Determinants of tonic and phasic reactions in transswitching

Forty-eight college students were assigned randomly to four groups in a 2 × 2 factorial arrangement of phasic conditional stimuli (samevs. different) and tonic conditional stimuli (samevs. different) to receive 2 days of classical conditioning with a transswitching procedure. Tonic stimuli were a 5-minute projected white triangle or circle; phasic stimuli were a 5-second red or green square superimposed over the tonic stimuli. There were six tonic stimulus segments each day, separated by 20-second periods of no stimulus, three containing six trials of the phasic stimulus paired with shock and three containing six trials of the phasic stimulus alone, in the counterbalanced order. Tonic responding at the onset of the tonic stimuli or during brief periods following its onset were recorded, along with phasic responses to the phasic stimuli. Responses included magnitude of skin conductance responses, frequency of unelicited skin conductance responses, and tonic heart rate. Both skin conductance measures of responding to the tonic stimuli differentiated significantly between positive and negative tonic segments during Day 2, but only in the group with two different tonic stimuli and one phasic stimulus (“standard” transswitching). This supported the hypothesis that tonic stimulus differentiation would be absent when two different phasic stimuli were present. The heart rate data did not support this hypothesis, showing tonic differentiation in both groups with two tonic stimuli. Phasic differentiation controlled by the different phasic stimuli was observed on Day 1; on Day 2, phasic differentiation was present only in the group with two tonic and one phasic stimuli and the group with one tonic and two phasic stimuli. The results were interpreted to mean that temporal contiguity between the tonic stimuli and shock or no shock is not sufficient to establish tonic response differentiation in transswitching.     

Color adaptation in a yellow-blue system: proof of a simple numerical relationship]

Three axes in color space are specified: a (unique) yellow - (unique) blue axis, a (unique) green - magenta axis and brightness. Based on the two chromatic axes two linear opponent colors systems are defined: a red/green-system and a yellowish/bluish-system. A numerical relation is presented to describe color adaptation for the yellowish/bluish-system under adaptation to (unique) yellow and (unique) blue: two pairs of color stimuli are equivalent with regard to the yellowish/bluish-system - consisting of a test stimulus and an adaptation stimulus, respectively - if the ratios from the yellowish/bluish-coordinates of test stimulus and adaptation stimulus are identical. A control of brightness and the red/green-system is presupposed. For several (unique) yellow and (unique) blue adaptation stimuli it is examined how a test stimulus that appears neither yellowish nor bluish changes its location on the (unique) yellow - (unique) blue axis within color space. Three observers take part in the experiment. For each observer a plane of constant brightness and the opponent colors axes are estimated experimentally. The data show that the ratios from the yellowish/bluish coordinates of test stimulus and adaptation stimulus are essentially constant. The results are compared with analogous data for the red/green-system. The findings provide evidence for the specification of the three phenomenal axes. The specification is discussed with regard to Hering's opponent colors theory and Krauskopf's three "cardinal" axes [1982, Vision Research, 22, 1123-1131].     

Differential fear conditioning induces reciprocal changes in the sensory responses of lateral amygdala neurons to the CS(+) and CS(-)

In classical fear conditioning, a neutral sensory stimulus (CS) acquires the ability to elicit fear responses after pairing to a noxious unconditioned stimulus (US). As amygdala lesions prevent the acquisition of fear responses and the lateral amygdaloid (LA) nucleus is the main input station of the amygdala for auditory afferents, the effect of auditory fear conditioning on the sensory responsiveness of LA neurons has been examined. Although conditioning was shown to increase CS-evoked LA responses, the specificity of the changes in responsiveness was not tested. Because conditioning might induce nonspecific increases in LA responses to auditory afferents, we re-examined this issue in conscious, head-restrained cats using a differential conditioning paradigm where only one of two tones (CS(+) but not CS(-)) was paired to the US. Differential conditioning increased unit and field responses to the CS(+), whereas responses to the CS(-) decreased. Such changes have never been observed in the amygdala except in cases where the CS(-) had been paired to the US before and fear responses not extinguished. This suggests that fear conditioning is not only accompanied by potentiation of amygdalopetal pathways conveying the CS(+) but also by the depression of sensory inputs unpaired to noxious stimuli.     

Stimulus-dependent dopamine release in attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is related to an attenuated and dysfunctional dopamine system. Normally, a high extracellular dopamine level yields a tonic dopaminergic input that down-regulates stimuli-evoked phasic dopamine responses through autoreceptors. Abnormally low tonic extracellular dopamine in ADHD up-regulates the autoreceptors so that stimuli-evoked phasic dopamine is boosted. The authors propose that these boosted phasic responses yield hypersensitivity to environmental stimuli in ADHD. Stimuli evoking moderate brain arousal lead to well-functioning performance, whereas either too little or too much stimuli attenuate cognitive performance. Strong, salient stimuli may easily disrupt attention, whereas an environment with impoverished stimuli causes low arousal, which is typically compensated for by hyperactivity. Stochastic resonance is the phenomenon that makes a moderate noise facilitate stimulus discrimination and cognitive performance. Computational modeling shows that more noise is required for stochastic resonance to occur in dopamine-deprived neural systems in ADHD. This prediction is supported by empirical data.     

The Horsley gantt medal address October 11, 1992

The concept of systemic quantization of behavior was used to study the interaction between dominant motivation and reinforcement on brain neurons. Feeding and escape were used as experimental models. Results showed that feeding and escape motivations are based on the mechanisms of ascending activating influences of lateral or ventromedial hypothalamic centers, respectively, on cortical neurons. Feeding and escape motivations evoked by electrical stimulation of hypothalamus, or the ones occurring naturally, modify the responses of single neurons of sensorimotor and insular cortex to sensory stimuli, to microiontophoretic application of neurotransmitters and neuropeptides, and especially to reinforcement. Dominant motivations are reflected in the burst-like activity and in a specific pattern of interpulse intervals of single units in various brain structures. Reinforcement transforms this activity into a regular pattern and also changes the neuronal responses of hypothalamic feeding and escape centers, to electrical stimulation and to microiontophoretic application of oligopeptides. Specific patterns of the unit responses to conditioned stimuli in the course of consecutive reinforcement was determined. After several instances of reinforcement, especially after repetitive reinforcement, the brain neurons influenced by the dominant motivation begin to produce specific protein molecules that are important for organization of an appropriate type of behavior. This process can be blocked by protein synthesis inhibitors.     

Stimulus Significance Effects in Habituation of the Phasic and Tonic Orienting Reflex

Phasic and tonic measures of electrodermal activity were examined in a simple habituation paradigm, using innocuous visual stimuli. Separate groups were used to investigate the effects of stimulus significance, as manipulated by instructions. One group had no stimulus-related task (indifferent group), while the other was asked to silently count the stimuli to report to the experimenter later (significant group). Prestimulus skin conductance levels were considered as measures of the arousal level at each stimulus presentation, and the subsequent electrodermal responses were taken as the phasic orienting reflex (OR) elicited by each stimulus. Changes in prestimulus arousal were taken as measures of the tonic OR to the experimental series. Marked group differences were found in both phasic and tonic components of the OR. Some, but not all, of the significance effects in the phasic OR were attributable to differences in arousal. The results are discussed in the context of theoretical accounts of the OR.     

Stimulus significance effects in habituation of the phasic and tonic orienting reflex

Phasic and tonic measures of electrodermal activity were examined in a simple habituation paradigm, using innocuous visual stimuli. Separate groups were used to investigate the effects of stimulus significance, as manipulated by instructions. One group had no stimulus-related task (indifferent group), while the other was asked to silently count the stimuli to report to the experimenter later (significant group). Prestimulus skin conductance levels were considered as measures of the arousal level at each stimulus presentation, and the subsequent electrodermal responses were taken as the phasic orienting reflex (OR) elicited by each stimulus. Changes in prestimulus arousal were taken as measures of the tonic OR to the experimental series. Marked group differences were found in both phasic and tonic components of the OR. Some, but not all, of the significance effects in the phasic OR were attributable to differences in arousal. The results are discussed in the context of theoretical accounts of the OR.     

Orienting, emotion, and memory: phasic and tonic variation in heart rate predicts memory for emotional pictures in men

Arousal-related processes associated with heightened heart rate (HR) predict memory enhancement, especially for emotionally arousing stimuli. In addition, phasic HR deceleration reflects "orienting" and sensory receptivity during perception of stimuli. We hypothesized that both tonic elevations in HR as well as phasic HR deceleration during viewing of pictures would be associated with deeper encoding and better subsequent memory for stimuli. Emotional pictures are more memorable and cause greater HR deceleration than neutral pictures. Thus, we predicted that the relations between cardiac activity and memory enhancement would be most pronounced for emotionally-laden compared to neutral pictures. We measured HR in 53 males during viewing of unpleasant, neutral, and pleasant pictures, and tested memory for the pictures two days later. Phasic HR deceleration during viewing of individual pictures was greater for subsequently remembered than forgotten pictures across all three emotion categories. Elevated mean HR across the entire encoding epoch also predicted better memory performance, but only for emotionally arousing pictures. Elevated mean HR and phasic HR deceleration were associated, such that individuals with greater tonic HR also showed greater HR decelerations during picture viewing, but only for emotionally arousing pictures. Results suggest that tonic elevations in HR are associated both with greater orienting and heightened memory for emotionally arousing stimuli.     

Electrodermal measures of attention and effort to stimulus onset and offset for intramodal and intermodal tasks.

Two experiments were designed to assess the relationship between task difficulty and arousal. Electrodermal measures of tonic and phasic arousal to four levels of task difficulty at stimulus onset and offset were studied in college students for intramodal and intermodal tasks. The students were presented for 18 trails with visual-auditory or visual-visual stimuli with either 2.0-, 0.2-, or 0.02-sec difference between stimuli onset or offset, and asked to judge which stimulus came on or went off first or merely to observe the stimuli. Both frequency and amplitude of skin conductance responses reliably differentiated the levels of task difficulty for both the intramodal and the intermodal task. None of the measures of tonic level of arousal was reliable. Electrodermal measures of phasic responses accurately reflected the task demands.     

Effects of tonic and phasic respiratory sinus arrhythmia on affective stress responses

Adaptive affective responses in the face of environmental challenges require flexible physiological responding. The present study examined the extent to which tonic respiratory sinus arrhythmia (RSA)-a putative marker of regulatory capacity-moderated the association between stress-related changes in RSA (i.e., phasic RSA) and concurrent changes in affect. Ninety-eight healthy, young adults completed ratings of affect during a resting baseline and following the recall of a recent stressor. Tonic RSA moderated the association of phasic RSA with stress-related change in positive affect (PA), such that change in RSA had a positive association with PA for individuals with higher tonic RSA and a negative association for those with lower tonic RSA. Examination of specific aspects of PA indicated that phasic RSA was positively associated with changes in ratings of attentive engagement among individuals with higher tonic RSA. These findings inform our understanding of phasic RSA and support the notion that flexible parasympathetic nervous system functioning is an important component of adaptive stress regulation.     

Contextual conditioning

Eastern and Western interpretations of contextual control of phasic conditional responses (transswitching) are contrasted. The Eastern (Asratyan, 1965) approach emphasizes the role of the tonic conditional stimulus and the (hypothetical) tonic response it evokes. The Western (Lachnit, 1986) approach emphasizes the role of compound conditional stimuli. Although Lachnit showed that transswitching-like results can be obtained without a tonic stimulus, attempts to simulate transswitching experiments using a computer model of the Rescorla-Wagner theory (Kimmel and Lachnit, 1988) have shown that predictions from the theory approximate empirical results in human classical conditioning only when the tonic stimulus is given far greater weight than the phasic stimulus. In other words, only when the Rescorla-Wagner theory is made more like Asratyan’s theory, can the compound conditional stimulus approach account for real empirical transswitching data.     

Stress-induced Fos-like Immunoreactivity in the Pons and the Medulla Oblongata of Rats

Immunoreactivity of the immediate early gene c-fos was used to investigate changes in the activity of brainstem neurons in response to acute stressors like immobilization, formalin-induced pain, cold exposure, hemorrhage and insulin-induced hypoglycemia. Different stressors induced Fos-like immunoreactivity in different pontine and medullary neurons. A single, 3 hour immobilization was found to be a very strong stimulus that activated brainstem catecholaminergic (tyrosine hydroxylase-immunopositive) neurons and cells in the raphe and certain pontine tegmental nuclei, as well as in the reticular formation. Pain, induced by a subcutaneous injection of formalin was also effective on catecholamine-synthesizing neurons and on others cells in the nucleus of the solitary tract. Cold exposure activated cells mainly in the sensory spinal trigeminal and parabrachial nuclei and in the so-called "pontine thermoregulatory area". Moderate Fos-like immunoreactivity was induced by a hypotonic (25%) hemorrhage in medullary catecholaminergic neurons, the nucleus of the solitary tract and the Barrington nucleus. Among stressful stimuli used, insulin-induced hypoglycemia elicited the smallest Fos activation in the lower brainstem. The present observations indicate that different stressors may use different neuronal pathways in the central organization of the stress response.     

Temporal kinetics of prefrontal modulation of the extrastriate cortex during visual attention

Single-unit, event-related potential (ERP), and neuroimaging studies have implicated the prefrontal cortex (PFC) in top-down control of attention and working memory. We conducted an experiment in patients with unilateral PFC damage (n=8) to assess the temporal kinetics of PFC-extrastriate interactions during visual attention. Subjects alternated attention between the left and the right hemifields in successive runs while they detected target stimuli embedded in streams of repetitive task-irrelevant stimuli (standards). The design enabled us to examine tonic (spatial selection) and phasic (feature selection) PFC-extrastriate interactions. PFC damage impaired performance in the visual field contralateral to lesions, as manifested by both larger reaction times and error rates. Assessment of the extrastriate P1 ERP revealed that the PFC exerts a tonic (spatial selection) excitatory input to the ipsilateral extrastriate cortex as early as 100 msec post stimulus delivery. The PFC exerts a second phasic (feature selection) excitatory extrastriate modulation from 180 to 300 msec, as evidenced by reductions in selection negativity after damage. Finally, reductions of the N2 ERP to target stimuli supports the notion that the PFC exerts a third phasic (target selection) signal necessary for successful template matching during postselection analysis of target features. The results provide electrophysiological evidence of three distinct tonic and phasic PFC inputs to the extrastriate cortex in the initial few hundred milliseconds of stimulus processing. Damage to this network appears to underlie the pervasive deficits in attention observed in patients with prefrontal lesions.     

On cross-modal similarity: auditory-visual interactions in speeded discrimination

A series of four experiments explored how cross-modal similarities between sensory attributes in vision and hearing reveal themselves in speeded, two-stimulus discrimination. When subjects responded differentially to stimuli on one modality, speed and accuracy of response were greater on trials accompanied by informationally irrelevant "matching" versus "mismatching" stimuli from the other modality. Cross-modal interactions appeared in (a) responses to dim/bright lights and to dark/light colors accompanied by low-pitched/high-pitched tones; (b) responses to low-pitched/high-pitched tones accompanied by dim/bright lights or by dark/light colors; (c) responses to dim/bright lights, but not to dark/light colors, accompanied by soft/loud sounds; and (d) responses to rounded/sharp forms accompanied by low-pitched/high-pitched tones. These results concur with findings on cross-modal perception, synesthesia, and synesthetic metaphor, which reveal similarities between pitch and brightness, pitch and lightness, loudness and brightness, and pitch and form. The cross-modal interactions in response speed and accuracy may take place at a sensory/perceptual level of processing or after sensory stimuli are encoded semantically.     

Different parameters support generalization and discrimination learning in Drosophila at the flight simulator

We have used a genetically tractable model system, the fruit fly Drosophila melanogaster to study the interdependence between sensory processing and associative processing on learning performance. We investigated the influence of variations in the physical and predictive properties of color stimuli in several different operant-conditioning procedures on the subsequent learning performance. These procedures included context and stimulus generalization as well as color, compound, and conditional discrimination (colors and patterns). A surprisingly complex dependence of the learning performance on the colors' physical and predictive properties emerged, which was clarified by taking into account the fly-subjective perception of the color stimuli. Based on estimates of the stimuli's color and brightness values, we propose that the different tasks are supported by different parameters of the color stimuli; generalization occurs only if the chromaticity is sufficiently similar, whereas discrimination learning relies on brightness differences.     

Dishabituation and spontaneous recovery of the electrodermal orienting response: Effects of extraversion,impulsivity, sociability,and caffeine

The relationship between extraversion and psychophysiological indices of arousal is not yet fully understood. The present study attempted to further clarify this relationship by using caffeine to systematically manipulate arousal. Subjects pretested on the Eysenck Personality Inventory were given caffeine or a placebo, then underwent habituation, dishabituation, and spontaneous recovery of the electrodermal OR. Separate analyses examined the main and interactive effects of extraversion, impulsivity, and sociability with caffeine. Several tonic and phasic measures showed group reversal effects, with introverts having higher tonic levels and larger phasic responses under placebo conditions and extraverts having larger phasic responses and higher tonic levels under caffeine. Although both tonic and phasic responses were differentially affected, the group reversal effects occurred at different points in time on tonic than they did on phasic measures relative to the theoretical buildup of inhibition. The findings for impulsivity were quite consistent with those for extraversion, and both sets of results were generally supportive of the Eysenck hypothesis.     

The influence of stimulus properties on multisensory processing in the awake primate superior colliculus.

Multisensory integration is a process whereby information converges from different sensory modalities to produce a response that is different from that elicited by the individual modalities presented alone. A neural basis for multisensory integration has been identified within a variety of brain regions, but the most thoroughly examined model has been that of the superior colliculus (SC). Multisensory processing in the SC of anaesthetized animals has been shown to be dependent on the physical parameters of the individual stimuli presented (e.g., intensity, direction, velocity) as well as their spatial relationship. However, it is unknown whether these stimulus features are important, or evident, in the awake behaving animal. To address this question, we evaluated the influence of physical properties of sensory stimuli (visual intensity, direction, and velocity; auditory intensity and location) on sensory activity and multisensory integration of SC neurons in awake, behaving primates. Monkeys were trained to fixate a central visual fixation point while visual and/or auditory stimuli were presented in the periphery. Visual stimuli were always presented within the contralateral receptive field of the neuron whereas auditory stimuli were presented at either ipsi- or contralateral locations. Many of the SC neurons responsive to these sensory stimuli (n = 66/84; 76%) had stronger responses when the visual and auditory stimuli were combined at contralateral locations than when the auditory stimulus was located on the ipsilateral side. This trend was significant across the population of auditory-responsive neurons. In addition, some SC neurons (n = 31) were presented a battery of tests in which the quality of one stimulus of a pair was systematically manipulated. A small proportion of these neurons (n = 8/31; 26%) showed preferential responses to stimuli with specific physical properties, and these preferences were not significantly altered when multisensory stimulus combinations were presented. These data demonstrate that multisensory processing in the awake behaving primate is influenced by the spatial congruency of the stimuli as well as their individual physical properties.     

Contextual stimulus control of conditional vasomotor and electrodermal reactions to angry and friendly faces

An experiment with 42 human Ss used the transswitching procedure to examine tonic stimulus control of phasic and tonic conditioned vasomotor heart rate, and electrodermal reactions. The conditional stimulus (CSs) were photos of angry and friendly human faces, and the unconditional stimulus (US) was a human scream. In one tonic context (blue light), the CSs were paired with the US, in the other context (yellow light), the CSs were presented unpaired. Following acquisition, an extinction series was run with the US omitted during both tonic contexts. Phasic vasomotor and skin conductance reactions differed in the positive and negative tonic segments (stronger in positive). The skin conductance responses also differed during extinction, but the vasomotor responses did not. Tonic differences (following onset of the tonic stimuli) in unelicited skin conductance response frequency, finger pulse volume, and heart rate were also found, although these developed more slowly than the phasic differences. The finger pulse volume tonic difference was greater in extinction than the skin conductance response frequency. There was no effect of the angry-friendly facial expressions, either directly or in interaction with the transswitching effects. The results were interpreted to mean that the transswitching phenomenon is not limited to one another autonomic effector, but is more generalized across the ANS (sympathetic branch). The absence of influence of the facial expressions indicates the relative weakness of the “preparedness” hypothesis in comparison with more influential contextual factors.     

Tonic and phasic stimulus control of blood pressure responses using opposing unconditional stimuli

The transswitching paradigm was used in the present study to investigate the effects of tonic (long duration) environmental stimuli paired with opposing unconditional stimuli on human blood pressure. Sixty volunteers participated for two sessions, one week apart. Subjects were presented with a pseudorandom sequence of four trials of red lights (five minutes each) and four trials of blue lights (five minutes each) within each session. All subjects received the cold pressor test during the red lights. During the blue lights, half the subjects received warm water and the other half received a neutral temperature water. Subjects received the presentations of the water in one of three methods: as determined by the experimenter, preceded by a warning signal, or self-administered. The results indicated that conditional and unconditional responses during the red lights were progressive increases in blood pressure. During the blue lights associated with warm water, conditional and unconditional responses were often progressive decreases in blood pressure. The method of administration of the water affected the magnitude of the unconditional responses. Evidence for phasic stimulus control was not as unequivocal as tonic stimulus control. The present results indicated that it is possible to modify blood pressure in two directions (increases and decreases) when two high contrast, opposing unconditional stimuli are presented.     

On using isoluminant stimuli to separate magno- and parvocellular responses in psychophysical experiments—A few words of caution

Isoluminant (or equiluminant) color stimuli (i.e., those that contain variations only in chromaticity) have been employed in attempts to separate magno- and parvocellular responses in psychophysical and noninvasive electrophysiological experiments. The justification for this has been the assumption that magnocellular cells, unlike parvocellular neurons, do not respond to stimuli varying only in hue. However, several problems are associated with this notion: (1) under many conditions, magnocellular neurons are not fully silenced at isoluminance, and (2) in many circumstances, parvocellular responses are substantially reduced at isoluminance. To rely upon isoluminant stimuli to “bias” stimuli toward the parvocellular system also faces obstacles. Therefore, caution is required when attempting to use isoluminant color to separate magno- and parvocellular responses.