Deficits in reflexive covert attention following cerebellar injury.

Traditionally the cerebellum has been known for its important role in coordinating motor output. Over the past 15 years numerous studies have indicated that the cerebellum plays a role in a variety of cognitive functions including working memory, language, perceptual functions, and emotion. In addition, recent work suggests that regions of the cerebellum involved in eye movements also play a role in controlling covert visual attention. Here we investigated whether regions of the cerebellum that are not strictly tied to the control of eye movements might also contribute to covert attention. To address this question we examined the effects of circumscribed cerebellar lesions on reflexive covert attention in a group of patients (n = 11) without any gross motor or oculomotor deficits, and compared their performance to a group of age-matched controls (n = 11). Results indicated that the traditional RT advantage for validly cued targets was significantly smaller at the shortest (50 ms) SOA for cerebellar patients compared to controls. Critically, a lesion overlap analysis indicated that this deficit in the rapid deployment of attention was linked to damage in Crus I and Crus II of the lateral cerebellum. Importantly, both cerebellar regions have connections to non-motor regions of the prefrontal and posterior parietal cortices-regions important for controlling visuospatial attention. Together, these data provide converging evidence that both lateral and midline regions of the cerebellum play an important role in the control of reflexive covert visual attention.

Evidence for the functional compartmentalization of the temporalis muscle: a 3-dimensional study of innervation.

PURPOSE: The temporalis muscle is commonly used for functional transfer. It is architecturally complex, but few studies have examined its intramuscular innervation and none has used 3-dimensional modeling techniques. Understanding neuromuscular compartmentalization may allow the design of local muscle transfers to minimize donor-site morbidity. The purpose of the present study was to document the intramuscular innervation patterns throughout the volume of the temporalis muscle and define functional units within the muscle. MATERIALS AND METHODS: In 10 formalin-embalmed cadaveric specimens, the foramen ovale was exposed and the branches of the mandibular nerve were identified. Each branch was digitized in short segments extramuscularly and intramuscularly. Three-dimensional models were reconstructed from the digitized data using Maya software, and the innervation patterns were documented. RESULTS: The temporalis muscle was found to have superior and inferior parts that were further grouped by innervation into regions, with each receiving its innervation from 1 primary nerve. The nerves originated directly from the mandibular nerve, except in 3 specimens, where the posterior deep temporal nerve arose from the masseteric nerve. CONCLUSION: These results provide a detailed mapping of innervation patterns and suggest there are at least 5 functional compartments. Each of these has the capacity for selective activation, 3 of which have clinical value. These findings may allow for decreased donor-site morbidity and more functionally sophisticated designs in clinical practice.

Immunohistochemical expression of pituitary tumor transforming gene (PTTG) in pituitary adenomas: a correlative study of tumor subtypes.

OBJECTIVE: We investigated the correlation between immunohistochemical expression of the pituitary tumor transforming gene (PTTG) and pituitary adenoma subtype. METHODS: Pituitary adenomas (n = 89) were stained for PTTG using the streptavidin-biotin-peroxidase complex method and a monoclonal PTTG antibody. RESULTS: PTTG staining was found to be cytoplasmic with a pronounced paranuclear expression pattern. Reactivity was highest in growth hormone (GH) adenomas as compared with other tumors, including prolactin (PRL), follicle-stimulating hormone/luteinizing hormone/alpha subunit, as well as adrenocorticotrophic hormone-secreting adenomas. PRL adenomas exhibited the lowest expression levels. Among GH adenomas, untreated tumors demonstrated significantly higher PTTG levels than octreotide-treated examples. Although dopamine agonist-treated PRL adenomas tended to show lower expression levels, statistical significance was not reached. CONCLUSIONS: Our finding that PTTG was differentially expressed in pituitary adenoma subtypes suggests a cell-specific function for PTTG. Moreover, treatment of GH adenomas with somatostatin analogues lowered PTTG expression. Further investigation into mechanisms mediating cell-specific expression of PTTG is warranted.

Role of the cerebellum in the neurocognitive sequelae of treatment of tumours of the posterior fossa: an update.

The lengthened survival of patients with tumours of the posterior fossa has brought awareness of the neurocognitive deficits present in this patient population. In the past, these deficits were thought to be caused by radiotherapy damaging supratentorial structures known to be responsible for cognitive processing. This notion led to the development of new treatment protocols to restrict damage to supratentorial regions by decreasing the radiation dose and the irradiated volume. However, these treatment protocols have only resulted in marginal improvements, sometimes at the expense of long-term survival. Moreover, the current published work reports that non-irradiated patients with tumours of the posterior fossa exhibit similar cognitive impairments to irradiated patients. The growth and treatment of tumours of the posterior fossa also damage infratentorial structures, including the cerebellum. Findings from anatomical, clinical, and neuroimaging studies support a role for the cerebellum in cognitive functions similar to those impaired in patients with a tumour of the posterior fossa. Despite these findings, research focused on the treatment of these patients and on decreasing their cognitive impairments either ignores that the cerebellum has been implicated in non-motor functions or argues against the possibility that damage to the cerebellum might result in cognitive sequelae. Future studies need to address the possibility that the cognitive impairments of patients with tumours of the posterior fossa might be determined by a combination of factors, including damage to the cerebellum. Recognition of the important cognitive contributions of the cerebellum might lead to improved cognitive outcome and quality of life for this patient population.