Using latent class growth analysis to form trajectories of premorbid adjustment in schizophrenia

Premorbid adjustment varies widely among individuals with schizophrenia and has been shown to bear significantly on prodrome and onset characteristics, and on cognition, symptoms, and functioning after onset. The current analysis focused on the Premorbid Adjustment Scale, a retrospective measure assessing social and academic function at several time points from early childhood to illness onset. In an effort to explore discrete developmental subtypes, we applied latent class growth analysis to data from the Premorbid Adjustment Scale in our sample of individuals with schizophrenia (N = 208), finding three latent trajectory classes. The first of these classes showed consistently adequate-to-good social and academic functioning before onset; the second showed initially good function and deterioration with time until onset; the third showed poor functioning in childhood that deteriorated further during the years up to diagnosis. The classes differed significantly in terms of age of onset, processing speed, and functioning after onset. There were no significant differences in symptomatology. Our findings illustrate a potentially powerful methodological approach to the problem of heterogeneity in schizophrenia research, and add weight to the notion that aspects of premorbid history may be useful for subtyping schizophrenia patients. The potential implications of this subtyping strategy, including those pertaining to potential genetics studies, are discussed.     

Associative priming in color naming: interference and facilitation

In Experiment 1, color-naming interference for target stimuli following associated primes was greater in a group making a lexical decision to the prime than in a group reading the prime silently. High-frequency targets were responded to more quickly than low-frequency targets. In Experiment 2, with subjects naming the prime, there was evidence of associative interference when the prime and the target were grouped temporally but not when the intertrial interval was comparable with the prime-target interval. Associative primes presented at a short (120-msec) prime-target stimulus onset asynchrony facilitated color naming in Experiment 3. Taken together, the results suggest that the effect of faster processing of the base word in a color-naming task is facilitatory and that color-naming priming interference arises when associative prime processing increases conflict between word and color responses by enhancing phonological or articulatory activation of the base word.     

Associative facilitation and interference in the Stroop color-word task

It is difficult to name the color of a stimulus when the stimulus is a word naming a different color. When the word is congruent with the color in which it is written, color naming is much quicker. Similar results are also obtained when color-related words are used instead of color names. These results are taken as evidence for the operation of associative factors that could facilitate or impair performance in the color-word task.     

Associative interference in recognition memory: A dual-process account

Associative interference from overlapping word pairs (A-B, A-D) reduces recall but has inconsistent effects on recognition. A dual-process account suggests that interference conditions reduce recollection but increase familiarity. This is predicted to increase recognition false alarms but have variable effects on recognition hits, depending on the relative contribution of recollection and familiarity. In three experiments that varied materials (sentences or random nouns) and test type (associative or pair recognition), interference conditions always increased recognition false alarms, but sometimes increased and sometimes decreased recognition hits. However, remember hits always decreased and know hits always increased with interference, patterns predicted of the recollection and familiarity processes, respectively. According to the dual-process view, a manipulation that affects the component processes in opposite ways can produce inconsistent patterns of recognition performance as the relative contribution of recollection and familiarity changes across tasks.     

Associative interference with taste aversions after contextual discrimination learning

In two experiments, rats were first given discriminative training with two distinctive contexts, such that a flavor was paired with lithium chloride (LiCl) in one context, alternating with presentations of the flavor alone in another context. Contextual control of the fluid ingestion was observed in that rats reduced the fluid intake in the LiCl-paired context but drank the solution in the context never paired with lithium. Having learned this discrimination, the rats were now given a second flavor in their home cage before being injected with LiCl and transferred to the previously lithium-paired context. In Experiment 1, the acquisition of an aversion to the novel flavor was blocked when this flavor and the contextual cues are conditioned as a compound. In Experiment 2, the blocking effect and the conditional control over fluid consumption were abolished when the associative strength of the LiCl-paired context had been extinguished by exposing the animals to water in the contexts after discriminative training. These results are interpreted as evidence that context dependency of conditioned taste aversions is mediated by a summative effect of the context–LiCl and flavor–LiCl associations.     

Electrodermal nonresponding, premorbid adjustment, and symptomatology as predictors of long-term social functioning in schizophrenics

The hypothesis that electrodermal nonresponsiveness to orienting stimuli delineates a core group of "Kraepelinian" type schizophrenics was tested by following up social functioning outcome over a 2-year period in 37 schizophrenics. Good social functioning outcome required both some self-supporting ability in the job market and a minimal social life. The prior assessments included monitoring of electrodermal responses to a series of moderately intense tones, ratings of reported and observed symptoms during an interview, and ratings of premorbid adjustment on the basis of an interview with a close relative. Electrodermal nonresponding, poor premorbid adjustment, and negative symptomatology predicted poor social functioning during the second follow-up year, but the relationship to nonresponding pertained exclusively to a group of 15 first-episode patients. Discriminant analysis showed that electrodermal nonresponding and symptoms were the only independent predictors of outcome.