Alzheimer's disease (AD) is slowly progressive with prominent memory disturbance in early stage. As the disease progresses, other cognitive domains become involved. Although current diagnostic criteria require memory impairment as a feature of ‘typical’ AD, there are ‘atypical’ forms of AD in which the most salient impairments are in non-memory domains. Such phenotypes include posterior cortical atrophy, logopenic variant of progressive aphasia, and frontal variant of AD. These findings have recently been extended to the non-amnestic mild cognitive impairment (MCI) as a dysexecutive form or visuospatial variant of MCI. Especially, some executive dysfunctions are detected early in the course of AD and MCI, and may be useful to predict conversion from MCI to AD and progression of AD.
     Dementia with Lewy bodies (DLB) tends to exhibit greater visuoperceptual, attentional and executive impairment and less pronounced memory impairment than AD. In the clock drawing test (CDT) , both AD and DLB patients tend to be equally impaired in drawing from memory, whereas DLB patients are more impaired in copying than AD. This pattern indicates a primary memory problem in AD and primary visual-perceptual and executive problems in DLB. Actually our SPECT studies reveal that the CDT impairment in AD is associated with decreased activity in the left posterolateral temporal cortex, which has an important role in semantic memory processing. In contrast, the CDT impairment in DLB is closely related to dysfunction of the frontal-subcortical network relevant to control of visuospatial attention and arousal, involving the frontal eye fields, supplementary eye fields, putamen and the thalamus. These features support the concept that DLB is a cortical-subcortical dementia, whereas AD is a cortical dementia.

View full abstract

Parkinson's disease (PD) is primarily a disorder of the motor system. However, recent studies have revealed that PD patients exhibit various kinds of cognitive and emotional impairment. Cognitive impairment seen PD is related to memory, executive function, visual perception. This paper focuses mainly on social cognition in PD. Social cognition plays an important role in the processing of emotional expression and mental state of others, and it is crucial for communications. Previous studies demonstrated that PD patients show impaired patterns in the facial expression recognition and decision making process to select the appropriate behavior. Recently, it has been also discussed whether or not Theory of mind (ToM) ability is affected by PD. ToM, defined as the ability to infer other people's mental states, is a crucial prerequisite of human social interaction. Cognitive and emotional impairment in PD is considered to have multiple causes, and careful attention is necessary in diagnosis and medication and rehabilitation.

View full abstract

Abstract attitude “also known as categorical attitude” is a concept to denote the ability to use conceptual categories in order to classify things according to their attributes and to think symbolically rather than concretely. Abstract attitude has been considered as one of the important background mechanisms under the semantic memory system. However, we hypothesize that the concept might be the mental process whose impairment leads to the changes in personality and behavior seen in frontotemporal lobar degeneration (FTLD) , rather than the semantic disturbance. Original tests to assess abstract attitude (Categorization task, the task to estimate approximate number, and the task to imagine a hypothetical scene) were given to 13 FTLD patients and a comparison group of Alzheimer's disease (AD) patients (n=13) . The magnitude of stereotyped behavior was assessed by using the Stereotypy Rating Inventory (SRI) . Patients with FTLD were impaired on all tests of abstract attitude. By contrast, the AD group had no difficulty with the tasks. There was a significant correlation between the SRI score and the performance of the tests of abstract attitude (r=0.59, p=0.032) . These results support the hypothesis that patients with FTLD, but not those with AD, are impaired on tests of abstract attitude, and may explain some behavioral abnormalities characterized in FTLD.

View full abstract

Features of motor speech disorders observed in frontotemporal lobar degeneration (FTLD) , especially chronological evolutions of symptoms and clinicopathological relations, are reviewed. In FTLD, motor speech disorders are classified into three main categories : progressive non fluent aphasia, progressive apraxia of speech, or progressive dysarthria. Degenerative process in the posterior part of the left inferior frontal gyrus lead to agrammatism and word retrieval disorder, which are main features of progressive non-fluent aphasia. The lesion in the lower part of the left precentral gyrus leads to anarthria or apraxia of speech. Progressive dysartirha is derived from progressive bulbar palsy (one of the main features of motor neuron disease with dementia) or progressive “cortical” pseudobulbar palsy, due to the lesions in the bilateral motor cortex. Detailed phonological-language analysis would enable to predict lesion distribution and pathological background.

View full abstract

We studied the memory disturbance induced by direct electrical stimulations (ES) of the left medial temporal lobe (MTL) . Stimulations were performed in 3 patients with drug-resistant epilepsy during stereoelectroencephalographic recordings in the setting of presurgical evaluation. All patients had electrodes that sampled the perirhinal (PC) and entorhinal (EC) cortices. Verbal memory was evaluated by three words memory test, in which the subjects were asked to repeat three common words which were aurally presented them (memorizing and immediate recall (MIR) condition) . After the distraction tasks for one minute, the subjects were asked to select the three words which were presented before the distraction tasks from six words (delayed recognition (DR) condition) . The ES during MIR condition did not induce immediate recall disturbance, but the ES during MIR and DR condition, especially the ES in the PC during DR, produced DR disturbance. There were some pairs of electrodes on which the ES during both MIR and DR conditions produced DR disturbance in this study, indicating some regions in the PC and EC play important roles in both memorizing and retrieving memory. False recognitions were induced only when the ES were performed on the electrodes in the PC during DR condition. False recognitions were induced not only during the application of ES, but also after the ES were stopped. The findings of this study indicated that the dysfunction in the PC and EC, without dysfunction in the hippocampus, could induce DR impairment and that dysfunction in the PC during retrieval induced false recognitions.

View full abstract

The neural circuit that arises from the hippocamupus via the fornix, the mammillary body, the mammillothalamic tract and the anterior thalamic nuclei and projects back to the hippocampus, known as the Papez or Delay-Brion circuit, has long been considered to play a critical role in memory. In addition, the significance of the neuroanatomical network among the rhinal / parahippocampal cortices, the mediodorsal nucleus of the thalamus and the prefrontal cortices has been recently recognized. Most researchers have placed a greater emphasis on the importance of the Papez circuit disruption in diencephalic amnesia. However, close inspection of neuropsychological literature and our recent study on anterior thalamic infarction in the tuberothalamic artery territory suggest that there are multiple circuit disruptions in cases of diencephalic amnesia.

View full abstract

Basal forebrain amnesia is characterized by both anterograde and retrograde amnesia, which is often accompanied by confabulation, attention deficit, and personality changes. Compared with medial temporal amnesia, spontaneous confabulation is a prominent feature of basal forebrain amnesia. This study investigated the neural basis of chronic spontaneous confabulation. Lesion overlap in eight patients with chronic spontaneous confabulation after basal forebrain damage extended to the orbitofrontal cortex and ventromedial frontal cortex with right hemisphere dominance to some extent. The mechanisms of spontaneous confabulation are considered to involve relieving past experiences, wishful distortion, failure to suppress irrelevant memory traces, and confusion of memory traces during retrieval.

View full abstract

Prefrontal lesion is involved in working memory deficits, but not amnesic syndrome that is the disorder of episodic memory. However, recent neuropsychological researches indicated that the damages of prefrontal lobes are related to the deficits of specific aspects of encoding and retrieval of long term memory, including the disorders of temporal ordering of memory items, false recognition, and prospective memory. On working memory and prefrontal lobe function in animals, dopamine D1 receptors in the prefrontal cortex are important for working memory functions, and it is suggested that stimulation of prefrontal D1 receptors induces an inverted U-shaped response, such that too little or too much D1 receptor stimulation impairs prefrontal functions. We described a interesting positron emission tomography (PET) finding in healthy human subjects. In this study, we found an inverted U-shaped relation between prefrontal dopamine D1 receptor binding and Wisconsin Card Sorting Test performance in human.

View full abstract

Dissociative amnesia, also called psychogenic amnesia or functional amnesia, is a psychiatric disorder, in which patients have an inability to retrieve specific autobiographical memories. It usually follows a psychotraumatic or stressful event and is not due to any direct organic injury to the brain. Although it has been argued from a psychiatric perspective for a long time, dissociative amnesia has begun to get approached with neuroscientific techniques recently. Studies with functional neuroimaging techniques have revealed functional abnormality of dissociative amnesia at brain level. There are two theories about brain mechanisms of dissociative amnesia ; frontal executive inhibition of the medial temporal memory system, and functional disconnection of right fronto-temporal regions engaged in triggering autobiographical memory retrieval. Recent studies have reported evidence supporting each of the two theories. The aim of this review is to summarize recent neuroscientific insights into neural basis of dissociative amnesia, and to make an outline and consideration of it from a neurological view.

View full abstract

     The Sentence Forming Test (SFT) has been developed as a quantitative and qualitative assessment tool for the ability to formulate situationally-appropriate communicative utterances (Takahashi et al., 2007) . The present study examined whether the SFT could elicit spontaneous speech from adult aphasics. SFT and SLTA were administered to 150 aphasics. Quantitative and qualitative analyses were performed on the responses elicited in the SFT and criterion validity was assessed through correlational analysis between SFT and SLTA results. Attempts were also made to examine if aphasics can be differentiated from normal adults based on the SFT data.
     The results indicated that SFT (Mean=16.75, and SD = 5.93) correlated significantly with the total scores of speech subtests in SLTA (r=0.639, p < 0.01) . The aphasics' responses were characterized by a wide range of vocabulary and various syntactic structures reflecting idiosyncrasy among subjects : such characteristics were also seen among normal speakers. The types and severity of aphasia were reflected in the types and numbers of errors in SFT except for semantic-lexical errors. The aphasics and the normal speakers in the previous study could be discriminated on the basis of the number of correct responses and time of performance in SFT.

View full abstract

     A 43-year-old, right-handed female showed severe auditory disorders and mild Wernicke's aphasia after bilateral temporo-parietal infarction. Severe hearing loss of more than of 90 dB was bilaterally revealed by pure tone audiometric examination from the onset. Meanwhile, auditory brain stem response (ABR) revealed V-component responses at 40 dB bilaterally, almost within the level of mild disorders. Her language disorders were mild and her writing ability was relatively preserved. From these examination results, she showed so-called “ cortical deafness. ” Notwithstanding her severe hearing loss, she rarely complained about it and even seemed to be in a euphoric state (anosodiaphoria) . We tried lip-reading rehabilitation, and as a result of this she was able to communicate with staff by listening and lip-reading in the training setting, but she was unable to communicate in everyday life situations.
     We investigated the relationship between anosodiaphoria and mental disability in similar case reports.

View full abstract

A 65-year-old right-handed woman is reported who shows severe complex visual hallucinations accompanying severe visual field defect. At first she revealed left homonymous hemianopia due to a right temporo-parietal hemorrhage. Visual hallucinations did not appear at that time, however. About 12 years later, the complex visual hallucinations started after a left occipital infarction which finally led to bilateral homonymous hemianopia. Since then the hallucinations have been appearing continually for over two years. The patient did not have self-awareness of the disorder for the first 16 months, however. In interpreting this case we discuss two important points : (1) she did not have self-awareness of the visual hallucinations because (a) they were very realistic, (b) she had no real visual image to compare with from the primary visual area, and (c) her self-awareness of the visual field defect had become weak ; (2) it is suggested that the complex visual hallucinations in this case are caused by severe visual field defect and by undamaged visual association cortices in the left temporo-parietal lobe functioning actively and provoking visual images spontaneously.

View full abstract

Most patients with visual agnosia are not aware of their impairment. The mechanism of anosognosia, however, has not been elucidated. We report a case of apperceptive agnosia after embolic cerebral infarctions involving the bilateral medial temporo-occipital lobes. The patient's anosognosia for visual cognition reduced when he suffered recurrence of cerebral infarction involving the left ventral medulla, leaving the right side hemiparalyzed. However, no change was noted in his visual agnosia or other cognitive functions after the recurrence. Given the clinical course of the patient, we speculate that the hemiparalysis, which forced visual cognition to compensate for his physical weakness, might play a role in the awareness of visual agnosia.

View full abstract

Aims : Our aim is to estimate the prevalence of apathy and examine neuropsychological features in mild cognitive impairment (MCI) subjects in community. Methods : We enrolled 368 community dwellers aged 75 years or more, who lived in Kurihara, Miyagi, and we obtained informed written consent from 200 subjects. One hundred eighty-nine of 200 subjects completed clinical examination, neuropsychiatric tests, and apathy assessment. We used the Clinical Assessment for Spontaneity Part 1 (CAS 1) to assess apathy. Healthy (Clinical Dementia Rating ; CDR 0) was 52, MCI (CDR 0.5) was 108, and dementia (CDR 1 + ) was 29 subjects. Analysis 1. Estimate of the prevalence of apathy in community-dwelling elderly. Analysis 2. Neuropsychological features in MCI subjects with apathy. Results : 1. In all subjects completed CAS1, 54.5 % of all subjects had apathy. There was significant difference among 3 CDR groups (p < 0.001) . 2. There were significant CDR effects in memory tasks between the healthy elderly and the MCI groups (p < 0.001) , but no apathy effects. There was significant correlation between CAS1 and WMS-R Logical Memory I (p = 0.001) . Conclusions : There were no neuropsychological differences between MCI subjects with and without apathy, but it is suggested that apathy of MCI subjects is related to encoding memory.

View full abstract