Functional and histological properties of caudal intraparietal area of macaque monkey.

In our previous studies, we found that cells in the caudal intraparietal (CIP) area of the macaque monkey selectively responded to three-dimensional (3D) features, such as the axis and surface orientations, and we suggested that this area played a crucial role in 3D vision. In this study, we investigated (1) whether cells in CIP respond to other 3D features, such as curvature, and (2) whether CIP has any histological property to distinguish it from neighboring areas. Curvatures defined by a random-dot stereogram were presented on a display while the monkey performed a fixation task. The shape and amount of curvature were manipulated by two independent variables, shape index and curvedness, respectively. Two-way ANOVA showed that 19 out of 56 visually responsive cells (34.0%) showed the main effect of shape index. We tentatively designated these cells as 3D curvature-selective (3DCS). Of these, six 3DCS cells showed the main effects of shape index and curvedness, whereas 13 showed the main effect of shape index only. In both types of 3DCS cells, preferred shape indices calculated from tuning curves at two levels of curvedness matched well. These results indicate that the majority of 3DCS cells responded equally to a particular shape of curvatures with different curvedness levels. An immunohistochemical study showed that the recording sites of 3DCS cells were in a cortical region characterized by a dense SMI-32 immunoreactivity in the caudal portion of the lateral intraparietal sulcus (IPS), which suggests that this region is comparable to the lateral occipital parietal (LOP) designated in the caudal IPS previously. Further investigations showed that this region was separated from LIPv, the ventral subdivision of lateral intraparietal (LIP) located rostral to CIP/LOP. These results suggest that CIP is a cortical area distinct from LIP histologically as well as functionally.

Impaired verbal description ability assessed by the Picture Description Task in Alzheimer's disease.

The language of patients with Alzheimer's disease (AD) is globally non-informative and characterized by selective impairment of lexical-semantic processing as compared with a relative sparing of syntactic and phonological aspects. Verbal picture description is one of the most sensitive tests for detecting language disorders in AD. We assessed verbal description ability in AD and investigated its relation to regional cerebral blood flow (CBF). In part I of the study, 23 AD patients and 17 age-matched normal subjects performed the Picture Description Task, which yields six variables: (1) the amount of information, (2) the number of constituent parts of the picture, (3) the number of relevant and irrelevant descriptions, (4) efficiency of description, (5) appropriateness, and (6) sentence structure. In the study, variables 1, 3 and 4 were analyzed. In part II of the study, regional CBF of 14 of the above AD patients was measured using N-isopropyl-p-[(123)I]iodoamphetamine and single photon emission CT. In part I, there were significant difference between the groups for variables 1 and 4. In part II, there were significant correlations between variable 1 and rCBF in the bilateral occipital lobes and left thalamus. Variables 1 and 4 were useful in discriminating between AD patients and controls. Variable 1 was suggested to be related to the function of the left thalamus and the bilateral visual cortex.

Postural and gait disturbance correlated with decreased frontal cerebral blood flow in Alzheimer disease.

In a group of 45 patients with Alzheimer disease (AD) and 15 control subjects, we studied the relationship between parameters showing postural and gait disturbance and regional cerebral blood flow (rCBF) measured with N-isopropyl-p-[123I]iodoam-phetamine single photon emission computed tomography at different clinical stages. Patients with AD with mild dementia exhibited only increased postural sway associated with a reduced mean value of rCBF in the cortex. At a moderate stage, the reduced mean values of rCBF in the cortex and in the frontal lobe were associated with increased postural sway and stride length variability and with decreased stride length. At a severe stage, reduced rCBF in the basal ganglia and in the frontal lobe additionally were associated with increased postural sway, double support time, and stride length variability, and with decreased walking speed and stride length. In multiple regression analysis, there was a high contribution by rCBF in the frontal lobe to account for postural and gait disturbance in AD. We propose that impaired frontal lobe circulation is an important factor causing postural and gait disturbance as AD progresses.

Mechanisms underlying orientation selectivity of neurons in the primary visual cortex of the macaque.

1. Effects of blocking intracortical inhibition by microiontophoretic administration of bicuculline methiodide (BMI), a selective antagonist for GABAA receptors, on orientation selectivity of 109 neurones were studied in the primary visual cortex (V1) of anaesthetized and paralysed monkeys. 2. The averaged orientation tuning of visual responses of cells was poor in cytochrome oxidaserich blobs of layer II/III and in layer IVc beta, moderate in layers IVb, IVc alpha and V, and sharp in the interblob region of layer II/III and in layers IVa and VI. 3. Iontophoretic administration of BMI reduced the sharpness of orientation tuning of cells to a varying extent in each layer. In most cells, furthermore, the originally ineffective stimuli induced visual responses during the BMI administration, suggesting that excitatory inputs evoked by the non-optimally oriented stimuli were masked by GABAergic inhibition. Nevertheless, the maximal facilitation was observed in the response to the optimally or near-optimally oriented stimuli. 4. There was a difference in such an effect of BMI among layers. Orientation selectivity of cells in interblobs in layer II/III and in layer IVb was sensitive to BMI whereas that of cells in layer VI was relatively insensitive to BMI, suggesting a larger contribution of excitatory mechanisms to the orientation selectivity in this layer. 5. In the orientation-selective cells, an analysis of the magnitude of excitation and inhibition evoked by stimuli at various orientations suggests that both inputs tune around the optimal orientation and their magnitudes are almost proportional to each other except at the optimal orientation. This analysis also indicates that the orientation tuning of inhibition had a less prominent peak around the optimal orientation than that of excitation. This dominance of excitation over inhibition around the optimal orientation may function to accentuate the response to the optimally oriented stimulus. 6. These results suggest that, in the monkey V1, the orientation selectivity of cells is largely dependent on the orientation-biased excitatory and inhibitory inputs which have a broader tuning profile, covering from the optimal to null-orientation, than that observed in extracellularly recorded responses at the control level.

Lateral suprasylvian visual cortex is activated earlier than or synchronously with primary visual cortex in the cat.

To explore functional connectivity between area 17 and posteromedial lateral suprasylvian (PMLS) area of the cat cerebral cortex, we carried out cross-correlation analysis of spike trains of neurons recorded simultaneously from both areas of anesthetized, paralyzed cat. Most of correlated pairs had peaks which indicate that PMLS cells were activated earlier than or simultaneously with their partners in area 17, suggesting that 'backward' as well as synchronous activation operates between these cortical areas.

Less segregated processing of visual information in V2 than in V1 of the monkey visual cortex.

To test the possibility of cross-talk between parallel pathways dealing with different aspects of visual information such as orientation, direction of motion and colour in cortical area V2, we quantitatively analysed visual responses of 121 V2 cells recorded from anaesthetized and paralysed macaques and compared them with those of 147 V1 cells. A selectivity index of visual responses was calculated for each neuron, which was then classified as selective or not to a particular attribute of visual stimuli. Twenty-one percent of the V2 neurons had dual selectivity to both colour and direction of stimulus motion (C&D cells). In V1, only 5% of the cells were C&D cells. Thus, the proportion of C&D cells significantly increased from V1 to V2. We also carried out cross-correlation analysis of spike trains recorded simultaneously from pairs of V2 neurons or pairs of V1 neurons. In V2, correlated firings could be observed between cells with completely different optimal orientation, such as orthogonal, while it was never observed in V1. The cross-correlation analysis further indicted that functional interactions in V2 were more widespread than those in V1. These results suggest that neurons which have different functional properties become less segregated, and that functional interactions become more widespread in V2 than in V1.

Mechanisms underlying direction selectivity of neurons in the primary visual cortex of the macaque.

1. We studied the effects of blocking intracortical inhibition by microiontophoretic administration of bicuculline methiodide (BMI), a selective antagonist for gamma-aminobutyric acid-A receptors, on direction sensitivity of 103 neurons in the primary visual cortex (VI) of anesthetized and paralyzed monkeys. 2. The direction selectivity index (DSI) of each cell was calculated for the control response and response during the BMI administration at the optimal stimulus orientation to assess the directionality of an individual cell. 3. The averaged direction tuning of visual responses of cells was sharp in layers IVa and IVb, moderate in both interblob and blob regions of layer II/III and layers V and VI, and poor in layers IVc alpha and IVc beta. 4. Iontophoretic administration of BMI uncovered or facilitated responses to stimuli moving in the nonpreferred direction, and reduced DSIs of cells to a varying extent in all the layers except layer VI. Responses to stimuli moving in the preferred direction were also facilitated so that a slight bias of response toward the originally preferred direction remained during BMI administration in most cells. 5. Most of the cells in layers II/III (both blobs and interblobs) and IVb that receive inputs from layers IVc alpha and IVc beta showed a clear reduction of direction selectivity during BMI administration. This result suggests that intracortical inhibition plays an important role in the elaboration of direction selectivity at the second stage of information processing in VI. 6. The direction selectivity of cells in layer VI was most resistant to the effects of BMI, suggesting that it is dependent on excitatory inputs that are already direction selective, even though the sample size of this layer was small. 7. In direction-selective cells outside layer VI, responses to a stimulus moving in the preferred direction were enhanced in a way that was linearly related with those in the nonpreferred direction as the BMI dose was increased. This suggests that various amounts of inhibition interact linearly with directionally biased excitatory inputs to raise the firing threshold to various levels so as to produce various degrees of directionality. 8. These results suggest that, in most of the directionally sensitive cells except for those in layer VI, there are excitatory inputs which are bidirectional but slightly biased to one direction, and that the intracortical inhibition raises a threshold level of responses to excitatory inputs so that the response become direction selective.

Broad-tuned chromatic inputs to color-selective neurons in the monkey visual cortex.

1. Input mechanisms of 21 color-selective cells in cytochrome oxidase-rich blobs in layer II/III of the anesthetized and paralyzed monkey primary visual cortex were studied by an iontophoretic administration of the GABAergic receptor antagonist bicuculline methiodide (BMI). 2. Color-selective blob cells become responsive to originally nonresponsive colors of stimuli or brightness contrast stimuli during removal of intracortical inhibition. 3. The magnitudes of the cells' responses to color stimuli during BMI administration were larger than the expected value of response calculated from the previously reported color tuning of color-selective geniculate cells and emission spectra of color stimulus. 4. These results suggest that color-selective blob cells receive a convergence of different types of chromatic inputs and that intracortical inhibition confers selectivity for a given color on them.

[Analysis of mesenteric thickening on computed tomography].

Computed Tomography (CT) provides a noninvasive information in the evaluation of abnormalities of the gastrointestinal tract by direct imaging of the bowel wall and adjacent mesentery. Several prior studies have discussed the variable CT appearances of mesenteric abnormalities, such as lymphoma, metastasis, inflammatory disease and edema. Although mesenteric thickening was mentioned in these studies, no study has provided a detailed analysis of the CT appearance of the thickened mesentery. Two characteristic types of mesenteric thickening were identified in 47 patients. Type I is "Intra-mesenteric thickening", which was noted in 25 patients with vascular obstruction, inflammatory disease and edema. Type II is "Mesenteric surface thickening", which was noted in 22 patients with peritonitis carcinomatosa, peritoneal mesothelioma, tuberculous peritonitis and pseudomyxoma peritoneal. An understanding of these two types of mesenteric disease is important in the identification of mesenteric pathology.

Bone mineral density of the spine and proximal femur in normal and osteoporotic subjects in Japan.

Bone mineral density (BMD) of the spine and proximal femur in Japanese men and women was investigated with dual photon absorptiometry, using gadolinium-153. Peak bone mass of the spine (L2-4) was 1.20 g/cm2 in women which was lower than that of men by 4.7%, whereas BMD of the femoral neck was 0.91 g/cm2 in women and lower than in men by 13.3%. Bone loss was faster in postmenopausal women than in men of the corresponding age, and the regressions of BMD on age were 6.7-times higher at L2-4 and 5.1-times higher at the femoral neck than in men. Such rates of loss became slower both in the lumbar spine and proximal femur in women after 70 years of age, but the density at the proximal femur kept decreasing in men after 70 years of age. Fracture thresholds of each region were evaluated at the 90th percentile for BMD of L2-4 in patients with vertebral crush fractures and for BMD of the proximal femur in patients with hip fractures. The fracture threshold was 0.97 g/cm2 at the spine and 0.67 g/cm2 at the femoral neck in women. BMD values at the spine and proximal femur in normal Japanese men and women appear to be lower than those in white American control population.

[Clinical efficacy of the liver scintigram--rates of interpretation of physiologically defective activity areas].

Liver scintigrams of 406 cases were interpreted by 11 physicians. The ratios of the interpretation of the physiologically decreased activity areas in the liver scintigrams were 27% in the regions of the porta hepatis, 23% in the gall bladder fossa, 20% in the inferior vena cava, 7% in the renal impression, 2% in the portal vein, 2% in the rib impression and 2% in others. The cases having space occupying lesions showed decreased ratio of the interpretation of the physiologically decreased activity areas, as compared with other groups. Cases of the liver cirrhosis showed decreased ratio in the region of inferior vena cava. Cases using Anger camera demonstrated more increased ratio than cases using a scanner. The 11 physicians could be divided for two groups. One group showed high ratios of the interpretation of the physiologically decreased activity areas, and another group showed very low ratio, because of the different interpretation about the physiologically decreased activity areas in the two groups. In our cases, a very few cases showing decreased activity on the liver image were false positive or false negative for diagnosis of space occupying lesions.