Memory deficits in young schizophrenics with normal general intellectual function

The aim of the present study was to examine different dimensions of memory functioning in young schizophrenics with normal general intellectual abilities. Thirty-three patients with schizophrenia and 33 healthy controls were included in the study. The results suggest that immediate short-term memory is intact, though there emerged a working memory deficit in the schizophrenia group. Deficient encoding of verbal material was observed in some, but not in other, testing conditions. There also seemed to be a retrieval deficit for verbal material in schizophrenia, though no storage deficit was indicated. Impaired memory for non-verbal material was also revealed. These results occurred in a context of intact executive functioning as measured by the Wisconsin Card Sorting Test. The results indicate that temporal and frontal structures, as well as their interconnections, may be compromised in schizophrenia.     

On the Correlation between Synchronized Oscillatory Activities and Consciousness

Recent experiments have shown that the amplitudes of cortical gamma band oscillatory activities that occur during anesthesia are often greater than amplitudes of similar activities that occur without anesthesia. This result is apparently at odds with the hypothesis that synchronized oscillatory activities constitute the neural correlate of consciousness. We argue that while synchronization and oscillatory patterning are necessary conditions for consciousness, they are not sufficient. Based on the results of a binocular rivalry study of Fries et al. (1997), we propose that the degrees of oscillatory strength and synchronization of neuronal activities determine the degree of awareness those activities produce. On the other hand, the overal firing rates of neurons in cortical sensory areas are not correlated with the degree of awareness the activities of those neurons produce. The results of the experiment of Fries et al. (1997) appear to conflict with the results of another binocular rivalry experiment, in which monkeys were trained to pull a lever in order to report which stimulus object was being perceived (Leopold & Logothetis, 1996). In the latter experiment, it was demonstrated that the firing rates of neurons in striate cortex did not change during perceptual alterations, while 90% of neurons in inferior and superior temporal cortices changed their firing rate when the perceived image changed. This result led to the conclusion that activities in temporal cortex are correlated with visual awareness, but those in striate cortex are not. We argue that activities in temporal cortex contribute little, if anything, to perceptual awareness, and that their primary function is computational. Thus the correlation between the firing rates of neurons in these areas and the responses of the monkeys is due to the recognition of a particular stimulus object, which in turn is due to the computations made there.     

Reduced right hemisphere activation in severely abused violent offenders during a working memory task: An fMRI study

This study uses functional magnetic resonance imaging (fMRI) to address two important gaps in our knowledge of brain functioning and violence: (1) What are the brain correlates of adults in the community who have suffered severe physical abuse early in life and who go on to perpetrate serious violence in adulthood? (2) What characterizes those who experience severe physical abuse but who refrain from serious violence? Four groups of participants recruited from the community (controls, severe physical child abuse only, serious violence only, and severely abused, seriously violent offenders) underwent fMRI while performing a visual/verbal working memory task. Violent offenders who had suffered severe child abuse show reduced right hemisphere functioning, particularly in the right temporal cortex. Abused individuals who refrain from serious violence showed relatively lower left, but higher right, activation of the superior temporal gyrus. Abused individuals, irrespective of violence status, showed reduced cortical activation during the working memory task, especially in the left hemisphere. Brain deficits were independent of IQ, history of head injury, task performance, cognitive strategy, and mental activity during the control task. Findings constitute the first fMRI study of brain dysfunction in violent offenders, and indicate that initial right hemisphere dysfunction, when combined with the effects of severe early physical abuse, predisposes to serious violence but that relatively good right hemisphere functioning protects against violence in physically abused children. Aggr. Behav. 27:111–129, 2001. © 2001 Wiley‐Liss, Inc.     

压后皮质在空间导航的作用：认知地图与环境的映射

压后皮质在大脑中紧邻胼胝体压部,在空间导航中起到重要作用,但其具体功能尚未明确。目前存在空间更新、地标领航和参照系转换三种观点。本文通过梳理上述观点,认为压后皮质的功能为对认知地图与环境布局进行映射,这种映射功能有助于解释压后皮质在基于认知地图进行导航过程中的激活。未来研究应该关注对压后皮质的功能分区,也要关注压后皮质与不同脑区的连接,这将对进一步理解其功能有重要的意义。     

熟悉性能够支持联结记忆:一体化编码的作用

双加工理论认为熟悉性和回想是支持情景记忆的两种基本加工过程。一般认为熟悉性和回想都可以支持项目记忆,但只有回想能够支持联结记忆。然而,一体化假说提出,当刺激材料在学习阶段得到一体化编码,形成一个单一、整合的表征时,熟悉性也能够支持联结记忆。以往研究主要利用实验材料的固有特征,或使用定义法、交互表象法来实现对刺激材料的一体化编码,然后通过配对联结再认范式或来源记忆范式验证一体化假说。神经成像研究发现,位于内侧颞叶的嗅周皮层能够支持编码阶段一体化表征的形成和基于熟悉性对一体化表征的提取。未来研究应克服以往研究中存在的方法学缺陷、从功能神经网络的角度考察一体化加工的脑神经机制、并注重一体化编码策略在特殊人群中的应用价值。     

隔区或皮质顶叶损毁对大鼠空间认知能力的影响及大鼠搜索策略差异的研究

本研究的目的是探讨隔区或皮质顶叶在大鼠空间认知加工中的作用。实验观察到隔区或皮质顶叶损毁大鼠Morris迷宫学习或记忆作业成绩显著低于控制组,并发现隔区损毁大鼠主要采用与皮质顶叶或控制组不同的“非国类”搜索策略。搜索策略的差异提示:隔区和皮质顶叶在大鼠图认知加工系统中处于不同的功能层次,隔区具有更重要的作用。     

Understanding symptoms of medical frontal lobe disorder: A clinical case study

A case of anterior communicating artery aneurysm with damage to inferior medial frontal areas (Brodmann areas 25, 32, 24-inferior) is presented. Four prominent deficits are discussed: (1) anterograde amnesia, (2) inert perseverative card sorting, (3) motor stereotypies, and (4) reduplicative paramnesia. These four deficits are discussed as negative or positive symptoms, related either to damage in inferior medial frontal (Brodmann areas 25, 32, 24-inferior) regions or release phenomena of superior medial frontal (Brodmann areas 6-medial and 24-superior) regions. It is concluded that the inferior and superior medial frontal regions act as opponent processors, with the inferior (B25, 32) area functioning to switch current mental set while the superior (B24-superior, 6-medial) region functions to maintain current mental set. Testable hypotheses about the opponent processor mechanism are suggested, as applied to neuropsychiatric disorders.     

A review of social disinhibition after traumatic brain injury

Acquired social disinhibition refers to a debilitating behavioural syndrome commonly reported after a severe traumatic brain injury (TBI) and is characterized by inappropriate social behaviour, often described as immaturity and insensitivity towards others. These behaviours can have enduring effects on the social capability of the individual and their relationships with others. However, research into socially disinhibited behaviour after TBI has been thwarted by a lack of consensus in the literature on definition and measurement. This review provides an overview of our current understanding of the definition, measurement, prevalence, associated outcomes, neuropathology, and underlying mechanisms of social disinhibition after TBI. In addition, suggestions are made for future research to further our understanding of this syndrome with the eventual aim of rehabilitating problematic behaviours. It is concluded that an improved understanding of what causes disinhibited behaviour after TBI will be necessary for the development of effective treatment strategies aimed at the rehabilitation of underlying impairments.     

Pure optic ataxia and visual hemiagnosia – extending the dual visual hypothesis

Goodale and Milner's two visual system hypothesis is an influential model for the understanding of the primate visual system. Lesions of either the ventral (occipito‐temporal) or the dorsal (occipito‐parietal) stream produce distinct and dissociated syndromes in humans: visual agnosia is typical for ventral damage, whereas optic ataxia (OA) for dorsal damage. We studied the case of a 59‐year‐old left‐handed woman with a circumscribed lesion around the left posterior occipital sulcus, extending to the underlying white matter. Initially, she presented with a central visual field OA, which regressed to an OA to the right visual hemifield during the 3 months observation period. In addition, tachistoscopic experiments showed visual hemiagnosia to the right visual hemifield. In line with the findings of the neuropsychological experiments, the analysis of the structural MR data by means of a trackwise hodologic probabilistic approach revealed damage to the left superior longitudinal fasciculus and to the left inferior longitudinal fasciculus, indicating an impairment of both the dorsal and the ventral stream. The combination of OA and visual hemiagnosia in the same patient has never been previously described. The present case study thus provides further insights for the understanding of visual processing.     

Dreaming and cognition in patients with frontotemporal dysfunction

Individuals with Parkinson’s disease (PD) and temporal lobe epilepsy (TLE) have hallucinations and mild cognitive dysfunction. The objective of this work was to study dreams in PD and TLE patients using a common functional model of dream production involving the limbic and paralimbic structures.Dreams were characterised in early-stage PD (19 males) and TLE patients (52) with dream diaries classified by the Hall van de Castle system and were compared with matched controls.In PD, there were significant differences between patients’ dreams and those of controls: animals, physical aggression, and a befriender were more common in patients, and aggressor and bodily misfortunes were less common. The dreams of patients with frontal dysfunction showed more aggressive features.TLE patients had lower recall than PD patients and a higher proportion of dreams involving family and familiar settings, lower proportions involving success, and a higher incidence of frontal dysfunction.The dreams of PD and TLE patients share important features.