Studies of Selective Attention in Dogs Using the Coherence-Phase Characteristics of Cortical Potentials over a Wide Range of Frequencies, 1–220 Hz

The state of selective attention formed during operant food-related behavior was studied using the coherence-phase characteristics between potentials in several areas of the neocortex at frequencies of 1–220 Hz. Functional groups were identified among the areas compared, which appear to have priority for this state. The temporal relationships between potentials in these groups were established from values for coherence functions at a particular optimum level (0.7) mainly in the band 1–15 Hz and the high-frequency range 40–200 Hz. The phenomenon of synchronicity appeared at phase shifts close to zero, while at significant phase shifts the phenomenon of non-synchronous time relationships with defined spatial directions was seen in the high-frequency range.     

Effects of intracerebroventricular administration of atrial natriuretic peptide on subcortical EEG activity in conscious rabbits

Atrial natriuretic peptide (ANP) influences the activity of rat hypothalamic neurons, modifies the membrane excitability of the rat forebrain neurons, and induces changes in membrane potentials in cultured rat glioma cells. In order to explore whether these effects are reflected in the electrical activity of larger subcortical brain areas, we investigated the electroenceophalographic activity (EEG) recorded from 20 male albino (New Zealand White) rabbits. Recordings of EEG were made on restrained, conscious animals 1 week after the implantation of an indwelling intracerebroventricular (i.c.v.) cannula (lateral right ventricle) and two stainless steel electrodes, implanted in the paraventricular (PVN) and supraoptic (SON) nuclei. Animals were classified into two main groups: those with water available ad libitum (group A) and those which were dehydrated for 24 h before EEG recordings (group B). Each group was divided into two subgroups (1 and 2) of five animals each. EEG was recorded at 0 min (control) and 30, 60, and 90 min following the i.c.v. injection of either 25 l artificial cerebrospinal fluid (aCSF; subgroup 1) or 1 g -human ANP in 25 l aCSF (subgroup 2). Each EEG record duration was 6 s. For each EEG record the power spectrum of the digitized waveform was estimated in the frequencies 0.5–48 Hz using the fast Fourier transform, and the energy of each waveform was subsequently calculated. The results were analyzed by repeated-measures ANOVA and by the t-test. The analysis revealed that (1) water deprivation does not affect mean EEG energy and value (2) ANP attenuates (P<0.05; in comparison with zero time) the mean energy value of EEG recorded from SON at 30 min and 60 min in the frequencies 8–48 Hz, whilst it tends to decrease (P<0.1) the mean energy of EEG recorded from PVN at 30 min in the frequencies 8–15 Hz. Mean EEG energy changes caused by ANP would reflect its various (mainly inhibitory) effects on the electrical activity recorded from PVN and SON neurons in in vitro and in vivo studies.     

Cortico-cortical coupling patterns during dual task performance

We investigated the neural correlates of dual task performance using EEG coherence as a measure of the functional coupling between cortical regions. Nine healthy participants performed a rhythmical movement with the right hand and an isometric contraction with the left hand, either initiated simultaneously or successively. EEG data revealed that dual task performance was associated with stronger coherence in left hemispheric and mesial areas than the sum of the tasks performed separately in the beta (>12–30 Hz), but not alpha (8–12 Hz), band. This effect was more pronounced when the two assignments were initiated simultaneously, as opposed to successively. The data demonstrate that the pattern of cortico-cortical coupling during bimanual actions is not just the sum of that associated with its component parts, but is increased according to coordinative demands and processing load.     

Auditory input to a vocal nucleus in the frog Rana pipiens: hormonal and seasonal effects

Summary In Rana pipiens, single unit recordings from the pretrigeminal nucleus (pre-V), a nucleus involved in call production, demonstrated neurons that respond to auditory stimuli. Most of these neurons had V-shaped tuning curves, with best excitatory frequencies between 200–1400 Hz, thresholds between 31–87 dB SPL, latencies between 10–50 ms, and Q (10 dB) between 1.3–5.1. The number of pre-V neurons that responded to acoustic stimulation increased after gonadotropin injections, and appeared to increase during the breeding season. In addition, a small number of neurons with more complex response properties, such as W-shaped tuning curves or sensitivity to white noise but not to pure tones, appeared after hormone treatments. The hormonal and possible seasonal effects on pre-V auditory activity suggest that the auditory input to this vocal nucleus may play a role in reproductive behavior.     

Non-Synaptic Integration of the Cell Bodies of Neurons into the Central Nervous System of the Snail

Single neurons (soma and proximal process) were isolated from the serotonergic (5-HT-ergic) PedA cluster in experiments on the pond snail Lymnaea stagnalis, and changes in the electrical activity of isolated neurons were observed during repeated movement of these cells towards and away from the surface of the CNS. The position of cell bodies of 5-HT-ergic neurons had excitatory effects on the isolated neuron. This effect was maximal (at 10^–8–10^–7 M 5-HT) when neurons were brought close to the PedA cluster and were further enhanced by addition of the 5-HT precursor 5-hydroxytryptophan at concentrations of (1–2)·10^–4 M. The results obtained here provide evidence 5-HT-ergic neurons cooperate during 5-HT-dependent behaviour, this being based on excitatory interactions at the level of cell bodies.     

Event-Related Desynchronization evoked by auditory stimuli

Summary Event-Related Desynchronization (ERD) and Synchronization (ERS) of several EEG alpha frequencies was studied in 19 subjects during the presentation of linguistic and/or melodic auditory stimuli. The stimulus length was 1300 msec (+/–100 msec) and the interstimulus interval was 2000 msec. A significant ERD was found during auditory stimulation in the 8–10 Hz and 10–12 Hz alpha frequency bands, and there were also significant differences in the spatiotemporal pattern of the ERD between these frequency bands. Significant ERD was elicited also in the 10–11 and 11–12 Hz frequency bands by auditory stimulation. There were no significant differences between these one-hertz frequency bands. The subjects were assigned to two analysis groups according to their individual alpha peak frequency (10–11 or 11–12 Hz) at rest. The ERD in these groups reached statistical significance and there were significant differences between the groups. The ERD of the two groups differed significantly also when their EEG data was studied in the 10–12 Hz frequency band. The results from this study show that ERD is not modality-specific, i.e., it can be elicited also by auditory stimuli. Moreover, they indicate that it is important to control over interindividual variation in the EEG when studying the ERD phenomenon.This study was financially supported by the The Cultural Scholarship Foundation of Southwestern Finland (Varsinais-Suomen Kulttruurirahasto) and by the Council for Social Sciences, Academy of Finland (project 7338).     

Electrical cortical activity in newborn infants under various conditions

Summary EEG records were obtained from infants aged 8 to 9 days in varying conditions of sleep and wakefulness. Records were made from the fronto-occipital lead. During the natural, sleep following breast feeding, slow waves occurred having frequencies of 2–3, 6–10, or rarely 20 cycles. During excitation of the feeding center (state of active wakefulness) the waves at a frequency of 30–40 cycles became dominant. During quiet waking, comparatively low frequency oscillations were recorded and according to the condition of nutritional excitation which varied with the period between feeds, the frequency resembled either those recorded during sleep or during wakefulness.It was only during a condition of nutritional excitation that high-frequency waves, representing generalized activation of the EEG typical of adult persons in the active waking state were recorded. In no cases did light or sound provoke the characteristic adult EEG response.(Presented by Active Member AMN SSSR V. V. Parin) Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 52, No. 8 pp. 12–17, August 1961     

Effects of acute hypoxia on the EEG and impulse activity of the neurons of various brain structures in rats

The EEG and impulse activity of the neurons of the cerebral cortex and other structures of the brain were studied in the dynamics of hypoxic influence. In the initial phase of hypoxia (2000–6000 m), activation of the EEG and impulse discharge of neurons set in; in this case EEG activation arose earlier and was more pronounced, In the second phase of hypoxia (7500–10,000 m), the EEG changed in the direction of a reorganization of the frequency spectrum from one rhythm to another — from fast to slow activity of the type of waves. At this time the impulse activity was gradually suppressed, and the cortical neurons exhibited higher sensitivity to hypoxia and were inhibited earlier than the cells of the hypothalamus and medulla oblongata.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 68, No. 5, pp. 576–582, May, 1982.     

Thalamocortical and intrathalamic interactions during slow repetitive stimulation of n. centralis lateralis

Summary 1. Extracellular single unit activity was recorded simultaneously in cortex (anterior part of the middle suprasylvian gyrus, MSSG) and thalamus (n. ventralis anterior, VA; n. lateralis posterior, LP) during repetitive low frequency stimulation (RLFS) of n. centralis lateralis (CL) in lightly anesthetized cats. Such stimulation induced typical recruiting responses in the cortical EEG consisting of long-latency, surface-negative waves reversing in polarity at 0.1–2 mm depth. 2. These cortical EEG responses were associated with long-latency (8–20 ms) action potential (AP) discharges of cortical neurons appearing with the 2nd stimulus of the train. The number of AP discharges and response latency increased as the train of CL stimuli progressed. In 12 of these neurons there was a short-latency (up to 2–5 ms) response which, however, did not show incremental features during RLFS. 3. Thalamic neurons in VA usually responded to the first stimulus within a train of RLFS of CL, while LP neurons responded only to the 2nd or 3rd stimulus. Peristimulus time histograms (PSTHs) of AP discharges in VA showed an increase in both number and latency of APs as the train of stimuli progressed. This was also observed in those thalamic neurons in LP which changed their firing during RLFS of CL. 4. The peak of firing of 20 VA neurons preceded, and that of 7 followed that of the MSSG neurons, while 6 VA and MSSG neuronal pairs reached their peak firing stimultaneous; peak firing of 29 LP neurons preceded, and that of 21 followed the firing peak of MSSG neurons. 5. The thresholds of the incremental responses of MSSG, VA and LP neurons to progressively increased intensity of RLFS of CL were different: MSSG and VA neurons changed their firing pattern at an intensity incapable of modifying the activity of LP neurons. When stimulation intensity was increased to a level sufficient to change the responses of both neurons of a given pair (either MSSG-VA or MSSG-LP) the time sequence of involvement in the incremental process was in the following order: VA, MSSG, LP. 6. Within a range of RLFS extending from 2–20 Hz, stimulation at 6.6 Hz (150 ms interstimulus intervals) induced the most prominent incremental responses both in the cortex and thalamus, i.e. response increases were largest when each subsequent stimulus occurred 50–130 ms before the expected rebound excitation following the preceding response. 7. Incremental responses in both cortex (MSSG) and thalamus (VA and LP) during RLFS of CL seem to result from secondary excitation which is dependent upon the temporal relation of the CL stimuli. Neurons in VA are more involved than LP neurons in recruiting responses induced in the MSSG by RLFS of CL and play a crucial role in mediating the thalamocortical recruiting phenomenon.Supported by MRC of Canada grant MT-3140 awarded to P.G.MRC fellow and FRSQ scholarMRC fellow     

The influence of high-frequency stimulation of the midbrain reticular formation on the interaction of neurons of the neocortex

The influence of the stimulation of the midbrain reticular formation (NRT) at a frequency of 75–100 Hz, current strength 33–400 A, on the interaction of neurons of the visual and sensorimotor areas of the neocortex of rabbits was investigated. Cross- and autocorrelation histograms of the impulse sequences were plotted. Stimulation of the NRT led to an increase in the number of pairs of neurons functioning in correlation and an increase in the probability of discharges of neurons one after the other with delays from 100 to 400 msec as compared with resting wakefulness. The mechanisms of the interaction of the cells were not altered in the process. Comparison with previously obtained data made it possible to conclude that activation of the NRT may lead to specific changes in the interaction of neurons which are observable during pseudoconditioning and at the beginning of the development of a conditioned reflex.Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol.41, No.6, pp.1177–1185, November–December, 1991.     

Dynamics of vestibular neurons during rotational motion in alert rhesus monkeys

The temporal processing in the encoding of head rotation was investigated by comparing the dynamics of vestibular nuclei neurons with those of the regularly and irregularly firing semicircular canal afferents in alert rhesus monkeys. During earth-vertical axis rotations, neurons without eye movement sensitivity differed in their response dynamics from both regularly and irregularly firing semicircular canal afferents. At high frequencies, central responses increased in sensitivity and maintained phase leads of nearly 30° relative to head velocity. These persistent high-frequency phase leads resembled those of irregularly firing (but not regularly firing) semicircular canal afferents. However, at low frequencies, central responses exhibited significantly smaller phase leads than those of irregularly firing semicircular canal afferents, and dynamics resembled more those of the regularly firing afferents. The response dynamics of central non-eye movement cells were significantly different from those of position-vestibular-pause and eye-head neurons (collectively referred to as eye movement cells). In contrast to the persistent phase leads of non-eye movement neurons, all eye movement cells modulated closely in phase with head velocity at all frequencies down to 0.05 Hz during visual suppression tasks. Vertical canal non-eye movement neurons that were insensitive to both translations and static head tilts led head velocity by approximately 5–30° during high-frequency earth-horizontal axis rotations. Unlike the earth-vertical axis responses that led head velocity at low frequencies by as much as 20–40°, vertical canal neurons only slightly led or even lagged behind head velocity during low-frequency earth-horizontal axis rotations. Posterior canal central non-eye movement cells lagged behind head velocity significantly more than anterior canal neurons. These frequency dependencies of central vestibular neurons in comparison with those of the afferents suggest that both low- and high-pass filtering might be necessary to convert primary semicircular canal afferent response dynamics to central neuron ones.     

EEG Correlates of Action Observation in Humans

To investigate electrophysiological correlates of action observation electroencephalogram (EEG) was recorded while participants observed repetitive biological (human) or non-biological movements (at a rate of 2 Hz). Steady-state evoked potentials were analyzed and their neural sources were investigated using low resolution electromagnetic tomography analysis (LORETA). Results revealed significantly higher activation in the primary motor and premotor cortex, supplementary motor area as well as the posterior parietal cortices during observation of biological movements, supporting mirror properties of cortical motor neurons. In addition interregional communication was analyzed. Increased coherence for distributed networks at delta (0.5–4 Hz) and lower alpha (8–10 Hz) frequencies were obtained suggesting integration and functional coupling between the activated cortical regions during human action observation.     

Whole cell recordings from respiratory neurons in the medulla of brainstem-spinal cord preparations isolated from newborn rats

In brainstem-spinal cord preparations isolated from newborn rats, a whole cell recording technique was applied to record membrane potentials of inspiratory (Insp) and pre-inspiratory (Pre-I) neurons in the ventrolateral medulla. Labelling of these respiratory neurons with Lucifer Yellow allowed analysis of their locations and morphology. Intracellular membrane potentials from 25 Insp neurons were recorded. Average resting membrane potential was –49 mV (n=25) and input resistance was 306 M. Insp neurons were classified into three types from the patterns of synaptic potentials. Type I neurons (n=11) had a high probability of excitatory postsynaptic potentials (EPSPs) in the pre- and post-inspiratory phases. Type II neurons (n=7) showed abrupt transition to the burst phase from the resting potential level without increased EPSPs in the preinspiratory phase. Type III neurons (n=7) were hyperpolarized by inhibitory postsynaptic potentials (IPSPs) in the pre- and post-inspiratory phases. These Insp neurons, located in the ventrolateral medulla 80–490m from the ventral surface, were 10–30 m in diameter, and had various soma shapes (pyramidal, spherical or fusiform). Intracellular membrane potentials from 24 Pre-I neurons were recorded. The average resting membrane potential was –45 mV (n=24), and the input resistance was 320 M. Typical Pre-I neurons showed fairly great depolarization accompanied by action potentials during their burst phase and repolarization during the inspiratory phase. Most Pre-I neurons appeared to have a high level of synaptic activity. These cells were located in the ventrolateral medulla 50–440 m below the ventral surface and had pyramidal or fusiform somas of 10–25 m in diameter. Stimulation of the ipsilateral IXth, Xth roots or the spinal cord (C3 level) induced orthodromic responses in most Insp or Pre-I neurons. An antidromic action potential was induced in only one Pre-I neuron by stimulation at the ipsilateral C3 level. Many Insp or Pre-I neurons had dendrites that terminated close to the ventral surface of the medulla. The present study revealed postsynaptic activity of respiratory neurons in the rostral ventrolateral medulla, which is consistent with the excitatory and inhibitory synaptic connections from Pre-I neurons to Insp neurons, and inhibitory synaptic connections for Insp neurons to Pre-I neurons.     

EEG phase synchronization in patients with paranoid schizophrenia

Recent findings suggest that specific deficits in neural synchrony and binding may underlie cognitive disturbances in schizophrenia and that key aspects of schizophrenia pathology involve discoordination and disconnection of distributed processes in multiple cortical areas associated with cognitive deficits. In the present study we aimed to investigate the underlying cortical mechanism of disturbed frontal-temporal-central-parietal connectivity in schizophrenia by examination of the synchronization patterns using wavelet phase synchronization index and coherence between all defined couples of 8 EEG signals recorded at different cortical sites in its relationship to positive and negative symptoms of schizophrenia. 31 adult schizophrenic outpatients with diagnosis of paranoid schizophrenia (mean age 27.4) were assessed in the study. The obtained results present the first quantitative evidence indicating direct relationship between wavelet phase synchronization and coherence in pairs of EEG signals recorded from frontal, temporal, central and parietal brain areas and positive and negative symptoms of schizophrenia. The performed analysis demonstrates that the level of phase synchronization and coherence in some pairs of EEG signals is inversely related to positive symptoms, negative symptoms and general psychopathology in temporal scales (frequency ranges) given by wavelet frequencies (WFs) equal to or higher than 7.56 Hz, and positively related to negative symptoms in wavelet frequencies equal to or lower than 5.35 Hz. This finding suggests that higher and lower frequencies may play a specific role in binding and connectivity and may be related to decreased or increased synchrony with specific manifestation in cognitive deficits of schizophrenia.     

Reaction of neurons of arcuate region of hypothalamus to microiontophoretic application of serotonin at different stages of the estrous cycle in rats

Sensitivity to serotonin was investigated in single neurons of the arcuate region of the hypothalamus as the center of tonic regulation of gonadotropic function in conditions of its microiontophoretic application in different stages of the estrous cycle in rats. It was shown that at the diestrus-II stage of the estrous cycle, especially during morning hours, cells predominate among neurons of the arcuate region with activated reaction to serotonin. During proestrus increased representation of cells with inhibited reaction is noted among spontaneously functioning neurons, which is especially pronounced during evening hours of this stage of the cycle. Serotonin induced reduction in the level of luteinizing hormone in blood and this effect was usually combined with an activating effect of indolamine on functioning of neurons. The combination of a delayed effect of the neurotransmitter on spontaneous activity of neurons of the arcuate nucleus with a reduced level of luteinizing hormone in blood was noted in the overwhelming majority of cases only at the proestrus stage.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 69, No. 7, pp. 881–886, July, 1983.     

Electroencephalographic spectral asymmetry index for detection of depression

This study is aimed to compare sensitivity of different electroencephalographic (EEG) indicators for detection of depression. The novel EEG spectral asymmetry index (SASI) was introduced based on balance between the powers of two special EEG frequency bands selected lower and higher of the EEG spectrum maximum and excluding the central frequency from the calculations. The efficiency of the SASI was compared to the traditional EEG inter-hemispheric asymmetry and coherence methods. EEG recordings were carried out on groups of depressive and healthy subjects of 18 female volunteers each. The resting eight-channel EEG was recorded during 30 min. The SASI calculated in an arbitrary EEG channel differentiated clearly between the depressive and healthy group (p < 0.005). Correlation between SASI and Hamilton Depression Rating Scale score was 0.7. The EEG inter-hemispheric asymmetry and coherence revealed some trends, but no significant differences between the groups of healthy controls and patients with depressive disorder.     

Spatial Synchronization of Cortical Electrical Activity at Different Stages of a Visual Set in 8-Year-Old Children with Different Levels of Development of the Frontothalamic Selective Attention System

Children of early school age (8.0 ± 0.1 years) were separated on the basis of EEG characteristics into the following groups: 1) those with normal development of the frontothalamic selective attention system (n = 21) and 2) those with functional immaturity of the frontothalamic system due to delays in its development (n = 29). The Uznadze paradigm was used to form a set to nonverbal visual stimuli (circles of different sizes). The set was rigid in most group 2 children. The coherence of cortical electrical potentials in the theta, alpha, and beta ranges recorded from the frontal, central, temporal, parietal, and occipital areas was analyzed. Intergroup differences were most marked at the set actualization stage in children with plastic sets: the coherence of potentials between the anterior and posterior zones was significantly more marked in subjects with immature frontothalamic systems than in the “normal” group. The relationship between the level of coherence of potentials with set plasticity was more defined in the “frontothalamic” group than in the control group. Rigid sets were associated with significantly lower levels of coherence of potentials in all ranges as compared with the baseline EEG with the eyes open. The increase in the coherence of theta potentials on set actualization occurring mainly in the right hemisphere in the “frontothalamic” group was interpreted as a measure of the compensatory increase in the role of the corticohippocampal system to support set plasticity.     

Cerebellar unit responses to repetitive stimulation of somatic nerves

Unit responses to stimulation of somatic nerves at 5–10/sec were recorded in the paramedian lobe of the cerebellum of unanesthetized cats. The results confirmed the model of afferent and interneuronal connections in the cerebellar cortex suggested previously. Three types of granule cells are distinguished. Fibers of the fast-conducting spino (cuneo)-cerebellar tracts, whose neurons transmit high frequencies of impulses, terminate on type I cells. Reticulo-cerebellar fibers, whose neurons cannot transmit frequencies higher than 4–5 stimuli/sec, terminate on type II cells. Type I granule cells excite all the other neurons in the cerebellar cortex. Responses of Purkinje cells, neurons of the molecular layer, and Golgi cells which they evoke are reproduced during repetitive nerve stimulation. Type II cells activate only Golgi cells. This component of the response is absent during repetitive stimulation.     

Discharge patterns in the cochlear nucleus of the chinchilla following noise induced asymptotic threshold shift

Summary Chinchillas were exposed to an 86 dB SPL octave band of noise centered at 4.0 kHz for 3.5–5 days. The noise elevated the hearing thresholds between 4.0 and 16.0 kHz to between 60 and 75 dB SPL. Measurements from single neurons in the cochlear nucleus revealed abnormalities in the response properties of neurons with characteristic frequencies (CF) above 2.0 kHz. Units above 2.0 kHz had elevated thresholds (between 50 and 90 dB SPL) and broad tuning curves due to a greater loss in sensitivity near CF than at lower frequencies. The tuning curve Q₁₀dB values for high frequency neurons were generally less than 3.0 and approached the Q₁₀dB values for basilar membrane displacement. Spontaneous activity rates in units above 2.0 kHz were also low. In a few units, the threshold for single tone inhibition was significantly lower than that for excitation; the best inhibitory frequencies were always below 2.0 kHz. Two-tone inhibition was present in both low and high threshold neurons, but its strength was not assessed. Cochleagrams obtained 12 hours postexposure revealed discrete hair cell lesions in the basal third of the cochlea. The locations of the lesions were consistent with the frequencies of maximum hearing loss. The behavioral thresholds and the thresholds at CF of the most sensitive units were within 10–15 dB of each other. The results indicate that intense sounds reduce the sensitivity, frequency selectivity and spontaneous activity of units in the cochlear nucleus. The findings are similar to those obtained in auditory nerve fibers with ototoxic drugs and hypoxia.     

Developmental changes in brain connectivity assessed using the sleep EEG

Adolescence represents a time of significant cortical restructuring. Current theories posit that during this period connections between frequently utilized neural networks are strengthened while underutilized synaptic connections are discarded. The aim of the present study was to examine the developmental evolution of connectivity between brain regions using the sleep EEG. All-night sleep EEG recordings in two longitudinal cohorts (children and teens) followed at 1.5–3 year intervals and one cross-sectional cohort (adults) were analyzed. The children and teen cohorts were 9/10 and 15/16 years at the initial assessment; ages of the adults were 20 to 23 years. Intrahemispheric, interhemispheric, and diagonal coherence was measured between all six possible pairings of two central (C3/A2 and C4/A1) and two occipital (O2/A1 and O1/A2) derivations during slow wave, stage 2, and, REM sleep. Within-subjects analyses were performed for the children and teen cohorts, and a linear regression analysis was performed across every assessment of all cohorts. Within-subject analyses revealed a maturational increase in coherence for both age cohorts, though the frequencies, sleep states, and regions differed between cohorts. Regression analysis across all age cohorts showed an overall linear increase in left and right intrahemispheric coherence for all sleep states across frequencies. Furthermore, coherence between diagonal electrode pairs also increased in a linear manner for stage 2 and REM sleep. No age-related trend was found in interhemispheric coherence. Our results indicate that sleep EEG coherence increases with age and that these increases are confined to specific brain regions. This analysis highlights the utility of the sleep EEG to measure developmental changes in brain maturation.