An inexpensive circuit for beta,alpha, theta,or delta EEG biofeedback

An inexpensive circuit is described for EEG biofeedback or measurement. The circuit is designed to interface easily with most basic EEG machines. It taps the output from a single recording channel of the basic EEG instrument and provides the following for each EEG band (beta, alpha, theta, and delta): (a) very selective bandpass discrimination, (b) variable center frequency, (c) variable threshold at which feedback will be provided, or the measurement made, and (d) use with any biofeedback stimulus or measurement device that one wishes to switch contingent with S’s EEG rhythms.     

Inter-digital variability in the palmer sweat indices of adult stutterers

This study examined the relationship of mean palmar sweat density of all fingers of each hand, thumbs excluded, to asymetrical interdigital sweat variability in adult stutterers. In addition, the relationship of mean print density to part word repetitions and prolongations was investigated.

A modification of the palmar sweat printer developed by Brutten (1957) enabling the accommodation of eight fingers, was employed to obtain simultaneous PSI under identical controlled conditions for all fingers.

Results indicated that the eight fingers are not reliable areas for the determination of palmar sweating in adult stutterers. Consequently, the PSI as it is currently employed, as well as the method used in the present study, does not appear to be an acceptable objective measure of ANS arousal in adult stutterers.     

The effect of warning interval on the electric phosphene and auditory thresholds

Using different warning signals and threshold stimuli, the thresholds, as determined by a method of limits, were found to rise monotonically as the interval between warning signal and threshold stimulus increased from I to 9 sec. It was found that the variability of the threshold did not increase as the threshold increased. Similar results were obtained for phosphene and auditory thresholds and with visual and auditory warnings; therefore the effect was considered to be central. Motokawa's finding of a minimum in the phosphene threshold 2 sec. after a flash of white light was not repeated. The rise in threshold was not obtained when the warning intervals were randomized and so seemed to depend on the use of fixed warning intervals. A model was developed relating threshold level to accuracy of anticipation of the end of the warning interval.