Richard C. Josiassen

Patterns of intellectual deficit in Huntington's disease

The study investigated patterns of intellectual deficit in 13 patients with recently diagnosed Huntingtons disease (mean duration of 2.3 years) and 46 offspring at risk for the illness using the Wechsler Adult Intelligence Scale (WAIS). The results support the idea that certain cognitive skills remain relatively intact at early stages of the disease while other skills are impaired. A consistent pattern of impairment was observed in the patient group which included the Arithmetic, Digit Span, Digit Symbol, and Picture Arrangement subtests. The most striking result was a demonstration of significantly increased variability among the at risk population of the Digit Span and Picture Arrangement subtests. These findings suggest that the WAIS may be a useful adjunct to neurological diagnosis for longitudinal monitoring of intellectual changes even at very early stages of the illness.

Combinations of evoked potential amplitude measurements in relation to psychiatric diagnosis

The purposes of this investigation were (1) to determine the extent to which single nonredundant measures, derived from optimal combinations of evoked potential (EP) amplitude measurements, could differentiate between various groups of psychiatric patients and between patients and nonpatients, and (2) to assess the replicability of such discriminations. Somatosensory, visual, and auditory EPs were recorded from 15 locations in 253 unmedicated patients and 99 nonpatients. Multivariate statistical methods were used to reduce the amplitude measurements to sets of factor scores that met specified criteria for entry into discriminant analyses between pairs of the following groups: nonpatients, neuroses, personality disorders, schizophrenias, schizotypal/borderlines, major depressives, and manics. Sensitivity, specificity, and predictive value were assessed for discriminant scores. The discriminant scores yielded many differences between groups, most of which were replicable in split-half analyses. Among these were differences between all six patient groups and nonpatients, and between schizophrenics and nonpsychotics. Split-half discriminant analyses were also performed with 12 measures that were obtained by taking the means of factor scores grouped by sensory modality, time, and spatial location; these variables, used without preselection, provided several replicable diagnostic discriminations.

Attention-Related Effects on Somatosensory Evoked Potentials in College Students at High Risk for Psychopathology

Attention directed to a stimulus elicits a late positive wave in the evoked potential, which has consistently been shown to be of lower than normal amplitude in schizophrenic patients. This study aimed to determine whether a similar deviation from normal occurs in nonpatient college students with extremely high scores on Chapmans Physical Anhedonia (AN) and Perceptual Aberration (PA) Scales. Individuals with such high scores have been shown to deviate from control subjects in ways analogous to schizophrenic patients and are considered to be at high risk for this disorder. Somatosensory evoked potentials (SEPs) were recorded from five scalp locations while subjects counted stimuli to one of four randomly stimulated fingers; SEPs to counted stimuli contained the attention-related late positive wave (P400). The AN (n = 10) and PA (n = 10) groups were compared with normal control subjects (n = 10); in addition, the AN group was compared with schizophrenic subjects (n = 7). P400 amplitudes of ANs were lower than those of normal control subjects matched for age and sex, whereas P400 amplitudes of PAs and their matched control subjects did not differ. P400 amplitudes of ANs did not differ significantly from those of the schizophrenic group, although AN means were somewhat higher. Measurements of SEP peaks preceding P400 yielded few consistent group differences with respect to attention-related changes. The results suggest that ANs, but not PAs, display a pattern of P400 deviation similar to that found in schizophrenic patients.

The attention-related somatosensory evoked potential late positive wave in psychiatric patients

Somatosensory evoked potential (SEP) late waves (P400) associated with selective attention were elicited by having subjects count electrical stimuli to one of four randomly stimulated fingers. P400 amplitude was lower in a diagnostically heterogeneous group of 20 psychiatric patients than in 16 nonpatients. Among patients, a general psychopathology factor derived from the Millon Clinical Multiaxial Inventory was significantly correlated with a factor accounting for most of the P400 amplitude variance. In psychiatric patients, attention-related late activity amplitude is apparently reduced from normal in evoked potentials of all modalities; degree of reduction appears quantitatively related to level of psychopathology.

Some Quantitative EEG Findings in Unmedicated and Medicated Major Depressives

To confirm previous quantitative EEG findings in major depressive disorder and to assess effects of medication, EEGs were recorded under eyes closed and open conditions in 68 patients (34 unmedicated and 34 medicated) and nonpatients matched for age and sex. Time series analyses of amplitude, frequency and wave symmetry were performed; differences between eyes open and closed were adjusted for eyes closed values to obtain measures of reactivity. These reactivity measures yielded the main differences between unmedicated patients and nonpatients; depressives were more reactive. Reactivity differences were eliminated or reversed in medicated patients. The EEGs of unmedicated depressives appear to be overreactive, while medications decrease EEG reactivity.

Evoked potential correlates of intelligence in nonpatient subjects

To evaluate possible influences of intelligence on evoked potential (EP) characteristics in nonpatients. EPs of age and gender matched groups (N = 19 each) of high, medium, and low IQ groups were compared. EPs elicited by left and right median nerve stimulation, checkerboard pattern visual flash, and acoustic clicks were recorded from 15 scalp leads. The results confirmed previous findings showing that higher IQs are associated with higher EP amplitudes. An unexpected finding was a trend towards higher IQ/EP correlations for left than right recording sites. It appears that intelligence is an important subject variable to be controlled in any EP investigation, and furthermore that EP topography should be considered in seeking IQ/EP correlations.

Dealing with differential gender and age effects in evoked potential studies of psychopathology.

Data selected from comprehensive EP studies of a large sample of psychiatric patients and nonpatients illustrate the point that matching patient and control populations for age and gender is essential, but not sufficient, to control for these subject variables. It is necessary to test for the interactions resulting from different relationships between EP measures and gender and/or age in different diagnostic groups and to examine differences between subgroups defined by gender and age.

Relationship between evoked potential and neuropsychological findings in persons “at risk” for Huntington's disease

Scalp-recorded evoked potentials (EPs) elicited by left and right median nerve stimulation (LSEP and RSEP), checkerboard pattern flash (VEP), and acoustic click (AEP) were obtained in 40 individuals at risk (AR) for Huntingtons disease (HD) and 40 nonpatients matched for age, sex, and intelligence. EPs of AR subjects were generally similar to those of nonpatients overall configuration; however, mean amplitudes were significantly lower for ARs. The lower amplitudes tended to occur primarily among a subgroup of ARs who manifested some degree of cognitive change, as defined by neuropsychological test criteria.

Early auditory information processing in schizophrenia: a preliminary report.

Numerous theorists have postulated that incoming environmental information is altered with schizophrenic illness, due to aberrant sensory processing in subcortical systems. Brainstem evoked potential recordings were obtained during passive auditory information processing in groups of chronic schizophrenic patients, affective disordered patients, and normals. These neuroelectric measures of brainstem and midbrain functioning suggest that the three study groups do not statistically differ in terms of latency characteristics. It is noteworthy, however, that a particular subset of chronic schizophrenic patients yielded latency characteristics falling more than one standard deviation from the total population mean under all experimental conditions.