Disruption of bradycardia associated with discriminative conditioning in combat veterans with PTSD.

The effects of combat-related posttraumatic stress disorder (PTSD) on heart rate (HR) responding associated with a discriminative delay eyeblink (EB) conditioning paradigm are reported. Combat PTSD+, Combat PTSD-, and Noncombat PTSD- veterans were assessed with psychometric self-report measures, and baseline heart rate variability (HRV) was measured before receiving a 72-trial session of discriminative EB classical conditioning. Two types (red or green light) of conditioned stimuli (CS) were used: one (CS+) predicted a tone, followed immediately by an aversive stimulus (corneal airpuff); the other (CS-) predicted a tone alone, not followed by the airpuff. The light signal was presented for 5 seconds, during which HR was measured. On all psychometric measures, the PTSD+ subgroup was significantly different from the PTSD- subgroups (Combat + Noncombat), and the PTSD- subgroups did not significantly differ from each other. A linear deceleration in HR to CS+ and CS- signals was found in the combined PTSD- subgroup and on CS- trials in the PTSD+ subgroup, but was not present on CS+ trials in the PTSD+ subgroup. Results are interpreted with respect to a behavioral stages model of conditioned bradycardia and in terms of neural substrates which are both critical to HR conditioning and known to be abnormal in PTSD.

Learning and memory impairment in PTSD: relationship to depression.

Memory function was studied in combat veterans with posttraumatic stress disorder (PTSD), combat veterans without PTSD, and noncombat veterans. The Vocabulary and Digit Span subtests of the WAIS and Logical Memory (LMS) and Verbal Paired Associates (VPAS) subtests of the Wechsler Memory Scale III were administered. Combat veterans with PTSD showed impaired memory on the LMS and VPAS compared to combat veterans without PTSD or noncombat veterans. Veterans with PTSD also showed lower WAIS Vocabulary subtest scores--but not digit span subtest scores--than combat veterans without PTSD or noncombat veterans. Medication status, co-morbid diagnosis, and age all failed to account for these memory differences, but when self-assessed depression--as measured by the Zung Self-Rating Depression Scale--or anxiety--as measured by the Spielberger State-Trait Anxiety Scale--was statistically removed, group differences on these memory measures were no longer significant. However, using a stepwise regression procedure, in which both anxiety and depression were employed to predict the LMS and VPAS scores, only the Zung scale reliably predicated performance. The present results, showing that PTSD is associated with general learning and memory impairments, is an important finding, but the specific effects of depression as a mediator of these deficits should be further studied.

Discriminative delay Pavlovian eyeblink conditioning in veterans with and without posttraumatic stress disorder.

BACKGROUND: Impaired eyeblink (EB) classical conditioning using a delay paradigm has previously been shown in combat veterans, as well as in a group of depressed adults, compared to normal individuals. Significant deficits in immediate memory (IM) in combat PTSD+ veterans, compared to normal controls, have also been previously shown, but these differences became non-significant after controlling for level of self-reported depression. Furthermore, EB conditioning has been shown to be significantly correlated with heart rate variability (HRV) in normal adults. The present study examined how depression (self-reported), IM, and resting HRV are related to discriminative delay classical EB conditioning in veterans with and without PTSD. METHOD: Three groups of subjects (combat PTSD+, combat PTSD-, and non-combat PTSD-) were assessed for self-report of depression and anxiety, as well as IM and HRV. Subjects received a single session of discriminative EB classical conditioning in which the conditioned stimulus (CS) was a light signal (either red or green) compounded with a tone. On CS+ trials, the light-tone compound stimulus co-terminated with a corneal airpuff (unconditioned stimulus, US), thus producing a delay paradigm. On CS- trials the appropriate light-tone stimulus was presented but not followed by the airpuff US. EB amplitude and frequency were recorded. RESULTS: PTSD+ subjects had greater self-reported depression and anxiety scores than the two control groups, as well as lower scores on a measure of IM. However, the IM difference was not significant after the effects of self-reported depression and anxiety were controlled. EB CR amplitude was significantly greater to CS+ than CS- for all three groups. EB amplitude to both the US (airpuff) and the CS+ declined over trials, but was significantly lower in the combat PTSD+ group compared to the combined PTSD- groups. Subjects who reached an EB CR acquisition criterion had significantly greater scores on IM than those who did not reach criterion. Factor analysis of the entire data set revealed four factors corresponding to (1) self-reported depression and anxiety, (2) IM, (3) HRV, and (4) EB amplitude. EB frequency was significantly predicted by IM and HRV. CONCLUSIONS: These data extend our previous results by showing deficits in EB conditioning among combat PTSD+ veterans that were associated with lower IM and resting HRV, but were not associated with self-report of depression.

Combat veterans show normal discrimination during differential trace eyeblink conditioning, but increased responsivity to the conditioned and unconditioned stimulus.

The question addressed in the present study was whether post-traumatic stress disorder (PTSD) results in associative learning impairments. To answer this question, differential trace eyeblink (EB) conditioning was studied in combat veterans with PTSD, combat veterans without PTSD, and non-combat veterans without PTSD. Veterans with PTSD showed normal EB discrimination, suggesting that associative learning is not impaired by PTSD. Veterans with PTSD also showed normal extinction. However, subjects with PTSD showed more EB conditioned responses (CRs), as well as increased CR amplitude. Increased response amplitude to the airpuff unconditioned stimulus presented alone (viz. the unconditioned response), as well as to the airpuff on CS+ trials during conditioning also occurred in the subjects with PTSD. These findings suggest increased reactivity in combat veterans with PTSD, compared to those without PTSD, but such heightened reactivity does not affect somatomotor associative learning.

Pavlovian eyeblink conditioning in combat veterans with and without post-traumatic stress disorder.

Several recent studies have investigated relationships between post-traumatic stress disorder (PTSD) and learning and memory problems. These reports have found in general that not only does PTSD affect trauma-related memories, but when patients with PTSD are compared with similar trauma patients without PTSD, general memory impairments have been found. The present paper reports a study in which associative learning, using Pavlovian eyeblink conditioning, was investigated in combat veterans with and without chronic PTSD, using interstimulus intervals of 500 and 1000 msec in two separate experiments. Although several recent reports suggest that larger-magnitude autonomic conditioned responses occur in patients with PTSD during Pavlovian conditioning, the present study found evidence of impaired Pavlovian eyeblink conditioning in combat veterans with and without PTSD, compared to non-combat veterans. Although these data suggest that combat leads to an impaired associative learning process regardless of whether PTSD is apparent, a group of community-dwelling combat veterans not under medical treatment showed normal conditioning, suggesting that variables other than prior combat must also be involved.

Multiple response measures during classical conditioning.

Animal research assessing multiple responses during Pavlovian conditioning has revealed a dichotomy between the central nervous system (CNS) substrates for somatomotor and visceral CRs. These findings have implications for the study of clinical/applied problems in human subjects, since differences in the acquisition functions for these response systems may suggest which CNS structures are involved in various neuropsychiatric disorders. The present paper describes methods and procedures utilized to assess the somatomotor conditioned eyeblink (EB) response and accompanying visceral changes in human subjects. Methods are described for assessing concomitant EB conditioned and unconditioned responses and the accompanying heart rate, skin conductance, and respiratory changes during Pavlovian conditioning in human subjects. It is stressed that utilization of concomitant conditioning of these different response systems may lead to inferences regarding the central nervous system structures involved in a variety of different kinds of clinical problems.