Perceptual Category Judgment Deficits are Related to Prefrontal Decision Making Abnormalities in Schizophrenia.

Previous studies of perceptual category learning in patients with schizophrenia generally demonstrate impaired perceptual category learning; however, traditional cognitive studies have often failed to address the relationship of different cortical regions to perceptually based category learning and judgments in healthy participants and patients with schizophrenia. In the present study, perceptual category learning was examined in 26 patients with schizophrenia and 25 healthy participants using a dot-pattern category learning task. In the training phase, distortions of a prototypical dot pattern were presented.

Dopaminergic therapy removal differentially effects learning in schizophrenia and Parkinson's disease.

Studies of patients with Parkinson's disease receiving dopamimetics report conflicting evidence for early learning of probabilistic cue-outcome associations that elicits frontal-striatal activity. Previous studies of probabilistic association learning in patients with schizophrenia administered antipsychotics have displayed conflicting evidence for normal and abnormal learning. The role of dopaminergic treatment (dopamimetic versus dopamine antagonistic) effects on probabilistic association learning in these diseases that directly impact the dopamine system is not fully understood.

Expression of GABA signaling molecules KCC2, NKCC1, and GAD1 in cortical development and schizophrenia.

GABA signaling molecules are critical for both human brain development and the pathophysiology of schizophrenia. We examined the expression of transcripts derived from three genes related to GABA signaling [GAD1 (GAD67 and GAD25), SLC12A2 (NKCC1), and SLC12A5 (KCC2)] in the prefrontal cortex (PFC) and hippocampal formation of a large cohort of nonpsychiatric control human brains (n = 240) across the lifespan (from fetal week 14 to 80 years) and in patients with schizophrenia (n = 30-31), using quantitative RT-PCR. We also examined whether a schizophrenia risk-associated promoter SNP in GAD1 (rs3749034) is related to expression of these transcripts.

Enuresis as a premorbid developmental marker of schizophrenia.

There is comparatively little information about premorbid maturational brain abnormalities in schizophrenia (SCZ). We investigated whether a history of childhood enuresis, a well-established marker of neurodevelopmental delay, is associated with SCZ and with measures of brain abnormalities also associated with SCZ. A Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) based history of enuresis, volumetric brain MRI scans and neuropsychological testing were obtained in patients with SCZ, their non-psychotic siblings (SIB) and non-psychiatric controls (NC).

Comparison of cognitive performances during a placebo period and an atypical antipsychotic treatment period in schizophrenia: critical examination of confounds.

Although previous studies report cognitive improvement following atypical antipsychotic administration in schizophrenia (SC), few placebo-controlled within-subject studies with examination of confounds (symptom reduction, cooperation, learning, and outliers) have been reported. The present study examines the effects of atypicals and confounds upon cognition in SC. The hypothesis tested was that relative to placebo, atypicals as a general class of medication would elicit cognitive improvement in SC.

Habit and skill learning in schizophrenia: evidence of normal striatal processing with abnormal cortical input.

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.