The precuneus may encode irrationality in human gambling.

Humans often make irrational decisions, especially psychiatric patients who have dysfunctional cognitive and emotional circuitry. Understanding the neural basis of decision-making is therefore essential towards patient management, yet current studies suffer from several limitations. Functional magnetic resonance imaging (fMRI) studies in humans have dominated decision-making neuroscience, but have poor temporal resolution and the blood oxygenation level-dependent signal is only a proxy for neural activity. On the other hand, lesion studies in humans used to infer functionality in decision-making lack characterization of neural activity altogether. Using a combination of local field potential recordings in human subjects performing a financial decision-making task, spectral analyses, and non-parametric cluster statistics, we analyzed the activity in the precuneus. In nine subjects, the neural activity modulated significantly between rational and irrational trials in the precuneus (p <; 0.001). In particular, high-frequency activity (70-100 Hz) increased when irrational decisions were made. Although preliminary, these results suggest suppression of gamma rhythms via electrical stimulation in the precuneus as a therapeutic intervention for pathological decision-making.

Modeling the motor striatum under Deep Brain Stimulation in normal and MPTP conditions.

Striatum (STR) is the major input stage of the basal ganglia (BG). It combines information from cortex, subthalamic nucleus (STN) and external globus pallidus (GPe), and projects to the output stages of the BG, where selection between concurrent motor programs is performed. Parkinson's disease (PD) reduces the concentration of dopamine (DA, a neurotransmitter) in STR and changes in the level of DA correlate with the onset of PD motor disorders. Though STR plays a pivotal role in BG, its behavior under PD and Deep Brain Stimulation (DBS) is still unclear. We develop point-process models of the STR neurons as a function of the activity in GPe, cortex, and DBS. We use single unit recordings from a monkey under STN DBS at different frequencies before and after treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine (MPTP) to develop PD motor symptoms. The models suggest that STR neurons have prominent bursting activity in normal conditions, positive correlation with cortex (3-10 ms delay), and mild negative correlation with GPe (1-5 ms lag). DA depletion evokes 30-60 Hz oscillations, and increases the propensity of each neuron to be inhibited by surrounding neurons. DBS elicits antidromical activation, masks existent dynamics, reinforces dependencies between nuclei, and entrains at the stimulation frequency in both conditions.

Modeling the effects of Deep Brain Stimulation on sensorimotor cortex in normal and MPTP conditions.

Deep Brain Stimulation (DBS) is an effective surgical therapy for the treatment of movement disorders in Parkinson's disease (PD) and other neurological pathologies. DBS is known to modulate the spiking activity of the neurons within the basal ganglia, but how such modulation impacts the primary sensorimotor cortex is still uncertain. In this study a monkey was stimulated with DBS at several frequencies in the subthalamic nucleus (STN) before and after treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to develop PD symptoms, while single unit recordings are simultaneously obtained from the sensorimotor cortex. We exploit such data to develop point-process input-output models of the cortical neurons. Our models describe the effects of stimulation in normal and MPTP conditions and investigate the influence of the stimulation frequency on the neuronal activity. Our models show increased synchronization of the cortical neurons in MPTP vs. normal conditions before stimulation, suggest that STN DBS impacts the cortical activity by antidromically eliciting spikes at the stimulation frequency, and support the hypothesis that high frequency DBS partially masks the effects of thalamo-cortical input.

Stereotactic cortical resection in non-lesional extra-temporal partial epilepsy.

The presentation and treatment of a patient with extra-temporal non-lesional partial epilepsy is discussed herein. His clinical semiology was consistent with supplementary motor area seizures; however, MR imaging did not demonstrate a lesion. A region of stable cortical glucose hypermetabolism in the left frontal region was noted with 2-fluoro-2-deoxy-D-glucose (FDG)-PET. This was consistent with the frequent interictal discharges evident over the left fronto-temporal region and the stereotypic high amplitude ictal discharges arising with highest amplitude from the left frontal region. Epileptiform activity evident on an intracranial 64-point subdural recording grid placed over the left dorsolateral frontal cortex confirmed a distribution concordant with FDG-PET findings. The subsequent resection was guided by the PET and EEG findings rather than structural MR imaging, and a limited cortical resection led to an immediate and substantial reduction in seizure frequency.

Benign mixed tumor of salivary gland origin presenting as a mediastinal mass.

Benign mixed tumor is a common neoplasm of the salivary gland. It may rarely occur as an intrabronchial lesion. A case of a mixed tumor of salivary gland origin presenting as a mediastinal mass is described.

Computer tomography demonstration of pulmonary artery calcification in Eisenmenger's syndrome.

Atherosclerotic change and pulmonary artery calcification is known to occur in patients with pulmonary artery hypertension. We present such a patient with Eisenmenger's syndrome. Computed tomography demonstrated atheromatous plaques and calcification of the pulmonary arteries.