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Biomedical subjects

A Ohman

Publications and source records attributed to A Ohman.

At least 91 records · Page 5Linked 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↗
PubMed1975

Effects of attention, activation and stimulus regularity on short-term 'habituation' of the averaged evoked response.

Three studies are reported in which the effects of direction of attention, level of activation and regularity of stimulation on the rate of amplitude decrement over time of the auditory evoked vertex responses in humans were examined. Short-term, stimulus-by-stimulus changes were assessed by averaging across trains each of 10 click stimuli. The effect of directing attentions towards the stimuli was to enhance the N1 - P2 component, but usually only under conditions of high activation and with irregular stimulus presentation. Habituation rate was hardly affected by the experimental manipulations. The most clear-cut relationship between psychological influences and the AER was that between level of activation and the P2 - N2 component.

Adult↗
PubMed1975

One-trial learning and superior resistance to extinction of autonomic responses conditioned to potentially phobic stimuli.

Human subjects were exposed to pictures of potentially phobic (snakes) and supposedly neutral (houses) objects as conditioned stimuli (CSs) in a Pavlovian conditioning experiment with shock as unconditioned stimulus (US), and skin conductance and finger pulse volume as dependent variables. The skin conductance responses conditioned to phobic stimuli were acquired after one CS-US pairing, and showed practically no extinction, whereas the responses to neutral stimuli showed very little resistance to extinction after both 1 and 5 reinforcements. The superior resistance to extinction of the phobic condition was interpreted to be a specific associative effect. In general, the skin conductance acquisition data showed tendencies similar to those during extinction. For finger pulse volume responses, however, there were very weak conditioning effects, and no effect of stimulus.

Adult↗
PubMed1975

Treatment of temporomandibular joint syndrome with biofeedback training.

Treatment of temporomandibular joint syndrome by the use of biofeedback training involves two stages. First, the patient is made aware of the level of tension in the masseter muscle and, second, he is taught to reduce the level of tension. In those individuals whose pain most likely is associated with high muscle tension, this treatment method is apparently successful. The successful treatment of a patient with a history of long-term TMJ pain is described.

Action Potentials↗
PubMed1975

Reconstruction of the defective mandible.

In a clinical material consisting of 31 cases of mandibular defects, caused by tumour resection or by trauma, reconstruction has been carried out by means of a stabilizing titanium splint and autologous bone and marrow transplantation, the longest period of observation being 9 years. The functional results obtained are assessed with reference to the cause of resection. Different technical procedures are described and the objectives and the planning of reconstruction of the lower jaw are discussed.

Adult↗