, progressive-ratio (PR) schedules, but the effects of dorsal striatal lesions on this task are not known. In this study, neither medial nor lateral dorsal striatal lesions produced deficits on the main motivational indices of PR performance. In contrast, significant impairments were observed in motoric or "executive" aspects of performance. Motivationally related manipulations of the task (food deprivation and reward magnitude) produced some subtle lesion-specific changes in behavior on these motoric or executive aspects of performance. Findings are discussed in relation to the roles of the dorsal and ventral striatum in reward-related behaviors.     

Episodic memory meets working memory in the frontal lobe: functional neuroimaging studies of encoding and retrieval

Recent functional-neuroimaging studies have provided a wealth of new information suggesting that regions of the prefrontal cortex play a role in episodic memory encoding and retrieval. This review seeks to evaluate the results of these studies in the context of one general model that has proposed that the left prefrontal cortex is preferentially involved in episodic memory encoding, whereas the right prefrontal cortex is preferentially involved in episodic memory retrieval, irrespective of the type (e.g., modality) of information being remembered. The origins of this framework are considered in some detail and then all relevant functional-neuroimaging studies are critically reviewed. The results of this review fail to provide support for the functional-asymmetry model, suggesting instead that episodic memory encoding and retrieval may actually involve similar regions of the lateral prefrontal cortex when all factors relating to the type of stimulus material (i.e., modality), are appropriately controlled.     

Imitative response tendencies in patients with frontal brain lesions

It is widely accepted that patients with frontal lesions have problems inhibiting automatic response tendencies. Whereas inhibition deficits of overlearned responses have been extensively investigated using interference tasks like the Stroop task (J. R. Stroop, 1935), it is controversial whether patients with frontal brain lesions also have problems inhibiting imitative responses. Using an interference paradigm, the present study investigated imitative response tendencies in patients with frontal lesions. In addition, it tested whether patients deficient in the inhibition of imitative responses correspondingly have problems inhibiting overlearned responses. It was found that the group with frontal lesions displayed significantly stronger imitative response tendencies than the group with nonfrontal lesions. Furthermore, it was shown that the inhibition of imitative responses is functionally unrelated to Stroop interference.     

单纯疱疹病毒性脑炎的脑电图分析

目的探讨脑电图（ＥＥＧ）对单纯疱疹病毒性脑炎（ＨＳＥ）提供诊断依据和评价疾病严重程度、疗效和预后的意义。方法：对４２例ＨＳＥ的ＥＥＧ行回顾性分析。结果：４２例中３７例ＥＥＧ异常,早期敏感性为８２％。结论：ＨＳＥ之ＥＥＧ早期敏感性高,对诊断有指导作用,可作为推断本病严重程度及治疗效果的依据之一