ERP study of pre-attentive auditory processing in treatment-refractory schizophrenia

Event-related potential (ERP) studies have demonstrated impaired auditory sensory processing in patients with schizophrenia, as reflected in abnormal mismatch negativity (MMN). We sought to extend this finding by evaluating MMN in 13 treatment-refractory patients with schizophrenia, and 14 age- and gender-matched healthy controls. Subjects responded to infrequent visual stimulation while ignoring binaurally presented auditory tones. The amplitude and topographical pattern of the MMN were analyzed. The control group presented the expected reduction in the amplitude of the MMN from frontal to central and parietal locations. In comparison, the MMN amplitude was not reduced in the treatment-refractory patients, and was largest at the central-posterior electrode location. In addition, patients displayed larger negativities at left frontal, and left- and right-temporal electrode locations than the control subjects. These findings are consistent with pre-attentive abnormalities in treatment-refractory patients with schizophrenia.     

Correlation between Changes in Stress-Induced Corticosterone Secretion and GR mRNA Levels

The current study was conducted to determine the potential relationship between stress-induced corticosterone secretion and corticosteroid receptor mRNA levels after 5 days of intermittent stress. In particular, we were interested in the rate at which animals terminate a stress response, and how this termination may be altered by repeated stress. Adult male Sprague-Dawley rats were subjected to either 5 days of restraint stress or 5 days of an unpredictable stress paradigm. Restraint-stress induced corticosterone secretion was measured on Days 1 and 5 in both groups, and animals were killed on Day 6. Glucocorticoid receptor (GR), and mineralocorticoid (MR) mRNA levels were determined using in-situ hybridization techniques. Five days of restraint stress caused an habituation of the plasma corticosterone response to stress measured 60 and 90 min post-stress initiation; this pattern of corticosterone secretion was not observed in the animals subjected to unpredictable stress. Five days of either stress paradigm did not alter MR mRNA levels measured within the hippocampus or GR mRNA levels within the hippocampus or the medial parvocellular division of the paraventricular nucleus of the hypothalamus (mpPVN). However, an individual's GR mRNA levels measured within the CA1/2 region of the hippocampus and the mpPVN were significantly correlated with the degree of habituation of the corticosterone response to stress measured on Day 5. This suggests that an increase in the rate of termination of the stress response and levels of GR within the hippocampus and mpPVN may be functionally related.     

Speed and accuracy on tests of executive function in obsessive-compulsive disorder

Slowness in obsessive-compulsive disorder (OCD) has been attributed to intrusive thoughts or meticulousness. Recent research suggests that slowness in OCD may be particularly evident on tests of executive function subserved by frontostriatal circuitry. In the present study, the speed and accuracy of responding on neuropsychological tests of executive functions and psychomotor speed were investigated in 27 non-depressed, unmedicated adults with OCD and 27 healthy controls. The only group difference was that patients took significantly longer to copy a complex geometric design than controls. This finding was unrelated to residual depression or overall OCD symptom severity. Results suggest that slowness in OCD may be most apparent on executive tests requiring self-initiated organizational strategies, consistent with frontostriatal abnormality.