Stimulus sensitivity and stimulus intensity control

Phenomenological dimensions of sensory gating

Contemporary sensory gating definitions are generally tied to the perceptual and attentional phenomenology described by McGhie and Chapman, including abnormalities in the quality of sensory input, heightened awareness of background noises, and poor selective attention reported by individuals with schizophrenia. Despite these explicit phenomenological origins, little is known about the experiential phenomena underlying contemporary operationalizations of the sensory gating construct, such as whether the construct is restricted to experiences associated with the modulation of sensory percepts includes selective attention and distractibility or even whether the construct is accessible via self-report. Because clarification of these issues has important implications for the development and testing of psychological theories and the study of psychopathology, a series of studies was conducted to (a) empirically identify the major dimensions of sensory gating-like perceptual and attentional phenomenology in healthy young adults and (b) develop a psychometrically sound self-report rating scale to capture these dimensions, the Sensory Gating Inventory (SGI). Factor analyses of Likert items measuring a broad range of sensory gating-like subjective experiences revealed 1 primary factor that encompassed anomalies of perceptual modulation (eg, perceptions of heightened stimulus sensitivity and sensory inundation) and 3 other factors measuring disturbances in the processes of focal and radial attention as well as exacerbation of sensory gating-like anomalies by fatigue and stress. Psychometrically, the SGI demonstrated strong reliability and validity. An empirically based conceptual demarcation of the sensory gating construct is offered, and directions for future research are described.

Enhanced intensity dependence as a marker of low serotonergic neurotransmission in borderline personality disorder

Dysfunction of central serotonergic activity has been assumed in patients with borderline personality disorder (BPD) characterized by a prominent impulsive behavioral style. Following the high serotonergic innervation of the primary auditory cortex, there is increasing evidence of the intensity dependence of auditory evoked potentials (AEP), especially the N1/P2 component, indicating serotonergic neurotransmission in animals and humans. 15 females who met the IPDE-criteria for BPD and a group of comparative healthy females (controls) completed extensive personality questionnaires which gave special regard to impulsiveness. We obtained event-related AEP through the application of various loudness stimuli. We examined the relevant N1/P2 amplitude of the tangential dipole of the auditory evoked response using dipole source analysis. The augmentation of the N1/P2 amplitude of tangential dipole source activity with rising stimulus intensity was significantly pronounced in BPD as opposed to controls, accompanied by a reduction in N1 and P2 latencies. The strong loudness dependency of AEP correlated with aspects of impulsiveness. These data imply reduced inhibiting control over cortical sensory processing in BPD. Our findings contribute a further argument to the hypothesis of low serotonergic neurotransmission in BDP and may point to a trait character of impulsiveness in this personality disorder.

Augmenter vs. Reducer: Kortikale und autonome Reaktivität auf Reize unterschiedlicher Intensität

Zusammenfassung: Ziel dieser Studie war es, Unterschiede zwischen anhand der Reducer-Augmenter Skala als extrem eingestuften Augmentern (N = 19, Petrie Reducer) und Reducern in elektrokortikalen (EEG), peripher-physiologischen (EDA, EKG) und subjektiven Reaktionen (EMI) auf weißes Rauschen (65 bis 105 dB; ISI 15-25s) sowie in einer Reaktionszeitaufgabe zu prüfen. In der P1-N1-Amplitude unterschieden sich die Gruppen nicht. Entgegen der Erwartung reagierten die Reducer (Petrie Augmenter) in den N1-P2-Amplituden, der Hautleitfähigkeit und tendenziell auch der Herzrate stärker als die Augmenter. Reducer gaben an, nervöser und weniger optimistisch zu sein als die Augmenter. Die Geräusche beurteilten sie als lauter. In der Reaktionszeitaufgabe wiesen sie längere Reaktionszeiten auf als die Augmenter. Die Ergebnisse sprechen für eine generell erhöhte Reaktivität der Reducer (Petrie-Augmenter) und stehen damit in Übereinstimmung mit der ursprünglichen Konzeption von Augmenting-Reducing nach Petrie .

Modality specificity of evoked potential augmenting/reducing

Visual and auditory evoked potentials to 4 stimulus intensities in each modality were recorded from Fz, Cz, and Oz (visual) and Fz and Cz (auditory). Response amplitudes for P1-N1 and N1-P2 components were analyzed. Visual responses at Oz showed no increase in amplitude with brighter stimuli for either component. At both Fz and Cz, response amplitude increased with stimulus intensity at each lead for both modalities. For P1-N1 the slope of the stimulus/response function was similar for both modalities. However, for N1-P2 the slope was significantly higher for auditory than for visual EPs. These results are inconsistent with a view of augmenting/reducing as resulting from sensory modulation by a non-specific mechanism, such as the mesencephalic reticular formation, and instead suggest that a more selective mechanism such as regulation of sensory transmission by the prefrontal cortex may underlie this phenomenon.

Intensity dependence of auditory evoked potentials as an indicator of central serotonergic neurotransmission: a new hypothesis

Because of the increasing importance of the central serotonergic neurotransmission for pathogenetic concepts and its role as a target of pharmacotherapeutic interventions in psychiatry, reliable indicators of this system are needed. It is proposed that the stimulus intensity dependence of auditory evoked N1/P2-component, which is probably modulated by cortical serotonergic innervation, may be a useful and noninvasive indicator of behaviorally relevant aspects of serotonergic activity. Converging evidence from our own studies as well as from the literature suggests that a pronounced intensity dependence of auditory evoked N1/P2-component reflects low central serotonergic neurotransmission. Recent findings concerning general functional aspects of the brain serotonin system reveal that this system is well qualified for adjusting individual levels of sensory processing ("set the tone"), especially in the primary auditory cortex in which the N1/P2-component is mainly generated. Dipole source analysis represents an important methodological advance in this context because it allows the separation of N1/P2-subcomponents generated in the primary auditory cortex from those generated in secondary auditory areas.

Augmentation of auditory evoked potentials in somatization disorder

Sensory input regulation was examined in terms of augmenting/reducing of auditory evoked potentials in 10 patients with somatization disorder (8 males and 2 females) and 10 age- and sex-matched normal controls. The slope of P1-N1 amplitude change as a function of stimulus intensity was greater in patients compared with controls, suggesting an enhanced central nervous system response to sensory input. Taken together with previous findings of a failure to habituate to incoming stimuli in a similar group of patients, and evidence obtained in somatizers of both over-responding to background stimuli in a simple tone-discrimination task and enhanced parietal activation during selective attention, this finding suggests disturbances in the processes of attention and in the regulation of afferent stimuli in somatization disorder, and may help explain the multiple and chronic complaints characteristic of patients with the disorder.

Frontal auditory evoked potentials and augmenting-reducing

Auditory evoked potentials (AEPs) to tones (750 Hz--200 msec) ranging from 50 to 80 dB SPL were studied at Cz and Fz leads in 29 normal adults (15 males) ranging in age from 20 to 22. Peak-to-trough amplitudes were measured for the P1-N1 and the N1-P2 wave forms as well as baseline (500 msec prestimulus)-to-peak amplitudes for each component, i.e., P1, N1 and P2. Amplitudes were examined as a function of intensity and electrode location. Cz-Fz amplitude differences increased with increasing stimulus intensity, the differentiating peak being the N1 component. An overall reducing phenomenon was found at Fz in the 70-80 dB range whereas an augmenting effect was observed at Cz for these intensities. The augmenting/reducing groups defined by analysis of individual amplitude-intensity patterns were different whether we considered Fz or Cz results: Fz reducers were more numerous than Cz reducers. These results on prominent reducing at the frontal level were examined in relation to the data concerning the modulatory function of the frontal cortex on auditory EPs. Implications were drawn for the role of the frontal cortex in cortical augmenting-reducing.

A model referenced method for the identification of evoked potential component wave forms

Visual evoked potentials from rat visual cortex are described as the sum of components. Each component wave form is based on a mathematical model of neural activity. The model referenced approach yields an accurate description of the evoked potential wave forms before and after administration of an anesthetic known to alter neural activity. Thus, the method is efficient, is based in neurophysiology and is sensitive to drug effect on brain activity.

Individual differences in stimulus intensity modulation of the elderly

The validity of the postulated perceptual style-personality dimension of modulation (augmenting vs. reducing) of stimulus intensity previously studied with young adults was examined in two elderly samples. It was hypothesized that in the elderly Stimulus Intensity Modulation (SIM) relates to degree of social engagement (assessed both behaviorally and by self-report), perceived life difficulty, attitudes toward death, and three previously validated behaviors (desired and obtained amount of sleep, future planning, and smoking). The Kinesthetic Aftereffect (KAE) task was used as the measure of SIM. Results from multivariate analyses of variance indicated a significant relationship between KAE and the validity variables. Additional correlational analysis indicate that there is a linear relationship between KAE and each of the domains, except attitudes toward death. Results from both studies are consistent with the views that KAE indexes the postulated SIM dimension and that the SIM approach can be applied fruitfully to the study of individual differences in the elderly.

Tobacco smoking and cortical evoked potentials: an opposite effect on auditory and visual systems

1. Auditory and visual evoked potentials produced by five intensities of tones and light flashes were recorded in twelve young men who were habitual smokers. 2. The subjects attended the laboratory on four occasions. Two recordings were made on each of the last three of these visits. They were made (i) before and after smoking, (ii) without smoking, (iii) before and after smoking after 12 h abstinence from smoking. 3. Smoking was associated with increases in the amplitudes of the components V-VI, VI-VII in the visual system and a decrease in the amplitude of N2P2 in the auditory system. Abstinence from smoking produced effects in the opposite direction. 4. These findings are consistent with the possibility that smoking has different and perhaps opposite effects on the visual and auditory system. 5. The findings may be helpful in re-evaluating some of the apparently conflicting reports on the effects of smoking on perceptual processes.

Somatosensory evoked potentials and noxious stimulation in patients with intractable, noncancer pain syndromes

Investigations of the evoked potentials (EPs) to noxious laser stimulation have indicated consistent strong linear relationships between subjective response (R), stimulus intensity (S), and EP amplitude (A). Thirty patients with chronic intractable benign pain syndromes (CIBPS) were tested to determine whether their patterns differed from previous studies with normal volunteers. Nearly half of the CIBPS patients were found to be relatively insensitive to acute pain stimuli. A large number were also found to show negative relationships between S and A. These differences from control subjects were considered of potential importance in their implications concerning the nature of chronic pain and its differences from the acute pain process.

Stimulus intensity control in depression: a study of the comparative effect of doxepin and amitriptyline on cortical evoked potentials

The perceived intensity of a stimulus may be magnified during depression. Stimulus intensity control can be studied by means of cortical evoked potentials. In a study of 33 depressives, cortical evoked potentials were greater during depression than on recovery. The effect of doxepin on the amplitudes of evoked potentials of depressives was compared with that of amitriptyline. Doxepin reduced amplitudes. Amitriptyline had a similar, but non-significant effect.

The effect of placebo and tricyclic antidepressants on cortical evoked potentials in depressed patients

Cortical evoked potentials in depressives were recorded in order to study stimulus intensity control in this group, and also to study the effect of treatment. In a sample of 33 psychiatric patients, the amplitudes of visual and auditory evoked potentials were found to be significantly greater during depression, than at recovery. The changes which appeared to be due to recovery were found not only in patients treated with tricyclic antidepressants (n = 22), but in those who had recovered following treatment with placebo (n = 11). The changes were most evident in the auditory system. In addition, no diagnostic predictors differentiated depressed patients who subsequently recovered on placebo from those who did not. It is concluded that: (i) cortical evoked potentials may change in amplitude with emotional state; (ii) placebo may have physiological consequences usually attributed to drugs alone.

Kinesthetic augmentation and reduction in adult females

The Petrie Block Test was used to measure kinesthetic after-effect in a sample of 60 normal adult female subjects. In addition to the establishment of normative data for this sample, several procedural questions raised by other investigators were addressed. It was determined that the use of ascending trials produced more accurate baseline measures than the alternate use of ascending and descending trials. Also, order of test presentation affected baseline measures. Since a rather large proportion of this sample was comprised of stimulus-governed individuals, some factors related to their particular perceptual style were examined.

Stimulus-governance and the hyperkinetic syndrome

The hypothesis that hyperkinetic children are stimulus-governed was tested. In a sample of 39 nonmedicated hyperkinetic boys 26 were found to be stimulus-governed. In a control sample of 20 nonmedicated boys 6 were found to be stimulus-governed. An association was found between the hyperkinetic syndrome and stimulus-governance. The hypothesis is raised that response to methylphenidate is related to stimulus-governance. Several issues raised by the research are discussed.

Cortical mechanisms that augment or reduce evoked potentials in cats

The augmenting or reducing of flash-evoked potentials in paralyzed cats was significantly correlated with their previously videotaped behaviors. Augmenting reducing was due to alterations in cortical rather than subcortical responsiveness, and was duplicated by increasing cortical arousal by means of reticular stimulation while the animal was exposed to visual stimuli of constant intensity. Brainstem activation of cortical inhibition may underlie the behavioral results as well as the results obtained with the evoked potentials.

Perceived exertion and stimulus intensity modulation

Perceptual augmentation and reduction were considered contrasting styles of Stimulus Intensity Modulation. Differences in perceived exertion between augmenters and reducers were determined for three cycle ergometer work loads. Subjects were 20 males having similar physiological characteristics. Stimulus Intensity Modulation was determined by kinesthetic figural aftereffect. Augmenters rated their perceptions of physical exertion to be more intense than reducers at 450, 750 and 1050 kpm/min. Differences in physiological responses between augmenters and reducers were not significant at the three work loads. Style of Stimulus Intensity Modulation appeared differentially to influence perceived exertion at the work levels studied.

Perceptual reactance and melanic density

Following assessment of eye color, a total of 108 college students (33 males and 75 females) estimated changes in sizes of standardized blocks while blindfolded. Subjects were classfied as perceptual augmenters, moderates or reducers as a function of their overestimation, accurate estimation, or underestimation, respectively, of the sizes of the blocks. A significant interaction of gender by perceptual reactance appeared, with augmenting males being rated the most dark-eyed and augmenting females being rated the most light-eyed. Interpretation of the findings was made in terms of attention to relevant cues.

Kinesthetic figural aftereffects: norms from four samples, and a comparison of methods for classifying augmenters, moderates, and reducers

Prior studies into the validity of Petrie's hypothesized augmentation-reduction dimension have apparently assumed that there is a linear relationship between scores from the Petrie variant of the kinesthetic figural aftereffects task and external validity variables. Empirical evidence for this assumption is either lacking or contradictory and it is here argued that the possibility of non-linear relationships should be explored systematically. Studies of this task typically involve small samples, however, making it difficult to ascertain whether both extremes of the augmentation-reduction dimension are adequately represented. Normative data are therefore presented from four samples, and the comparability of several methods which can be used to classify individuals as Augmenters, Moderates, and Reducers is explored.

Tobacco and evoked potential

Significant changes were found in two indices of the averaged visual evoked potentials in nine smokers after 12 and 36 hours of abstinence and after resumption of smoking. There was a decrease of the amplitude envelope accompanying withdrawal and an increase with resumption of smoking. These changes are consistent with the contention that tobacco increases arousal. Amplitude changes were found in a specific component of the evoked potential occurring between 100 and 125 milliseconds after the onset of the flash. The latter changes suggest the possibility that smoking selectively enhances the perceptiont of weak stimuli.

Relationship between dimensions of cognitive style: field-articulation control and stimulus-intensity control

There has been only one study with normals which examines relationships among Silverman's three dimensions of attention (cf. Silverman & King, 1970). The present study examined the relationship between scores of normal females on tasks that correlate with factors interpreted as field-articulation control and stimulus-intensity control. No significant linear or curvilinear relationships were obtained from Ss' scores on the rod-and-frame test and the kinesthetic figural aftereffects' test. These results support the belief that field-articulation control and stimulus-intensity control are independent cognitive controls in normals.

Phenothiazine effects on auditory signal detection in paranoid and nonparanoid schizophrenics

The differential effects of phenothiazine medication on auditory signal detection performance were compared in two types of schizophrenic subjects and in normal subjects. With increasing phenothiazine dosage a decrease in efficiency of signal detection performance occurred among nonparanoid schizophrenics and an increase in efficiency occurred among paranoid schizophrenics. These and related findings were interpreted in terms of differences in neuropsychological response and information processing characteristics in the two types of schizophrenics. The primary deficit in information processing in nonparanoid schizophrenics may be related primarily to their hypersensitivity to sensory stimuli, whereas in paranoids it may be related primarily to their impaired focusing of attention. Phenothiazines appear to decrease sensitivity to stimuli in nonparanoids but increase the ability to focus attention in paranoids. The possibility of treatment regimens which take into account the differential effects of phenothiazine medication was suggested.