Mika Otsuki

Deficits of working memory during mental calculation in patients with Parkinson's disease.

Using the dual task paradigm, previous studies have suggested that working memory (WM) deficit is due to depleted attention resources in patients with Parkinsons disease (PD). The aim of this study is to establish whether the WM problems in PD are due to reduced attentional set-shifting resources rather than depletion of attention resources. The task design attempts to eliminate confounding of the deficits in dealing with novel material, a problem documented in PD, by concentrating on WM tasks of mental calculation that are familiar to subjects in daily living. We also administered attention tasks, the Trail Making Test (TMT) that relies primarily on attentional set-shifting and the Kana (Japanese syllabogram) Pick-out Test instead primarily depending on depleted attention resources for allocation. A total of 24 patients with PD and 24 normal controls participated in this study. The PD group showed deficits in mental calculation span and in attentional set-shifting in the TMT-b.Considering the common deficits in alternating processing of mental calculation and TMT-b in PD, the results suggested that the central executive dysfunction in PD during mental calculations was due to reduced attentional set-shifting resources for rapidly alternating operations, rather than the depletion of attentional resources.

Dystypia: Isolated Typing Impairment without Aphasia, Apraxia or Visuospatial Impairment

We report a 60-year-old right-handed Japanese man who showed an isolated persistent typing impairment without aphasia, agraphia, apraxia or any other neuropsychological deficit. We coined the term ‘dystypia’ for this peculiar neuropsychological manifestation. The symptom was caused by an infarction in the left frontal lobe involving the foot of the second frontal convolution and the frontal operculum. The patient’s typing impairment was not attributable to a disturbance of the linguistic process, since he had no aphasia or agraphia. The impairment was not attributable to the impairment of the motor execution process either, since he had no apraxia. Thus, his typing impairment was deduced to be based on a disturbance of the intermediate process where the linguistic phonological information is converted into the corresponding performance. We hypothesized that there is a specific process for typing which branches from the motor programming process presented in neurolinguistic models. The foot of the left second frontal convolution and the operculum may play an important role in the manifestation of ‘dystypia’.

Writing errors as a result of frontal dysfunction in Japanese patients with amyotrophic lateral sclerosis.

Loss of communication is a critical problem for advanced amyotrophic lateral sclerosis (ALS) patients. This loss of communication is mainly caused by severe dysarthria and disability of the dominant hand. However, reports show that about 50% of ALS patients have mild cognitive dysfunction, and there are a considerable number of case reports on Japanese ALS patients with agraphia. To clarify writing disabilities in non-demented ALS patients, eighteen non-demented ALS patients and 16 controls without neurological disorders were examined for frontal cognitive function and writing ability. To assess writing errors statistically, we scored them on their composition ability with the original writing error index (WEI). The ALS and control groups did not differ significantly with regard to age, years of education, or general cognitive level. Two patients could not write a letter because of disability of the dominant hand. The WEI and results of picture arrangement tests indicated significant impairment in the ALS patients. Auditory comprehension (Western Aphasia Battery; WAB IIC) and kanji dictation also showed mild impairment. Patients’ writing errors consisted of both syntactic and letter-writing mistakes. Omission, substitution, displacement, and inappropriate placement of the phonic marks of kana were observed; these features have often been reported in Japanese patients with agraphia resulted from a frontal lobe lesion. The most frequent type of error was an omission of kana, the next most common was a missing subject. Writing errors might be a specific deficit for some non-demented ALS patients.

Pure Topographical Disorientation Following a Right Forceps Major of the Splenium Lesion: A Case Study

A 72-year-old man with pure topographical disorientation following a focal hemorrhage in the right forceps major of splenium was assessed at 2 weeks and 3 months after the onset. Initially, he could identify familiar buildings and landmarks, but noted topographical disorientation, dysfunction in sense of quarters, and in visuo-spatial function. The improvement of topographical disorientation was attained in 3 months, while the inability of the sense of quarters and manipulating visuo-spatial information remained unchanged. These results suggested the heading disorientation was accompanied with impaired sense of quarters, although disabled sense of quarters continued beyond the recovery of heading disorientation.

Writing errors in ALS related to loss of neuronal integrity in the anterior cingulate gyrus

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by loss of motor neuron and various cognitive deficits including writing errors. (11)C-flumazenil (FMZ), the positron emission tomography (PET) GABA(A) receptor ligand, is a marker of cortical dysfunction. The objective of this study was to investigate the relationship between cognitive deficits and loss of neuronal integrity in ALS patients using (11)C-FMZ PET. Ten patients with ALS underwent both neuropsychological tests and (11)C-FMZ-PET. The binding potential (BP) of FMZ was calculated from (11)C-FMZ PET images. There were no significant correlations between the BP and most test scores except for the writing error index (WEI), which was measured by the modified Western Aphasia Battery - VB (WAB-IVB) test. The severity of writing error was associated with loss of neuronal integrity in the bilateral anterior cingulate gyrus with mild right predominance (n=9; x=4 mm, y=36 mm, z=4 mm, Z=5.1). The results showed that writing errors in our patients with ALS were related to dysfunction in the anterior cingulate gyrus.

Dynamic brain activation during improvement in a sequential motor performance: An NIRS/I study

Introduction: Learning is essential to efficiently realize the complex information processing in the brain, however, its basic mechanism has not been elucidated. Near-infrared spectroscopic and imaging (NIRS/I) techniques have recently been developed as a high timeresolved method to noninvasively detect the hemodynamic response caused by focal activation in human cortex. We have aimed to investigate with time-series analysis how dynamically weighting changes occur in the neuron networks according to the stage during a procedural learning.