Joel Ellwanger

Motor and cognitive aspects of motor retardation in depression.

BACKGROUND Motor retardation is a common feature of major depressive disorder having potential prognostic and etiopathological significance. According to DSM-IV, depressed patients who meet criteria for psychomotor retardation, must exhibit motor slowing of sufficient severity to be observed by others. However, overt presentations of motor slowing cannot distinguish slowness due to cognitive factors from slowness due to neuromotor disturbances. METHODS We examined cognitive and neuromotor aspects of motor slowing in 36 depressed patients to test the hypothesis that a significant proportion of patients exhibit motor programming disturbances in addition to psychomotor impairment. A novel instrumental technique was used to assess motor programming in terms of the subjects ability to program movement velocity as a function of movement distance. A traditional psychomotor battery was combined with an instrumental measure of reaction time to assess the cognitive aspects of motor retardation. RESULTS The depressed patients exhibited significant impairment on the velocity scaling measure and longer reaction times compared with nondepressed controls. Approximately 40% of the patients demonstrated abnormal psychomotor function as measured by the traditional battery; whereas over 60% exhibited some form of motor slowing as measured by the instruments. Approximately 40% of the patients exhibited parkinsonian-like motor programming deficits. A five-factor model consisting of motor measures predicted diagnosis among bipolar and unipolar depressed patients with 100% accuracy. LIMITATIONS The ability of motor measures to discriminate bipolar from unipolar patients must be viewed with caution considering the relatively small sample size of bipolar patients. CONCLUSIONS These findings suggest that a subgroup of depressed patients exhibit motor retardation that is behaviorally similar to parkinsonian bradykinesia and may stem from a similar disruption within the basal ganglia.

The relationship of age to prepulse inhibition and habituation of the acoustic startle response.

Prepulse inhibition (PPI) of the startle response reflects an early stage of information processing that is abnormal in schizophrenia and certain other specific neuropsychiatric disorders that are distinguished by the inability to inhibit redundant or relatively irrelevant sensory, cognitive, or motor information. The goal of the present study was to characterize the effect of normal aging on PPI and habituation of the startle response and to examine the hypothesis that normal aging is characterized by a global decline in inhibitory function. Ninety-seven non-psychiatric controls (age range 18-88) were tested for startle eyeblink response using electromyogram (EMG) recording. Startle magnitude decreased and startle latency increased with aging. PPI demonstrated an inverted U-shaped function with age (greatest PPI at intermediate ages) while there was no significant effect of age on startle habituation. The results do not support the theory that aging is associated with a general decline in inhibitory function and contrast with previous studies that have compared only extreme age groups and have found no effects of age on PPI.

P300 scalp amplitude distribution as an index of deception in a simulated cognitive deficit model

Truth-telling (Truth) and simulated malingering (Malinger) groups were tested in a matching-to-sample procedure in which each sample three-digit number was followed by a series of nine test numbers, only one of which matched the sample. P300 was recorded during test-number presentation. Group analyses revealed differences between the P300s of the groups in unscaled amplitude, but not latency, in response to match and mismatch stimuli. P300 amplitudes at Fz, Cz, and Pz were scaled to remove possible confounding effects of amplitude in tests of the interactions of site with other variables. Significant interactions of both stimulus-type (match vs. mismatch) and group (Truth vs. Malinger) with site were obtained. Within the Malinger group, a significant interaction was obtained (scaled data) between site and response type (honest vs. dishonest). These interactions suggest that deceptive and honest responding are associated with different neurogenerator sets or different sets of P300-overlapping components. In within-individual analyses, 100% of the Truth participants and 87% of the Malinger participants were found to have larger P300 responses at Pz to match stimuli than to mismatch stimuli on the basis of intra-individual bootstrap tests. This represents an improvement in comparison with our related, previous report on a matching-to-sample test using only one test stimulus per sample.

Detecting simulated amnesia for autobiographical and recently learned information using the P300 event-related potential.

To investigate whether the P300 (P3) event-related potential (ERP) can be used as an index of the intactness of recognition memory in subjects trying to simulate amnesia, two groups of subjects (n = 12 and n = 15) were instructed to simulate amnesia and one group of control subjects (n = 14) did not simulate amnesia while taking three recognition tests, during which ERPs were recorded. The three tests consisted of three different types of memory items: (1) the subjects birthday (birth), (2) the experimenters name (name), (3) a word list of 14 nouns (words). The memory item was presented in a random series with other, similar in type, non-memory items. In group tests, memory items evoked larger amplitude P3s than non-memory items (p < 0.001). Within-subjects tests were used to determine whether the P3 amplitude in response to memory items was larger than the P3 amplitude in response to non-memory items for each individual. There was no difference between the sensitivity of the best within-subjects tests for amnesia simulators (birth = 0.9, name = 0.85, words = 0.53) versus non-simulators (birth = 1.0, name = 0.81, words = 0.5) averaged across the three test types. This suggests that P3 used as an index of the intactness of recognition memory may be useful in cases of suspected malingering.

Female Schizophrenia Patients Have Prepulse Inhibition Deficits

BACKGROUND Prepulse inhibition (PPI) of startle shows sexual dimorphism: women have lower levels of PPI than do men, and have menstrual cycle shifts in PPI. Many studies report PPI deficits in male schizophrenia patients; one recent report identified PPI deficits in male but not female patients. This study was designed to determine whether female schizophrenia patients have lower levels of PPI than normal females. METHODS Twenty-five female schizophrenia patients, and 26 normal females were tested in a startle paradigm using 115 dB startle pulses and prepulses of 8 and 16 dB above a 70 dB background, with 30 and 120 msec prepulse intervals. RESULTS Female patients had significantly less PPI compared with normal females, particularly when 16 dB prepulses were utilized. Patients also exhibited a nonsignificant trend towards lower levels of habituation compared to normal subjects. CONCLUSIONS Under the present paradigmatic and subject acquisition conditions, female schizophrenia patients had PPI deficits compared to normal females.

Detection of simulated malingering using forced choice recognition enhanced with event-related potential recording

Abstract A modified forced-choice procedure (HFCP) based on that of Hiscock and Hiscock (1989) for use with suspected malingerers is described. The major modification involves recording of the P300 event-related brain potential in response to the screen to which the subject responds. This “probe” screen is, in turn, modified to contain either a match or a mismatch to the initial sample number, as opposed to having the subject choose the match from a pair of stimuli (match and mismatch) which are simultaneously presented in the standard HFCP. The P300 recording procedure necessitated this change, which also forces the subject to say “yes” or “no” (to match and mismatch, respectively), rather than choosing the match. We found that behavioral performance on the standard HFCP correlated highly and significantly with performance on the P300-enhanced HFCP. Three variants of the modified HFCP were explored. In all variants, P300 amplitude was significantly larger to the match than to the mismatch in standard gro...

P300 correlates of simulated malingered amnesia in a matching-to-sample task: topographic analyses of deception versus truthtelling responses

Two experiments using a P300-enhanced Forced Choice Procedure (P3FCP) investigated simulated amnesia in a matching-to-sample task. In Experiment 1, successful manipulation of subjects towards different behavioral hit rates (75-80% vs. 85-90%) did not adversely affect the diagnostic sensitivity of match-mismatch Pz-P300 amplitude analyses, allowing detection of 69% of simulators. P300 amplitudes of simulators (Malinger group) were as large as those of truth-tellers (truth group, a control), indicating no dual task-related (Malingering) reduction across different behavioral hit rates. Experiment 2 found no main effect of oddball type, match vs. mismatch, on P300 (P3) amplitude with a mismatch-rare variant of the P3FCP. This study also revealed larger Pz-P3s in the Malingering (vs. Truth-telling) condition. Subsequent topographic analyses suggested different Truth and Malinger scaled P3 amplitude topographies in both these sets of P3FCP data and in those from a previous autobiographical memory paradigm. Further analysis yielded preliminary evidence for a common deception-related P3 amplitude topography across different paradigms/conditions.

P300 event-related brain potential as an index of recognition response to autobiographical and recently learned information in closed-head-injury patients

Abstract Fourteen patients who sustained a closed-head injury had their P300 (P3) measured in a visual recognition paradigm to test the use of P3 as an index of recognition in this population. Subjects participated in recognition tests for both autobiographical information (their birthday) and for a word list learned immediately before testing while event-related potentials were recorded. Within-subjects tests were used to determine that the P3 amplitude in response to oddball items (the subjects birthday and the studied word list) was larger than the P3 in response to non-oddball items for 9 of 11 subjects in the autobiographical condition, and 6 of 12 subjects in the word-list condition. Averaged P3s to oddball items were also larger than P3s to non-oddball items in standard group tests (p < .001), suggesting this difference can be used as an index of recognition in closed-head-injury patients.

Fire-related cognitions moderate the impact of risk factors on adjustment following wildfire disaster

This study builds upon current understanding of risk and protective factors for post-disaster adjustment by examining relationships between disaster-related cognitions, three empirically supported risk factors for poorer adjustment (i.e., greater disaster impact, female gender, and racial/ethnic minority status), and three common post-disaster outcomes (i.e., depression, anxiety, and somatic complaints). Participants were 200 students exposed to wildfire disaster. Simultaneous hierarchical regression analyses revealed that, during the acute stress period: (1) disaster-related cognitions in interaction with fire impact and minority status, as well as gender, were related to anxiety symptoms, (2) cognitions were related to depression symptoms, and (3) cognitions in interaction with minority status, as well as fire impact, were related to somatic symptoms. No examined variables predicted symptom change.