Language representation in the human brain: evidence from cortical mapping.

The manner in which the human brain processes grammatical-syntactic and lexical-semantic functions has been extensively debated in neurolinguistics. The discreteness and selectivity of the representation of syntactic-morphological properties in the dominant frontal cortex and the representation of the lexical-semantics in the temporo-parietal cortex have been questioned. Three right-handed adult male neurosurgical patients undergoing left craniotomy for intractable seizures were evaluated using various grammatical and semantic tasks during cortical mapping. The sampling of language tasks consisted of trials with stimulation (experimental) and without stimulation (control) from sites in the dominant fronto-temporo-parietal cortex The sampling of language implicated a larger cortical area devoted to language (syntactic-morphological and lexical-semantic) tasks. Further, a large part of the fronto-parieto-temporal cortex was involved with syntactic-morphological functions. However, only the parieto-temporal sites were implicated with the ordering of lexicon in sentence construction. These observations suggest that the representation of language in the human brain may be columnar or multilayered.

Stuttering acquired from subcortical pathologies and its alleviation from thalamic perturbation.

Acquired stuttering subsequent to subcortical pathology of mesothalamus was observed in four neurosurgical subjects. The patients suffered from chronic pain, seizures, and somatosensory disorders. They also exhibited unpredictable and uncontrollable speech, spasmodic blocks which were devoid of accessory features, and adaptation effect. Therapeutic mesothalamic stimulation, used as a treatment of last resort to relieve the pain and associated symptoms, also had an ameliorating effect on the stuttering. Spontaneously occurring focal abnormal EEG discharges were anatomically delineated and used as a guide for therapeutic stimulation electrode placement. Attentuation of the abnormal discharges was followed by alleviation of symptoms. This investigation examines the clinical characteristics of stuttering in four neurosurgical patients and suggests an electropathologic basis for their mesothalamic-generated speech dysfluencies. The cooccurrence of pain, seizures, somatosensory disorders, and stuttering, and their concurrent amelioration, suggests that both chronic pain and stuttering may be implicated by similar or related reticular electropathologic generators, couched in overlapping reticular networks extending from the brain stem to the thalamus, and that the acquired stuttering may be recruited as one component of a larger syndrome complex.

Thalamic-induced stuttering (surgical observations).

Repetitive dysfluencies of speech were elicited by mechanical perturbation of the thalamus in a patient, preparatory to therapeutic lesion placement for chronic pain. Perturbation consisted of a 2 mm advancement of a 1 mm diameter electrode in the posteroventromedial thalamus. A thalamogram revealed electropathologic discharges at the site of perturbation. These findings are of special interest anatomically because in other patients, electrical stimulation at the same site was found to alleviate stuttering (Andy, 1987; Andy, 1989; Andy & Jurko, 1985; Bhatnagar & Andy, 1989). It is suggested that dysfluencies in this patient may have resulted from an electrophysiologic disturbance of the mesothalamic component of a speech-regulating corticomesothalamic feedback circuit.

Alleviation of acquired stuttering with human centremedian thalamic stimulation.

Despite many investigations, the cerebral mechanism for stuttering remains unknown. Recently, increased attention has been paid to acquired stuttering of adult onset in the hope that the events associated with it might provide clues to the biological mechanism underlying stuttering. This attention has focused exclusively on the cortical substrates. We present our observations of acquired dysfluency, presumably of subcortical origin in a neurosurgical subject with intractable pain. The stuttering was relieved by thalamic electric stimulation. The effect of thalamic stimulation on the stuttering suggests that the pathophysiology of transient asynchronisation in the balancing and sequencing of multiple impulses is amenable to a diffusely orchestrated functional tuning of the thalamic and brainstem implicated subcortical structures and pathways.

Tonotypic cortical representation in man (case report).

Cortical stimulation--evoked perception of tones differing in pitch suggests that the perception of pitch may be discretely organized in the human auditory parakoniocortex. Findings, obtained from a neurosurgical patient undergoing temporal lobectomy, are discussed with reference to anatomical and functional considerations of the auditory parakoniocortex in humans. These tonotypic findings are potentially significant since, as previously reported, auditory sensations have not been analyzed in relation to perceptual categories of pitch.

Activity of quassinoids as antifeedants against aphids.

A series of quassinoids was tested for antifeedant activity against the aphidMyzus persicae (Hemiptera, Aphididae). Isobrucein B, brucein B and C, glaucarubinone, and quassin decreased feeding at concentrations down to 0.05% and isobrucein A was effective at 0.01%. Only quassin showed no phytotoxic effects and is therefore the most promising compound for further development.

Thalamic functional tuning of the cortex in dichotic listening tasks.

In dichotic listening tasks, the (dominant) right ear's superiority in processing verbal stimuli has been attributed to its direct access to the linguistically dominant left hemisphere. The roles played by the extralinguistic factors, such as induced attentiveness and functional tuning of the auditory system, have not been carefully examined. The evidence for the facilitating effects of subcortical stimulation on processing dichotic stimuli is presented.

Right-hemispheric language evidence from cortical stimulation.

While the left-hemispheric dominance for language in most right-handers is unquestionable, clinical observations suggest that the right, nondominant hemisphere has a considerable capacity for language. Under certain neuroanatomical conditions, the right-hemispheric capacity becomes functional and, thus, measurable. This study focuses on evoked language responses during electrical stimulation of the right hemisphere in three left-dominant patients undergoing temporal lobe resections for medically intractable seizures.

A framework for designing an MIS for health delivery system in rural India.

A framework for designing an information system for planning and monitoring of rural health services is proposed in the Indian context. For effective monitoring the framework emphasises selection of a set of programmed and non-programme indicators on inputs, activities, efficiency and impact and their integration at the district level. For planning, a village level data base is proposed which will integrate environmental data with health programme data. Illustrative examples are provided for key features of the MIS and finally those elements of the information system which are either too complex or too voluminous to be handled manually are identified and the possibility of using computers for such analysis is explored.