Right hemisphere has the last laugh: neural dynamics of joke appreciation.

Understanding a joke relies on semantic, mnemonic, inferential, and emotional contributions from multiple brain areas. Anatomically constrained magnetoencephalography (aMEG) combining high-density whole-head MEG with anatomical magnetic resonance imaging allowed us to estimate where the humor-specific brain activations occur and to understand their temporal sequence. Punch lines provided either funny, not funny (semantically congruent), or nonsensical (incongruent) replies to joke questions. Healthy subjects rated them as being funny or not funny. As expected, incongruous endings evoke the largest N400m in left-dominant temporo-prefrontal areas, due to integration difficulty. In contrast, funny punch lines evoke the smallest N400m during this initial lexical-semantic stage, consistent with their primed "surface congruity" with the setup question. In line with its sensitivity to ambiguity, the anteromedial prefrontal cortex may contribute to the subsequent "second take" processing, which, for jokes, presumably reflects detection of a clever "twist" contained in the funny punch lines. Joke-selective activity simultaneously emerges in the right prefrontal cortex, which may lead an extended bilateral temporo-frontal network in establishing the distant unexpected creative coherence between the punch line and the setup. This progression from an initially promising but misleading integration from left frontotemporal associations, to medial prefrontal ambiguity evaluation and right prefrontal reprocessing, may reflect the essential tension and resolution underlying humor.

Focal cortical and subcortical atrophy in early Parkinson's disease.

Neurodegeneration in clinically manifest Parkinson's disease affects the substantia nigra pars compacta, and gradually spreads to the limbic cortices and the neocortex. We used MRI imaging coupled with automated surface reconstruction and segmentation methods to examine cortical thickness and subcortical volumes in nondemented, early-stage Parkinson's disease patients compared to matched healthy control participants. These methods, which have been previously used to document cortical thickness changes in patients with Alzheimer's disease and Huntington's disease but not Parkinson's disease, use MR signal intensity information and the geometric constraints of the cortical and subcortical structures for an accurate tissue classification. Parkinson's disease patients were matched to the control group in psychomotor processing speed and executive functioning, but showed higher anxiety state scores. Our results demonstrated focal cortical thinning in the Parkinson's disease group in the orbitofrontal cortex, ventrolateral prefrontal cortex, and occipito-parietal areas. Subcortically, striatal volume loss was noted. These results demonstrate that both cortical and subcortical structural changes occur at relatively early stages of the disease, and are discussed in terms of the emotional dysregulation that occurs early on in patients with Parkinson's disease.

Compromised fronto-striatal functioning in HIV: an fMRI investigation of semantic event sequencing.

The human immunodeficiency virus (HIV) damages fronto-striatal regions, and is associated with deficits in executive functioning. We recently developed a semantic event sequencing task based on the Picture Arrangement subtest of the Wechsler Adult Intelligence Scale-III for use with functional magnetic resonance imaging (fMRI) and found recruitment of dorsolateral prefrontal cortex and basal ganglia in healthy participants. To assess the impact of HIV on the functioning of the basal ganglia and prefrontal cortex, we administered this task to 11 HIV+ and 11 Control participants matched for age and education. Neuropsychological evaluation demonstrated that the HIV+ group had mild impairment in memory retrieval and motor functioning, but was not demented. Morphometric measurements suggested no atrophy in basal ganglia regions. The results of the fMRI analysis revealed hypoactivation of the left caudate, left dorsolateral prefrontal cortex, and bilateral ventral prefrontal cortex in the HIV+ group. Functional connectivity analysis demonstrated less functional connectivity between the caudate and prefrontal cortex and basal ganglia regions in the HIV+ group. In contrast, the HIV+ group demonstrated increased activation of right postcentral/supramarginal gyrus, and greater connectivity between the caudate and this same anterior parietal region. The results of this study extend previous investigations by demonstrating compromised function of the caudate and connected prefrontal regions in HIV during cognition. This disruption of fronto-striatal circuitry likely precedes the development of cognitive impairment in HIV.

Putamen hypertrophy in nondemented patients with human immunodeficiency virus infection and cognitive compromise.

BACKGROUND: Documented death and dysfunction of basal ganglia cells in patients seropositive for human immunodeficiency virus (HIV) suggest that the virus may cause structural compromise to these regions. OBJECTIVES: To examine subcortical volumes in nondemented patients seropositive for HIV (HIV+) by means of a novel automated neuroanatomic morphometric analysis tool, and to investigate relationships among cognitive function, immune health, and subcortical volumes. DESIGN AND SETTING: Cross-sectional study of subcortical morphometry and cognitive function conducted at the Boston University Center for Memory and Brain and the Massachusetts General Hospital Athinoula A. Martinos Center for Biomedical Imaging. PATIENTS: Twenty-two nondemented HIV+ patients and 22 age- and education-matched healthy control participants. MAIN OUTCOME MEASURES: Subcortical segmentation volumes, neuropsychological performance, and immunological variables. RESULTS: Nondemented HIV+ patients demonstrated relative and isolated putamen hypertrophy compared with control participants. Putamen volume enlargement in HIV+ patients was related to motor slowing and immune status, such that higher CD4 lymphocyte levels were associated with larger putamen volumes. There were no other subcortical volume differences between the groups. CONCLUSIONS: This study suggests that basal ganglia hypertrophy accompanies HIV-related mild cognitive compromise. These findings may represent a structural imaging parallel to functional imaging studies demonstrating basal ganglia hypermetabolism in HIV+ patients with mild cognitive compromise and early HIV-associated brain disease.

Spatio-temporal dynamics and laterality effects of face inversion, feature presence and configuration, and face outline.

Although a crucial role of the fusiform gyrus (FG) in face processing has been demonstrated with a variety of methods, converging evidence suggests that face processing involves an interactive and overlapping processing cascade in distributed brain areas. Here we examine the spatio-temporal stages and their functional tuning to face inversion, presence and configuration of inner features, and face contour in healthy subjects during passive viewing. Anatomically-constrained magnetoencephalography (aMEG) combines high-density whole-head MEG recordings and distributed source modeling with high-resolution structural MRI. Each person's reconstructed cortical surface served to constrain noise-normalized minimum norm inverse source estimates. The earliest activity was estimated to the occipital cortex at ~100 ms after stimulus onset and was sensitive to an initial coarse level visual analysis. Activity in the right-lateralized ventral temporal area (inclusive of the FG) peaked at ~160 ms and was largest to inverted faces. Images containing facial features in the veridical and rearranged configuration irrespective of the facial outline elicited intermediate level activity. The M160 stage may provide structural representations necessary for downstream distributed areas to process identity and emotional expression. However, inverted faces additionally engaged the left ventral temporal area at ~180 ms and were uniquely subserved by bilateral processing. This observation is consistent with the dual route model and spared processing of inverted faces in prosopagnosia. The subsequent deflection, peaking at ~240 ms in the anterior temporal areas bilaterally, was largest to normal, upright faces. It may reflect initial engagement of the distributed network subserving individuation and familiarity. These results support dynamic models suggesting that processing of unfamiliar faces in the absence of a cognitive task is subserved by a distributed and interactive neural circuit.