Development of visual texture segregation during the first year of life: a high-density electrophysiological study

There are important developmental changes occurring during infancy in visual cortical structures that underlie higher-order perceptual abilities. Using high-density electrophysiological recording techniques, the present study aimed to examine the development of visual mechanisms, during the first year of life, associated with texture segregation. Forty-two normal full term infants were tested at 1, 3, 6 or 12 months of age. Visual-evoked potentials to low-level stimuli varying in orientation (oriVEP) and higher-level textured stimuli (texVEP) were recorded from 128 scalp electrodes. Difference potentials were obtained to extract the VEP component associated specifically with texture segregation (tsVEP). Results show a clear developmental pattern regarding amplitude, latency and scalp distribution of tsVEP, which appears at around 3 months but does not reach maturity by 12 months of age. A reduction in latency is particularly evident between 3 and 6 months, whereas amplitude shows a gradual increase with a marked increment between 3 and 6 months for low-level orientation stimuli and between 6 and 12 months for higher-level textured stimuli. These developmental patterns are attributed to neural maturational processes such as myelination and synaptogenesis. The differential developmental rates can be explained by delayed maturational processes of brain regions involved in more complex visual processing.     

Histopathogenesis of early-stage mitral annular calcification

Mitral annular calcification (MAC) is a common condition in elderly subjects that sometimes causes degenerative mitral valvular diseases. To investigate the early histopathogenesis of MAC, we examined 180 consecutive autopsies of elderly subjects. After a macroscopic and radiological examination, 5-mm-thick serial tissue blocks obtained from the mitral annulus were examined in all MAC cases. Five cases without MAC were also studied using histology, immunostaining, electron microscopy, analytical electron microscopy and the TUNEL method. The incidence of MAC in females (23%) was higher than that in males (15%). Most MAC was located at the posterior cusp (91%). The mitral annulus showed signs of microscopic calcification and lipid-deposition in some degenerated areas in all of the cases without MAC. The interstitial cells were positive for vimentin and partially positive for smooth muscle actin, indicating the myofibroblastic differentiation. Ultrastructural studies showed an abundance of cellular degradation products and foci of calcium- and phosphorus-deposition on these products in the interstitium. Several interstitial cells tested positive for both single-stranded DNA immunostaining and the TUNEL reaction. In conclusion, the microscopic calcification of mitral annulus is an early stage of MAC and caused by calcium-deposition on cellular degradation products, probably released from apoptotic or necrotic interstitial cells.     

Auditory scene analysis following unilateral inferior colliculus infarct

Event-related potentials in the form of mismatch negativity were recorded to investigate auditory scene analysis capabilities in a person with a very circumscribed haemorrhagic lesion at the level of the right inferior colliculus. The results provide the first objective evidence that processing at the level of the inferior colliculus plays an important role in human auditory frequency discrimination. Moreover, the electrophysiological data suggest that following this unilateral lesion, the auditory pathways fail to reorganize efficiently.     

Improving tuberculosis case detection rate with a lay informant questionnaire: an experience from the Lao People's Democratic Republic

PROBLEM: In many countries, the tuberculosis (TB) annual case detection rate is below the target of 70%. In the Lao People's Democratic Republic in 2005, it did not exceed 55% APPROACH: The DOTS strategy promotes passive case detection of TB. In order to increase the detection rate, we validated a questionnaire targeting lay informants at village level to notify patients with chronic cough and assessed the relevance for TB case-finding. A three-item questionnaire was sent through the district health departments to all villages in six districts in six provinces. The village headmen were asked to notify chronic cough patients. Answers were validated in a door-to-door survey (20 villages/district). In a sub-sample (four villages/district) all confirmed patients were screened for TB and paragonimiasis. LOCAL SETTING: Attapeu, Luang Namtha, Luang Prabang, Saravane, Savanakhet and Vientiane provinces in the Lao People's Democratic Republic. RELEVANT CHANGES: Lay informant questionnaires sent from district health offices to villages are cost-effective and foster interaction between the health services and remote and underserved communities. Although the correct detection of patients is highly dependent on direct respondents, a substantial number of new TB and paragonimiasis cases were consistently diagnosed in chronic cough patients. LESSONS LEARNED: Out of 456 questionnaires, 295 were returned (65%). Return rates were highly variable between districts (48-87%), questionnaires' sensitivity (56-98%), positive predictive value (34-88%) and correlation between number of notified and confirmed patients (r: 0.26-0.78). In sub-sampled villages (13,541 population) 19 (5.1%) TB and 26 (7.0%) paragonimiasis cases were detected in 374 chronic cough patients. This quick questionnaire approach proved motivating for district authorities and village key informants, although no incentives were provided. The highly operator-dependent approach yielded a consistent detection rate of TB and paragonimiasis cases. This approach brings health services and populations in need in close contact, which is particularly crucial in remote and underserved areas.     

Spatiotemporal dynamics of affective picture processing revealed by intracranial high‐gamma modulations

Our comprehension of the neural mechanisms underlying emotional information processing has largely benefited from noninvasive electrophysiological and functional neuroimaging techniques in recent years. However, the spatiotemporal dynamics of the neural events occurring during emotional processing remain imprecise due to the limited combination of spatial and temporal resolution provided by these techniques. This study examines the modulations of high‐frequency activity of intracranial electroencephalography recordings associated with affective picture valence, in epileptic patients awaiting neurosurgery. Recordings were obtained from subdural grids and depth electrodes in eight patients while they viewed a series of unpleasant, pleasant and neutral pictures from the International Affective Picture System. Broadband high‐gamma (70–150 Hz) power was computed for separate 100‐ms time windows and compared according to ratings of emotional valence. Compared to emotionally neutral or pleasant pictures, unpleasant stimuli were associated with an early and long‐lasting (≈200–1,000 ms) bilateral increase in high‐gamma activity in visual areas of the occipital and temporal lobes, together with a late and transient (≈500–800 ms) decrease found bilaterally in the lateral prefrontal cortex (PFC). Pleasant pictures were associated with increased gamma activity in the occipital cortex, compared to the emotionally neutral stimuli. Consistent with previous studies, our results provide direct evidence of emotion‐related modulations in the visual ventral pathway during picture processing. Results in the lateral PFC also shed light on the neural mechanisms underlying its role in negative emotions processing. This study demonstrates the utility of intracranial high‐gamma modulations to study emotional process with a high spatiotemporal precision. Hum Brain Mapp, 36:16–28, 2015.. © 2014 Wiley Periodicals, Inc.     

Noninvasive continuous functional near‐infrared spectroscopy combined with electroencephalography recording of frontal lobe seizures

Purpose: To investigate spatial and metabolic changes associated with frontal lobe seizures. Methods: Functional near‐infrared spectroscopy combined with electroencephalography (EEG‐fNIRS) recordings of patients with confirmed nonlesional refractory frontal lobe epilepsy (FLE). Key Findings: Eighteen seizures from nine patients (seven male, mean age 27 years, range 13–46 years) with drug‐refractory FLE were captured during EEG‐fNIRS recordings. All seizures were coupled with significant hemodynamic variations that were greater with electroclinical than with electrical seizures. fNIRS helped in the identification of seizures in three patients with more subtle ictal EEG abnormalities. Hemodynamic changes consisted of local increases in oxygenated (HbO) and total hemoglobin (HbT) but heterogeneous deoxygenated hemoglobin (HbR) behavior. Furthermore, rapid hemodynamic alterations were observed in the homologous contralateral region, even in the absence of obvious propagated epileptic activity. The extent of HbO activation adequately lateralized the epileptogenic side in the majority of patients. Significance: EEG‐fNIRS reveals complex spatial and metabolic changes during focal frontal lobe seizures. Further characterization of these changes could improve seizure detection, localization, and understanding of the impact of focal seizures.     

Sleep Disturbances in Prepubertal Children with Attention Deficit Hyperactivity Disorder: A Home Polysomnography Study

Study Objectives:

To examine sleep architecture and reported sleep problems in children with ADHD and normal controls, while considering the roles of pertinent moderating factors.

Design:

Overnight sleep recordings were conducted in 15 children diagnosed with ADHD (DSM-IV) without comorbid psychiatric problems and in 23 healthy controls aged 7 to 11 years. Children were on no medication, in good health and did not consume products containing caffeine ≥ 7 days prior to the polysomnography (PSG) study. PSG evaluation was performed at each child''s home; children slept in their regular beds and went to bed at their habitual bedtimes.

Measurements

Standard overnight multichannel PSG evaluation was performed using a portable polysomnography device. In addition, parents were asked to complete a sleep questionnaire.

Results:

Compared to controls, children in the ADHD group had significantly shorter duration of REM sleep, smaller percentage of total sleep time spent in REM sleep, and shorter sleep duration. In addition, the ADHD group had higher scores on the insufficient sleep and sleep anxiety factors than children in the control group.

Conclusions:

The present findings support the hypothesis that children with ADHD present sleep disturbances.

Citation:

Gruber R; Xi T; Frenette S; Robert M; Vannasinh P; Carrier J. Sleep disturbances in prepubertal children with attention deficit hyperactivity disorder: A home polysomnography study. SLEEP 2009;32(3):343-350.     

A noninvasive, presurgical expressive and receptive language investigation in a 9-year-old epileptic boy using near-infrared spectroscopy

The intracarotid amobarbital test (IAT) is used for presurgical evaluation of language lateralization. However, this procedure has many limitations, especially in children. As an alternative to IAT, in the case described here, near-infrared spectroscopy (NIRS) was used to investigate expressive and receptive language lateralization as part of the presurgical evaluation of a 9-year-old Yiddish-speaking boy with a probable left temporal epileptic focus. This child could not tolerate IAT or functional MRI. He underwent two NIRS recording sessions while performing expressive and receptive language tasks. Results indicated predominantly left-sided expressive language in Broca's area with ipsilateral cortical recruitment of more posterior regions. Receptive language showed a bilateral cerebral pattern, perhaps as an expression of cerebral plasticity or compensation in this young patient. This case report illustrates that NIRS may contribute to presurgical investigation and could become a noninvasive alternative to IAT and functional MRI in determining speech lateralization in children.     

Gamma frequency SSVEP components differentiate children with febrile seizures from normal controls

Gamma band electroencephalography (EEG) abnormalities have been reported in patients with epilepsy. We aimed to investigate whether patients with febrile seizures (FS) show abnormalities of the gamma frequency steady‐state visual evoked potential (SSVEP) components evoked by intermittent photic stimulation (IPS). We analyzed the magnitude and phase alignment of the 50–100 Hz SSVEP components elicited by IPS from 12 FS patients, 5 siblings of FS patients, and 15 control children between 6 and 36 months of age. Patients with FS showed significantly higher SSVEP magnitude and phase alignment values when compared to both the siblings and control groups. Detected abnormalities could either represent the direct consequence of seizures or indicate a preexisting tendency to hypersynchrony in FS patients. Future prospective studies could assess whether SSVEP abnormalities are associated with complex rather than simple FS, or have a prognostic value for the development of epilepsy following FS.     

Multichannel wearable fNIRS‐EEG system for long‐term clinical monitoring

Continuous brain imaging techniques can be beneficial for the monitoring of neurological pathologies (such as epilepsy or stroke) and neuroimaging protocols involving movement. Among existing ones, functional near‐infrared spectroscopy (fNIRS) and electroencephalography (EEG) have the advantage of being noninvasive, nonobstructive, inexpensive, yield portable solutions, and offer complementary monitoring of electrical and local hemodynamic activities. This article presents a novel system with 128 fNIRS channels and 32 EEG channels with the potential to cover a larger fraction of the adult superficial cortex than earlier works, is integrated with 32 EEG channels, is light and battery‐powered to improve portability, and can transmit data wirelessly to an interface for real‐time display of electrical and hemodynamic activities. A novel fNIRS‐EEG stretchable cap, two analog channels for auxiliary data (e.g., electrocardiogram), eight digital triggers for event‐related protocols and an internal accelerometer for movement artifacts removal contribute to improve data acquisition quality. The system can run continuously for 24 h. Following instrumentation validation and reliability on a solid phantom, performance was evaluated on (1) 12 healthy participants during either a visual (checkerboard) task at rest or while pedalling on a stationary bicycle or a cognitive (language) task and (2) 4 patients admitted either to the epilepsy (n = 3) or stroke (n = 1) units. Data analysis confirmed expected hemodynamic variations during validation recordings and useful clinical information during in‐hospital testing. To the best of our knowledge, this is the first demonstration of a wearable wireless multichannel fNIRS‐EEG monitoring system in patients with neurological conditions. Hum Brain Mapp 39:7–23, 2018. © 2017 Wiley Periodicals, Inc.