(Re)-wiring a brain with light: Clinical and visual processing findings after application of specific coloured glasses in patients with symptoms of a visual processing disorder (CVPD): Challenge of a possible new perspective?

The present investigation examined whether changes of electrophysiological late event related potential pattern could be used to reflect clinical changes from therapeutic intervention with coloured glasses in a group of patients with symptoms of central visual processing disorder. Subjects consisted of 13 patients with average age 16years (range 6-51years) with attention problems and learning disability, respectively. These patients were provided with specified coloured glasses which were required to be used during day time. Results indicated that specified coloured glasses significantly improved attention performance. Furthermore electrophysiological parameters revealed a significant change in the late event related potential distribution pattern (latency, amplitudes). This reflects a synchronization of together firing wired neural assemblies responsible for visual processing, suggesting an accelerated neuromaturation process when using coloured glasses. Our results suggest that the visual event related potentials measures are sensitive to changes in clinical development of patients with deficits of visual processing wearing appropriate coloured glasses. It will be discussed whether such a device might be useful for a clinical improvement of distraction symptoms caused by visual processing deficits. A model is presented explaining these effects by inducing the respiratory chain of the mitochondria such increasing the low energy levels of ATP of our patients.

Methods for pulse artefact reduction: experiences with EEG data recorded at 9.4 T static magnetic field.

BACKGROUND: The feasibility of recording electroencephalography (EEG) at ultra-high static magnetic fields up to 9.4 T was recently demonstrated and is expected to be incorporated into functional magnetic resonance imaging (fMRI) studies at 9.4 T. Correction of the pulse artefact (PA) is a significant challenge since its amplitude is proportional to the strength of the magnetic field in which EEG is recorded. NEW METHOD: We conducted a study in which different PA correction methods were applied to EEG data recorded inside a 9.4 T scanner in order to retrieve visual P100 and auditory P300 evoked potentials. We explored different PA reduction methods, including the optimal basis set (OBS) method as well as objective and subjective component rejection using independent component analysis (ICA). RESULTS: ICA followed by objective rejection of components is optimal for retrieving visual P100 and auditory P300 from EEG data recorded inside the scanner. COMPARISON WITH EXISTING METHODS: Previous studies suggest that OBS or OBS followed by ICA are optimal for retrieving evoked potentials at 3T. In our EEG data recorded at 9.4 T OBS performed alone was not fully optimal for the identification of evoked potentials. OBS followed by ICA was partially effective. CONCLUSIONS: In this study ICA has been shown to be an important tool for correcting the PA in EEG data recorded at 9.4 T, particularly when automated rejection of components is performed.

Visual evoked potentials in neonatal hyperbilirubinemia.

The management of neonatal hyperbilirubinemia is very standardized. However, there is a lack of an objective method to evaluate the cerebral effects of bilirubin apart from brainstem auditory evoked potentials. There were few studies evaluating the effects of hyperbilirubinemia or phototherapy on the visual pathway in infants with hyperbilirubinemia. Serial visual evoked potentials of two groups of term neonates (N = 24)--group 1 with moderate hyperbilirubinemia (n = 16) and group 2 with severe hyperbilirubinemia (n = 8)--were evaluated prospectively. All infants had regular physical, neurologic, visual, and auditory evaluations until 3 years. Four (16%) had abnormal visual evoked potentials before 1 year, and the abnormalities returned to normal thereafter. There was no significant difference in visual evoked potentials between the two groups. All had normal neurodevelopmental status by 3 years, with the exception of one child from the severe group with ABO incompatibility with transient mild motor delay, hypotonia, and abnormal visual evoked potential. There were no abnormal effects of phototherapy on visual evoked potentials in infants with neonatal hyperbilirubinemia after 1 year of age. Although our sample size was small, the results suggest that the effects of hyperbilirubinemia on visual evoked potentials might be transient. (J Child Neurol 2006;21:58-62).

Thalamic burst mode and inattention in the awake LGNd.

Awake mammals are often inattentive in familiar environments, but must still respond appropriately to relevant visual stimulation. Such "inattentive vision" has received little study, perhaps due to difficulties in controlling eye position in this state. In rabbits, eye position is exceedingly stable in both alert and inattentive states. Here, we exploit this stability to examine temporal filtering of visual information in LGNd neurons as rabbits alternate between EEG-defined states. Within a single second of shifting from alert to an inattentive state, both peak temporal frequency and bandwidth were sharply reduced, and burst frequency increased dramatically. However, spatial dimensions of receptive field centers showed no significant state dependence. We conclude that extremely rapid and significant changes in temporal filtering and bursting occur in the LGNd as awake subjects shift between alert and inattentive states.

Effects of continuous conditioning noise and light on the auditory- and visual-evoked potentials of the guinea pig.

Neurophysiological studies aiming to explore how the brain integrates information from different brain regions are increasing in the literature. The aim of the present study is to explore intramodal (binaural, binocular) and intermodal (audio-visual) interactions in the guinea pig brain through the observation of changes in evoked potentials by generalized continuous background activity. Seven chronically prepared animals were used in the study and the recordings were made as they were awake. Epidural electrodes were implanted to the skulls by using stereotaxic methods. Continuous light for retinal or continuous white noise for cochlear receptors were used as continuous conditioning stimuli for generalized stimulation. To evoke auditory or visual potentials, click or flash were used as transient imperative stimuli. The study data suggest that (a) white noise applied to one ear modifies the response to click in the contralateral ear which is a binaural interaction; (b) continuous light applied to one eye modifies the response to flash applied to the contralateral eye which is interpreted as a binocular interaction; (c) regardless of the application side, white noise similarly modified the response to flash applied to the either eye connoting a nonspecific effect of white noise on vision, independent from spatial hearing mechanisms; (d) on the other hand, continuous light, in either eye, did not affect the response to click applied to any ear, reminding a 'one-way' interaction that continuous aural stimulation affects visual response.

MEG recording from the human ventro-occipital cortex in response to isoluminant color stimulation.

In contrast to PET and fMRI studies, color-selective responses from the ventro-occipital area have rarely been reported in MEG studies. We tried to minimize the stimulation to all areas in the visual system except the color-processing ones by using a color space based on psychophysical and physiological knowledge in order to maximize the signal-to-noise ratio for MEG responses from the ventro-occipital area. MEG obtained from long intermittent reversals (2.0-3.5 s) of isoluminant chromatic gratings showed two major peaks at the latencies of approximately 100 and 150 ms. The estimated location of the equivalent-current dipole for response at 100-ms latency was in the calcarine sulcus and that of the dipole for the response at 150 ms was in the collateral sulcus in the ventro-occipital area. The response around 150 ms was uniquely observed in MEG elicited by chromatic reversals. The average of lags between MEG responses from the calcarine sulcus and ventro-occipital area was 43 ms, which suggests sequential processing of color information across the visual cortices.

[The characteristics of perceptive learning and memory in psychopathological states]. / Osobennosti pertseptivnogo obucheniia i pamiati pri psikhopatologicheskikh sostoianiiakh.

Dynamics is studied of visual images recognition in patients with schizophrenia under the influence of small doses of ionizing radiation used with therapeutic purpose. Functional state of the brain is evaluated by amplitude-temporal parameters of visual and auditory EPs. After conducted therapy no changes in responses to light flashes are found, and in auditory EPs in a part (the first group) of patients there is an increase of the component N1 amplitude in the frontal area. The same group is characterized by lower parameters of visual images recognition. Conclusion is made about the presence of non-specific changes of visual gnosis in patients with schizophrenia and about involvement of the associative frontal structures in pathologic process. Possible mechanisms of disturbance of the perceptive learning and memory processes in schizophrenia are discussed.