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Biomedical subjects

K Hugdahl

Publications and source records attributed to K Hugdahl.

143 records · Page 8Linked to original sources
PubMed1977

Effects of instruction on acquisition and extinction of electrodermal responses to fear-relevant stimuli.

In the present study we examined the hypothesis that electrodermal responses conditioned to fear-relevant stimuli are insensitive to verbal instructions. In the first experiment, different groups of subjects were conditioned to fear-relevant and fear-irrelevant control stimuli in a long interstimulus interval differential paradigm with shock as the unconditioned stimulus. Then half of the subjects were informed that no more shocks would be presented, and a number of extinction trials followed. The instruction completely abolished responding to fear-irrelevant stimuli, while leaving responses to the fear-relevant stimuli unaffected. In the second experiment, subjects were "conditioned" to fear-relevant or irrelevant stimuli by an instruction involving threat of shock. This manipulation potentiated potentiated responses to fear-relevant stimuli significantly more than responses to fear-irrelevant stimuli. Thus, instruction had a symmetrical effect on acquisition and extinction to fear-irrelevant stimuli, whereas it facilitated acquisition but was ineffective in reducing responding to the other class of stimuli. These results are related to a preparedness theory, and their relevance for an understanding of phobias is discussed.

Adult↗
PubMed1976

Electrodermal conditioning to potentially phobic stimuli in male and female subjects.

There are clear sex differences in incidence of phobias for small animals, and in questionnaire-measured fear for animals. The present study examined whether these sex differences were reflected also in electrodermal conditioning to potentially phobic stimuli. Separate groups of males and females were exposed to a conditioning session involving either potentially phobic, snakes and spiders, or fear-irrelevant, flowers and mushrooms, conditioned stimuli with electric shock as the unconditioned stimulus. A long interstimulus interval differential paradigm was used, allowing analysis of first- and second interval anticipatory responses, and third-interval omission responses. There were 8 habituation trials, 16 acquisition trials and 40 extinction trials. Half of the trials involved the reinforced cue, and the other half the unreinforced cue. There were clear conditioning effects, with superior acquisition and resistance to extinction to the phobic as compared to the fear-irrelevant stimuli. However, there were no differences between the two sexes. The results were interpreted in terms of the preparedness theory of phobias, and in terms of social learning factors.

Adult↗
PubMed1976

The premise of equipotentiality in human classical conditioning: conditioned electrodermal responses to potentially phobic stimuli.

The premise of equipotentiality, which has been widely adhered to among learning theorists, states that the laws of learning should not vary with the use of particular stimuli, responses, or reinforcements. This premise has recently been challenged by some data originating within the learning tradition itself, for example, studies on the effects of verbal stimuli in eye-lid conditioning. More importantly, however, the premise of equipotentiality is incompatible with data from experiments carried out within a biological-ethological framework. The results of such studies indicate that a given species is prepared to associate certain stimuli, responses, and reinforcers but not others. In an attempt to examine the validity of this premise in human classical conditioning, we investigated the effect of pictures of potentially phobic objects as conditioned stimuli (CSs) for electrodermal responses, since it has been suggested that phobias may be instances of biologically prepared learning. Three experiments are reported, all of them involving a long interstimulus interval differential conditioning paradigm with different pictures as CSs and electric shock as the unconditioned stimulus (UCS). In Experiment 1 we established that different pictures are differentially effective as CSs. A groupconditioned to potentially phobic stimuli, snakes or spiders, showed greater resistance to extinction than a group conditioned to fear-irrelevant pictorial stimuli, that is, flowers or mushrooms. A third group conditioned to "representative laboratory stimuli," circles or triangles, fell in between thses two groups. Experuce similar effects to those observed with phobic and fear-irrelevant stimuli in Experiment 1. In Experiment 3 superior resistance to extinction for phobic stimuli was demonstrated when the UCS was an electric shock, but not when it was a tone to which the subject produced reaction times. Thus, the effect appears specific for aversive UCSs, and CS-UCS "belongingness" has been demonstrated. It was concluded that our data do challenge the premise of equipotentiality in human conditioning. There are several learning-theory accounts that could accommodate at least some aspects of the data, but they seem to be best explained in terms of biologically orsiented constructs, such as preparedness.

Acoustic Stimulation↗
PubMedDate not supplied

Nonaware classical conditioning to pictorial facial stimuli in a between-groups paradigm.

The present experiment investigated the effects of aware and nonaware modes of extinction in classical conditioning to facial emotional stimuli. The subjects participated in three different experimental phases. In the first (habituation) phase they were presented with a 500 ms angry face. In the second (acquisition) phase, for half of the subjects the 500 ms face was paired with an aversive noise (experimental group) while for the other half of the subjects the face and the noise presentations were separated by 6-10 s intervals (sensitization control group). In the third (extinction) phase, these two groups were further divided into two subgroups. One subgroup of both the experimental and control group had the face stimulus presented for 30 ms, and immediately masked with a neutral picture. The other two subgroups had the face presented for 500 ms with no mask. The results showed that conditioning only occurred in the experimental subgroups which was indicated by a significant difference between skin conductance responses during habituation and corresponding responses during extinction. Secondly, comparing the experimental and control groups during the extinction phase, a significant conditioning effect was observed for both the aware and nonaware masked modes of extinction for the experimental group. The results suggest that conditioned autonomic responses may be elicited in a nonaware mode.

Adolescent↗
PubMedDate not supplied

Brain asymmetry and human electrodermal conditioning.

Two experiments are reviewed that demonstrate effects of brain laterality on human classical conditioning. Pictures of facial emotional expressions were used as conditioned stimuli (CSs) together with shock as unconditioned stimulus (UCS). Bilateral electrodermal responses were recorded as dependent measures. In the first experiment, one group was conditioned to an angry face, and one group to a happy face. During extinction, the face-CSs were presented to the right hemisphere on half of the trials and to the left hemisphere on the other half of the trials. Results showed that the right hemisphere was superior in showing persisting effects of learning, and especially to the angry CS+. In the second experiment, lateralized presentations of the angry and happy faces were made during acquisition, with foveal presentations during extinction. Once again, the angry face elicited greater skin conductance responses (SCRs) during extinction in the group that had this stimulus presented to the right hemisphere during acquisition. It is concluded that emotional conditioning is differentially regulated by the two hemispheres of the brain.

Adult↗
PubMedDate not supplied

Hemispheric asymmetry and human associative learning: interactions with attention.

In a previous study (Hugdahl & Brobeck, 1986) it was shown that Pavlovian conditioning to an auditory verbal conditioned stimulus (CS) initially presented only to the left cerebral hemisphere was stronger than when the same CS was presented to the right hemisphere. This was followed up in the present study by controlling for the possibility that the effect was caused by laterally biased attention. The study was performed using the "dichotic extinction paradigm," which consists of three different phases. During the habituation phase, the CS+ and CS- were presented binaurally and separated in time. During the acquisition phase, the CS+ was followed by a white-noise unconditioned stimulus (UCS). During the dichotic extinction phase, the CS+ and CS- were presented dichotically, i.e., simultaneous presentations on each trial. Half of the subjects had the CS+ in the right ear, and half had the CS+ in the left ear. Each group was further divided into two subgroups, with one subgroup instructed to attend only to the right ear input, and the other subgroup to attend only to the left ear input. During acquisition, larger electrodermal responses were obtained to the CS+ than to the CS-. During dichotic extinction, the CS+ right ear group showed superior resistance to extinction compared to the CS+ left ear group, with no effect of the manipulation of attention. The effect was, however, attenuated when levels of acquisition was used as covariates in an analysis of covariance. There were overall larger responses from the left hand recording.

Adult↗
PubMedDate not supplied

Brain asymmetry and autonomic conditioning: sensitization control.

In the present experiment we report effects of cerebral asymmetry, or laterality, during classical conditioning to facial emotional stimuli. Twenty-five female subjects were presented with slides of a happy face in one visual half-field (VHF), and simultaneously a slide of an angry face in the other VHF, followed by shock as the unconditioned stimulus (UCS). To control for effects of sensitization, a new stimulus, never associated with the UCS, was introduced in the extinction phase. Dependent measures were phasic heart rate responses (HR) and skin conductance responses (SCR). The HR results showed a significant right hemisphere effect for the CS-UCS association, that was not attributable to UCS sensitization. No significant effects were found for the SCRs. The basic HR finding was a right hemisphere superiority for learning of a conditioned association.

Adult↗
PubMedDate not supplied

Effects of hemispheric asymmetry on electrodermal conditioning in a dichotic listening paradigm.

It was predicted that when an auditive verbal conditional stimulus (CS+), previously associated with an aversive unconditional stimulus (UCS), is presented to the right ear (initial left hemisphere input), in a dichotic listening task, with the CS- simultaneously presented in the left ear, the result would be greater resistance to extinction than when the same CS+ is presented to the left ear (initial right hemisphere input). In the same vein, it was predicted that, when a tonal CS+ is presented to the left ear, greater resistance to extinction would occur as compared with when it is presented to the right ear. During a dichotic test phase, each group was split into two subgroups, and the CS+ and CS- repeatedly were presented simultaneously to each ear. Half of the subjects in each subgroup had the CS+ presented to the left ear. The other half had the CS+ presented to the right ear. Skin conductance responses were recorded from both hands. Results showed significantly larger responding in all groups to the CS+/UCS compound during the acquisition phase. However, during the dichotic extinction phase, the verbal CS+ right-ear subgroup showed significantly larger resistance to extinction as compared with the verbal CS+ left-ear subgroup. No differences were found between the two tonal subgroups.

Adult↗
PubMedDate not supplied

Heart-rate responses (HRR) to lateralized visual stimuli.

Direction of changes in heart-rate responses (HRR) were investigated in three separate experiments as a measure of differential cognitive and emotional specialization of the cerebral hemispheres. Visual stimuli were presented via the visual half-field technique in all three experiments. Slides with different contents were flashed for 200 msec on each trial either to the left or right of a center LED fixation point. The LED went on 5 seconds prior to slide onset. HR changes were scored as second-by-second deviations during 10 seconds after LED onset from pre-LED base line. In the first experiment it was hypothesized that emotionally relevant stimuli initially projected to only the right hemisphere would result in more anticipatory acceleration than when the same stimulus was initially projected to the left hemisphere. A picture of a snake and of a geometric figure were repeatedly briefly flashed to the right of the LED for half of the subjects, and to the left for the other half. There were 25 trials with an intertrial interval of 25-40 seconds. Results showed significant effects of deceleration as a function of the slide stimulus in all groups on seconds 5, 6, or 7 after onset of the center LED. Furthermore, an anticipatory acceleration was observed during the first trial-block on seconds 3 and 4 in the right hemisphere groups only with no differences between the neutral and emotional stimuli. In Experiments 2 and 3, a letter-string of six letters and a complex symmetric pattern were used as stimuli. These stimuli were chosen because previous research has clearly implicated the hemispheres to be differentially specialized in their ability to process verbal and visuo-spatial stimuli. The set-up was identical to Experiment 1, with the exception that differences in response to the two types of stimuli were evaluated on a within-subjects basis. The results from Experiments 2 and 3 showed stimulus-related deceleration, peaking on seconds 5-7 in all groups and an anticipatory acceleration peaking on seconds 3 and 4 in the right hemisphere groups, with decelerations during the corresponding seconds in the left hemisphere groups. The results are discussed in relation to recent findings by Walker and Sandman (1982) about the possibility of hemispheric specialization in psychologic influences on heart rate changes in response to environmental demands.

Adult↗
PubMedDate not supplied

Habituation of the electrodermal orienting reaction is dependent on the cerebral hemisphere initially stimulated.

The purpose of the present study was to investigate the relationship between habituation of the electrodermal orienting reaction (OR) and asymmetrical hemisphere functioning. Subjects were exposed to lateralized visual input with fear-relevant and neutral content. Skin conductance recordings were taken bilaterally. The experiment consisted of four groups in a randomized 2 X 2 factorial design (N = 40). Half of the subjects habituated to repeated presentations (25 trials) of a snake-slide, whereas the other half viewed a slide of a rectangular black geometric shape. Within each stimulus category, half of the subjects had the picture presented 6 degrees of visual angle lateral to the right of a central fixation point (i.e. initial right hemisphere input). The other half had the picture presented to the left (i.e. initial right hemisphere input). Results showed a significant overall decrease in response magnitude over trials, and a significant main effect of type of projection field. Responses in the left field groups were larger than responses in the right field groups on all trials. No other comparisons reached significance. The results are discussed in terms of hemisphere asymmetry and its role in the regulation of the habituation process.

Adult↗
PubMedDate not supplied

Effects of stimulus content and brain lateralization on the habituation of the electrodermal orienting reaction (OR).

Slides with either a six-letter word or a complex spatial pattern were repeatedly flashed either to the left or to the right of a center fixation point (i.e. visual half-field technique) in an electrodermal orienting paradigm. Skin conductance (SC) was recorded from both the left and right hand. Half of the subjects had the slides projected 6.0 degrees of visual angle lateral to fixation, the other half had the stimuli projected 2.5 degrees lateral to fixation. There were 15 presentations of each stimulus with a mean inter-trial interval (ITI) of 30 sec. Results showed significantly larger mean SCR-amplitudes across trials to the verbal stimuli compared to the spatial patterns when presented in the right visual half-field, and larger amplitudes to the spatial stimuli when presented in the left half-field. However, this was only true for the 6.0 degrees condition, but not for the 2.5 degrees condition. No differences were found between left and right hand recording. The present data imply a functional relationship between electrodermal orienting habituation and hemispheric asymmetry.

Adult↗
PubMedDate not supplied

Habituation of electrodermal reactivity to visual alcohol stimuli in alcoholics.

This study address the question of cued reactivity in alcoholics. Twenty alcoholic in-patients and 20 control subjects were presented with repeated exposures to a alcohol-related (A) and a neutral (B) slide, in either an ABA or BAB sequence. Skin Conductance Level (SCL) and Skin Conductance Responses (SCR) were recorded. Alcohol-dependent subjects showed increased SCR compared to the control subjects. This was, however, independent of whether the presented stimuli were alcohol-related or neutral. Thus, the results did not support the hypothesis of cued reactivity, but point to a nonspecific hyper-reactivity in alcohol-dependent subjects. The results are discussed in relation to risk-factors for alcoholism and relapse.

Adult↗
PubMedDate not supplied

Autonomic cued reactivity in alcoholics: the effect of olfactory stimuli.

The present study was designed to investigate autonomic cued reactivity to olfactory alcohol stimuli in alcoholics. Twenty outpatient alcoholics and 20 social drinkers were exposed to high- and low-potency alcohol and neutral odors. The alcoholics showed greater skin conductance responses and increased heart rate acceleration responses to the high-potency alcohol odor than social drinkers, while there was no difference between the groups' responses to the low-potency alcohol odor. Alcoholics also reported greater difficulties in resisting a potential offer for a drink after relative to before the experiment, while there was no change in the desire to drink. The results indicate that alcohol cues are perceived as emotionally aversive and elicit a defensive response to avoid further processing of these stimuli. The increased autonomic reactivity may thus reflect a shift of focus from the environmental alcohol cues to internal thoughts and feelings. A rigid internal focus may constrain the ability to resist alcohol consumption and thus be a critical determinant in promoting craving and relapse in alcoholics.

Adult↗
PubMedDate not supplied

Selective processing of visual alcohol cues in abstinent alcoholics: an approach-avoidance conflict?

When symptomatic individuals selectively attend to emotionally relevant stimuli, the ability to shift attention away from such material is impaired. Subjects may, however, seek to avoid further processing of these stimuli, which would facilitate attentional shifts. This was examined in a group of abstinent alcoholics' responses to stimuli related to alcohol. Eight alcohol and eight neutral words served as cues in a covert attention task. The cues were either valid (2/3 of trials) or invalid (1/3 of trials) indicators of where a response target would appear after 100 or 500 milliseconds. The short interval was expected to interact with an initial approach toward the alcohol word, while the long interval would interact with a subsequent avoidance of the stimulus. As predicted, the alcoholics showed slower reaction times (RTs) to targets invalidly cued by alcohol words in the short interval, reflecting increased difficulties to shift attention. However, the alcoholics demonstrated faster RTs to targets invalidly cued by the alcohol words in the long interval. This indicates that the alcohol cue elicited emotional associations that, subsequent to initial stimulus identification, trigger an interrupting function of the attentional system.

Adult↗
PubMedDate not supplied

Heart rate responses indicate locked-in attention in alcoholics immediately prior to drinking.

Twenty alcohol-dependent subjects and 10 social drinkers were tested in two experimental conditions: (a) when they were informed that their drinks contained alcohol and (b) when they were informed that their drinks were soft drinks. When told "alcohol," alcoholics evidenced a heart rate (HR) acceleration, whereas control subjects were unaffected by the instruction. Moreover, severely dependent (SD) alcoholics' HR remained elevated within the evaluation period whereas moderately dependent (MD) alcoholics' HR returned to baseline levels. The sustained HR acceleration in SD alcoholics suggests that their attention became "locked in" on the alcohol information immediately prior to drinking in the "told-alcohol" condition. Such an inward focus of attention will seriously reduce the alcoholic's ability to shift attention away from alcohol information, which may explain the difficulties alcoholics experience in coping with high-risk situations for drinking. In the SD alcoholics, HR acceleration correlated with the time it took to start drinking subsequent beverages containing alcohol in the told-alcohol instruction. In the MD alcoholics, HR responses were related to the reported urge to drink, whereas it was only in the nondependent subjects that self-reported urge to drink was related to the actual alcohol-use behavior.

Alcohol Drinking↗
PubMedDate not supplied

Functional magnetic resonance imaging (fMRI) study of sex differences in a mental rotation task.

The main purpose of the present study was to: 1) to investigate differences between males and females in brain activation when performing a mental rotation task, 2) investigate hemisphere differences in brain activation during mental rotation. Brain activation was measured with functional magnetic resonance imaging (fMRI). Image acquisition was performed with a 1.5 Tesla Siemens Vision MR scanner equipped with 25 m T/m gradients. Scanning of anatomy was done with a T1-weighted 3D FLASH pulse sequence. Serial imaging with 70 BOLD sensitive echo planar (EPI) whole brain measurements was done during stimulus presentations, divided into 7 blocks of 10 EPI multi-slice volume measurements each. Eleven subjects were presented with black-and-white drawings of 3-D shapes taken from the set of 3-D perspective drawings developed by Shepard and Metzler [1], alternated with 2-D white bars as control stimuli. In the experimental condition, the subjects were shown 36 pairs of 3-D drawings, presented in three blocks of 12 pairs of drawings. The drawings were always presented pairwise. On half of the trials, the two 3-D shapes were congruent but portrayed with different orientation, in the other half the two shapes were incongruent. MR data were analyzed with the SPM-96 analysis software. After subtraction of activity related to the 2-D control stimuli, clusters of significant activation were found in the superior parietal lobule (BA 7), more intensely over the right hemisphere, and bilaterally in the inferior frontal gyrus (BA 44/45). Males showed predominantly parietal activation, while the females showed inferior frontal activation. It is suggested that males and females may differ in the processing strategy used when approaching a 3-D mental rotation task, males using a 'gestalt' strategy and females using a 'serial' reasoning strategy.

Adult↗