Post-Surgical Language Reorganization Occurs in Tumors of the Dominant and Non-Dominant Hemisphere.

PURPOSE: Surgical resection of brain tumors may shift the location of cortical language areas. Studies of language reorganization primarily investigated left-hemispheric tumors irrespective of hemispheric language dominance. We used functional magnetic resonance imaging (fMRI) to investigate how tumors influence post-surgical language reorganization in relation to the dominant language areas. METHODS: A total of, 17 patients with brain tumors (16 gliomas, one metastasis) in the frontotemporal and lower parietal lobes planned for awake surgery underwent pre-surgical and post-surgical language fMRI. Language activation post-to-pre surgery was evaluated visually and quantitatively on the statistically thresholded images on patient-by-patient basis. Results were qualitatively compared between three patient groups: temporal, with tumors in the dominant temporal lobe, frontal, with tumors in the dominant frontal lobe and remote, with tumors in the non-dominant hemisphere. RESULTS: Post-to-pre-surgical distributions of activated voxels changed in all except the one patient with metastasis. Changes were more pronounced in the dominant hemisphere for all three groups, showing increased number of activated voxels and also new activation areas. Tumor resection in the dominant hemisphere (frontal and temporal) shifted the activation from frontal towards temporal, whereas tumor resection in the non-dominant hemisphere shifted the activation from temporal towards frontal dominant areas. CONCLUSION: Resection of gliomas in the dominant and in the non-dominant hemisphere induces postsurgical shifts and increase in language activation, indicating that infiltrating gliomas have a widespread influence on the language network. The dominant hemisphere gained most of the language activation irrespective of tumor localization, possibly reflecting recovery of pre-surgical tumor-induced suppression of these activations.

Contributions of sensory input, auditory search and verbal comprehension to cortical activity during speech processing.

We studied eight normal subjects in an fMRI experiment where they listened to natural speech sentences and to matched simple or complex speech envelope noises. Neither of the noises (simple or complex) were understood initially, but after the corresponding natural speech sentences had been heard, comprehension was close to perfect for the complex but still absent for the simple speech envelope noises. This setting thus involved identical stimuli that were understood or not and permitted to identify (i) a neural substrate of speech comprehension unconfounded by stimulus acoustic properties (common to natural speech and complex noises), (ii) putative correlates of auditory search for phonetic cues in noisy stimuli (common to simple and complex noises once the matching natural speech had been heard) and (iii) the cortical regions where speech comprehension and auditory search interact. We found correlates of speech comprehension in bilateral medial (BA21) and inferior (BA38 and BA38/21) temporal regions, whereas acoustic feature processing occurred in more dorsal temporal regions. The left posterior superior temporal cortex (Wernicke's area) responded to the acoustic complexity of the stimuli but was additionally sensitive to auditory search and speech comprehension. Attention was associated with recruitment of the dorsal part of Broca's area (BA44) and interaction of auditory attention and comprehension occurred in bilateral insulae, the anterior cingulate and the right medial frontal cortex. In combination, these results delineate a neuroanatomical framework for the functional components at work during natural speech processing, i.e. when comprehension results from concurrent acoustic processing and effortful auditory search.

Mnestic block syndrome.

The case of a patient with largely preserved intelligence, but severe and persistent memory impairments is reported. FA, a 46-year-old patient with the diagnosis of prolonged depression was investigated repeatedly over a two year period with neuroradiological, neuropsychological, neuromonitoring and other methods. While no brain damage was detectable in FA, he manifested continued and severe anterograde and retrograde memory disorders together with an inhibition in his thinking processes. Otherwise, his intellectual capabilities were in the normal range, that is he was not pseudo-demented. Various approaches with drug treatment and psychotherapy failed to improve his condition. The condition is interpreted as 'mnestic block syndrome' and is considered to be related to an altered brain metabolism which may include changes in various transmitter and hormonal systems (GABA-agonists, glucocorticoids, acetylcholine). Whether depression contributes to this syndrome is uncertain from FA's cognitive performance, but may be a possibility.

The effect of task complexity on reaction times in memory scanning and visual discrimination in Parkinson's disease.

Within the context of the bradyphrenia debate, two experiments designed to measure the cognitive speed of Parkinson patients (PD) were conducted with 58 subjects. The experiments took the form of a high-speed memory scanning task using memory sets consisting of one-six words or one-six abstract figures. In a visual discrimination task, two simultaneously presented abstract images had to be compared, the complexity of the images being varied through four stages. Motor response was constant, reaction time was the dependent variable. PD differed from matched controls in the level (significant only in scanning) but in neither experiment in the slope of reaction time curves. Interaction group x complexity (MANOVA) was not significant. Correlations between disease parameters and a 'complexity effect' measure were low throughout. However, the link to general intelligence was significant. The findings contradict the conventional bradyphrenia hypothesis.