Skin Conductance Conditioning to Potentially Phobic Stimuli as a Function of Interstimulus Interval and Delay Versus Trace Paradigm

Because prepared learning has been defined in terms of response acquisition in spite of degraded input, it was expected that differences in resistance to extinction between skin conductance responses conditioned to potentially phobic and neutral stimuli would increase with increased interstimulus interval (ISI) and be larger with a trace than with a delay conditioning paradigm. Twelve groups with 10 subjects each were observed in a differential conditioning experiment manipulating ISI (2, 8, or 16 sec), paradigm (delay versus trace), and fear-relevance of the conditioned stimulus (potentially phobic versus neutral). The results showed highly reliable resistance to extinction of first-interval anticipatory responses to phobic stimuli, and no resistance to extinction of the corresponding responses to the neutral stimuli. This difference did not interact either with the ISI or the paradigm factor. Thus, although underscoring the reliability of the difference in conditioning to potentially phobic and neutral stimuli, the results did not support the specific hypothesis of conditioning to phobic stimuli as being less dependent on the ISI parameters than conditioning to neutral stimuli.     

Bilateral Skin Conductance and Skin Potential in Schizophrenic and Normal Subjects: The Identification of the Fast Habituator Group of Schizophrenics

Chronic schizophrenics from three different hospitals were compared to normal subjects on skin conductance parameters. In addition to “Responders” and “Nonresponders” as reported by Gruzelier and Venables (1972), a group of “Fast Habituator” schizophrenics was found. These subjects produce one or at most two responses before habituation in an orienting series. The SC waveform of fast habituator subjects shows long latency, slow risetime and long recovery, although the amplitude of response is within normal limits.     

Sensation Seeking, Trait and State Anxiety, and the Electrodermal Orienting Response

The relationship between sensation seeking and the orienting reflex (OR) using skin conductance change is investigated in two experiments. In Experiment I, high sensation seekers gave a greater initial OR In novel visual stimuli while not differing in habituation on subsequent trials. In Experiment II. the paradigm was extended to include auditory as well as visual stimuli. Again, high sensation seekers were found to be more arousable with respect to initial ORs while not differing in habituation rates. The results suggest that sensation seekers may be characterized as having strong excitatory CNS processes. In Experiment II, anxiety (trait and state) was also related to the OR. There were no effects due to trait anxiety but state anxiety did yield significant differences. The more highly anxious (state) subjects had weaker initial ORs than lows in both novel tones, but not to repeated tones. The findings with state anxiety are consistent with findings by others using anxiety neurotics as subjects.     

Autonomic Correlates of Depression and Clinical Improvement Following Electroconvulsive Shock Therapy

Electrodermal responses (EDRs) and heart rate (HR) were recorded during a variety of tasks from 20 hospitalized depressed patients before and after a series of electroconvulsive shock treatments (ECTs). The depressed patients, compared to nondepressed controls during the pre-ECT test, exhibited lower skin conductance levels, smaller phasic skin conductance responses with longer latencies, higher tonic HR, and smaller HR changes to stimuli. This response pattern suggests a complex state of “environmental rejection” coupled with “low arousal” in the depressed patients. Certain EDR measures were related to the severity of depressive symptomatology while tonic HR was related to the agitation/retardation symptoms. Patients who subsequently responded well following ECT were more like the controls on certain pre-treatment measures than those who failed to respond favorably. There were little EDR or HR changes following ECT and what changes did occur were unrelated to differences in clinical improvement. It was suggested that, despite temporary clinical improvement following ECT, depressed patients have a chronic affective disorder which is reflected in the EDR and HR measures.     

The Psychological Significance of Task-Induced Tonic Changes in Somatic and Autonomic Activity

Two experiments tested the view that task-induced autonomic-somatic gradient parallelism does exist and that the steeper the physiological gradients, over the course of a task, the more involved the subject and the greater the effort. Thirty-three male subjects performed easy and difficult versions of a continuous reaction time task. In both experiments the difficult task prompted steeper electromyographic (EMG) activity gradients than did the easy version. Scores on heart rate (HR) and skin conductance did not show clear gradients. However, task-dependent effort was positively related to the magnitude of the initial HR acceleration and to the steepness of the EMG gradient. The autonomic-somatic coupling hypothesis of Obrist did not explain the results. Instead, evidence for ventilatory-somatic parallelism was found.     

Interaction of a Motor Response, and Reaction Time and Time Estimation Tasks, on Heart Rate and Skin Conductance

The influence of motor responding and typical psychophysiological tasks on heart rate was tested by manipulating motor requirements of reaction time (RT) and time estimation (TE) tasks. Thirty-four volunteers were assigned randomly to four groups. Two groups squeezed a hand dynamometer at the start of a trial and the other two groups squeezed at the finish of the trial. The force of the squeeze was also manipulated: either 3 kg (3) or 7 kg (7). The four groups were Start 3, Start 7, Finish 3, and Finish 7. All subjects participated in the TE and RT tasks. The dependent variables were measurements of forearm flexor muscle tension, heart rate and skin conductance. It was found that the manipulations of when and with what force a person squeezed the dynamometer resulted in reliable group differences in muscle tension. The magnitude of acceleratory components of the triphasic (acceleration-deceleration-acceleration) cardiac response was amplified by tension. The magnitude of the deceleratory component seemed to depend on both muscle tension and stimulus processing. Except for the magnitude of the response-bound deceleration, RT and TE produced very similar heart rate responses, and skin conductance did not differ among groups. The data were interpreted as providing evidence that motor response acts as an amplifier for the phasic HR produced by common psychological paradigms.     

Recommendations for the examination of peripheral nerve biopsies

 Peripheral nerve biopsy is now an established, valuable investigative procedure, but as it can give rise to significant residual symptoms it should only be undertaken after careful consideration of the indications and with informed consent from the patient. Nerve biopsies should only be processed and evaluated in a laboratory with the relevant particular expertise. It is generally recommended that a sural nerve biopsy be performed in combination with a muscle biopsy but not vice versa (muscle biopsies together with a nerve biopsy). Nerve biopsy is not the only means of sampling peripheral nerve tissue to study the peripheral nervous system. Examination of the innervation of the skin may be informative. The same is likely to be true for motor point muscle biopsy. Nerve biopsy is mainly used for morphology although molecular genetic techniques using fresh or archival nerve biopsies are increasingly available. Chemical analysis is undertaken mainly for research purposes. Received: 10 June 1997 / Accepted: 29 October 1997     

Neuroanatomical Correlates of Skin Conductance Orienting in Normal Humans: A Magnetic Resonance Imaging Study

Although little is known about the neuroanatomical basis of skin conductance orienting in intact normal humans, the limited literature on animals and humans with neurological and clinical disorders implicate prefrontal, temporal/amygdala, and pons brain areas in mediating skin conductance orienting. This study relates area of these structures using magnetic resonance imaging techniques to skin conductance orienting responses in 17 normal humans in order to test hypotheses that larger area of these excitatory structures will be associated with more orienting responses. Left and right hand skin conductance orienting was significantly associated with left and right prefrontal area (r = .44-.60), area of the pons (r = .43-.54), and left but not right temporal/amygdala area (r = .47-.53). No relationships were observed with areas thought to be unrelated to skin conductance activity (cerebellum, nonfrontal cortical area), medial prefrontal cortex, or the third ventricle. This appears to be the first study relating brain structure to skin conductance orienting in intact normal humans. Although preliminary at the present time, these results implicate prefrontal, pons, and temporal/amygdala areas in the mediation of skin conductance orienting in normal humans.     

Effect of maximal arm exercise on skin blood flux in the paralyzed lower limbs in persons with spinal cord injury

 The purpose of the present study was to examine the effect of maximal arm exercise on the skin blood circulation of the paralyzed lower limbs in persons with spinal cord injury (PSCI). Eight male PSCI with complete lesions located between T3 and L1 performed graded maximal arm-cranking exercise (MACE) to exhaustion. The skin blood flux at the thigh (SBFT) and that at the calf (SBFC) were monitored using laser-Doppler flowmeter at rest and for 15 s immediately after the MACE. The subject's mean peak oxygen uptake and peak heart rate was 1.41 ± 0.22 l · min^–1 and 171.6 ± 19.2 beats · min^–1, respectively. No PSCI showed any increase in either SBFT or SBFC after the MACE, when compared with the values at rest. These results suggest that the blood circulation of the skin in the paralyzed lower limbs in PSCI is unaffected by the MACE. Accepted: 12 September 1996