ABSTRACT
Characteristic preterm EEG patterns of "Delta-brushes" (DBs) have been reported in the temporal cortex following auditory stimuli, but their spatio-temporal dynamics remains elusive. Using 32-electrode EEG recordings and co-registration of electrodes' position to 3D-MRI of age-matched neonates, we explored the cortical auditory-evoked responses (AERs) after 'click' stimuli in 30 healthy neonates aged 30-38 post-menstrual weeks (PMW). (1) We visually identified auditory-evoked DBs within AERs in all the babies between 30 and 33 PMW and a decreasing response rate afterwards. (2) The AERs showed an increase in EEG power from delta to gamma frequency bands over the middle and posterior temporal regions with higher values in quiet sleep and on the right. (3) Time-frequency and averaging analyses showed that the delta component of DBs, which negatively peaked around 550 and 750 ms over the middle and posterior temporal regions, respectively, was superimposed with fast (alpha-gamma) oscillations and corresponded to the late part of the cortical auditory-evoked potential (CAEP), a feature missed when using classical CAEP processing. As evoked DBs rate and AERs delta to alpha frequency power decreased until full term, auditory-evoked DBs are thus associated with the prenatal development of auditory processing and may suggest an early emerging hemispheric specialization.
Subject(s)
Audiometry, Evoked Response , Cerebral Cortex/physiology , Infant, Premature/physiology , Acoustic Stimulation , Alpha Rhythm/physiology , Delta Rhythm/physiology , Electroencephalography , Evoked Potentials, Auditory/physiology , Female , Gamma Rhythm , Humans , Infant, Newborn , Magnetic Resonance Imaging , Male , Sleep/physiologyABSTRACT
Recordings of the intrinsic optical signal (IOS) are widely used in the functional imaging of the central nervous system in vivo. However, the IOS technique has been mainly described in the adult brain and the possibility of using IOS for the robust functional imaging of the immature brain and the optimal parameters for IOS recording and analysis in the analysis in the immature brain tissue remain largely unknown. Here, we show that the use of the near to infrared light and automatic PCA enable efficient detection of IOS in the neonatal rat pups' whisker-related somato- sensory cortex during the first three weeks after the birth. IOS detection using automatic PCA survived fourfold artificial noise increase in the baseline, indicating on the robustness of this approach. Thus, our findings indicate that IOS imaging using near infrared light and automatic PCA is efficient technique for the functional imaging of somatosensory cortex in the neonatal rats.
Subject(s)
Principal Component Analysis/methods , Somatosensory Cortex/physiology , Synaptic Transmission/physiology , Vibrissae/physiology , Animals , Animals, Newborn , Electrodes, Implanted , Female , Infrared Rays , Male , Rats, Wistar , Signal-To-Noise Ratio , Somatosensory Cortex/anatomy & histology , Stereotaxic TechniquesABSTRACT
Amphipols (APols) have become important tools for the stabilization, folding, and in vitro structural and functional studies of membrane proteins (MPs). Direct crystallization of MPs solubilized in APols would be of high importance for structural biology. However, despite considerable efforts, it is still not clear whether MP/APol complexes can form well-ordered crystals suitable for X-ray crystallography. In the present work, we show that an APol-trapped MP can be crystallized in meso. Bacteriorhodopsin (BR) trapped by APol A8-35 was mixed with a lipidic mesophase, and crystallization was induced by adding a precipitant. The crystals diffract beyond 2 Å. The structure of BR was solved to 2 Å and found to be indistinguishable from previous structures obtained after transfer from detergent solutions. We suggest the proposed protocol of in meso crystallization to be generally applicable to APol-trapped MPs.
