Biomedical subjects

Naoyuki Osaka

Publications and source records attributed to Naoyuki Osaka.

15 recordsLinked to original sources

PubMed2005

Involvement of V5/MT+ in object substitution masking: evidence from repetitive transcranial magnetic stimulation.

The visibility of a briefly presented target can be reduced by a subsequent weak mask that does not touch it, when the target is encoded in low spatiotemporal resolution. This phenomenon, called object substitution masking, has recently been proposed to reflect information updating in object-level representation, with perception of the target and the mask belonging to a single object through apparent motion. We investigated this issue by applying repetitive transcranial magnetic stimulation over V5/MT+, specialized in visual motion processing. The transient functional disruption of V5/MT+ produced by repetitive transcranial magnetic stimulation attenuated object substitution masking, while sham stimulation did not. Our results suggest that object substitution masking is mediated by normal functioning of V5/MT+. We conclude that repetitive transcranial magnetic stimulation of V5/MT+ impaired perceived object continuity and reduced object substitution masking accordingly.

Adult↗

PubMed2005

Kanizsa figure does not defend against saccadic compression of visual space.

Recent studies have suggested that the apparent shape of a perceptually organized object flashed immediately before saccade is not distorted although a perisaccadic flash is mislocalized as if the visual space is compressed toward the goal of the saccade. We report that the apparent width of a Kanizsa illusory rectangle flashed in the perisaccadic period was compressed as much as that of a control stimulus that did not induce illusory rectangle, while that of a rectangle with real contour was less compressed. Our results imply that the process of saccadic compression of visual space completes faster than the interpolation process of illusory contours.

Adult↗

PubMed2004

A word expressing affective pain activates the anterior cingulate cortex in the human brain: an fMRI study.

We present an fMRI study demonstrating that an onomatopoeia word highly suggestive of subjective pain, heard by the ear, significantly activates the anterior cingulate cortex (ACC) while hearing non-sense words that did not imply affective pain under the same task does not activate this area in humans. We concluded that the ACC would be a pivotal locus for perceiving affective pain evoked by an onomatopoeia word that implied affective pain closely associated with the unpleasantness of pain. We suggest that the pain affect sustained by pain unpleasantness may depend on ACC-prefrontal cortical interactions that modify cognitive evaluation of emotions associated with word-induced pain.

Adult↗

PubMed2004

A case of renal sarcoidosis: a special reference to calcium metabolism as a diagnostic and the therapeutic implications.

Sarcoidosis is a systemic granulomatous disease of unknown etiology and is associated with a wide variety of renal disorders including nephrolithiasis, hypercalciuria, hypercalcemia, nephrocalcinosis, tubular defect, glomerulonephritis, and granulomatous interstitial nephritis. We report a case of renal sarcoidosis in which we could not detect any evidence of extrarenal involvements that was diagnosed by renal biopsy and abnormal calcium metabolism incompatible with chronic renal insufficiency. On laboratory findings, decreased creatinine clearance, proteinuria, hypercalcemia, hypercalciuria, and mildly elevated serum angiotensin-converting enzyme (ACE) were seen. Serum intact parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D (1,alpha-25 vit D) were lower and higher than normal range, respectively, whereas the patient was already in chronic renal insufficiency. He was treated with oral corticosteroid. Serum ACE tended to fall, and 1,alpha-25 vit D level decreased with substantial fall of serum calcium and daily calcium excretion. In contrast, intact PTH increased slowly in accordance with a fall of serum calcium compatible with the level of renal impairment. Creatinine clearance and daily excretion of protein improved. The case reported here may propose that serial measurement of serum level of 1,alpha-25 vit D, calcium level, and magnitude of daily calcium excretion into urine is a simple and meaningful tool to detect the therapeutic response in sarcoidosis with abnormal calcium metabolism.

Anti-Inflammatory Agents↗

PubMed2004

Functional roles of the cingulo-frontal network in performance on working memory.

We examined the relationship between brain activities and task performance on working memory. A large-scale study was initially administered to identify good and poor performers using the operation span and reading span tasks. On the basis of those span scores, we divided 20 consenting participants into high- and low-span groups. In an fMRI study, the participants performed verification of arithmetic problems and retention of target words either concurrently or separately. The behavioral results showed that performance was better in the high-span group than in the low-span group under a dual-task condition, but not under two single-task conditions. The anterior cingulate cortex (ACC), left prefrontal cortex (PFC), left inferior frontal cortex, and bilateral parietal cortex were primarily activated for both span groups. We found that signal changes in the ACC were greater in the high-span group than in the low-span group under the dual-task condition, but not under the single-task conditions. Structural equation modeling indicated that an estimate of effective connectivity from the ACC to the left PFC was positive for the high-span group and negative for the-low span group, suggesting that closer cooperation between the two brain regions was strongly related to working memory performance. We conclude that central executive functioning for attention shifting is modulated by the cingulo-frontal network.

Adult↗

PubMed2004

The neural basis of executive function in working memory: an fMRI study based on individual differences.

Using fMRI, neural substrates of the executive system were investigated with respect to differences in working memory capacity. To explore the executive control processes, reading span test (RST) and read conditions were performed. Two subject groups were selected: those with large working memory capacities, labeled high-span subjects (HSS) according to the reading span test, and those with small working memory capacities, labeled low-span subjects (LSS). Significant activation was found mainly in three regions in comparison with the control: anterior cingulate cortex (ACC), left inferior frontal gyrus (IFG), visual association cortex (VAC) and superior parietal lobule (SPL). For both groups, the fMRI signal intensity increased in ACC and IFG during the RST condition compared to that under the read condition. A group difference was also found in the ACC and IFG region, specifically a significant increase in signal intensity was observed only for the HSS group but not for the LSS group. Behavioral data also showed that the performance was better in HSS than in LSS. Moreover, the cross correlation of signal change between ACC and IFG was higher in HSS than in LSS, indicating that the network system between ACC and IFG was more activated in HSS compared to that of LSS. These results suggest that executive function, that is, working attention controlling system is more active in HSS than in LSS. Moreover, the results confirmed our hypothesis that there is a general neural basis for the central executive function in both RST and previous LST (listening span test) tasks despite differences in modality-specific buffers.

Adult↗

PubMed2004

Cooperation of the anterior cingulate cortex and dorsolateral prefrontal cortex for attention shifting.

Attention shifting in the working memory system plays an important role in goal-oriented behavior, such as reading, reasoning, and driving, because it involves several cognitive processes. This study identified brain activity leading to individual differences in attention shifting for dual-task performance by using the group comparison approach. A large-scale pilot study was initially conducted to select suitable good and poor performers. The fMRI experiment consisted of a dual-task condition and two single-task conditions. Under the dual-task condition, participants verified the status of letters while concurrently retaining arrow orientations. The behavioral results indicated that accuracy in arrow recognition was better in the good performers than in the poor performers under the dual-task condition but not under the single-task condition. Dual-task performance showed a positive correlation with mean signal change in the right anterior cingulate cortex (ACC) and right dorsolateral prefrontal cortex (DLPFC). Structural equation modeling indicated that effective connectivity between the right ACC and right DLPFC was present in the good performers but not in the poor performers, although activations of the task-dependent posterior regions were modulated by the right ACC and right DLPFC. We conclude that individual differences in attention shifting heavily depend on the functional efficiency of the cingulo-prefrontal network.

Adult↗

PubMed2003

An emotion-based facial expression word activates laughter module in the human brain: a functional magnetic resonance imaging study.

We report an fMRI experiment demonstrating that visualization of onomatopoeia, an emotion-based facial expression word, highly suggestive of laughter, heard by the ear, significantly activates both the extrastriate visual cortex near the inferior occipital gyrus and the premotor (PM)/supplementary motor area (SMA) in the superior frontal gyrus while non-onomatopoeic words under the same task that did not imply laughter do not activate these areas in humans. We tested the specific hypothesis that an activation in extrastriate visual cortex and PM/SMA would be modulated by image formation of onomatopoeia implying laughter and found the hypothesis to be true.

Acoustic Stimulation↗

PubMed2003

The neural basis of individual differences in working memory capacity: an fMRI study.

Using fMRI, neural substrates of verbal working memory were investigated with respect to differences in working memory capacity. Listening-span test (LST), Listen, and Remember conditions were performed. Two subjects groups were selected: those who had large working memory capacities, labeled high-span subjects (HSS) according to the working memory span test, and those who had small working memory capacities, labeled low-span subjects (LSS). Significant activation was found mainly in three regions in comparison with resting control: left prefrontal cortex (PFC), anterior cingulate cortex (ACC) and temporal language area. For both groups, fMRI signal intensity increased in PFC during the LST condition compared to the Listen condition. A group difference was found in the ACC region; specifically, a significant increase in signal intensity was observed in ACC only for the HSS group and not for the LSS group. Behavioral data also showed that the performance was better in HSS than in LSS. These results indicate that the attention controlling system, supported by ACC, is more effective in HSS compared to that of LSS.

Adult↗

PubMed2003

[Reading comprehension and working memory: structural equation modeling approach].

We examined the relationship among intelligence, working memory, and reading comprehension using structural equation modeling (SEM). Ninety-six participants were instructed to perform two reading comprehension tests and six cognitive tasks: two verbal intelligence subtests, two spatial intelligence subtests, and two reading span tasks. Three latent variables that were called verbal ability, spatial ability, and working memory were derived from the six cognitive tasks. SEM demonstrated that the latent variables of working memory and verbal ability contribute to reading comprehension, suggesting that central executive functioning related to attention control was mediated among these cognitive abilities.

Adolescent↗

PubMed2003

[Effect of aging on priming of pop-out].

In visual search tasks using pop-out stimuli, memory of the stimuli in previous 3 to 10 trials affects search performance in the present trial. This is called priming of pop-out. We examined the adult age difference of the effect with Memory Kernel Analysis (Maljkovic & Nakayama, 1994, 1996). It was revealed that with respect to target color and position, facilitation by the stimulus repetition and inhibition by the stimulus change lasted over the succeeding approximately three to eleven trials in both age groups. While eye movements were frequently observed in older subjects and their reaction times were longer than younger subjects', the priming effect was robustly observed. These results suggest that facilitation and inhibition for pop-out features are intact in older adults. The number of trials the effect persisted was discussed in terms of age-related differences of capacities of the memory mediating the effect.

Adult↗

PubMed2002

Effects of inter-stimulus interval on perceived locations of successively flashed perisaccadic stimuli.

We investigated the perceived locations of two stimuli flashed successively near the time of saccade execution in a dark room. The inter-stimulus interval (ISI) between the flashes ranged from 80 to 240 ms. The results show that when the ISI was 120 ms or shorter, perceived locations of the flashes interacted with each other so that the perceived distance between them was equal to the distance between these flashes on the retina. When the ISI was 240 ms, this interaction was weak. These results suggest two hypotheses. Firstly, the relation of retinal locations of flashes is a strong cue for perceiving the flash locations when the ISI is shorter than about 120 ms.Secondly, the process of perceiving or memorizing a flash location requires some time. Therefore, the perceived location of the succeeding flash affects that of the preceding flash when the ISI as shorter than about 120 ms.

Cues↗

PubMed2002

Effect of focus on verbal working memory: critical role of the focus word in reading.

The effect of focus on working memory was investigated with the reading span test (RST). In two experiments, the span scores and the number of intrusion errors were compared between the focused RST the and the nonfocused RST. Focus word was defined as the most important word for comprehending a sentence. For the focused RST, the target word to be maintained was the focus word for the sentence. In the nonfocused RST, however, the target word was not the focus word for the sentence. The results of both experiments showed that RST span scores were higher for the focused RST than for the nonfocused RST, and intrusion errors were found to increase for the nonfocused RST. In Experiment 2, the effect of focus was compared between high-span and low-span subjects. An effect of sentence length was also investigated. The result showed that low-span subjects were more affected than were high-span subjects by whether the word to be remembered was the focus word. The effect of sentence length was not confirmed. These findings suggest that the low-span subjects had deficits in their ability to establish and/or inhibit mental focus when faced with conflict situations in reading.

Humans↗

PubMed2002

[Effects of focus on working memory].

Effects of focus on a target word during performance of the reading span test (RST) were investigated. A focus word in the sentence was defined as the most critical word with a core meaning to integrate the sentence. Two kinds of RST were compared. One was focus-RST (F-RST) in which the target word to be maintained was a focus word of the sentence. The other was a non-focus-RST (NF-RST) in which the target word was not a focus word of the sentence, although the sentence did contain a focus word. Results showed that RST scores were found to be higher for F-RST than for NF-RST. Moreover, the effect of focus was proved to be dominant for low span subjects. Intrusion errors also increased in NF-RST. Sentence length effect, however, was not found. The results showed that low span subjects had severe deficits in making and updating the focus, which is critical for sentence comprehension.

Humans↗

PubMed2002

Individual differences in working memory during reading with and without parafoveal information: a moving-window study.

We examined individual differences in working memory appearing in the effective visual field size while reading Japanese text. Working memory capacity was measured by a Japanese reading span test, and the subjects were divided into high- and low-score groups. Reading performance was measured by reading time, comprehension, and eye movements using a variable moving window through which the subject could read areas of the Japanese text. As the window size decreased, the reading time increased significantly. High-span subjects showed better performance in reading time, comprehension, and fixation duration than low-span subjects even in small visual fields. Interestingly, high-span subjects appear to show better information integration during reading, whereas low-span subjects showed less integration without parafoveal vision. These findings suggest that reading performance was better for subjects with larger working memory resources in a parafoveal restriction condition.

Eye Movements↗