EEG in extreme conditions: An advanced analysis pipeline for the human electroencephalographic signals recorded in space during the ALTEA experiment

The Anomalous Long Term Effects in Astronauts (ALTEA) project originally aimed at disentangling the mechanisms behind astronauts' perception of light flashes. To this end, an experimental apparatus was set up in order to concurrently measure the tracks of cosmic radiation particles in the astronauts' head and the electroencephalographic (EEG) signals generated by their brain. So far, the ALTEA data set has never been analyzed with the broader intent to study possible interference between cosmic radiation and the brain, regardless of light flashes. The aim of this work is to define a pipeline to systematically pre-process the ALTEA EEG data. Compared to the analysis of standard EEG recording, this task is made more difficult by the presence of unconventional artifacts due to the extreme recording conditions that, in particular, require the EEG cap to be positioned next to another noisy electronic device, namely the particle detectors. Here we show how standard tools for the analysis of EEG data can be tuned to deal with these unconventional artifacts. After pre-processing the available data we were able to elucidate a shift of the center frequency of the α rhythm induced by visual stimulation, thus proving the effectiveness of the implemented pipeline. This work represents the first study presenting results of signal processing of ALTEA EEG time series. Further, it is the starting point of a future work aimed at analyzing the interaction between EEG and cosmic radiation.

Stochastic resonance and 'gamma band' synchronization in the human visual system

Cortical synchronization in the gamma-frequency range (above ~30.0 Hz) and the signal/noise interplay described by stochastic resonance models have been proposed as basic mechanisms in neuronal synchronization and sensory information processing, particularly in vision. Here we report an observation in humans of linear and inverted-U distributions of the electrophysiological (EEG) responses to visual contrast stimulation in the gamma band and in the low frequency components of the visual evoked responses (VER), respectively. The combination of linear and inverted-U distributions is described by a stochastic resonance model (SR). The observation needs replication in larger subjects' samples. It nevertheless adds to the available evidence of a role of gamma oscillatory signals and SR mechanisms in neuronal synchronization and visual processing. Some functional adaptation in human vision appears conceivable and further investigation is warranted.

Biocompatibility of a Conjugated Polymer Retinal Prosthesis in the Domestic Pig

The progressive degeneration of retinal photoreceptors is one of the most significant causes of blindness in humans. Conjugated polymers represent an attractive solution to the field of retinal prostheses, and a multi-layer fully organic prosthesis implanted subretinally in dystrophic Royal College of Surgeons (RCS) rats was able to rescue visual functions. As a step toward human translation, we report here the fabrication and in vivo testing of a similar device engineered to adapt to the human-like size of the eye of the domestic pig, an excellent animal paradigm to test therapeutic strategies for photoreceptors degeneration. The active conjugated polymers were layered onto two distinct passive substrates, namely electro-spun silk fibroin (ESF) and polyethylene terephthalate (PET). Naive pigs were implanted subretinally with the active device in one eye, while the contralateral eye was sham implanted with substrate only. Retinal morphology and functionality were assessed before and after surgery by means of in vivo optical coherence tomography and full-field electroretinogram (ff-ERG) analysis. After the sacrifice, the retina morphology and inflammatory markers were analyzed by immunohistochemistry of the excised retinas. Surprisingly, ESF-based prostheses caused a proliferative vitreoretinopathy with disappearance of the ff-ERG b-wave in the implanted eyes. In contrast, PET-based active devices did not evoke significant inflammatory responses. As expected, the subretinal implantation of both PET only and the PET-based prosthesis locally decreased the thickness of the outer nuclear layer due to local photoreceptor loss. However, while the implantation of the PET only substrate decreased the ff-ERG b-wave amplitude with respect to the pre-implant ERG, the eyes implanted with the active device fully preserved the ERG responses, indicating an active compensation of the surgery-induced photoreceptor loss. Our findings highlight the possibility of developing a new generation of conjugated polymer/PET-based prosthetic devices that are highly biocompatible and potentially suitable for subretinal implantation in patients suffering from degenerative blindness.

Circadian Rhythms, Sleep, and Aging

Abstract. Circadian mechanisms and the sleep-wakefulness rhythms guarantee survival, adaptation, efficient action in everyday life or in emergencies and well-being. Disordered circadian processes at central and/or cellular levels, sleep disorders, and unhealthy wakefulness/sleep rhythms can impair the physiological circadian organization and result in subjective, professional, or behavioral changes ranging from functional inadequacy to higher risks at work or on the road to medical relevance. Circadian rhythms and the sleep organization change ontogenetically; major changes result from normal aging and from the multiple diseases that are often associated. There are circular functional interactions involving sleep/sleep disorders, the autonomic and immune systems, and the functional changes in the circadian system due to aging that deserve attention but have been overlooked thus far.

Circadian Rhythms and Measures of CNS/Autonomic Interaction

The physiological role and relevance of the mechanisms sustaining circadian rhythms have been acknowledged. Abnormalities of the circadian and/or sleep-wakefulness cycles can result in major metabolic disorders or behavioral/professional inadequacies and stand as independent risk factors for metabolic, psychiatric, and cerebrovascular disorders and early markers of disease. Neuroimaging and clinical evidence have documented functional interactions between autonomic (ANS) and CNS structures that are described by a concept model (Central Autonomic Network) based on the brain-heart two-way interplay. The circadian rhythms of autonomic function, ANS-mediated processes, and ANS/CNS interaction appear to be sources of variability adding to a variety of environmental factors, and may become crucial when considering the ANS major role in internal environment constancy and adaptation that are fundamental to homeostasis. The CNS/ANS interaction has not yet obtained full attention and systematic investigation remains overdue.

Measures of CNS-Autonomic Interaction and Responsiveness in Disorder of Consciousness

Neuroimaging studies have demonstrated functional interactions between autonomic (ANS) and brain (CNS) structures involved in higher brain functions, including attention and conscious processes. These interactions have been described by the Central Autonomic Network (CAN), a concept model based on the brain-heart two-way integrated interaction. Heart rate variability (HRV) measures proved reliable as non-invasive descriptors of the ANS-CNS function setup and are thought to reflect higher brain functions. Autonomic function, ANS-mediated responsiveness and the ANS-CNS interaction qualify as possible independent indicators for clinical functional assessment and prognosis in Disorders of Consciousness (DoC). HRV has proved helpful to investigate residual responsiveness in DoC and predict clinical recovery. Variability due to internal (e.g., homeostatic and circadian processes) and environmental factors remains a key independent variable and systematic research with this regard is warranted. The interest in bidirectional ANS-CNS interactions in a variety of physiopathological conditions is growing, however, these interactions have not been extensively investigated in DoC. In this brief review we illustrate the potentiality of brain-heart investigation by means of HRV analysis in assessing patients with DoC. The authors' opinion is that this easy, inexpensive and non-invasive approach may provide useful information in the clinical assessment of this challenging patient population.

Co-Morbidity, Mortality, Quality of Life and the Healthcare/Welfare/Social Costs of Disordered Sleep: A Rapid Review

Sleep disorders are frequent (18%-23%) and constitute a major risk factor for psychiatric, cardiovascular, metabolic or hormonal co-morbidity and mortality. Low social status or income, unemployment, life events such as divorce, negative lifestyle habits, and professional requirements (e.g., shift work) are often associated with sleep problems. Sleep disorders affect the quality of life and impair both professional and non-professional activities. Excessive daytime drowsiness resulting from sleep disorders impairs efficiency and safety at work or on the road, and increases the risk of accidents. Poor sleep (either professional or voluntary) has detrimental effects comparable to those of major sleep disorders, but is often neglected. The high incidence and direct/indirect healthcare and welfare costs of sleep disorders and poor sleep currently constitute a major medical problem. Investigation, monitoring and strategies are needed in order to prevent/reduce the effects of these disorders.

A new treatment in the rehabilitation of the paretic upper limb after stroke: the ARAMIS prototype and treatment protocol

BACKGROUND

In recent years, as part of the rehabilitation of post stroke patients, the use of robotic technologies to improve recovery of upper limb has become more widespread. The Automatic Recovery Arm Motility Integrated System (ARAMIS) is a concept robot and prototype designed to promote the functional interaction of the arms in the neurorehabilitation of the paretic upper limb. Two computer-controlled, symmetric and interacting exoskeletons compensate for the inadequate strength and accuracy of the paretic arm and the effect of gravity during rehabilitation. Rehabilitation is possible in 3 different modalities; asynchronous, synchronous and active-assisted.

OBJECTIVES

To compare the effectiveness of robotic rehabilitation by an exoskeleton prototype system with traditional rehabilitation in motor and functional recovery of the upper limb after stroke.

METHODS

Case-control study, 52 patients enrolled in the study, 28 cases (women: 8, age: 65 ± 10 yrs) treated with ARAMIS and 24 controls (women: 11, age: 69 ± 7 yrs) with conventional rehabilitation. Motor impairment assessed before and after treatment with Fugl-Meyer scale and Motricity Index, level of disability assessed with the Functional Independence Measure. A questionnaire was also administered to assess the patient's tolerance to robotic therapy.

RESULTS

After 28 ± 4 sessions over a 54 ± 3.6-day period, the patients treated by ARAMIS had an improvement on the Fugl-Meyer scale (global score from 43 ± 18 to 73 ± 29; p < 0.00001), Motricity Index scale (p < 0.004) and Functional Independence Measure (p < 0.001). A lesser degree of improvement was achieved using conventional rehabilitation, the Fugl-Meyer global score of the control group improved from 41 ± 13 to 58 ± 16 (p < 0.006) and the motor function item from 9.4 ± 4.1 to 14.9 ± 5.8 (p < 0.023).

CONCLUSIONS

Motor improvement was greater at the wrist and hand than at shoulder and elbow level in patients treated by ARAMIS and controls, but it was significantly greater in ARAMIS-treated patients than in controls. The results indicate a greater efficacy of ARAMIS compared to conventional rehabilitation.

Coma recovery scale-r: variability in the disorder of consciousness

Background

Despite evidence from neuroimaging research, diagnosis and early prognosis in the vegetative (VS/UWS) and minimally conscious (MCS) states still depend on the observation of clinical signs of responsiveness. Multiple testing has documented a systematic variability during the day in the incidence of established signs of responsiveness. Spontaneous fluctuations of the Coma Recovery Scale-revised (CRS-r) scores are conceivable.

Methods

We retrospectively analyzed the CRS-r repeatedly administered to 7 VS/UWS and 12 MCS subjects undergoing systematic observation during a conventional 13 weeks. rehabilitation plan.

Results

The CRS-r global, visual and auditory scores were found higher in the morning than at the afternoon administration in both VS/UWS and MCS subgroups over the entire period of observation. The probability for a VS/UWS subject of being classified as MCS at the morning testing at least once during the 13 weeks. observation was as high as 30 %, i.e., compatible with the reported misdiagnosis rate between the two clinical conditions.

Conclusions

Multiple CRS-r testing is advisable to minimize the risk of misclassification; estimates of spontaneous variability could be used to characterize with greater accuracy patients with disorder of consciousness and possibly help optimize the rehabilitation plan.

Nutritional parameters predicting pressure ulcers and short-term mortality in patients with minimal conscious state as a result of traumatic and non-traumatic acquired brain injury

BACKGROUND

The association between malnutrition and worse outcomes as pressure ulcers and mortality is well established in a variety of setting. Currently none investigation was conducted in patients with long-term consequences of the acquired brain injury in which recovery from brain injury could be influenced by secondary complications. The aim of this study was to investigate the association between various nutritional status parameters (in particular albumin) and pressure ulcers formation and short-term mortality in minimal conscious state patients.

METHODS

In this prospective, observational study of 5-months duration, a 30 patients sample admitted to a Neurological Institute was considered. All patients underwent a complete medical examination. Anthropometric parameters like mid-arm circumference and mid-arm muscle circumference and nutritional parameters as serum albumin and blood hemoglobin concentration were assessed.

RESULTS

At univariate and logistic regression analysis, mid-arm circumference (p = 0.04; beta = -0.89), mid-arm muscle circumference (p = 0.050; beta = -1.29), hemoglobin (p = 0.04, beta -1.1) and albumin (p = 0.04, beta -7.91) were inversely associated with pressure ulcers. The area under the ROC curve for albumin to predict sores was 0.76 (p = 0.02) and mortality was 0.83 (p = 0.03). Patient with lower albumin had significantly higher short-term mortality than those with higher serum albumin (p = 0.03; χ(2) test = 6.47).

CONCLUSION

Albumin, haemoglobin and mid-arm circumference are inversely associated with pressure ulcers. Albumin is a prognostic index in MCS patients. Since albumin and haemoglobin could be affected by a variety of factors, this association suggests to optimize nutrition and investigate on other mechanism leading to mortality and pressure ulcers.

The Autonomic System Functional State Predicts Responsiveness in Disorder of Consciousness

Diagnosis and early prognosis of the vegetative state/unresponsive wakefulness syndrome (VS/UWS) and its differentiation from the minimally-conscious state still rest on the clinical observation of responsiveness. The incidence of established clinical indicators of responsiveness also has proven variable in the single subject and is correlated to measures of heart rate variability (HRV) describing the sympathetic/parasympathetic balance. We tested responsiveness when the HRV descriptors nuLF and peakLF were or were not in the ranges with highest incidence of response based on findings from previous studies (10.0-70.0 and 0.05-0.11 Hz, respectively). Testing was blind by The Coma Recovery Scale-revised in the two conditions and in two experimental sessions with a one-week interval. The incidence of responses was not randomly distributed in the "response" and "no-response" conditions (McNemar test; p < 0.0001). The observed incidence in the "response" condition (visual: 55.1%; auditory: 51.5%) was higher than predicted statistically (32.1%) or described in previous clinical studies; responses were only occasional in the "no-response" condition (visual, 15.9%; auditory, 13.4%). Models validated the predictability with high accuracy. The current clinical criteria for diagnosis and prognosis based on neurological signs should be reconsidered, including variability over time and the autonomic system functional state, which could also qualify per se as an independent indicator for diagnosis and prognosis.

Interaction of (12)C ions with the mouse retinal response to light

Astronauts in orbit reported phosphenes varying in shape and orientation across the visual field; incidence was correlated with the radiation flux. Patients with skull tumors treated by (12)C ions and volunteers whose posterior portion of the eye was exposed to highly ionizing particles in early studies reported comparable percepts. An origin in radiation activating the visual system is suggested. Bursts (∼ 4 ms) of (12)C ions evoked electrophysiological mass responses comparable to those to light in the retina of anesthetized wild-type mice at threshold flux intensities consistent with the incidence observed in humans. The retinal response amplitude increased in mice with ion intensity to a maximum at ∼ 2000 ions/burst, to decline at higher intensities; the inverted-U relationship suggests complex effects on retinal structures. Here, we show that bursts of (12)C ions presented simultaneously to white light stimuli reduced the presynaptic mass response to light in the mouse retina, while increasing the postsynaptic retinal and cortical responses amplitude and the phase-locking to stimulus of cortical low frequency and gamma (∼ 25-45 Hz) responses. These findings suggest (12)C ions to interfere with, rather than mimicking the light action on photoreceptors; a parallel action on other retinal structures/mechanisms resulting in cortical activation is conceivable. Electrophysiological visual testing appears applicable to monitor the radiation effects and in designing countermeasures to prevent functional visual impairment during operations in space.

A computer analysis of specific and aspecific interictal epileptic activity in man

The preliminary results are reported for a systematic computerized analysis of interictal EEG recordings from patients with different epileptic syndromes. Both interical specific epileptic activity and non-specific background EEG signals are processed by special programs. Specific achievement are: a) Automatic recognition of spikes and quantification in every channel of their temporal incidence; b) definition of morphology and temporal relationship among spikes simultaneously recorded from different cortical and subcortical structures. Non-specific achievement: a) Characterization of background pattern; b) identification, quantification and localization of pathological frequencies. The study of changes in the described parameters induced by pharmacological therapies and measured drug plasma levels, has supplied additional criteria for the evaluation of epileptic dynamics and the monitoring of optimal treatment modes.

A study of the reliability of the Nociception Coma Scale

OBJECTIVE

In this study, we investigated the reliability of the Nociception Coma Scale which has recently been developed to assess nociception in non-communicative, severely brain-injured patients.

DESIGN

Prospective cross-sequential study.

SETTING

Semi-intensive care unit and long-term brain injury care.

SUBJECTS

Forty-four patients diagnosed as being in a vegetative state (n=26) or in a minimally conscious state (n=18).

INTERVENTIONS

Patients were assessed by two experts (rater A and rater B) on two consecutive weeks to measure inter-rater agreement and test-retest reliability.

MAIN MEASURES

Total scores and subscores of the Nociception Coma Scale.

RESULTS

We performed a total of 176 assessments. The inter-rater agreement was moderate for the total scores (k = 0.57) and fair to substantial for the subscores (0.33 ≤ k ≤ 0.62) on week 2. The test-retest reliability was substantial for the total scores (k = 0.66) and moderate to almost perfect for the subscores (0.53 ≤ k ≤ 0.96) for rater A. The inter-rater agreement was weaker on week 1, whereas the test-retest reliability was lower for the least experienced rater (rater B).

CONCLUSIONS

This study provides further evidence of the psychometric qualities of the Nociception Coma Scale. Future studies should assess the impact of practical experience and background on administration and scoring of the scale.

Miscoded Visual Processing in Degenerative Retinal Disorder?

Standard electrophysiological procedures for visual testing were applied to record the retinal and cortical electrophysiological responses to contrast stimulation from 35 subjects with unambiguously diagnosed retinitis pigmentosa and severe impairment of visual acuity and field. Stimuli (central 9° of visual field) were sinusoidal bars with spatial frequencies of 0.6–1.2 cycle/degree and 1.3–5.0 cycle/degree for the retinal (pattern-ERG) and cortical (pattern-VEP) responses, respectively; contrast was 80%; reversal at 2.13 Hz. Structured pattern-ERG above noise level was recorded from 29 subjects at 0.6 cycle/degree and from 24 subjects at 1.2 cycle/degree; latencies were increased and amplitude reduced. Pattern-VEP responses above noise level, with increased latencies and reduced amplitude, were observed in 92% of subjects with unilateral and in all subjects with bilateral retinal response. Both responses were phase-locked to stimulus. No correlation with the residual visual acuity or field was detected. The observation is consistent with evidence of the disease sparing the neuroretina and with unconscious visual processing and suggests miscoding of visual information processing.

Visual pursuit response in the severe disorder of consciousness: modulation by the central autonomic system and a predictive model

Background

A visual pursuit response is reportedly observed in ~20-30% of subjects in vegetative state (VS/UWS) and predicts better outcome; it is a key marker of evolution into the minimally conscious state (MCS). The probability of observing a positive response, however, has proven variable during the day, with comparable timing of the minima and maxima in VS/UWS and MCS. We verified if measures of sympathetic/parasympathetic balance are possible independent variables on which the occurrence of a pursuit response could depend and be predicted.

Methods

Fourteen subjects in VS/UWS and sixteen in MCS for more than one year were studied. A mirror was used to test the pursuit response for a total 231 useful trials. Non-invasive measures of the sympathetic/parasympathetic functional state (Heart rate variability descriptors nuLF and peakLF) used in the study of responsiveness in VS/UWS and MCS subjects were recorded and processed by descriptive statistics and advanced Support Vector Machine (SVM).

Results

A pursuit response was observed in 33% and 78.2% of subjects in VS or MCS, respectively. Incidence was higher at HRV nuLF values in the 20–60 range and peakLF values at 0.06-0.12 Hz (76.6%) and at nuLF values in the 10–60 range and peakLF values at 0.05-0.10 Hz (80.7%) in the VS and MCS, respectively. The SVM generated model confirmed the results in the training leave one out and 10 fold cross validation tests (81% and 81.4%).

Conclusion

The pursuit response incidence depends to a relevant extent on the sympathetic/parasympathetic balance and autonomic functional state. Extensive monitoring appears advisable.

Bovine rod rhodopsin: 2. Bleaching in vitro upon 12C ions irradiation as source of effects as light flash for patients and for humans in space

PURPOSE

In a previous paper, we showed that chemiluminescence from radical recombination (initiated by lipid peroxidation and propagated by polyunsaturated fatty acids [PUFA]) has a bleaching effect comparable to that caused by light on the rhodopsin of retinal rod outer segment (RdOS) prepared from bovine eyes. Photons generated by radical recombination were suggested to be the origin of phosphenes perceived as light flashes by the human eye. Irradiation with (12)C carbon ions was used in this study to stimulate radical production, propagation and recombination leading to photoluminescence.

MATERIALS AND METHODS

(12)C radiation bleached RdOS rhodopsin, but structural damage increasing with the radiation dose was also observed. For this reason, only the effects on rhodopsin at doses producing next to negligible biodamage and permitting regeneration have been considered as bleaching effects.

RESULTS

(12)C irradiation bleached RdOS rhodopsin, but increasing structural damage with radiation dose was also observed. For the measure of bleaching and to reveal dose response effects on rhodopsin that were able to be regenerated only results from doses producing nearly negligible biodamage have been considered.

CONCLUSIONS

Recombination of radicals appears responsible for the release of photons with subsequent bleaching of rhodopsin. This effect could have an important role in the generation of the anomalous visual effects (phosphenes) experienced by patients during hadrotherapy or by astronauts in space.

Ambient intelligence for monitoring and research in clinical neurophysiology and medicine: the MIMERICA* project and prototype

Ambient Intelligence (AmI) provides extended but unobtrusive sensing and computing devices and ubiquitous networking for human/environment interaction. It is a new paradigm in information technology compliant with the international Integrating Healthcare Enterprise board (IHE) and eHealth HL7 technological standards in the functional integration of biomedical domotics and informatics in hospital and home care. AmI allows real-time automatic recording of biological/medical information and environmental data. It is extensively applicable to patient monitoring, medicine and neuroscience research, which require large biomedical data sets; for example, in the study of spontaneous or condition-dependent variability or chronobiology. In this respect, AML is equivalent to a traditional laboratory for data collection and processing, with minimal dedicated equipment, staff, and costs; it benefits from the integration of artificial intelligence technology with traditional/innovative sensors to monitor clinical or functional parameters. A prototype AmI platform (MIMERICA*) has been implemented and is operated in a semi-intensive unit for the vegetative and minimally conscious states, to investigate the spontaneous or environment-related fluctuations of physiological parameters in these conditions.

Heart rate variability and the central autonomic network in the severe disorder of consciousness

OBJECTIVE

To review the applicability of heart rate variability measures in research on severe disorder of consciousness.

METHODS

The available evidence on the correlation between heart rate variability measures and the outcome or residual functional state/responsiveness of severely brain-injured patients (including those in vegetative or minimally conscious states) are reviewed and discussed with reference to the central autonomic network model.

RESULTS AND CONCLUSION

Heart rate variability analyses appear to be applicable to assess residual or emerging (higher level) function in brain-injured patients with disordered consciousness and to predict outcome. In this regard, the central autonomic network model is heuristic in the understanding of heart rate variability descriptors of the central nervous system/autonomic systems relationship.

Bovine rod rhodopsin. 1. Bleaching by luminescence in vitro by recombination of radicals from polyunsaturated fatty acids

Rod outer segments of photoreceptors are characterized by rhodopsin, a membrane protein surrounded by phospholipids containing a very high concentration of polyunsaturated fatty acids. These fatty acids can propagate free radicals, initiated by peroxidation, whose recombination is eventually associated with light emission as chemiluminescence. The results reported here indicate that this effect produces an isomerization of the retinal (bleaching effect) of the rhodopsin, similar to that induced by light in normal vision. In vitro experiments on detergent-suspended rod outer segments (RdOS) from bovine eyes, using an enzymatic source of radicals, xanthine/xanthine oxidase, were carried out. The results indicate that the proposed mechanism is likely, because they can show the bleaching of rhodopsin in RdOS, owing to its extraordinary sensitivity. Thus this mechanism is, also, a possible explanation for anomalous visual effects such as light flashes (phosphene-like) perceived by humans. The functionality of the rhodopsin in the RdOS was first tested by visible light. Rhodopsin reactivation after bleaching was obtained by adding cis-retinal to the suspension, demonstrating the reversibility of the bleaching process. A special experimental system was developed to observe the bleaching from luminescence by radical recombination, avoiding physical contact between the rod outer segment suspension and the radicals to prevent radical-induced damage and modifications of the delicate structure of the rod outer segment.

Heart Rate Variability, Homeostasis, and Brain Function

Measures of heart rate variability (HRV) are major indices of the sympathovagal balance in cardiovascular research. These measures are thought to reflect complex patterns of brain activation as well and HRV is now emerging as a descriptor thought to provide information on the nervous system organization of homeostatic responses in accordance with the situational requirements. Current models of integration equate HRV to the affective states as parallel outputs of the central autonomic network, with HRV reflecting its organization of affective, physiological, “cognitive,” and behavioral elements into a homeostatic response. Clinical application is in the study of patients with psychiatric disorders, traumatic brain injury, impaired emotion-specific processing, personality, and communication disorders. HRV responses to highly emotional sensory inputs have been identified in subjects in vegetative state and in healthy or brain injured subjects processing complex sensory stimuli. In this respect, HRV measurements can provide additional information on the brain functional setup in the severely brain damaged and would provide researchers with a suitable approach in the absence of conscious behavior or whenever complex experimental conditions and data collection are impracticable, as it is the case, for example, in intensive care units.

Visual pursuit in the severe disorder of consciousness

Visual pursuit is a key descriptor of the minimally conscious state (above 80% of cases). It is also observable in about 20% of subjects in vegetative state. Its reappearance after severe brain damage anticipates a favorable outcome, with recovery of consciousness in 73% of subjects (45% in the absence of it). We considered retrospectively 395 subjects in vegetative state because of traumatic (63%), massive acute vascular (30%), or diffuse anoxic-hypoxic (7%) brain damage consecutively admitted to one dedicated unit during the years 1998-2008. Visual tracking was observed in 290 subjects (73.4%) and was already detectable within 50 days from brain injury in about 60% of post-traumatic or vascular subjects and 21% of anoxic-hypoxic patients. After 230 days of follow-up or more, it was observed in 89% and 88% of post-traumatic and vascular subjects and in 67% of anoxic-hypoxic patients. Rating with the Glasgow Outcome Scale (GOS) was better in those subjects with recovered visual tracking and inversely correlated with the time of reappearance in post-traumatic and vascular subjects; also the subjects with late recovery of eye tracking (230 days or more) had better GOS outcome than those without it. The observation of visual tracking reappearing in subjects in vegetative state would reflect recuperation of the brainstem-cortical interaction and overall brain functional organization that are thought to sustain consciousness and are interfered with by the "functional disconnection," resulting in the vegetative state.

Unresponsive wakefulness syndrome: a new name for the vegetative state or apallic syndrome

BACKGROUND

Some patients awaken from coma (that is, open the eyes) but remain unresponsive (that is, only showing reflex movements without response to command). This syndrome has been coined vegetative state. We here present a new name for this challenging neurological condition: unresponsive wakefulness syndrome (abbreviated UWS).

DISCUSSION

Many clinicians feel uncomfortable when referring to patients as vegetative. Indeed, to most of the lay public and media vegetative state has a pejorative connotation and seems inappropriately to refer to these patients as being vegetable-like. Some political and religious groups have hence felt the need to emphasize these vulnerable patients' rights as human beings. Moreover, since its first description over 35 years ago, an increasing number of functional neuroimaging and cognitive evoked potential studies have shown that physicians should be cautious to make strong claims about awareness in some patients without behavioral responses to command. Given these concerns regarding the negative associations intrinsic to the term vegetative state as well as the diagnostic errors and their potential effect on the treatment and care for these patients (who sometimes never recover behavioral signs of consciousness but often recover to what was recently coined a minimally conscious state) we here propose to replace the name.

CONCLUSION

Since after 35 years the medical community has been unsuccessful in changing the pejorative image associated with the words vegetative state, we think it would be better to change the term itself. We here offer physicians the possibility to refer to this condition as unresponsive wakefulness syndrome or UWS. As this neutral descriptive term indicates, it refers to patients showing a number of clinical signs (hence syndrome) of unresponsiveness (that is, without response to commands) in the presence of wakefulness (that is, eye opening).

Function-Related Gamma Oscillations and Conscious Perception

Frequency-domain techniques describe oscillations as a fundamental behavior of neurons and brain signals. Oscillations synchronize over large portions of cortex and mediate in the spatiotemporally coherent activation of neuron assemblies required for brain processing to occur. Oscillations in the gamma band (~20.0–80.0 Hz) originate from the tonic excitation of inhibitory interneuron networks, sustain rhythms and frequency constancy, and are enhanced during sensory, motor, or “cognitive” processes through frequency-dependent and function-related neuronal synchronization. Experimental work indicates a role of gamma activity in conscious perception. Further investigation is, nevertheless, warranted as gamma-band synchronization plays a functional role in low-level phase coding as well as in high-complexity neural processes related to perception, such as selective attention, focused arousal, multistable or ambiguous perceptive conditions, visuomotor integration, and associative learning.

'Gamma' band oscillatory response to chromatic stimuli in volunteers and patients with idiopathic Parkinson's disease

The signal structure of the responses to equiluminant chromatic and achromatic (contrast) stimuli was studied in normal volunteers and patients with mild to moderate idiopathic Parkinson's disease. Visual stimuli were full-field (14 x 16 deg) achromatic or equiluminant (red-green or blue-yellow) sinusoidal gratings at 2c/deg and 90% contrast presented in onset-offset mode. The signal was processed offline by DFT and factor analysis was performed in the frequency domain. The conventional VEPs to chromatic onset stimuli showed a monophasic negative wave, while the response to offset stimuli was comparable in shape to the on-/offset achromatic responses; latencies were longer and amplitudes higher than those of responses to contrast stimulation. In patients, latencies were longer than in controls after achromatic and (to a lesser extent) red-green stimulations, but not after blue-yellow stimulation; amplitudes were comparable in all stimulus conditions. In healthy subjects, two non-overlapping factors accounted for the approximately 2-30.0 Hz and approximately 25.0-50.0 Hz signal components (representative of the low-frequency VEP and gamma oscillatory responses, respectively); the frequency of the approximately 25.0-50.0 Hz factor was lower after color than after contrast stimulation. The same factor structure was identified in patients, but the peak frequency of the factor on gamma activity was higher than in controls and did not vary with color-opponent stimulation. These observations indicate that stimulus-related gamma activity originates in cortex irrespective of the activated (magno-, parvo-, or konio-cellular) visual pathway, consistent with the suggested role in the phase coding of neuronal activities. Some dopaminergic modulation of gamma activity is conceivable.

Quantitative EEG and neurochemical aspects of memory and learning

Different, established or putative animal models of learning were studied by electrophysiological (EEG) and neurochemical methodologies. The training of rats to new behavioral patterns proved to result in the stimulation of total RNA synthesis rate in specific brain structures, as well as in modifications of the EEG organization of hippocampus. This two-fold approach to the assessment of modifications in learning-involved brain structures was extended to the study of mirror focus and kindling, to verify the suitability of these phenomena as experimental models of learning. Reduced (3H) uridine incorporation and proportion of poly (A)-associated RNA were found in mirror focus in comparison with control regions. These variations seem related to brain damage rather than be congruent with learning-related modifications. Further studies are necessary to verify whether the kindling phenomena are to be equated to learning models.