Temporal lobe asymmetry in FDG-PET uptake predicts neuropsychological and seizure outcomes after temporal lobectomy.

OBJECTIVE: The objective of this study was to determine whether preoperative [18F]fludeoxyglucose (FDG)-positron emission tomography (PET) asymmetry in temporal lobe metabolism predicts neuropsychological and seizure outcomes after temporal lobectomy (TL). METHODS: An archival sample of 47 adults with unilateral temporal lobe epilepsy who underwent TL of their language-dominant (29 left, 1 right) or nondominant (17 right) hemisphere were administered neuropsychological measures pre- and postoperatively. Post-TL seizure outcomes were measured at 1year. Regional FDG uptake values were defined by an automated technique, and a quantitative asymmetry index (AI) was calculated to represent the relative difference in the FDG uptake in the epileptic relative to the nonepileptic temporal lobe for four regions of interest: medial anterior temporal (MAT), lateral anterior temporal (LAT), medial posterior temporal (MPT), and lateral posterior temporal (LPT) cortices. RESULTS: In language-dominant TL, naming outcomes were predicted by FDG uptake asymmetry in the MAT (r=-0.38) and LPT (r=-0.45) regions. For all patients, visual search and motor speed outcomes were predicted by FDG uptake asymmetry in all temporal regions (MPT, r=0.42; MAT, r=0.34; LPT, r=0.47; LAT, r=0.51). Seizure outcomes were predicted by FDG uptake asymmetry in the MAT (r=0.36) and MPT (r=0.30) regions. In all of these significant associations, greater hypometabolism in regions of the epileptic temporal lobe was associated with better postoperative outcomes. CONCLUSIONS: Our results support the conclusion that FDG uptake asymmetry is a useful clinical tool in assessing risk for cognitive changes in patients being considered for TL.

Behavioral patterns and lesion sites associated with impaired processing of lexical and conceptual knowledge of actions.

To further investigate the neural substrates of lexical and conceptual knowledge of actions, we administered a battery of six tasks to 226 brain-damaged patients with widely distributed lesions in the left and right cerebral hemispheres. The tasks probed lexical and conceptual knowledge of actions in a variety of verbal and non-verbal ways, including naming, word-picture matching, attribute judgments involving both words and pictures, and associative comparisons involving both words and pictures. Of the 226 patients who were studied, 61 failed one or more of the six tasks, with four patients being impaired on the entire battery, and varied numbers of patients being impaired on varied combinations of tasks. Overall, the 61 patients manifested a complex array of associations and dissociations across the six tasks. The lesion sites of 147 of the 226 patients were also investigated, using formal methods for lesion-deficit statistical mapping and power analysis of lesion overlap maps. Significant effects for all six tasks were found in the following left-hemisphere regions: the inferior frontal gyrus; the ventral precentral gyrus, extending superiorly into what are likely to be hand-related primary motor and premotor areas; and the anterior insula. In addition, significant effects for 4-5 tasks were found in not only the regions just mentioned, but also in several other left-hemisphere areas: the ventral postcentral gyrus; the supramarginal gyrus; and the posterior middle temporal gyrus. These results converge with previous research on the neural underpinnings of action words and concepts. However, the current study goes considerably beyond most previous investigations by providing extensive behavioral and lesion data for an unusually large and diverse sample of brain-damaged patients, and by incorporating multiple measures of verb comprehension. Regarding theoretical implications, the study provides new support for the Embodied Cognition Framework, which maintains that conceptual knowledge is grounded in sensorimotor systems.

A test for measuring recognition and naming of landmarks.

There have been considerable giants in recent years in understanding cognitive and neural correlated for retrieval of various types of knowledge, such as the meanings and lexical forms for categories such as a familiar faces, animals and tools, and actions. An important category that has been largely neglected so far is landmarks, and one likely reason for this is a lack of suitable stimulus materials. Here, we report a study in which we designed a Landmark Recognition and Naming Test. The test contains 65 natural (e.g., "Old Faithful") and artifactual (e.g., "U.S Capitol") landmarks from around the world. Preliminary recognition and naming data about the participants (e.g., educational level, participants, experience traveling to national parks), the stimuli (e.g., visual complexity, image agreement), and participant-stimulus interactions (e.g., familiarity, age of acquisition), and analyzed how such factors influenced landmark recognition and naming. There was a pronounced sex-related difference in landmark recognition favoring men; however, men and women performed similarly in landmark naming. We provide here extensive data regarding the stimuli, and we encourage other investigators to make use of our stimuli and data in future investigations of landmark recognition and naming.

An exaggerated effect for proper nouns in a case of superior written over spoken word production.

We describe a brain-damaged subject, RR, who manifests superior written over spoken naming of concrete entities from a wide range of conceptual domains. His spoken naming difficulties are due primarily to an impairment of lexical-phonological processing, which implies that his successful written naming does not depend on prior access to the sound structures of words. His performance therefore provides further support for the "orthographic autonomy hypothesis," which maintains that written word production is not obligatorily mediated by phonological knowledge. The case of RR is especially interesting, however, because for him the dissociation between impaired spoken naming and relatively preserved written naming is significantly greater for two categories of unique concrete entities that are lexicalised as proper nouns-specifically, famous faces and famous landmarks-than for five categories of nonunique (i.e., basic level) concrete entities that are lexicalised as common nouns-specifically, animals, fruits/vegetables, tools/utensils, musical instruments, and vehicles. Furthermore, RR's predominant error types in the oral modality are different for the two types of stimuli: omissions for unique entities vs. semantic errors for nonunique entities. We consider two alternative explanations for RR's extreme difficulty in producing the spoken forms of proper nouns: (1) a disconnection between the meanings of proper nouns and the corresponding word nodes in the phonological output lexicon; or (2) damage to the word nodes themselves. We argue that RR's combined behavioural and lesion data do not clearly adjudicate between the two explanations, but that they favour the first explanation over the second.