Differential mesolimbic and prefrontal alterations during reward anticipation and consummation in positive and negative schizotypy.

Schizotypy is associated with anhedonia. However, previous findings on the neural substrates of anhedonia in schizotypy are mixed. In the present study, we measured the neural substrates associated with reward anticipation and consummation in positive and negative schizotypy using functional MRI. The Monetary Incentive Delay task was administered to 33 individuals with schizotypy (18 positive schizotypy (PS),15 negative schizotypy (NS)) and 22 healthy controls. Comparison between schizotypy individuals and controls were performed using two-sample T tests for contrast images involving gain versus non-gain anticipation condition and gain versus non-gain consummation condition. Multiple comparisons were corrected using Monte Carlo Simulation correction of p<.05. The results showed no significant difference in brain activity between controls and schizotypy individuals as a whole during gain anticipation or consummation. However, during the consummatory phase, NS individuals rather than PS individuals showed diminished left amygdala and left putamen activity compared with controls. We observed significantly weaker activation at the left ventral striatum during gain anticipation in NS individuals compared with controls. PS individuals, however, exhibited enhanced right ventral lateral prefrontal activity. These findings suggest that different dimensions of schizotypy may be underlied by different neural dysfunctions in reward anticipation and consummation.

Functional magnetic resource imaging assessment of altered brain function in hypothyroidism during working memory processing.

CONTEXT: Hypothyroidism is related to multiple cognitive deficits including working memory dysfunction, of which the underlying neural correlates were rarely studied. In this study, the impact of hypothyroidism on neural circuits involved in working memory processing was explored by functional magnetic resource imaging (fMRI). DESIGN: Using fMRI, we conducted a longitudinal study investigating alterations of brain function during a working memory task, the four-digit backward recall (BR) and forward recall (FR), in hypothyroid patients and controls. METHODS: fMRI scan was used in 13 female patients at two time points: before and after having been treated with levothyroxine (L-T(4)) for ∼6 months, and 12 matched euthyroid controls were also scanned. Wechsler Memory Scale-Chinese Revision was used to assess the memory states of each participant. RESULTS: The hypothyroid patients showed poorer memory states than that in controls. Furthermore, significant differences of task-induced deactivation (TID, task-dependent decreases in neural activity relative to rest) between patients and controls were found in the bilateral medial prefrontal cortices, posterior cingulate cortices, and left inferior partial lobule (P<0.05). These regions were considered as parts of a task-negative network, namely the default mode network (DMN). Concretely, relative to controls, patients showed diminished TID during BR in contrast to FR. After the L-T(4) treatment, neither the poor memory states nor the alteration of TID was detectable in patients. CONCLUSION: Hypothyroidism is related to alterations of TID within DMN regions during working memory processing. These exploratory findings may imply potential neural correlates in hypothyroidism-related cognitive deficits and their recoveries.