Parkinsonism reversed from treatment of pineal non-germinomatous germ cell tumor.

BACKGROUND: Parkinsonism is a rare complication of non-germinomatous germ cell tumors (NGGCTs) arising from the pineal region. CASE DESCRIPTION: We describe a 23-year-old man who presented with Parinaud syndrome, fatigue, and hypersomnia that were caused by a pineal region NGGCT with yolk sac component and an initial α-fetoprotein (AFP) of 1011.0 ng/ml. MRI revealed that the tumor was causing 10 mm of midline shift and compressing the cerebral aqueduct, the left thalamus, and the midbrain. Obstructive hydrocephalus was relieved by ventriculoperitoneal shunting. Six cycles of induction chemotherapy with ifosfamide, carboplatin, and etoposide reduced tumor size and decreased AFP levels in both serum and cerebrospinal fluid. Following the first cycle, the patient developed asymmetric, bilateral Parkinsonism consisting of bradykinesia, bradyphrenia, facial hypomimia, drooling, and dysphagia. Levodopa, amantadine, and methylphenidate were administered and resulted in symptom improvement. Second look neurosurgery revealed residual yolk sac tumor and a second induction regimen of gemcitabine, paclitaxel, and oxaliplatin was administered for rising AFP. The patient eventually received an autologous bone marrow transplant using a regimen of high-dose carboplatin, thiotepa, and etoposide with concomitant colony-stimulating factor and romiplostim support followed by consolidative proton craniospinal radiotherapy. Posttreatment head MRI showed that no evidence of tumor growth and serum AFP was within normal limits. His Parkinsonism eventually resolved and he was weaned off all dopaminergic drugs. CONCLUSION: Bilateral Parkinsonism from NGGCT in this patient is probably caused by pressure on nigrostriatal tracts, substantia nigra, or both. The Parkinsonian symptoms can be reversed by aggressive treatment of the tumor and administration of dopaminergic drugs.

The role of piriform associative connections in odor categorization.

Distributed neural activity patterns are widely proposed to underlie object identification and categorization in the brain. In the olfactory domain, pattern-based representations of odor objects are encoded in piriform cortex. This region receives both afferent and associative inputs, though their relative contributions to odor perception are poorly understood. Here, we combined a placebo-controlled pharmacological fMRI paradigm with multivariate pattern analyses to test the role of associative connections in sustaining olfactory categorical representations. Administration of baclofen, a GABA(B) agonist known to attenuate piriform associative inputs, interfered with within-category pattern separation in piriform cortex, and the magnitude of this drug-induced change predicted perceptual alterations in fine-odor discrimination performance. Comparatively, baclofen reduced pattern separation between odor categories in orbitofrontal cortex, and impeded within-category generalization in hippocampus. Our findings suggest that odor categorization is a dynamic process concurrently engaging stimulus discrimination and generalization at different stages of olfactory information processing, and highlight the importance of associative networks in maintaining categorical boundaries.

De Novo Emergence of Odor Category Representations in the Human Brain.

Categorization allows organisms to efficiently extract relevant information from a diverse environment. Because of the multidimensional nature of odor space, this ability is particularly important for the olfactory system. However, categorization relies on experience, and the processes by which the human brain forms categorical representations about new odor percepts are currently unclear. Here we used olfactory psychophysics and multivariate fMRI techniques, in the context of a paired-associates learning task, to examine the emergence of novel odor category representations in the human brain. We found that learning between novel odors and visual category information induces a perceptual reorganization of those odors, in parallel with the emergence of odor category-specific ensemble patterns in perirhinal, orbitofrontal, piriform, and insular cortices. Critically, the learning-induced pattern effects in orbitofrontal and perirhinal cortex predicted the magnitude of categorical learning and perceptual plasticity. The formation of de novo category-specific representations in olfactory and limbic brain regions suggests that such ensemble patterns subserve the development of perceptual classes of information, and imply that these patterns are instrumental to the brain's capacity for odor categorization. SIGNIFICANCE STATEMENT: How the human brain assigns novel odors to perceptual classes and categories is poorly understood. We combined an olfactory-visual paired-associates task with multivariate pattern-based fMRI approaches to investigate the de novo formation of odor category representations within the human brain. The identification of emergent odor category codes within the perirhinal, piriform, orbitofrontal, and insular cortices suggests that these regions can integrate multimodal sensory input to shape category-specific olfactory representations for novel odors, and may ultimately play an important role in assembling each individual's semantic knowledge base of the olfactory world.

Part-set cuing facilitation for spatial information.

Part-set cuing inhibition refers to the counterintuitive finding that hints--specifically, part of the set of to-be-remembered information--often impair memory performance in free recall tasks. Although inhibition is the most commonly reported result, part-set cuing facilitation has been shown with serial order tasks. The present study examined the influence of part-set cuing for spatial locations using novel methods and materials. Participants viewed the construction of Snap Circuit objects and then attempted to reconstruct the objects in either the presence or absence of part-set cues. Two experiments revealed robust part-set cuing facilitation on the spatial memory tasks. Generally, these results are consistent with the predictions of the retrieval strategy disruption hypothesis (e.g., D. R. Basden & Basden, 1995) and the 2- and 3-mechanism accounts of part-set cuing (Bäuml & Aslan, 2006; Bäuml & Samenieh, 2012).