Gender differences in chemosensory perception and event-related potentials

The present study investigated chemosensory gender differences by means of ratings of total nasal chemosensory intensity, unpleasantness and sensory irritation and simultaneous recordings of chemosensory event-related potentials (CSERPs) for three concentrations of the olfactory/trigeminal stimulus pyridine in 19 women and 17 men, all young adults. Results show that, compared to men, women gave higher intensity and unpleasantness ratings, in particular for the highest stimulus concentration. The gender differences in perceived intensity are reflected in the signal-to-noise ratio of the individual CSERP averages, revealing more identifiable early components (P1, N1) in women than in men. The late positive component, labeled P2/P3, displayed larger amplitudes at all electrode sites and shorter latencies at Cz, in women compared to men. The effects of increased pyridine concentration on perception (larger in women) and CSERPs (similar across gender) imply that the two measures involve partially different neural processing. CSERP component identifiability is proposed here as a general means of assessing signal-to-noise ratio of the CSERPs.     

Sex and ear differences of brain-stem acoustic evoked potentials in a sample of normal full-term newborns. Normative study

The present paper reports a normative study of the BAEPs recorded from 80 normal full-term newborns by using a rarefaction click at 70, 60, 40, 20 dB HL.Positive, negative peaks and the relative amplitudes were measured. Means, standard deviations and 95% and 99% confidence limits were calculated for each component, for positive and negative IPLs and amplitude ratios. A normality test distribution showed that each component had normal distribution except for wave PIII at 70 dB and at 60 dB HL beacause of its index of kurtosis and for IPLs PII-PIII and NII-NIII at 70 and 60 dB HL. MLRA was performed and significant statistical differences were found for sex, ears and intensities. Females had the latencies of waves PIII, PIV, PV, NII and NIV shorter than males. The BAEPs obtained from the left ear had shorter latencies for positive and negative peaks. Latencies, amplitude and morphology of the BAEPs vary with variations of the intensity. The IPLs PII-PV, PIII-PV and PIV-PV were not affected by changes of intensity.     

Personality-related differences in recognition of facial emotional expression and cortical evoked potentials

A correlation between some characteristics of the visual evoked potentials and individual personality traits (by the Kettell scale) was revealed in 40 healthy subjects when they recognized facial expressions of anger and fear. As compared to emotionally stable subjects, emotionally unstable subjects had shorter latencies of evoked potentials and suppressed late negativity in the occipital and temporal areas. In contrast, amplitude of these waves in the frontal areas was increased. In emotionally stable group of subjects differences in the evoked potentials related to emotional expressions were evident throughout the whole signal processing beginning from the early sensory stage (P1 wave). In emotionally unstable group differences in the evoked potentials related to recognized emotional expressions developed later. Sensitivity of the evoked potentials to emotional salience of faces was also more pronounced in the emotionally stable group. The involvement of the frontal cortex, amygdala, and the anterior cingulate cortex in the development of individual features of recognition of facial expressions of anger and fear is discussed.     

Spatio-temporal source modeling of evoked potentials to acoustic and cochlear implant stimulation

Spatio-temporal source modeling (STSM) of event-related potentials was used to estimate the loci and characteristics of cortical activity evoked by acoustic stimulation in normal hearing subjects and by electrical stimulation in cochlear implant (CI) subjects. In both groups of subjects, source solutions obtained for the N₁/P₂ complex were located in the superior half of the temporal lobe in the head model. Results indicate that it may be possible to determine whether stimulation of different implant channels activates different regions of cochleotopically organized auditory cortex. Auditory system activation can be assessed further by examining the characteristics of the source wave forms. For example, subjects whose cochlear implants provided auditory sensations and normal hearing subjects had similar source activity. In contrast, a subject in whom implant activation evoked eyelid movements exhibited different source wave forms. STSM analysis may provide an electrophysiological technique for guiding rehabilitation programs based on the capabilities of the individual implant user and for disentangling the complex response patterns to electrical stimulation of the brain.     

A simple method for the evaluation of differences in averaged evoked potentials as demonstrated of visual evoked potentials changed through hippocampal stimulation]

A simple method is presented which by subtraction of amplitudes of averaged evoked potentials (AEP) within regular time-intervals enables us to estimate differences in the course of the potential. First results demonstrate that all parts of the potential may be influenced and that most striking differences must not necessarily occur in the peak region of the AEP. The late negative complex of the AEP is likely to be a result of summation of some subcomponents, which may be altered differently. The method presented allows exact measurements of each of them.     

Gender differences in source location for the N100 auditory evoked magnetic field

Auditory evoked magnetic fields were recorded in response to contralateral stimulation over the right hemisphere in 6 adult males and 6 adult females. The data were fit to a model of a current-dipole source in a homogeneous sphere and 5 parameters of the dipole were computed — 3 spatial coordinates, orientation, and strength. When average values for the dipole parameters were compared between sexes, it was found that the current source for the N100_m is located more than 1 cm posterior in females and is oriented pointing more downward. These findings were replicated in separate measurements sessions. Viewing of individual magnetic resonance images did not reveal a corresponding anatomical disparity in the location of the primary auditory cortex which is assumed to produce the N100_m. Therefore, functional organization of the auditory cortex may be different for the sexes.     

Human brain evoked potentials and discrimination of short acoustic stimuli with various frequency

We found that the mismatch negativity (MMM) was absent in evoked potentials in passive condition for frequency deviant acoustical stimuli when stimulus duration was only 11-30 ms. But it was shown that it is possible for participants to fairly well discriminate these stimuli and the component N2b in RP was generated without preceding MMN. Processing negativity also was absent in potentials by the minimal stimulus duration (11 ms). Auditory discrimination nevertheless was still possible, but reaction time and number of committed errors increased significantly.     

Analysis of variance delimitation of factors influencing studies of acoustic evoked potentials]

The effect of the variables "stimulus intensity", "residual effect of previous stimulus intensity", "period effect" and "subject effect" on the amplitudes and on the peak latencies of the N1 and P1 components of the acoustical EEG evoked potentials was studied in human subjects with the use of an orthogonal experimental design. The stimulus intensity (30, 50 and 80 dB) accounts for the greatest part of the total variance of the amplitudes and of the peak latencies of N1.-The existence of a totalvariance component due to differences between the subjects is also statistically significant (P equals 5%), As far as the period effect (habituation effect) is concerned, only its effect on the amplitude of N1 - P2 is statistically significant. - The residual effect of the stimulus intensity used in the previous series was not significant.