Spontaneous recovery of visually-triggered saccades after focal lesions of the frontal and parietal eye fields: A combined longitudinal oculomotor and fMRI study

To analyze oculomotor recovery in a patient with ischemic lesions restricted to the left frontal eye field (FEF) and the left parietal eye field (PEF).

The assessment of cognition in visually impaired older adults

Background: visual and cognitive impairments are common in later life. Yet there are very few cognitive screening tests for the visually impaired. Objective: to screen for cognitive impairment in the visually impaired. Methods: case-control study including 150 elderly participants with visual impairment (n = 74) and a control group without visual impairment (n = 76) using vision-independent cognitive tests and cognitive screening tests (MMSE and clock drawing tests (CDT)) which are in part vision dependent. Results: the scoring of the two groups did not differ in the vision-independent cognitive tests. Visually impaired patients performed poorer than controls in the vision-dependent items of the MMSE (T = 7.3; df: 148; P < 0.001) and in CDT (T = 3.1; df: 145; P = 0.003). No group difference was found when vision-independent items were added to MMSE and CDT. The test score gain by the use of vision-independent items correlated with the severity of visual impairment (P < 0.002). Conclusion: visually impaired patients benefit from cognitive tests, which do not rely on vision. The more visually impaired the greater the benefit.

Whole-body motion discrimination in the visually impaired

Visually impaired people show superior abilities in various perception tasks such as auditory attention, auditory temporal resolution, auditory spatial tuning, and odor discrimination. However, with the use of psychophysical methods, auditory and olfactory detection thresholds typically do not differ between visually impaired and sighted participants. Using a motion platform we investigated thresholds of passive whole-body motion discrimination in nine visually impaired participants and nine age-matched sighted controls. Participants were rotated in yaw, tilted in roll, and translated along the y-axis at two different frequencies (0.3 Hz and 2 Hz). An adaptive 3-down 1-up staircase procedure was used along with a two-alternative direction (leftward vs. rightward) discrimination task. Superior performance of visually impaired participants was found in the 0.3 Hz roll tilt condition. No differences between the visually impaired and controls were observed in all other types of motion. The superior performance in the 0.3 Hz roll tilt condition could reflect differences in the integration of extra-vestibular cues and increased sensitivity towards changes in the direction of the gravito-inertial force. In the absence of visual information, roll tilts entail a more pronounced risk of falling, and this could eventually account for the group difference. It is argued that differences in experimental procedures (i.e. detection vs. discrimination of stimuli) explain the discrepant findings across perceptual tasks comparing blind and sighted participants.

Consciousness and choking in visually-guided actions

Choking under pressure describes the phenomenon of people performing well below their expected standard under circumstances where optimal performance is crucial. One of the prevailing explanations for choking is that pressure increases the conscious attention to the underlying processes of the performer's task execution, thereby disrupting what would normally be a relatively automatic process. However, research on choking has focused mainly on the influence of pressure on motor performance, typically overlooking how it might alter the way that vision is controlled when performing these motor actions. In this article we ask whether the visual component of expert motor-skill execution is susceptible to choking much like the motor component is thought to be. To do so, we draw heavily on empirical findings from studies of sporting expertise, in particular focussing on the role of gaze in three types of visually-guided actions: interceptive actions, aiming tasks, and anticipatory skill. For each of these skills we evaluate the nature of the expert advantage, discuss the role of consciousness in their control, examine the potential impact of pressure on task performance, and consider interventions designed to reduce the likelihood of choking when performing these tasks

Self-motion direction discrimination in the visually impaired

Despite the close interrelation between vestibular and visual processing (e.g., vestibulo-ocular reflex), surprisingly little is known about vestibular function in visually impaired people. In this study, we investigated thresholds of passive whole-body motion discrimination (leftward vs. rightward) in nine visually impaired participants and nine age-matched sighted controls. Participants were rotated in yaw, tilted in roll, and translated along the interaural axis at two different frequencies (0.33 and 2 Hz) by means of a motion platform. Superior performance of visually impaired participants was found in the 0.33 Hz roll tilt condition. No differences were observed in the other motion conditions. Roll tilts stimulate the semicircular canals and otoliths simultaneously. The results could thus reflect a specific improvement in canal–otolith integration in the visually impaired and are consistent with the compensatory hypothesis, which implies that the visually impaired are able to compensate the absence of visual input.

In vivo performance of a laser fluorescence device for the approximal detection of caries in permanent molars

OBJECTIVES: The aim of this randomised clinical trial was to investigate if a laser fluorescence device is able to discriminate between sound and carious approximal sites and between enamel and dentinal lesions, as well as to find appropriate cut-off values. METHODS: One hundred and seventeen sound or uncavitated carious sites in permanent molars were visually and radiographically examined, then either opened or not, after which their laser fluorescence was measured. Forty-three lesions were opened, the caries removed and the clinically identified caries depths were registered in addition to the radiographical scoring. Seventy-four sites were radiographically deemed sound or had enamel caries and were not opened. Here, the radiographical scorings were registered. RESULTS: Taking the radiographic scoring as gold standard for all investigated approximal sites, sound sites (D(0), n=40) showed significantly lower laser fluorescence measurements than carious sites (D(1-4), n=77) (Mann-Whitney test, P<0.025) suggesting a cut-off at 7 (sensitivity=0.68, specificity=0.7). Comparing measurements of D(0-2) (n=74) and D(3,4) (n=43), the results were also different by a statistically significant amount (P<0.025) and the cut-off calculated to be 16 (sensitivity=0.6, specificity=0.84). A fair positive correlation between laser fluorescence values and radiographical scoring was found (rho=+0.47, P<0.01). Analysing the 43 opened lesions with their clinically found lesion depths as gold standard, there was a fair positive correlation to the laser fluorescence values (rho=+0.34, P=0.03) and a moderately strong correlation to the radiographic scoring (rho=+0.67, P<0.01). CONCLUSION: The device may be an adjunct tool in the approximal detection of caries along with established procedures.

Analysis of clinical forensic examination reports on sexual assault

Medical-forensic examination of sexual assault victims and alleged offenders is a common task of many forensic institutes. In the current study, the results from samples taken at the Institute of Legal Medicine, Hanover Medical School, during a period from 2005 to 2007 were retrospectively evaluated. In total, 292 victims (283 females and nine males) and 88 suspects were examined. At the time of the assault, 41.8% of the victims and 43.2% of the alleged perpetrators were under the influence of alcohol. Injuries were found in 84.9% of the victims and 39.8% of the suspects. Thirty victims (10.3%) reported having been choked or strangled. Cytology was performed in 218 victims. In 81 cases (38.0%), sperm could be detected in vaginal swabs up to 3 days post-assault. In seven (18.9%) out of 37 anal samples, evidence of sperm could be found 24 h post-assault. None of 22 oral samples was positive for sperm. Out of 301 sexual assault cases, 171 could be proved by means of medical-forensic examination. In summary, our evaluation shows that an early medical-forensic examination of both victim and suspect can secure numerous medical findings. Furthermore, persons intoxicated by alcohol, handicapped persons and persons with psychiatric disorders are more vulnerable to become a sexual assault victim.

Semantic memory involvement in the default mode network: a functional neuroimaging study using independent component analysis

The Default Mode Network (DMN) is a higher order functional neural network that displays activation during passive rest and deactivation during many types of cognitive tasks. Accordingly, the DMN is viewed to represent the neural correlate of internally-generated self-referential cognition. This hypothesis implies that the DMN requires the involvement of cognitive processes, like declarative memory. The present study thus examines the spatial and functional convergence of the DMN and the semantic memory system. Using an active block-design functional Magnetic Resonance Imaging (fMRI) paradigm and Independent Component Analysis (ICA), we trace the DMN and fMRI signal changes evoked by semantic, phonological and perceptual decision tasks upon visually-presented words. Our findings show less deactivation during semantic compared to the two non-semantic tasks for the entire DMN unit and within left-hemispheric DMN regions, i.e., the dorsal medial prefrontal cortex, the anterior cingulate cortex, the retrosplenial cortex, the angular gyrus, the middle temporal gyrus and the anterior temporal region, as well as the right cerebellum. These results demonstrate that well-known semantic regions are spatially and functionally involved in the DMN. The present study further supports the hypothesis of the DMN as an internal mentation system that involves declarative memory functions.

Core networks for visual-concrete and abstract thought content: a brain electric microstate analysis

Commonality of activation of spontaneously forming and stimulus-induced mental representations is an often made but rarely tested assumption in neuroscience. In a conjunction analysis of two earlier studies, brain electric activity during visual-concrete and abstract thoughts was studied. The conditions were: in study 1, spontaneous stimulus-independent thinking (post-hoc, visual imagery or abstract thought were identified); in study 2, reading of single nouns ranking high or low on a visual imagery scale. In both studies, subjects' tasks were similar: when prompted, they had to recall the last thought (study 1) or the last word (study 2). In both studies, subjects had no instruction to classify or to visually imagine their thoughts, and accordingly were not aware of the studies' aim. Brain electric data were analyzed into functional topographic brain images (using LORETA) of the last microstate before the prompt (study 1) and of the word-type discriminating event-related microstate after word onset (study 2). Conjunction analysis across the two studies yielded commonality of activation of core networks for abstract thought content in left anterior superior regions, and for visual-concrete thought content in right temporal-posterior inferior regions. The results suggest that two different core networks are automatedly activated when abstract or visual-concrete information, respectively, enters working memory, without a subject task or instruction about the two classes of information, and regardless of internal or external origin, and of input modality. These core machineries of working memory thus are invariant to source or modality of input when treating the two types of information.

Identification of adequate neurally adjusted ventilatory assist (NAVA) during systematic increases in the NAVA level

Neurally adjusted ventilatory assist (NAVA) delivers airway pressure (P(aw)) in proportion to the electrical activity of the diaphragm (EAdi) using an adjustable proportionality constant (NAVA level, cm·H(2)O/μV). During systematic increases in the NAVA level, feedback-controlled down-regulation of the EAdi results in a characteristic two-phased response in P(aw) and tidal volume (Vt). The transition from the 1st to the 2nd response phase allows identification of adequate unloading of the respiratory muscles with NAVA (NAVA(AL)). We aimed to develop and validate a mathematical algorithm to identify NAVA(AL). P(aw), Vt, and EAdi were recorded while systematically increasing the NAVA level in 19 adult patients. In a multistep approach, inspiratory P(aw) peaks were first identified by dividing the EAdi into inspiratory portions using Gaussian mixture modeling. Two polynomials were then fitted onto the curves of both P(aw) peaks and Vt. The beginning of the P(aw) and Vt plateaus, and thus NAVA(AL), was identified at the minimum of squared polynomial derivative and polynomial fitting errors. A graphical user interface was developed in the Matlab computing environment. Median NAVA(AL) visually estimated by 18 independent physicians was 2.7 (range 0.4 to 5.8) cm·H(2)O/μV and identified by our model was 2.6 (range 0.6 to 5.0) cm·H(2)O/μV. NAVA(AL) identified by our model was below the range of visually estimated NAVA(AL) in two instances and was above in one instance. We conclude that our model identifies NAVA(AL) in most instances with acceptable accuracy for application in clinical routine and research.

Evaluation of perpendicular reflection intensity for assessment of caries lesion activity/inactivity

The aim of this study was to evaluate, using visual assessment, an experimental optical sensor measuring perpendicular reflection intensity (PRI) as an indicator of enamel caries lesion activity/inactivity. Forty teeth with either an active or an inactive enamel lesion were selected from a pool of extracted teeth. Each tooth was cut into halves, with a clinically sound half and a half with a non-cavitated enamel lesion. After gentle plaque removal, the teeth were kept moistened. The lesions were then photographed and a defined measuring site per lesion was chosen and indicated with an arrow on a printout. Independently, the chosen site was visually assessed for lesion activity, and its glossiness was measured with PRI assessment. Surface roughness (SR) was assessed with optical profilometry using a confocal microscope. Visual assessment and PRI were repeated after several weeks and a reliability analysis was performed. For enamel lesions visually scored as active versus inactive, significantly different values were obtained with both PRI and SR. PRI values of the clinically sound control surfaces were significantly different only from active lesions. Generally, inactive lesions had the same glossiness and the same roughness as the sound control surfaces. The reliabilities for visual assessment (? = 0.89) and for PRI (ICC = 0.86) were high. It is concluded that, within the limits of this study, PRI can be regarded as a promising tool for quantitative enamel lesion activity assessment. There is scope and potential for the PRI device to be considerably improved for in vivo use.

White matter lesions and intra-arterial thrombolysis

The aim of the study was to assess the influence of white matter lesions in patients with acute ischemic stroke treated with intra-arterial thrombolysis (IAT). From September 2003 to January 2010, we treated 400 patients with IAT at our institution. Of these patients, 292 were evaluated with MRI scans and included in this observational study. Clinical data were collected prospectively. Outcome after 3 months was measured with the modified Rankin Scale (mRS); mRS 0-1 was considered as favorable outcome. White matter lesions were scored visually by two observers using the semiquantitative Scheltens and Fazekas scores. Logistic regression analysis was used to identify the association of white matter lesions and clinical outcome, recanalization, and cerebral hemorrhage. The severity of white matter lesions was inversely correlated with favorable outcome, survival and successful recanalization. White matter lesions were an independent predictor of outcome (OR 0.569, p = 0.007) and survival (OR 0.550, p = 0.018) and a weak but independent predictor for recanalization (OR 0.949, p = 0.038). Asymptomatic intracerebral bleeding after IAT was associated with white matter lesions in the basal ganglia in the univariate analysis (p = 0.036), but not after multivariable analysis. The severity of white matter lesions independently predicts clinical outcome and survival in patients treated with IAT. White matter lesions are also a weak but independent predictor for recanalization. Symptomatic intracranial bleeding after IAT are not associated with white matter lesions. Therefore, white matter lesions should not be considered as a contraindication against IAT.

The influence of body temperature on image contrast in post mortem MRI

To assess the temperature dependency of tissue contrast on post mortem magnetic resonance (PMMR) images both objectively and subjectively; and to visually demonstrate the changes of image contrast at various temperatures.

Electrophysiological and behavioral correlates of stable automatic semantic retrieval in aging

Previous studies have shown both declining and stable semantic-memory abilities during healthy aging. There is consistent evidence that semantic processes involving controlled mechanisms weaken with age. In contrast, results of aging studies on automatic semantic retrieval are often inconsistent, probably due to methodological limitations and differences. The present study therefore examines age-related alterations in automatic semantic retrieval and memory structure with a novel combination of critical methodological factors, i.e., the selection of subjects, a well-designed paradigm, and electrophysiological methods that result in unambiguous signal markers. Healthy young and elderly participants performed lexical decisions on visually presented word/non-word pairs with a stimulus onset asynchrony (SOA) of 150 ms. Behavioral and electrophysiological data were measured, and the N400-LPC complex, an event-related potential component sensitive to lexical-semantic retrieval, was analyzed by power and topographic distribution of electrical brain activity. Both age groups exhibited semantic priming (SP) and concreteness effects in behavioral reaction time and the electrophysiological N400-LPC complex. Importantly, elderly subjects did not differ significantly from the young in their lexical decision and SP performances as well as in the N400-LPC SP effect. The only difference was an age-related delay measured in the N400-LPC microstate. This could be attributed to existing age effects in controlled functions, as further supported by the replicated age difference in word fluency. The present results add new behavioral and neurophysiological evidence to earlier findings, by showing that automatic semantic retrieval remains stable in global signal strength and topographic distribution during healthy aging.