It is ironic that the prototype of the oscilloscope--for that is what Hertz's apparatus amounted to--should be instrumental in demonstrating that cathode rays have no closer relation to electricity than has light produced by an electric lamp. Indeed, Hertz argued that since "cathode rays are electrically indifferent,... the phenomenon most nearly allied to them is light.".

It follows from the temporal nature of mind—the main concern of this essay—that mind functions are not localized in brain space.“ Time is extendedness, probably of the mind itself”, concludes Saint Augustine in Book XI of his Confessions (26.33), and, in our days, this extendedness can be made visible through an oscilloscopic “line” or trace of slow potentials. These graded, additive (not all-or-none) autorhythmic and seemingly self-generating potentials are primary events recorded at synapses. Autorhythmic brain structures (Zabara, 1973) appear to (...) be the source of time frames, while a change in time frames (as reflected in the EEG) leads to synchronization and desynchronization of brain structures respectively. Synchronization forms a homogeneous time domain, such as obtained during rhythmic exercises, chanting, listening to music and mental processes that are the hallmark of religious practices (Rogers, 1973). Desynchronization of brain structures on the other hand marks a functional independence of neuronal elements with each element available for separate channels of data processing, for example, during hallucinogenic drug-induced central sympathetic arousal, that is, a waking dream state (Fischer, 1979). (shrink)

Repeatedly performing a submaximal motor task for a prolonged period of time leads to muscle fatigue comprising a central and peripheral component, which demands a gradually increasing effort. However, the brain contribution to the enhancement of effort to cope with progressing fatigue lacks a complete understanding. The intermittent motor tasks closely resemble many activities of daily living, thus remaining physiologically relevant to study fatigue. The scope of this study is therefore to investigate the EEG-based brain activation patterns in healthy subjects (...) performing IMT until self-perceived exhaustion. Fourteen participants repeated elbow flexion contractions at 40% maximum voluntary contraction by following visual cues displayed on an oscilloscope screen until subjective exhaustion. Each contraction lasted ≈5 s with a 2-s rest between trials. The force, EEG, and surface EMG data were simultaneously collected. After preprocessing, we selected a subset of trials at the beginning, middle, and end of the study session representing brain activities germane to mild, moderate, and severe fatigue conditions, respectively, to compare and contrast the changes in the EEG time-frequency characteristics across the conditions. The outcome of channel- and source-level TF analyses reveals that the theta, alpha, and beta power spectral densities vary in proportion to fatigue levels in cortical motor areas. We observed a statistically significant change in the band-specific spectral power in relation to the graded fatigue from both the steady- and post-contraction EEG data. The findings would enhance our understanding on the etiology and physiology of voluntary motor-action-related fatigue and provide pointers to counteract the perception of muscle weakness and lack of motor endurance associated with ADL. The study outcome would help rationalize why certain patients experience exacerbated fatigue while carrying out mundane tasks, evaluate how clinical conditions such as neurological disorders and cancer treatment alter neural mechanisms underlying fatigue in future studies, and develop therapeutic strategies for restoring the patients' ability to participate in ADL by mitigating the central and muscle fatigue. (shrink)