Habit and Skill Learning in Schizophrenia: Evidence of Normal Striatal Processing With Abnormal Cortical Input

Abstract

Different forms of nondeclarative learning involve regionally specific striatal circuits. The motor circuit (involving the putamen) has been associated with motor-skill learning and the dorsolateral prefrontal cortex (DLPFC) circuit (involving the caudate) has been associated with cognitive-habit learning. Efforts to differentiate functional striatal circuits within patient samples have been limited. Previous studies have provided mixed results regarding striatal-dependent nondeclarative learning deficits in patients with schizophrenia. In this study, a cognitive-habit learning task (probabilistic weather prediction) was used to assess the DLPFC circuit and a motor-skill learning task (pursuit rotor) was used to assess the motor circuit in 35 patients with schizophrenia and 35 normal controls. Patients with schizophrenia displayed significant performance differences from controls on both nondeclarative tasks; however, cognitive-habit learning rate in patients did not differ from controls. There were performance and learning-rate differences on the motor-skill learning task between the whole sample of patients and controls, however, analysis of a subset of patients and controls matched on general intellectual level eliminated learning rate differences between groups. The abnormal performance offset between patients with schizophrenia and controls in the absence of learning rate differences suggests that abnormal cortical processing provides altered input to normal striatal circuitry.

Probabilistic reversal learning impairments in schizophrenia: Further evidence of orbitofrontal dysfunction

“…This result is consistent with the finding of several studies (Keri et al 2000;Weickert et al 2002;Beninger et al 2003;Keri et al 2005) indicating that the gradual acquisition of probabilistic contingencies in schizophrenia patients may be relatively intact, as well as the idea that different neural systems may support rapid and gradual feedback integration. The gradual integration of probabilistic feedback over many trials seems to rely more on the basal ganglia.…”

“…By contrast, there is evidence that the gradual acquisition of probabilistic contingencies depends more heavily on subcortical structures in the basal ganglia, and less on cortical structures (Knowlton et al 1996;Seger and Cincotta 2005). The results of multiple studies (Keri et al 2000;Weickert et al 2002;Beninger et al 2003;Keri et al 2005) suggest that the acquisition of probabilistic contingencies in schizophrenia patients may be relatively unimpaired, perhaps indicative of a relatively intact basal ganglia function in schizophrenia. Thus, patients with SZ could show intact initial discrimination learning, but impaired reversal learning.…”

The effects of category overlap on information-integration and rule-based category learning

“…Even so, participants can achieve almost optimal accuracy with an explicit strategy in which they simply respond on the basis of the presence or absence of the most informative card (i.e., approximately 73% correct). Because the weatherprediction task is probabilistic, and optimal accuracy requires information integration, it has often been assumed that learning in the task is mediated by a single system that recruits some implicit, incremental process (Knowlton et al, 1996;Weickert et al, 2002;Witt, Nuhsman, & Deuschl, 2002). However, our results suggest that explicit strategies should be common in the weather-prediction task, because a simple explicit strategy is nearly optimal.…”

Circumstances Under Which Practice Does Not Make Perfect: A Review of the Practice Effect Literature in Schizophrenia and Its Relevance to Clinical Treatment Studies

“…Thus, once an item is encoded successfully, it is not subject to rapid forgetting, translating into relatively normal savings. Second, patients have relatively intact procedural learning and probabilistic learning that may be responsible for stimulus response mappings (Weickert et al, 2002). To the extent that some practice-related improvement may be sub-served by such learning systems, patients may be expected to benefit from setting up more efficient responding patterns even if the core abilities indexed by the test are unaffected.…”