Alpha wave phase and alpha attenuation

In Search of a Safe Natural Sleep Aid

Sleep deprivation is associated with an elevated risk of various diseases and leads to a poor quality of life and negative socioeconomic consequences. Sleep inducers such as drugs and herbal medicines may often lead to dependence and other side effects. L-Theanine (γ-glutamylethylamide), an amino acid naturally found abundant in tea leaves, has anxiolytic effects via the induction of α brain waves without additive and other side effects associated with conventional sleep inducers. Anxiolysis is required for the initiation of high-quality sleep. In this study, we review the mechanism(s), safety, and efficacy of L-theanine. Collectively, sleep studies based on an actigraph, the obstructive sleep apnea (OSA) sleep inventory questionnaire, wakeup after sleep onset (WASO) and automatic nervous system (ANS) assessment, sympathetic and parasympathetic nerve activities, and a pediatric sleep questionnaire (PSQ) suggest that the administration of 200 mg of L-theanine before bed may support improved sleep quality not by sedation but through anxiolysis. Because L-theanine does not induce daytime drowsiness, it may be useful at any time of the day. The no observable adverse effect level (NOAEL) for the oral administration of L-theanine was determined to be above 2000 mg/kg bw/day. KEY TEACHING POINTS: Sleep deprivation-associated morbidity is an increasing public health concern posing a substantial socioeconomic burden. Chronic sleep disorders may seriously affect quality of life and may be etiological factors in a number of chronic diseases such as depression, obesity, diabetes, and cardiovascular diseases. Most sleep inducers are sedatives and are often associated with addiction and other side effects. L-Theanine promotes relaxation without drowsiness. Unlike conventional sleep inducers, L-theanine is not a sedative but promotes good quality of sleep through anxiolysis. This review suggests that L-theanine is a safe natural sleep aid.

The sniff as a unit of olfactory processing

Sniffing is a rhythmic motor process essential for the acquisition of olfactory information. Recent behavioral experiments show that using a single sniff rats can accurately discriminate between very similar odors and fail to improve their accuracy by taking multiple sniffs. This implies that each sniff has the potential to provide a complete snapshot of the local olfactory environment. The discrete and intermittent nature of sniffing has implications beyond the physical process of odor capture as it strongly shapes the flow of information into the olfactory system. We review electrophysiological studies-primarily from anesthetized rodents-demonstrating that olfactory neural responses are coupled to respiration. Hence, the "sniff cycle" might play a role in odor coding, by allowing the timing of spikes with respect to the phase of the respiration cycle to encode information about odor identity or concentration. We also discuss behavioral and physiological results indicating that sniffing can be dynamically coordinated with other rhythmic behaviors, such as whisking, as well as with rhythmic neural activity, such as hippocampal theta oscillations. Thus, the sniff cycle might also facilitate the coordination of the olfactory system with other brain areas. These converging lines of empirical data support the notion that each sniff is a unit of olfactory processing relevant for both neural coding and inter-areal coordination. Further electrophysiological recordings in behaving animals will be necessary to assess these proposals.

Dynamic shifts in the parameters of the traditional frequency range of the EEG during learning in dogs

The parameters of the electrical activity of various regions of the neocortex (NC) and the olfactory bulbs (OB) of dogs were studied by means of correlation-spectral analysis during the development of a food-dispenser paw pedal-pressing motor skill; a wide band of frequencies (1-100 Hz), which included both the traditional range (1-20 Hz) as well as high frequencies (HF), were used. Differences were demonstrated in the dynamics of the parameters in the NC and OB. The energy level of the potentials of the NC increased in the HF range (beta 3 and gamma), while in the OB it increased in the HF and alpha range. The coherence-phase characteristics of the NC potentials suggest that more stable (by comparison with resting wakefulness) temporal relationships between the oscillations not only within the limits of HF, but also in the alpha band, are formed in the presence of the developed skill. At the same time, greater phase shifts are characteristic for the interrelationships of the OB potentials and those of the NC, and the increase in coherence relates only to the HF range, whereas the oscillations of the traditional range are characterized by a decrease in coherence. The possible role of the alpha range (along with the HF) in the processing of information which supports appropriate behavior is stressed.

Relations between slow (4 cps) EEG activity, sensorimotor speed, and psychopathology

Slow rhythmic activity (SRA) in the frequency range from 2.5 to 5.0 cps was studied in 20 subjects (Ss) in order to examine its effect upon sensorimotor reactions and its possible relationship to psychological findings. With monopolar EEG derivations, maximal power density of SRA is found in frontal regions, whereas bipolar leads reveal maximum occurrence of SRA over posterior areas. Reaction times (RT) to visual and auditory stimuli increase significantly during the occurrence of SRA; the amount of this prolongation (ca. 74 ms) is independent of stimulus modality but significantly correlates with SRA frequency: the lower the frequency, the higher the RT increment. In psychological tests, most Ss with SRA displayed disturbances of emotionality as well as 'pathological' values in the subscales hysteria, hypochondria, psychasthenia, and paranoia, but none of our Ss was diagnosed as psychotic. There is a high correlation between the SRA frequency and the extent of psychological deviations: Ss with low SRA frequency values are more likely to reveal psychological disturbances than Ss with high SRA frequency. The possible origin and physiological impact of SRA is discussed and the desirability of further neurophysiological studies is emphasized.

Monosynaptic spinal reflexes elicited at various phases of the EEG alpha cycle

Relationships between the phase of EEG alpha waves and motor activities have been reported in the literature. In this study such a relation was investigated for electrically or mechanically evoked monosynaptic reflexes in the soleus muscle of normal humans. EEG alpha activity, derived from electrodes widespread over the ipsilateral and contralateral hemispheres, was tested but no relationships between alpha phase and reflex amplitudes were found.

Changes in amplitude of the EEG induced by a photic stimulus

Occipital EEG responses to a single photic flash were studied by using a complex demodulation technique. Individual EEGs were first digitally filtered by making use of the Ormsby band-pass filter. Envelopes of the alpha (8-12 c/sec) and of the low frequency (3-7 c/sec) activities were obtained in terms of the demodulation calculation. Both individual and averaged data of raw, filtered, and demodulated EEGs were utilized for the present study. Two typical kinds of EEG responses were observed. One showed clearly the blocking as well as the enhancement of the alpha activity. The alpha activity first exhibited a reduction in amplitude in the range 50-200 msec after the stimulus (the minimum amplitude at about 150 msec). Then an evocation, rather than merely a recovery, of the alpha was observed in the range 500-800 msec (maximum amplitude at about 650 msec). The other typical example showed the low frequency evoked potential prominently. This response appeared almost locked to the stimulus and showed roughly a bi-phasic pattern in the time range where the alpha blocking took place (30-200 msec). Phases of the evoked low frequency component were almost locked to the stimulus but no distinct phase coherence was observed for the enhanced alpha wavetrains. Detection by demodulation of the phase change of the alpha was critical for a single EEG. It is pointed out that changes of the alpha must be studied on individual EEGs.