The neural correlates of implicit sequence learning in schizophrenia.

Twenty-seven schizophrenia spectrum patients and 25 healthy controls performed a probabilistic version of the serial reaction time task (SRT) that included sequence trials embedded within random trials. Patients showed diminished, yet measurable, sequence learning. Postexperimental analyses revealed that a group of patients performed above chance when generating short spans of the sequence. This high-generation group showed SRT learning that was similar in magnitude to that of controls. Their learning was evident from the very 1st block; however, unlike controls, learning did not develop further with continued testing. A subset of 12 patients and 11 controls performed the SRT in conjunction with positron emission tomography. High-generation performance, which corresponded to SRT learning in patients, correlated to activity in the premotor cortex and parahippocampus. These areas have been associated with stimulus-driven visuospatial processing. Taken together, these results suggest that a subset of patients who showed moderate success on the SRT used an explicit stimulus-driven strategy to process the sequential stimuli. This adaptive strategy facilitated sequence learning but may have interfered with conventional implicit learning of the overall stimulus pattern. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impairment of probabilistic reward-based learning in schizophrenia.

Recent models assume that some symptoms of schizophrenia originate from defective reward processing mechanisms. Understanding the precise nature of reward-based learning impairments might thus make an important contribution to the understanding of schizophrenia and the development of treatment strategies. The present study investigated several features of probabilistic reward-based stimulus association learning, namely the acquisition of initial contingencies, reversal learning, generalization abilities, and the effects of reward magnitude. Compared to healthy controls, individuals with schizophrenia exhibited attenuated overall performance during acquisition, whereas learning rates across blocks were similar to the rates of controls. On the group level, persons with schizophrenia were, however, unable to learn the reversal of the initial reward contingencies. Exploratory analysis of only the subgroup of individuals with schizophrenia who showed significant learning during acquisition yielded deficits in reversal learning with low reward magnitudes only. There was further evidence of a mild generalization impairment of the persons with schizophrenia in an acquired equivalence task. In summary, although there was evidence of intact basic processing of reward magnitudes, individuals with schizophrenia were impaired at using this feedback for the adaptive guidance of behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intact implicit habit learning in Alzheimer's disease.

Habit learning refers to the incremental implicit learning of associations. Patients with Alzheimer's disease (AD) exhibit deficits in explicit memory and in conceptual implicit memory tasks that rely on the cortical areas damaged in AD. The authors tested patients with AD and controls on a probabilistic classification task in which participants implicitly acquire cue-outcome associations. Both groups showed evidence of learning across 50 trials, and performance did not differ significantly between the groups. In contrast, patients with AD exhibited a profound impairment in explicit memory for the testing episode. These results are consistent with the idea that habit learning relies on subcortical structures, including the basal ganglia, and is independent of the medial temporal and cortical areas damaged in AD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychometric intelligence dissociates implicit and explicit learning.

The hypothesis that performance on implicit learning tasks is unrelated to psychometric intelligence was examined in a sample of 605 German pupils. Performance in artificial grammar learning, process control, and serial learning did not correlate with various measures of intelligence when participants were given standard implicit instructions. Under an explicit rule discovery instruction, however, a significant relationship between performance on the learning tasks and intelligence appeared. This finding provides support for Reber's hypothesis that implicit learning, in contrast to explicit learning, is independent of intelligence, and confirms thereby the distinction between the 2 modes of learning. However, because there were virtually no correlations among the 3 learning tasks, the assumption of a unitary ability of implicit learning was not supported. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Qualitative differences between implicit and explicit sequence learning.

Four experiments investigate the differences between implicit and explicit sequence learning concerning their resilience to structural and superficial task changes. A superficial change that embedded the SRT task in the context of a selection task, while maintaining the sequence, did selectively hinder the expression of implicit learning. In contrast, a manipulation that maintained the task surface, but decreased the sequence validity, affected the expression of learning specifically when it was explicit. These results are discussed in the context of a dynamic framework (Cleeremans & Jime'nez, 2002), which assumes that implicit knowledge is specially affected by contextual factors and that, as knowledge becomes explicit, it allows for the development of relevant metaknowledge that modulates the expression of explicit knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Altered probabilistic learning and response biases in schizophrenia: Behavioral evidence and neurocomputational modeling.

Objective: Patients with schizophrenia (SZ) show reinforcement learning impairments related to both the gradual/procedural acquisition of reward contingencies, and the ability to use trial-to-trial feedback to make rapid behavioral adjustments. Method: We used neurocomputational modeling to develop plausible mechanistic hypotheses explaining reinforcement learning impairments in individuals with SZ. We tested the model with a novel Go/NoGo learning task in which subjects had to learn to respond or withhold responses when presented with different stimuli associated with different probabilities of gains or losses in points. We analyzed data from 34 patients and 23 matched controls, characterizing positive- and negative-feedback-driven learning in both a training phase and a test phase. Results: Consistent with simulations from a computational model of aberrant dopamine input to the basal ganglia patients, patients with SZ showed an overall increased rate of responding in the training phase, together with reduced response-time acceleration to frequently rewarded stimuli across training blocks, and a reduced relative preference for frequently rewarded training stimuli in the test phase. Patients did not differ from controls on measures of procedural negative-feedback-driven learning, although patients with SZ exhibited deficits in trial-to-trial adjustments to negative feedback, with these measures correlating with negative symptom severity. Conclusions: These findings support the hypothesis that patients with SZ have a deficit in procedural “Go” learning, linked to abnormalities in DA transmission at D1-type receptors, despite a “Go bias” (increased response rate), potentially related to excessive tonic dopamine. Deficits in trial-to-trial reinforcement learning were limited to a subset of patients with SZ with severe negative symptoms, putatively stemming from prefrontal cortical dysfunction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A learning theory approach to research in schizophrenia.

"An attempt has been made to view schizophrenia as a problem in learning theory. The research in conditioning, learning, and generalization in schizophrenia has been reviewed in these terms. It was found that this research supported such an interpretation. An explication of the causes of an acute schizophrenic break and the transition to chronicity was attempted." 79 references. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptually based implicit learning in severe closed-head injury patients.

This study suggests that perceptually based implicit learning may either be preserved following a severe closed-head injury (CHI) or recover within the 1st year. Nineteen severe CHI patients and 19 controls searched visual matrices and indicated the quadrant location of a target. Participants were exposed to the following covariation pattern: AAAABAAA. For Covariation A blocks, the matrices systematically co-occurred with a unique location of the target. This relationship was altered for the B block. Despite CHI participants' overall slower response times (RTs), both groups demonstrated the expected decline in RTs across the first 4 Covariation A blocks followed by an increase when the covariation changed. Both groups also exhibited retention of their learning after a 20-min delay. Explicit knowledge tests indicated that participants lacked awareness for the covariation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pure perceptual-based sequence learning: A role for visuospatial attention.

Learning the structure of a sequence of target locations when target location is not the response dimension and the sequence of target locations is uncorrelated with the sequence of responses is called pure perceptual-based sequence learning. The paradigm introduced by G. Remillard (2003) was used to determine whether orienting of visuospatial attention is an important component of the learning process. Three experiments revealed that the presence of an attention-capturing distractor impaired learning, whereas the presence of a distractor that was expected not to capture attention did not impair learning. These results suggest that the learning mechanism associates only those locations receiving visuospatial attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is implicit sequence learning impaired in Parkinson's disease? A meta-analysis.

The aim of the present study was to examine impairment of implicit learning in Parkinson's disease (PD) by means of a meta-analysis of studies that used the serial reaction time (SRT) task. The authors performed a systematic review and meta-analysis of published journal articles (1987-2005) that used the SRT task with patients with PD. The principal outcome measures used to compare studies were (a) the difference in reaction time between the last block of ordered sequence trials and the randomized block for PD and control participants and (b) fixed and random effects pooled estimates by the inverse weighting method. Six studies, including 67 patients with PD, met the inclusion criteria. The meta-analysis showed that implicit learning was impaired in PD, relative to healthy controls, with a standardized mean difference of 0.73 (95% confidence interval = 0.38, 1.07). Implicit sequence learning appears to be impaired in patients with PD. Some common methodological weaknesses and limitations in the reporting of statistical data are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging and implicit learning: Explorations in contextual cuing.

In contextual cuing, faster responses are made to repeated displays containing context–target associations than to novel displays without such covariances. We report that healthy older adults showed learning impairments in contextual cuing when compared with younger adults. The display properties in the task were altered to artificially increase younger adults' response times to match those of older adults and to produce faster responses in older participants; however, younger participants' learning remained intact, whereas older participants continued to show impairments under these conditions. These results suggest that older adults have intrinsic deficits in contextual cuing that cannot be attributed to their slower overall response speed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Neurocognition in first-episode schizophrenia: A meta-analytic review.

Compromised neurocognition is a core feature of schizophrenia. Following Heinrichs and Zakzanis’s (1998) seminal meta-analysis of middle-aged and predominantly chronic schizophrenia samples, the aim of this study is to provide a meta-analysis of neurocognitive findings from 47 studies of first-episode (FE) schizophrenia published through October 2007. The meta-analysis uses 43 separate samples of 2,204 FE patients with a mean age of 25.5 and 2,775 largely age- and gender-matched control participants. FE samples demonstrated medium-to-large impairments across 10 neurocognitive domains (mean effect sizes from ?0.64 to ?1.20). Findings indicate that impairments are reliably and broadly present by the FE, approach or match the degree of deficit shown in well-established illness, and are maximal in immediate verbal memory and processing speed. Larger IQ impairments in the FE compared to the premorbid period, but comparable to later phases of illness suggests deterioration between premorbid and FE phases followed by deficit stability at the group level. Considerable heterogeneity of effect sizes across studies, however, underscores variability in manifestations of the illness and a need for improved reporting of sample characteristics to support moderator variable analyses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Making children gesture brings out implicit knowledge and leads to learning.

Speakers routinely gesture with their hands when they talk, and those gestures often convey information not found anywhere in their speech. This information is typically not consciously accessible, yet it provides an early sign that the speaker is ready to learn a particular task (S. Goldin-Meadow, 2003). In this sense, the unwitting gestures that speakers produce reveal their implicit knowledge. But what if a learner was forced to gesture? Would those elicited gestures also reveal implicit knowledge and, in so doing, enhance learning? To address these questions, the authors told children to gesture while explaining their solutions to novel math problems and examined the effect of this manipulation on the expression of implicit knowledge in gesture and on learning. The authors found that, when told to gesture, children who were unable to solve the math problems often added new and correct problem-solving strategies, expressed only in gesture, to their repertoires. The authors also found that when these children were given instruction on the math problems later, they were more likely to succeed on the problems than children told not to gesture. Telling children to gesture thus encourages them to convey previously unexpressed, implicit ideas, which, in turn, makes them receptive to instruction that leads to learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional changes during implicit learning: Signal validity protects a target stimulus from the attentional blink.

Participants in 2 experiments performed 2 simultaneous tasks: one, a dual-target detection task within a rapid sequence of target and distractor letters; the other, a cued reaction time task requiring participants to make a cued left–right response immediately after each letter sequence. Under these rapid visual presentation conditions, it is usually difficult to identify the 2nd target when it is presented in temporal proximity of the 1st target—a phenomenon known as the attentional blink. However, here participants showed an advantage for detecting a target presented during the attentional blink if that target predicted which response cue would appear at the end of the trial. Participants also showed faster reaction times on trials with a predictive target. Both of these effects were independent of conscious knowledge of the target–response contingencies assessed by postexperiment questionnaires. The results suggest that implicit learning of the association between a predictive target and its outcome can automatically facilitate target recognition during the attentional blink and therefore shed new light on the relationship between associative learning and attentional mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neurocognitive basis of impaired empathy in schizophrenia.

Patients with schizophrenia show impaired emotional and social behavior, such as lack of theory of mind and misinterpretation of social situations. However, there is a paucity of work focusing on the empathic abilities of these patients. The present study was designed to examine the degree of impairment in cognitive and affective empathy in schizophrenia and to evaluate the contribution of executive prefrontal functions to empathy in these patients. To explore the neurocognitive processes that underlie the empathic ability in schizophrenic patients, the relationship between empathy scores and the performance on a cognitive flexibility task that assesses dorsolateral and orbitofrontal functioning (set shifting and reversal, respectively) was examined in 26 patients with schizophrenia and 31 healthy control subjects. Results indicated that patients with schizophrenia were significantly impaired in both cognitive and affective empathy compared with healthy control subjects. The degree of impaired empathy related to the severity of negative symptoms. In addition, patients showed impaired performance on measures of both shifting and reversal. However, while cognitive empathy was particularly related to measurements of orbitofrontal (rather than dorsolateral) functioning, affective empathy was related to measures of social functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired visual working memory consolidation in schizophrenia.

This study investigated working memory (WM) consolidation, that is, the time required to create durable WM representations, at different levels of WM load in schizophrenia. Twenty-three schizophrenia spectrum patients and 16 control subjects participated in a change-detection task in which a sample array of 1-3 squares appeared followed by a delay and a test array. An array of pattern masks was inserted into the delay interval--covering the locations of the sample-array squares--100-800 ms after the offset of the sample array. If a durable WM representation is formed prior to mask onset, the mask should not impair performance. The degree of masking at an interval reflects the degree of WM consolidation at that time. Neither group showed masking at set size 1. Unlike controls, patients demonstrated robust masking effects at set size 2. Both groups showed masking at set size 3, but masking effects were larger and longer lasting in patients. These data demonstrate abnormally prolonged WM consolidation in schizophrenia. This impairment may slow the formation of stable representations of the visual environment, impacting everyday visually guided behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective corticostriatal dysfunction in schizophrenia: Examination of motor and cognitive skill learning.

[Correction Notice: An erratum for this article was reported in Vol 22(3) of Neuropsychology (see record 2008-05020-015). Table 1 on page 102 should have included the BPRS Depression-Anxiety subscale score 9.00 (3.99) under the column heading Schiz pts. Table displays means with standard deviations in parentheses.] [Correction Notice: An erratum for this article was reported in Vol 22(2) of Neuropsychology (see record 2008-02526-002). The DOI for the supplemental materials was printed incorrectly. The correct DOI is as follows: http://dx.doi.org/10.1037/0894-4105.22.1.100.supp.] It has been suggested that patients with schizophrenia have corticostriatal circuit dysfunction (Carlsson & Carlsson, 1990). Skill learning is thought to rely on corticostriatal circuitry and different types of skill learning may be related to separable corticostriatal loops (Grafton, Hazeltine, & Ivry, 1995; Poldrack, Prabhakaran, Seger, & Gabrieli, 1999). The authors examined motor (Serial Reaction Time task, SRT) and cognitive (Probabilistic Classification task, PCT) skill learning in patients with schizophrenia and normal controls. Development of automaticity was examined, using a dual task paradigm, across three training sessions. Patients with schizophrenia were impaired at learning on the PCT compared to controls. Performance gains of controls occurred within the first session, whereas patients only improved gradually and never reached the performance level of controls. In contrast, patients were not impaired at learning on the SRT relative to controls, suggesting that patients with schizophrenia may have dysfunction in a specific corticostriatal subcircuit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired control of visual attention in schizophrenia.

To investigate attentional impairment in schizophrenia, the authors examined the performance of 22 patients with schizophrenia and 16 healthy control subjects in 4 visual search tasks that varied in perceptual requirements and in the need for precise attentional control. The rate of search was slowed in the patients in all tasks. However, the degree of slowing was largest in tasks requiring precise attentional control and smallest in tasks that were perceptually difficult but required less attentional control. This pattern of results indicates that the primary impairment of attention in schizophrenia lies in the control of attention and not in the selection processes that operate once attention has been directed to an object. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intact implicit learning of spatial context and temporal sequences in childhood autism spectrum disorder.

Autism spectrum disorder (ASD) is defined by atypicalities in domains that are posited to rely on implicit learning processes such as social communication, language, and motor behavior. The authors examined 2 forms of implicit learning in 14 children with high-functioning ASD (10 of whom were diagnosed with Asperger's syndrome) and 14 control children, learning of spatial context known to be mediated by the medial temporal lobes (using the contextual cueing task) and of sequences known to be mediated by frontal-striatal and frontal-cerebellar circuits (using the alternating serial reaction time task). Both forms of learning were unimpaired in ASD. Spatial contextual implicit learning was spared in ASD despite slower visual search of spatial displays. The present findings provide evidence for the integrity of learning processes dependent on integration of spatial and sequential contextual information in high-functioning children with ASD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The process-reactive classification of schizophrenia.

Research on the process-reactive classification of schizophrenia indicates there are 2 groups of schizophrenic patients differing in prognostic and life-history variables. It is also possible to demonstrate differences between the 2 groups in physiological measures and psychological dimensions. The evidence does not support a process-organic vs. a reactive-psychogenic formulation of schizophrenic etiology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)