Event-related electric microstates of the brain differ between words with visual and abstract meaning

The present study shows that different neural activity during mental imagery and abstract mentation can be assigned to well-defined steps of the brain's information-processing. During randomized visual presentation of single, imagery-type and abstract-type words, 27 channel event-related potential (ERP) field maps were obtained from 25 subjects (sequence-divided into a first and second group for statistics). The brain field map series showed a sequence of typical map configurations that were quasi-stable for brief time periods (microstates). The microstates were concatenated by rapid map changes. As different map configurations must result from different spatial patterns of neural activity, each microstate represents different active neural networks. Accordingly, microstates are assumed to correspond to discrete steps of information-processing. Comparing microstate topographies (using centroids) between imagery- and abstract-type words, significantly different microstates were found in both subject groups at 286–354 ms where imagery-type words were more right-lateralized than abstract-type words, and at 550–606 ms and 606–666 ms where anterior-posterior differences occurred. We conclude that language-processing consists of several, well-defined steps and that the brain-states incorporating those steps are altered by the stimuli's capacities to generate mental imagery or abstract mentation in a state-dependent manner.

Internet video telephony allows speech reading by deaf individuals and improves speech perception by cochlear implant users

OBJECTIVE To analyze speech reading through Internet video calls by profoundly hearing-impaired individuals and cochlear implant (CI) users. METHODS Speech reading skills of 14 deaf adults and 21 CI users were assessed using the Hochmair Schulz Moser (HSM) sentence test. We presented video simulations using different video resolutions (1280 × 720, 640 × 480, 320 × 240, 160 × 120 px), frame rates (30, 20, 10, 7, 5 frames per second (fps)), speech velocities (three different speakers), webcameras (Logitech Pro9000, C600 and C500) and image/sound delays (0-500 ms). All video simulations were presented with and without sound and in two screen sizes. Additionally, scores for live Skype™ video connection and live face-to-face communication were assessed. RESULTS Higher frame rate (>7 fps), higher camera resolution (>640 × 480 px) and shorter picture/sound delay (<100 ms) were associated with increased speech perception scores. Scores were strongly dependent on the speaker but were not influenced by physical properties of the camera optics or the full screen mode. There is a significant median gain of +8.5%pts (p = 0.009) in speech perception for all 21 CI-users if visual cues are additionally shown. CI users with poor open set speech perception scores (n = 11) showed the greatest benefit under combined audio-visual presentation (median speech perception +11.8%pts, p = 0.032). CONCLUSION Webcameras have the potential to improve telecommunication of hearing-impaired individuals.

Callosal connections of primary visual cortex predict the spatial spreading of binocular rivalry across the visual hemifields

In binocular rivalry, presentation of different images to the separate eyes leads to conscious perception alternating between the two possible interpretations every few seconds. During perceptual transitions, a stimulus emerging into dominance can spread in a wave-like manner across the visual field. These traveling waves of rivalry dominance have been successfully related to the cortical magnification properties and functional activity of early visual areas, including the primary visual cortex (V1). Curiously however, these traveling waves undergo a delay when passing from one hemifield to another. In the current study, we used diffusion tensor imaging (DTI) to investigate whether the strength of interhemispheric connections between the left and right visual cortex might be related to the delay of traveling waves across hemifields. We measured the delay in traveling wave times (ΔTWT) in 19 participants and repeated this test 6 weeks later to evaluate the reliability of our behavioral measures. We found large interindividual variability but also good test-retest reliability for individual measures of ΔTWT. Using DTI in connection with fiber tractography, we identified parts of the corpus callosum connecting functionally defined visual areas V1-V3. We found that individual differences in ΔTWT was reliably predicted by the diffusion properties of transcallosal fibers connecting left and right V1, but observed no such effect for neighboring transcallosal visual fibers connecting V2 and V3. Our results demonstrate that the anatomical characteristics of topographically specific transcallosal connections predict the individual delay of interhemispheric traveling waves, providing further evidence that V1 is an important site for neural processes underlying binocular rivalry.

Atypical findings in delayed presentation of unilateral acute idiopathic maculopathy

Unilateral acute idiopathic maculopathy is a rare disease affecting young healthy patients resulting in moderate to severe unilateral visual loss preceded by prodromal flu-like illness. We present a case of delayed presentation of unilateral acute idiopathic maculopathy associated with hand, foot and mouth disease.

An unusual stroke-like clinical presentation of Creutzfeldt-Jakob disease: acute vestibular syndrome

INTRODUCTION Vertigo and dizziness are common neurological symptoms in general practice. Most patients have benign peripheral vestibular disorders, but some have dangerous central causes. Recent research has shown that bedside oculomotor examinations accurately discriminate central from peripheral lesions in those with new, acute, continuous vertigo/dizziness with nausea/vomiting, gait unsteadiness, and nystagmus, known as the acute vestibular syndrome. CASE REPORT A 56-year-old man presented to the emergency department with acute vestibular syndrome for 1 week. The patient had no focal neurological symptoms or signs. The presence of direction-fixed, horizontal nystagmus suppressed by visual fixation without vertical ocular misalignment (skew deviation) was consistent with an acute peripheral vestibulopathy, but bilaterally normal vestibuloocular reflexes, confirmed by quantitative horizontal head impulse testing, strongly indicated a central localization. Because of a long delay in care, the patient left the emergency department without treatment. He returned 1 week later with progressive gait disturbance, limb ataxia, myoclonus, and new cognitive deficits. His subsequent course included a rapid neurological decline culminating in home hospice placement and death within 1 month. Magnetic resonance imaging revealed restricted diffusion involving the basal ganglia and cerebral cortex. Spinal fluid 14-3-3 protein was elevated. The rapidly progressive clinical course with dementia, ataxia, and myoclonus plus corroborative neuroimaging and spinal fluid findings confirmed a clinicoradiographic diagnosis of Creutzfeldt-Jacob disease. CONCLUSIONS To our knowledge, this is the first report of an initial presentation of Creutzfeldt-Jacob disease closely mimicking vestibular neuritis, expanding the known clinical spectrum of prion disease presentations. Despite the initial absence of neurological signs, the central lesion location was differentiated from a benign peripheral vestibulopathy at the first visit using simple bedside vestibular tests. Familiarity with these tests could help providers prevent initial misdiagnosis of important central disorders in patients presenting vertigo or dizziness.