Localization of cerebral lesions in aphasia – a computer aided comparison between men and women

It is still a matter of debate whether there are differences between men and women concerning the localization of higher cerebral functions. To further elucidate this problem we conjointly evaluated the aphasia protocols and corresponding computer-assisted tomography (CT) scans of 49 men and 35 women who presented with unilateral ischemic cerebral lesions. Both, the aphasia tests and CT scans, were fed into computer programs warranting a high degree of objectivity. Comparing the four main aphasic syndromes we found differences for each of them displaying a more posterior extension of lesions with global and amnestic aphasia in men and larger lesions with Broca and Wernicke aphasia in women. When all templates were compared, men displayed a wider extension within the left hemisphere than women whose lesions were more focused in the perisylvian area. This study confirms earlier findings claiming that aphasic men and women differ regarding the anterior-posterior extension and the frequency of lesions within the classical language zones. However, while the predominance of men's lesions in the posterior areas was in accordance with previous findings, the greater overall scatter within the left hemisphere contradicts published studies.     

Is math lateralised on the same side as language? Right hemisphere aphasia and mathematical abilities

The main purpose of the present study was to learn how mathematical abilities are located and develop in the brain with respect to language. Mathematical abilities were assessed in six right-handed patients affected by aphasia following a lesion to their non-dominant hemisphere (crossed aphasia) and in two left-handed aphasics with a right-sided lesion. Acalculia, although in different degrees, was found in all cases. The type of acalculia depended on the type of aphasia, following patterns that have been previously observed in the most common aphasias resulting from left hemisphere lesions. No sign of right hemisphere or spatial acalculia (acalculia in left lateralised right-handed subjects) was detected. These results suggest that, as a rule, language and calculation share the same hemisphere. A primitive computational mechanism capable of recursion may be the precursor of both functions.     

Lesion symptom mapping of manipulable object naming in nonfluent aphasia: Can a brain be both embodied and disembodied?

Embodied cognition offers an approach to word meaning firmly grounded in action and perception. A strong prediction of embodied cognition is that sensorimotor simulation is a necessary component of lexical–semantic representation. One semantic distinction where motor imagery is likely to play a key role involves the representation of manufactured artefacts. Many questions remain with respect to the scope of embodied cognition. One dominant unresolved issue is the extent to which motor enactment is necessary for representing and generating words with high motor salience. We investigated lesion correlates of manipulable relative to nonmanipulable name generation (e.g., name a school supply; name a mountain range) in patients with nonfluent aphasia (N?=?14). Lesion volumes within motor (BA4, where BA = Brodmann area) and premotor (BA6) cortices were not predictive of category discrepancies. Lesion symptom mapping linked impairment for manipulable objects to polymodal convergence zones and to projections of the left, primary visual cortex specialized for motion perception (MT/V5+). Lesions to motor and premotor cortex were not predictive of manipulability impairment. This lesion correlation is incompatible with an embodied perspective premised on necessity of motor cortex for the enactment and subsequent production of motor-related words. These findings instead support a graded or “soft” approach to embodied cognition premised on an ancillary role of modality-specific cortical regions in enriching modality-neutral representations. We discuss a dynamic, hybrid approach to the neurobiology of semantic memory integrating both embodied and disembodied components.     

Comments on Nickels and Howard (2004) “dissociating effects of number of phonemes,number of syllables,and syllable complexity on word production in aphasia: It's the number of phonemes that counts”

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