Attentional stages of information processing during a continuous performance test: a startle modification analysis

This study of 31 college students employed the startle eye-blink modification (SEM) technique to index both early and later stages of attentional processing during a memory-load version of the Continuous Performance Test (CPT). Participants viewed a series of digits and pressed a button after the digit 7 of each 3-7 sequence. A startling noise burst was presented either 120 or 1,200 ms following three preselected prepulses: target (3), nontarget (non-3 and non-7 digits), or target plus distractor (3 and simultaneous tone distractor). Greater startle inhibition occurred 120 ms following target and target-plus-distractor prepulses compared with nontargets, indicating early selective attention. No difference was observed between SEM during target and target-plus-distractor prepulses, suggesting the distractor was effectively ignored. At 1,200 ms, the three prepulse types produced nondifferential inhibition, suggesting that modality-specific selective attention occurs in anticipation of the presentation of the next CPT prepulse. These findings indicate that SEM distinguishes between different early selective attention and later anticipatory attention subprocesses underlying the CPT.

Startle reactivity and PTSD symptoms in a community sample of women

Exaggerated startle and PTSD symptoms have been investigated primarily in relation to acute or Type I stressors. The present study examined PTSD symptoms and startle eyeblink response in relation to chronic or Type II stressors. Type II stressors were operationally defined as high levels of childhood corporal punishment and high levels of current partner aggression. This study recruited a sample of 52 women from a metropolitan community and administered several questionnaires assessing experience of corporal punishment in childhood, current intimate partner aggression and level of PTSD symptoms. Following questionnaires, women were presented with eight auditory startle probes (white noise). Results showed that both childhood corporal punishment and intimate partner aggression were associated with women's PTSD symptom scores. However, only PTSD symptom scores were associated with reduced startle. Results are discussed in light of Type I and Type II stressors, and recent suggestions in the PTSD literature that a subgroup of individuals may experience physiological suppression rather than heightened physiological reactivity.

On the clinical and cognitive meaning of impaired sensorimotor gating in schizophrenia

Schizophrenia patients have been shown to have a defective sensorimotor gating process as indexed by impaired prepulse inhibition of the startle eyeblink reflex. Moreover, we have previously reported that schizophrenia patients have dysfunctional attentional modulation of prepulse inhibition. The present experiment combined our previous sample of 14 schizophrenia outpatients and 12 demographically matched control subjects with a new sample of 10 outpatients and 6 control subjects. All participants performed a tone-length judgement task that involved attending to one pitch of tone (the attended prepulse) and ignoring another pitch of tone (the ignored prepulse). During this task the acoustic startle eyeblink reflex was electromyographically recorded from the orbicularis oculi muscle. The results replicated the finding of impaired attentional modulation of prepulse inhibition in the new sample of schizophrenia outpatients compared to demographically matched control subjects. Specifically, the new control group exhibited greater startle modification during the attended prepulse, whereas the new patient group failed to show this differential effect. In addition, impaired prepulse inhibition following the attended prepulse was significantly correlated with heightened delusions, conceptual disorganization, and suspiciousness as measured with the expanded Brief Psychiatric Rating Scale. These correlations were significant with prepulse inhibition to the attended prepulse but not with prepulse inhibition to the ignored prepulse. Impaired prepulse inhibition was not correlated with negative symptoms. All in all, the results support the hypothesis that impaired attentional modulation of startle prepulse inhibition reflects basic neurocognitive processes related to thought disorder in schizophrenia.

Automatic and controlled attentional processes in startle eyeblink modification: effects of habituation of the prepulse

The effect of prehabituation of the prepulse on startle eyeblink modification was studied in two experiments. In Experiment 1, college student participants were either prehabituated or nonhabituated to a tone that served as a prepulse in a startle modification passive attention paradigm. Neither short lead interval (60 and 120 ms) prepulse inhibition (PPI) nor long lead interval (2,000 ms) prepulse facilitation (PPF) was affected by the prehabituation procedure. In Experiment 2, participants were presented with an active attention paradigm in which one of two tone prepulses was attended while the other was ignored. One group was prehabituated to the prepulses and the other was not. Unlike the results with the passive paradigm in Experiment 1, prehabituation did significantly diminish attentional modulation of PPI and PPF. These results are consistent with the hypothesis that passive PPI and PPF are primarily automatic processes, whereas attentional modulation involves controlled cognitive processing.

Discrete and continuous prepulses have differential effects on startle prepulse inhibition and skin conductance orienting

The effectiveness of different types of auditory prepulses in eliciting skin conductance orienting and in producing prepulse inhibition (PPI) of the acoustic startle eyeblink was studied in two experiments. A discrete white noise prepulse produced greater PPI than either a continuous white noise, a discrete tone, or a continuous tone. The discrete white noise advantage was not due to similarity in bandwidth to the startle pulse or to a refractory effect of the prepulse. Moreover, a dissociation between PPI and skin conductance orienting was seen in both experiments. PPI using auditory prepulses appears to be dependent primarily on the acoustic characteristics of the transient portion of the prepulse, whereas skin conductance orienting is more dependent on the sustained portions of the stimulus.

Attentional modulation of short- and long-lead-interval modification of the acoustic startle eyeblink response: comparing auditory and visual prestimuli

Studies in our laboratory have shown that modification of startle by lead stimuli with short- and long-lead-intervals is modulated by stimulus significance. The significant stimulus in a tone duration judgement task generates enhanced short-lead-interval startle inhibition as well as pronounced long-lead-interval startle facilitation. The present study was designed to compare tones with simple visual stimuli as lead stimuli in a counterbalanced within-subjects design (Experiment I) or between-subjects design (Experiment II). The results show that auditory compared to visual lead stimuli generate more short-lead-interval inhibition but comparable amounts of long-lead-interval startle facilitation, which was significantly enhanced on to-be-attended trials independent of sensory modality. The attentional manipulation did not yield short-lead-interval effects in Experiment I, but previously reported attention effects were replicated in Experiment II. The results suggest early modality effects on startle modification, reflected by the differing levels of inhibition. Late effects of both modality and attention, however, seem to reflect a sensory modality independent process in startle modification.

The psychological significance of human startle eyeblink modification: a review

The human startle eyeblink reflex is reliably modified by both cognitive and emotional processes. This review provides a comprehensive survey of the current literature on human startle modification and its psychological significance. Issues raised for short lead interval startle inhibition include its interpretation as a measure of protection of processing, sensorimotor gating and early attentional processing. For long lead interval effects, interpretations related to attentional and emotional processing are discussed. Also reviewed are clinical applications to information processing dysfunctions in the schizophrenia spectrum disorders, and to emotional processing disorders. Finally, an integrative summary that incorporates most of the cognitive findings is presented and directions for future research are identified regarding both cognitive and emotional modification of startle.

Autonomic orienting and the allocation of processing resources in schizophrenia patients and putatively at-risk individuals

The differential allocation of attentional resources to attended and ignored stimuli was examined by measuring skin conductance orienting responses and secondary reaction time in relatively asymptomatic schizophrenia outpatients, demographically matched normal controls, college students putatively at risk for psychosis, and a college student control group. At-risk participants were those with extreme scores on scales for either anhedonia or perceptual aberration-magical ideation (per-mags). Compared to control groups, the patients and per-mags showed secondary reaction time results suggesting a delay in the differential allocation of attentional resources. This deficit was observed particularly in patients and matched controls with few or no skin conductance orienting responses, suggesting that impaired autonomic orienting is related to underlying cognitive-attentional vulnerability factors.

Autonomic orienting and the allocation of processing resources in schizophrenia patients and putatively at-risk individuals

The differential allocation of attentional resources to attended and ignored stimuli was examined by measuring skin conductance orienting responses and secondary reaction time in relatively asymptomatic schizophrenia outpatients, demographically matched normal controls, college students putatively at risk for psychosis, and a college student control group. At-risk participants were those with extreme scores on scales for either anhedonia or perceptual aberration-magical ideation (per-mags). Compared to control groups, the patients and per-mags showed secondary reaction time results suggesting a delay in the differential allocation of attentional resources. This deficit was observed particularly in patients and matched controls with few or no skin conductance orienting responses, suggesting that impaired autonomic orienting is related to underlying cognitive-attentional vulnerability factors.

The varying time courses of attentional and affective modulation of the startle eyeblink reflex

In previous research on modulation of the startle eyeblink reflex, emotional effects have been demonstrated only at late probe positions, whereas attentional effects have been found at both early and late positions but only when the prepulses were affectively neutral. In Experiment 1, participants viewed emotionally valenced pictures and were instructed to attend to the duration of half of the slides. Affective modulation of the startle eyeblink occurred at long lead intervals, but attentional modulation also occurred late. In Experiment 2, participants viewed the same slides used in Experiment 1 but were instructed to attend to the duration of only the positive or the negative slides. Affective modulation occurred at both early and late probe positions, whereas attentional effects occurred only following slide offset. Early (250 ms) affective modification of startle eyeblink has not been previously reported. These results suggest that the time courses of emotional and attentional modulation of startle are variable and can occur at both early and late startle probe positions, depending on task requirements.

Tracking early and late stages of information processing: contributions of startle eyeblink reflex modification

Startle eyeblink modification was examined as a measure of information processing. College students were presented with tones of 5 and 7 s duration of either high or low pitch, followed by startle-eliciting stimuli at lead intervals of 120, 2,000, 4,500, or 6,000 ms. Attention to tones was manipulated by instructing the task group to count the longer tones of either pitch. The no-task group had no instructed task. Startle eyeblink was inhibited at the short lead interval and facilitated at the long lead intervals in both groups. The task group showed greater inhibition and facilitation during attended than during ignored tones, indicating that early and late controlled processing was occurring. In the task group, the degree of facilitation appeared to reflect the degree of cognitive demands of the task. Startle eyeblink modification may provide a sensitive measure of the nature and timing of stages of processing in active and passive attentional conditions.

Attentional modulation of startle in psychosis-prone college students

Attentional modulation of startle eyeblink was studied in college students putatively at risk for psychosis and in normal controls. At-risk subjects had extreme scores on scales for either anhedonia or perceptual aberration-magical thinking (per-mags). Subjects were presented with to-be-attended and to-be-ignored tones; white noise startle probes were presented at lead intervals of 60, 120, 240, or 2,000 ms following the onset of attended and ignored tones and during intertone intervals. Controls showed greater inhibition of startle blink at 120 ms and greater facilitation at 2,000 ms during to-be-attended than to-be-ignored tone, demonstrating attentional modulation of prepulse inhibition and facilitation. Both at-risk groups showed normal overall levels of early inhibition and late facilitation. However, per-mags failed to show attentional modulation of either inhibition at 120 ms or facilitation at 2,000 ms; anhedonics showed no modulation of inhibition and modulation of facilitation was delayed in development. The results for the per-mags are strikingly similar to those observed in schizophrenic patients and suggest that these deficits index a trait-linked vulnerability to disorders in the schizophrenic spectrum.

Autonomic abnormalities in schizophrenia. State or trait indicators?

BACKGROUND

Tonic electrodermal measures have been widely used to index autonomic abnormalities in schizophrenia, whereas phasic electrodermal nonresponsiveness has been frequently used to index attentional orienting abnormalities. The primary objective of the present study was to assess whether these electrodermal abnormalities are episode indicators or vulnerability indicators.

METHODS

Twenty patients with a recent first episode of schizophrenia were tested during symptomatically remitted states and psychotic states. Twenty demographically matched normal controls were tested at two comparable intervals. Testing for stability of abnormalities across remitted and psychotic states allowed us to determine whether tonic and phasic electrodermal measures qualify as episode indicators or vulnerability indicators.

RESULTS

Tonic electrodermal activity was abnormally elevated only during the psychotic state, which indicates that it is an episode indicator in schizophrenia. Phasic hyporesponsiveness relative to levels of general activation was present in both the remitted and the psychotic states, most strikingly during the psychotic state, and the proportion of patients who were electrodermally nonresponsive tended to be abnormally high during the remission test.

CONCLUSION

Tonic electrodermal hyperarousal appears to be a state-sensitive episode indicator, whereas phasic electrodermal hyporesponsiveness to innocuous stimuli relative to activation level appears to be a mediating vulnerability factor.

Preferential neural processing of attended stimuli in attention-deficit hyperactivity disorder and normal boys

Event-related auditory and visual potentials were recorded from 36 attention-deficit hyperactivity disorder (ADHD) and 35 normal 6-year-old subjects engaged in a two-choice discrimination task. When normal subjects attended to stimuli in a given modality, enhanced negative (N2) and positive (P3b) responses (as compared with responses to nonattended stimuli) were found for auditory and visual target stimuli. In contrast, when ADHD subjects attended, little or no enhanced negative responses were found in either modality, and enhanced positive P3b responses were found only in response to visual target stimuli. Auditory N1, N2, and P3b and visual N2 amplitudes to attended target stimuli were significantly reduced in ADHD subjects as compared with normal subjects. No between-group differences were found for responses to nonattended stimuli. Both amplitude and latency abnormalities indicate that ADHD boys suffer from deficient preferential processing of attended stimuli. P3b and N2 abnormalities found here suggest deficiencies in two independent cognitive processes thought to be crucial to what we perceive, learn, and remember.

Probing the orienting response with startle modification and secondary reaction time

Current models of orienting suggest a relationship between the orienting response and attentional processing. This relationship was examined using two independent probe techniques to index attentional processing: secondary reaction time and startle eyeblink modification. Twenty-eight college-age subjects received intermixed presentations of to-be-attended and to-be-ignored tones. Skin conductance orienting responses were obtained during a subset of the tones. Each of the remaining tones contained either a secondary reaction time probe at lead intervals of 150 or 2,000 ms or a startle eyeblink probe presented at lead intervals of 120 or 2,000 ms. In addition, reaction time and startle probes also were presented during selected intertone intervals, and responses to these stimuli served as the baselines from which to compare changes in reaction time and blink amplitude produced by the attended and ignored tones. The results revealed that, compared with the ignored tones, the attended tones were associated with larger skin conductance orienting responses, greater blink inhibition at the 120-ms lead interval, greater blink facilitation at the 2,000-ms lead interval, and greater reaction time slowing at the 2,000-ms lead interval. Consistent with previous findings, the ignored tone was associated with greater reaction time slowing than was the attended tone at the 150-ms lead interval. The results support a relationship between elicitation of the skin conductance orienting response and attentional processes and suggest that the secondary reaction time and blink modification techniques may provide unique information regarding this relationship.

Attention and schizophrenia: impaired modulation of the startle reflex

The startle reflex (SR) elicited by abrupt stimuli can be modified by attention to nonstartling stimuli that shortly precede the startle-eliciting stimulus. The present study of 15 recent-onset, relatively asymptomatic schizophrenic outpatients and 14 demographically matched normal control subjects demonstrated that attentional modulation of SR is impaired in schizophrenic patients. Specifically, the control group exhibited greater startle eye-blink modification following to-be-attended prestimuli than following to-be-ignored prestimuli, whereas the patients failed to show the attentional modulation effect. These results suggest traitlike attentional deficits in schizophrenia because the patients were relatively asymptomatic. The measurement of attentional modulation of SR may provide a nonverbal, reflexive, state-independent marker of the vulnerability to schizophrenia.

Modification of the acoustic startle-reflex eyeblink: a tool for investigating early and late attentional processes

The present experiment examined the sensitivity of short and long lead interval startle eyeblink modification to attentional processing. Eighteen college student subjects were presented with a series of intermixed high and low pitched tones and instructed to attend to tones of one pitch and to ignore tones of the other pitch. The majority of the attended and ignored tones served as prepulses for an eyeblink-eliciting burst of white noise presented at lead intervals of 60, 120, 240 and 2000 ms following prepulse onset. Results indicate that both attended and ignored prepulses produce significant startle eyeblink modification: significant blink inhibition at the 60, 120 and 240 ms short lead intervals, and blink facilitation at the 2000 ms long lead interval. In addition, compared with the ignored prepulse, the attended prepulse produced significantly greater blink inhibition at the 120 ms lead interval as well as significantly greater blink facilitation at the 2000 ms lead interval. These results suggest that both short and long lead interval startle eyeblink modification measures may be useful tools for future investigations of the early and later stages of attentional processing.

Restrained and nonrestrained eaters' orienting responses to food and nonfood odors

Dietary restraint was assessed by Stunkard and Messick's (1985) three-factor eating questionnaire, using the restraint subfactor score only in normal-weight college students (n = 41). The subjects were than assessed for skin conductance orienting responses (ORs) to food and nonfood odors when hungry and sated (after a standard breakfast and after an overnight fast). Subjects also rated their hunger and each odorant for pleasantness on separate 7-point scales. Results indicated that restrained eaters oriented less to odors than did nonrestrained subjects. Food deprivation did not differentially affect the ORs in restrained and nonrestrained eaters. The ORs, however, tended to be decreased in all of subjects who had had breakfast. Finally, nonrestrained subjects rated food and nonfood odors approximately equal in pleasantness, while the restrained eaters rated food odors as more pleasant than the nonfood odors. These results suggest that restrained eaters must certainly process odor stimuli related to foods, but also suggests that orienting to these salient (informative) cues is restricted. Perhaps in defense of the diet, restrained eaters learn methods/responses (cognitive strategies, instructional sets) to block orienting to food related cues such as odors.

Concurrent and predictive electrodermal correlates of symptomatology in recent-onset schizophrenic patients

Electrodermal activity and symptomatology were interrelated in a group of 56 male and 13 female recent-onset schizophrenic patients. Electrodermal activity was indexed by the frequency of nonspecific skin conductances responses and the number of trials to habituation of the skin conductance orienting response. Symptomatology was assessed by the Brief Psychiatric Rating Scale (BPRS) on two separate test occasions. The first test occasion was during the inpatient period when psychotic symptoms were prevalent and medications were variable. The second test occasion was several months later during an outpatient period when symptoms were stabilized and medications held constant. Electrodermal activity was positively and significantly related to a number of symptoms in male patients, most reliably the BPRS factors Activation and Hostility/Suspiciousness. These relationships were most consistent during the outpatient period. Of particular theoretical interest, greater electrodermal activity during the inpatient period was associated with greater outpatient psychopathology. The results suggest that heightened inpatient electrodermal activity is predictive of poor short-term symptomatic recovery in recent-onset, acute, male schizophrenic patients.

Concurrent and predictive electrodermal correlates of symptomatology in recent-onset schizophrenic patients

Electrodermal activity and symptomatology were interrelated in a group of 56 male and 13 female recent-onset schizophrenic patients. Electrodermal activity was indexed by the frequency of nonspecific skin conductances responses and the number of trials to habituation of the skin conductance orienting response. Symptomatology was assessed by the Brief Psychiatric Rating Scale (BPRS) on two separate test occasions. The first test occasion was during the inpatient period when psychotic symptoms were prevalent and medications were variable. The second test occasion was several months later during an outpatient period when symptoms were stabilized and medications held constant. Electrodermal activity was positively and significantly related to a number of symptoms in male patients, most reliably the BPRS factors Activation and Hostility/Suspiciousness. These relationships were most consistent during the outpatient period. Of particular theoretical interest, greater electrodermal activity during the inpatient period was associated with greater outpatient psychopathology. The results suggest that heightened inpatient electrodermal activity is predictive of poor short-term symptomatic recovery in recent-onset, acute, male schizophrenic patients.

Electrodermal anomalies in recent-onset schizophrenia: relationships to symptoms and prognosis

Electrodermal activity was measured in recent-onset schizophrenic patients (n = 98) and matched normal control subjects (n = 40) as part of an ongoing longitudinal study. Results at the initial inpatient test were generally consistent with the current consensus in the literature. A large subgroup of the patients was found to be nonresponsive with the phasic skin conductance orienting response measure, whereas the remaining subgroup of patients was found to be electrodermally tonically hyperaroused. Heightened electrodermal activity at the inpatient test was associated with a number of symptoms in male patients and with poor recovery from the acute schizophrenic episode. Followup tests conducted when the patients were in states of remission and psychotic relapse revealed that tonic electrodermal arousal measures qualify as state-sensitive episode indicators, whereas phasic nonresponding may qualify as an atypical vulnerability indicator. Moreover, preliminary data from three patients suggest that increases in tonic electrodermal arousal may temporally precede psychotic relapses. The principal findings are consistent with a vulnerability/stress model that posits that electrodermal hyperarousal is part of a transient intermediate state that may lead to a psychotic episode in a vulnerable individual.