Evaluation of Retinal Function and Pathology After Intravitreal Injection of Povidone-Iodine and Polyvinyl Alcohol-Iodine in Rabbits.

Purpose: This study compared intraocular toxicity of intravitreally injected povidone-iodine (PI) and polyvinyl alcohol-iodine (PAI) in rabbits. Methods: In each rabbit, 0.1 mL of PI or PAI solution was injected intravitreally into one eye and saline was injected into the other. PI was tested at available iodine concentrations of 0.05%, 0.1%, 0.2%, and 0.5%, and PAI at 0.05%, 0.1%, and 0.2% (n = 6 each). Electroretinograms were recorded before injection and 1, 7, and 14 days after injection. Pathological examinations of eyeballs were performed on day 15. Results: Mean b-/a-wave ratios of the electroretinograms did not change in eyes injected with 0.05%, 0.1%, or 0.2% PI (PI-0.05, PI-0.1, and PI-0.2, respectively) or in eyes injected with 0.05% or 0.1% PAI (PAI-0.05 and PAI-0.1, respectively) compared to saline-injected eyes, but was transiently impaired on day 1 in PAI-0.2 eyes. Histopathologically, no retinal abnormalities were observed in PI-0.05, PAI-0.05, or PAI-0.1 eyes. One PI-0.1 eye first showed localized inflammatory cell infiltration in the inferior retinal region. Two PI-0.2 eyes and one PAI-0.2 eye had retinal degeneration and inflammatory cell infiltration. In the PI-0.5 group, extensive inflammatory cell infiltration was observed in six eyes and inferior retinal detachment in five eyes. Conclusions: PI and PAI have equivalent retinal toxicity profiles, and retinal toxicity first affects the inner retinal layer in the inferior region. The highest non-retinotoxic vitreous concentration is 0.0033% available iodine from intravitreal injection of PI or PAI containing 0.05% available iodine. Translational Relevance: Low concentrations of PI or PAI can be used to wash the ocular surface during surgery or intravitreal injection to prevent endophthalmitis.

Early functional network alterations in asymptomatic elders at risk for Alzheimer's disease.

Amyloid-ß (Aß) deposition is known to starts decades before the onset of clinical symptoms of Alzheimer's disease (AD), however, the detailed pathophysiological processes underlying this preclinical period are not well understood. This study aimed to investigate functional network alterations in cognitively intact elderly individuals at risk for AD, and assessed the association between these network alterations and changes in Aß deposition, glucose metabolism, and brain structure. Forty-five cognitively normal elderly subjects, who were classified into Aß-positive (CN+) and Aß-negative (CN-) groups using 11C-Pittsburgh compound B PET, underwent resting state magnetoencephalography measurements, 18F-fluorodeoxyglucose PET (FDG-PET) and structural MRI. Results demonstrated that in the CN+ group, functional connectivity (FC) within the precuneus was significantly decreased, whereas it was significantly enhanced between the precuneus and the bilateral inferior parietal lobules in the low-frequency bands (theta and delta). These changes were suggested to be associated with local cerebral Aß deposition. Most of Aß+ individuals in this study did not show any metabolic or anatomical changes, and there were no significant correlations between FC values and FDG-PET or MRI volumetry data. These results demonstrate that functional network alterations, which occur in association with Aß deposition, are detectable using magnetoencephalography before metabolic and anatomical changes are seen.

Visual Search Load Effects on Age-Related Cognitive Decline: Evidence From the Yakumo Longitudinal Study.

The validity of Bucur and Madden's (2010) proposal that an age-related decline is particularly pronounced in executive function measures rather than in elementary perceptual speed measures was examined via the Yakumo Study longitudinal database. Their proposal suggests that cognitive load differentially affects cognitive abilities in older adults. To address their proposal, linear regression coefficients of 104 participants were calculated individually for the digit cancellation task 1 (D-CAT1), where participants search for a given single digit, and the D-CAT3, where they search for 3 digits simultaneously. Therefore, it can be conjectured that the D-CAT1 represents primarily elementary perceptual speed and low-visual search load task. whereas the D-CAT3 represents primarily executive function and high-visual search load task. Regression coefficients from age 65 to 75 for the D-CAT3 showed a significantly steeper decline than that for the D-CAT1, and a large number of participants showed this tendency. These results support the proposal by Brcur and Madden (2010) and suggest that the degree of cognitive load affects age-related cognitive decline.

Age-Related Changes in Attentional Control Using an N-Back Working Memory Paradigm.

BACKGROUND/STUDY CONTEXT: Older adults tend to be affected by task-irrelevant distracters. However, whether or not this aging effect is evident when task-irrelevant and relevant stimuli are presented across different sensory modalities is still a subject of debate. The purpose of the present study was to clarify age-related differences in the effects of auditory distraction on visual information processing. METHODS: Participants included 20 young individuals, 20 younger-old individuals in their 60s, and 20 older-old individuals in their 70s. Visual n-back (1-back, 2-back) working memory (WM) tasks using Japanese words were examined with and without auditory distracter conditions. Participants' performances were analyzed using a three-way analysis of variance: 3 (age group) × 2 (distraction) × 2 (working memory load). RESULTS: The effects of auditory distractions were influenced by aging and WM load. Auditory distractions disturbed WM performances preferentially in older adults. Further, participants in the older-old group were more affected by auditory distractions than those in the younger-old group, especially during the 2-back task. CONCLUSION: These results suggested that the WM performances for visual n-back tasks were largely disturbed by auditory distractions in older adults but not in young adults.

Priority for one's own stimulus in joint performance: evidence from an event-related potential study.

To investigate priority of shared task representations (own vs. other) formed during joint task performance, event-related potentials were recorded while participants performed an auditory three-stimulus oddball task alone (individual condition) and with another participant (joint condition). Participants were required to discriminate between frequent standard tones and rare target tones, while ignoring nontargets assigned to a partner's action (i.e. no-go stimuli for one's own task performance). The parietal P3b was elicited for targets under both conditions. In contrast, P3b for nontargets was observed only in the joint condition, and in addition, it accompanied the frontal no-go P3. This implies that coactors share one another's task representations. Importantly, the emergence of P3b and no-go P3 for nontargets was delayed compared with P3b for targets, suggesting that shared task representations are serially applied to the stimulus processing and that one's own representations precede the other individual's representations.

Rax Homeoprotein Regulates Photoreceptor Cell Maturation and Survival in Association with Crx in the Postnatal Mouse Retina.

The Rax homeobox gene plays essential roles in multiple processes of vertebrate retina development. Many vertebrate species possess Rax and Rax2 genes, and different functions have been suggested. In contrast, mice contain a single Rax gene, and its functional roles in late retinal development are still unclear. To clarify mouse Rax function in postnatal photoreceptor development and maintenance, we generated conditional knockout mice in which Rax in maturing or mature photoreceptor cells was inactivated by tamoxifen treatment (Rax iCKO mice). When Rax was inactivated in postnatal Rax iCKO mice, developing photoreceptor cells showed a significant decrease in the level of the expression of rod and cone photoreceptor genes and mature adult photoreceptors exhibited a specific decrease in cone cell numbers. In luciferase assays, we found that Rax and Crx cooperatively transactivate Rhodopsin and cone opsin promoters and that an optimum Rax expression level to transactivate photoreceptor gene expression exists. Furthermore, Rax and Crx colocalized in maturing photoreceptor cells, and their coimmunoprecipitation was observed in cultured cells. Taken together, these results suggest that Rax plays essential roles in the maturation of both cones and rods and in the survival of cones by regulating photoreceptor gene expression with Crx in the postnatal mouse retina.

[Hemispheric difference in the time course of semantic activation: evidence from event-related potentials].

To investigate hemispheric differences of semantic activation, event-related potentials were recorded when two pairs of words were successively presented with a SOA of 200 ms or 800 ms. Each word pair was simultaneously exposed to the left (LVF) and right (RVF) visual fields. Participants were required to attend one visual field and make a judgment whether the words (prime-target) presented at the attended visual field were semantically related or not. A priming effect on reaction time was observed for RVF targets with SOA 200 ms, and for both LVF and RVF targets with SOA 800 ms, consistent with the idea that semantic activation is faster in the left than the right hemisphere. In contrast, the priming effect on N400 amplitude was not affected by the SOA and visual field, and the onset latency was shorter for RVF than for LVF targets, irrespective of SOA. The N400 priming effects were interpreted to be associated with task-induced semantic processing.

Hemisphere division and its effect on selective attention: a generality examination of Lavie's load theory.

The present study examined the role of visual presentation mode (unilateral vs. bilateral visual fields) on attentional modulation. We examined whether or not the presentation mode affects the compatibility effect, using a paradigm involving two task-relevant letter arrays. Sixteen participants identified a target letter among task-relevant letters while ignoring either a compatible or incompatible distracter letter that was presented to both hemispheres. Two letters arrays were presented to visual fields, either unilaterally or bilaterally. Results indicated that the compatibility effect was greater in bilateral than in unilateral visual field conditions. Findings support the assumption that the two hemispheres have separate attentional resources.

[Semantic priming within and between the visual fields: an event-related brain potential study].

To investigate interhemispheric transfer of language information, event-related brain potentials (ERPs) were recorded during performance of a semantic matching task in which prime and target word pairs were sequentially presented to either the left (LVF) or the right (RVF) visual field. A posterior slow negative shift prior to the target presentation developed over both hemispheres for LVF primes, whereas for RVF primes the negative shift declined over the right hemisphere. An N400 attenuation was observed for targets semantically related to the primes and was predominant over the left parietal site. The N400 priming effect was significantly reduced for LVF targets preceded by RVF primes, compared to other patterns of presentation. These findings indicate that semantic priming is attenuated in the right hemisphere when information is transferred from the left hemisphere.