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The article focuses on the author's findings on an experiment done to obtain differences in evoked potentials which are related to differences in psychological events. The author has realized that the sense of strangeness and awe that follows discovery of a new symbolic code is not diminished by even a sophisticated appreciation of the arbitrary nature of all codes. Furthermore, he has also indicated that there is a positive-going process which is present when an event occurs about which the subject is uncertain, but which is absent when the identical event occurs in the context of certainty.

Rods and cones in Necturus respond with graded hyperpolarization to test flashes spanning about 3.5 log units of intensity. Steady background levels hyperpolarize the rods, and the rod responses become progressively smaller as background level is increased. In cones, higher background levels reduce the effectiveness of test flashes, so higher ranges of test intensities are required to elicit the full range of graded responses. When backgrounds are terminated, cones return rapidly, but rods return slowly to the dark potential level. The effects of backgrounds on both rods and cones can be observed at intensities that cause negligible bleaching as determined by retinal densitometry. During dark adaptation, changes are observed in the rods and cones that are similar to those produced by backgrounds. Receptor sensitivities, derived from these results, show that rods saturate, cones obey Weber's law, and sensitization during dark adaptation follows a two-phase time-course.

Test stimuli, presented at the center of the bipolar cell receptive field, spanning less than 2 log units of intensity, elicit the full range of graded response. The intensity range of test stimuli that elicits the graded response depends upon the background conditions. A higher range of log test intensities is required to elicit the graded bipolar response in the presence of surround backgrounds. But surround backgrounds can also serve to unsaturate the bipolar response and thereby increase sensitivity under certain conditions. The results suggest that a second stage of sensitivity-control is mediated by the horizontal cell system at the outer plexiform layer, concatenated with the effects of adaptation in the photoreceptors.

ALL OF TIIE vmth NERVE FIBERS originatingin the coch lea terminate in the cochlear nucleus,the first central station of the auditorypathway. Extracellular recordings fromunits in this nucleus have shown a diversityof both spontaneous and tone-evoked activitiescompared to activity in Vlllth nervefibers. Tone-evoked inhibition of spontaneousactivity occurs with certainty in thecochlear nucleus (8, 9, 12), but has not beensecurely demonstrated in VIIlth nerve (5,9, 10, 18, 22), and response patterns tosteady tones are quite varied in cochlearnucleus (15), whereas a single response patterncharacterizes VIII th nerve fibers (I 0).The synaptic events in cochlear nucleusthat accompany acoustic stimulation haveonly recently begun to be explored (4, 6).The present study utilizes intracellular recordingsand stimulating techniques in thecochlear nucleus to further delineate thesynaptic basis for central processing of auditorysignals.

THE ACCESSORY, or medial nucleus of thesuperior olivary complex is the first nucleusin the classical ascending auditory pathwaythat receives bilateral input. Both the anatomicalstructure and electrophysiologicalresponses of the accessory nucleus suggest thatit is a locus of binaural signal processing. Thecells of the accessory nucleus have been shownto be responsive to interaural time and intensitydisparities of binaurally presented clicks(5, 6) and to the interaural phase relations ofbinaurally presented tones (11). The fieldpotentials of the accessory nucleus evoked byclick and pure-tone stimuli have been correlatedwith the anatomical distribution ofsynaptic input from the two ears (3, 5, 17).Evidence of binaural interaction in the slowwaveresponses of the superior olivary complexto binaurally presented clicks was foundby Rosenzweig and Amon (13). In the presentstudy the field potentials of the superiorolivary complex evoked by binaurally presentedpure tones were analyzed to definefurther the mechanisms of binaural interaction.

THE OLIVOCOCHLEAR BUNDLE (OCB) is knownto modify afferent auditory input at thecochlea. Electrical stimulation of the bundlein the floor of the IVth ventricle causes a suppressionof neural response to clicks recordedat the cochlea (lo), and a paradoxical enhancementof microphonics (8). Fex (8) and,more recently, Wiederhold (23) have shownthat both spontaneous and tone-evoked activitiesof single units in the VIIIth nerve aresimilarly suppressed during such OCB stim-/ Jwhile the carotid arteries were ligated, a trephineulation. The purpose of the present study wasto investigate the effects of OCB stimulationon spontaneous and tone-evoked activities ofsingle units in cochlear nucleus, the first centralauditory station receiving cochlear input.Rasmussen’s finding that OCB collateralsterminate in cochlear nucleus (1 S), raises thepossibility that this efferent system may havea central regulatory role as well. Our resultsindicate that OCB stimulation can modifycochlear nucleus units in a variety of ways.Al though suppression of spontaneous activitywas frequently observed, there were manyunits in which OCB stimulation affected anincrease in spontaneous discharge rates.Furthermore, the effects of OCB stimulationon tone-evoked responses were found to vary with tone intensity in complex ways.

The hypothesis that discharges from afferent nerves from muscle stretch receptors do not participate in kinesthesis has been substantiated by test of discrimination thresholds. In awake, unrestrained cats, nerve stimulation activating group I and most group II sensory fibers (from muscle spindles and Golgi tendon organs) in pure muscular nerves failed to evoke sensory discrimination. Cutaneous nerve stimulation in the same animals produced sensory discrimination even below intensities required to elicit detectable nerve thresholds.

A PERIOD OF SENSORY STIMULATION may alter the perception of subsequentsensory events. After sounds, for example, there may be changes in threshold(19), in the quality of acoustic sensation (20, 29), or tinnitus (20). Theneurophysiological mechanisms underlying these alterations in sensation arenot well understood. Working with cats, Starr and Livingston (30) describeda profound and reversible suppression of summated spontaneous activity insubcortical stations of the auditory pathway as an aftereffect of sustainedsound exposure. The period of altered spontaneous activity lengthened asthe intensity or duration of the sound was increased. The experiments onsingle units in cochlear nucleus presented in this report were undertaken todefine more precisely the relationship between the physical parameters ofthe sound stimulus and the period of altered spontaneous activity.

A method is described for analyzing skin impedance data and applied to the determination of a steady-state electrical model for intact human skin. An algorithm is presented for the analytical procedure, Bode analysis, and a sample impedance function is obtained. Bode plots are employed to synthesize a passive equivalent circuit from sample measurements of "black box" skin impedance magnitude and phase angle, and representative values for the circuit elements are presented. [ABSTRACT FROM AUTHOR]

Prevalence of the cephalic skin potential (CSP) artifact was studied in 21 Ss during EEG recording of the Contingent Negative Variation (CNV), averaged evoked response (AER), and verbal free association test. Skin potential response and electro-oculogram (EOG) were also recorded. Subdermal pin electrodes and local anesthesia infusion were employed to eliminate the CSP artifact in the EEG. Results indicated that EEG recorded from subdermal pin electrodes or from locally anesthetized scalp was free of CSP artifact. The EEG recorded from subdermal pin electrodes demonstrated spontaneous potential shifts but appeared adequate for EEG recording of the CNV or the AER. Significant CSP artifact was demonstrated in the EEG of 10 of 21 Ss, both evoked by stimuli (10 Ss) and spontaneous (3 Ss). CSP artifact significantly increased CNV amplitude. CSP artifact significantly increased the AER late positive wave (P3) to infrequent tones. Studies of CNV and AER can be confounded by CSP artifact. Above techniques appear promising for recording EEG free of CSP artifact. [ABSTRACT FROM AUTHOR]

Two evoked potential tests of augmenting-reducing, using flash and sine wave modulated light stimuli, were administered to 23 normal Ss to determine: a) generalizability between tests; b) short-term reliability; c) influence of electrooculographic (EOG) activity; d) relationships between perceptual discrimination of stimuli and evoked response measurements; e) correlation between evoked responses, extraversion and neuroticism (Eysenck Personality Inventory). Four months later 11 Ss were retested before and after pilocarpine fixation of the pupil in miosis, to assess long-term reliability and pupillary factors. Although mean amplitudes of sine and flash responses were significantly positively correlated, correlations between linear slope measures of their intensity-response functions were low. Both short- and long-term reliability were high for mean amplitudes, but relatively low for most slope measures. Ocular factors, as reflected in EOG and changes with pupillary miosis, appeared to exert relatively little influence on the evoked potential measures of augmenting-reducing. Subjective perceptual discrimination performance was not correlated with evoked potential measures. Extraversion was correlated with some evoked response augmenting indicators; neuroticism yielded inconsistent results. Generally, results varied with lead placement. [ABSTRACT FROM AUTHOR]

The electrophoretic patterns of skin washings from the calf, sheep, goat, pig, horse and man have been compared. It was concluded that protein in these washings was derived mainly from sweat. The amounts of protein lost and the nature of the proteins in the sweat differed markedly between species. The horse had relatively the highest protein loss during active sweating and man the lowest. The potential biological role of these sweat proteins is discussed, including the possibility that they may provide the animal with an outer defence, on the skin surface, against invasion by foreign organisms. [ABSTRACT FROM AUTHOR]

The thermodynamic formulation of isotope interaction (coupling of abundant and tracer isotope flows) has been tested in a highly permselective anion exchange membrane in the absence of significant electroosmosis. A previous study of Cl permeation has now been extended to include permeation of I, Acetate, and SO in different bath concentrations, with the use of both electrical and chemical driving forces. The flux ratios were 'abnormal' according to the usual criteria for simple passive flow, but were closely predicted by the theoretical expression incorporating the influence of isotope interaction. In the absence of coupled flows of other chemical species the extent of isotope interaction can be determined either from the flux ratio or from the measurement of a single unidirectional flux at two settings of the electrochemical potential difference. Direct evidence of negative isotope interaction was presented. [ABSTRACT FROM AUTHOR]