Subhash C. Bhatnagar

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.

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.

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.

Neurogenic Stuttering: Its Reticular Modulation

Emerging neurologic evidence has suggested that developmental and acquired stuttering may have a cerebral base. Investigations have revealed compensatory activation in the right cortical motor areas and deactivation in the left perisylvian region in subjects with persistent developmental stuttering. The evidence has also implicated limbic (cingulate)-basal ganglia regions. Increased speech fluency with treatment in such subjects eliminated compensatory brain activity and shifted activation back to the left hemisphere. We assess the neurology of stuttering and then present our own observations of deep brain stimulation of the thalamus with some ameliorating effect on the encompassing syndrome with speech dysfluency.

Aphasia type and aging in Hindi-speaking stroke patients

In this study, the clinical profile of Hindi-speaking stroke patients with aphasia from northern India has been investigated. We examined the interactional effect between age and gender with aphasia type in 97 Hindi-speaking right-handed individuals, the majority of them with a confirmed diagnosis of a cerebrovascular accident. The subjects included in the study ranged from 3 weeks to two years post-onset with a diagnosis of a common classical aphasia (Brocas, Wernickes, anomic, global, conduction, and transcortical) types involving both males and females. Also examined was the interaction between literacy and aphasia type since the subjects had varied exposures to education (total illiteracy to professional/university education). While the data reported here about Hindi-speaking aphasics are relatively in agreement with the age-aphasia type patterns discussed in western countries, nonetheless some differences were also observed. The mean age of Indian patients with aphasia was significantly lower. Also, in addition to some gender and literacy related differences, an outstanding difference was that many clinical symptoms that are known to co-occur with aphasia were not readily reported by subjects with stroke.

Thalamic Functional Tuning of the Cortex in Dichotic Listening Tasks

In dichotic listening tasks, the (dominant) right ears 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.

Crossed aphasia in a patient with congenital lesion in the right hemisphere

Background: Described over 100 years ago by Bramwell (1899) as an example of atypical cerebral dominance, crossed aphasia is a clinical condition where a lesion in the right hemisphere in a right-handed person leads to aphasia. Occurring worldwide only in a few cases, it is not known what initially leads to the ontogenetic lateralisation of language to the right brain. However, we know that certain kinds of pre-existing congenital lesions in the brain, in utero or post-partum, can usually impact the language lateralisation such that it develops in the opposite hemisphere. Aims: We present neurolinguistic data from a right-handed patient with crossed aphasia, who had an atypical subcortical crossed aphasia marked with a fractionated lateralisation of functions. Early in her life she had an unsuspected, pre-existing congenital (subcortical AVM) abnormality in the right hemisphere. Methods & Procedures: Clinical data in this single-participant study was obtained from a 20-year-old female who was seen for an evaluation of her residual language functions at a university speech and hearing clinic after her ruptured right subcortical AVM. The participant was reassessed 5 years after the first examination and also received treatment for impaired verbal output. Data taken from two diagnostic evaluations are compared and discussed. Outcomes & Results: The patients language nonetheless lateralised to the right hemisphere without any obvious consequence of the subcortical AVM. This would not be puzzling since a silently sitting AVM itself may not generally interfere with lateralisation. However our participant exhibited an atypical allocation of functions. The left hemisphere appeared to have lost its dominance for speech to the right hemisphere, while it nevertheless maintained the limb praxis control, since the participant was right-handed from the outset. Interestingly the right hemispheric inherent visuospatial functions remained unimpaired, while its paralinguistic functions were impaired to a certain extent. Conclusions: We present evidence of an atypical language-cognitive lateralisation in crossed aphasia in a participant with a congenital (subcortical AVM) abnormality in the right hemisphere. We discuss the mechanisms that might have contributed to the atypical allocation of the functions.

A unique modality‐specific domain for the production of neologisms: Recurrent perseveration and oral reading

Background: Two commonly prevalent neurolinguistic constructs that have been clinically challenging are neologisms and perseveration. Both are integral parts of the language deficit that are seen in the spontaneous verbal output of patients with paragrammatism and neologistic jargon types of anomia. Both can appear in modality‐specific domains and usually co‐occur, adumbrating verbal output impairments. These are also known to occur in selected phases of the restitution, usually in the acute and sub‐acute periods, generally disappearing with recovery. Both constructs have been extensively investigated but largely as isolated phenomena. We show here that neologisms can occur in oral reading and that perseveration can be a major factor in the genesis of neologism. Aims: To date, most patients observed to have neologistic jargon aphasia also exhibited anomia and impaired auditory comprehension. Traditionally, neologisms have been studied in spontaneous verbal output, or at confrontation naming or repetition contexts. This study focuses on oral reading of a patient with aphasia who produced neologisms, but who nevertheless demonstrated good comprehension for the spoken language. There was no neologism present in her spontaneous verbal output. Methods & Procedures: The patient studied was a 76‐year‐old woman post removal of temporal lobe mass with subsequent haemorrhagic CVA. Neurolinguistic data were obtained from a standardised assessment and five treatment sessions in a 2‐month period. Transcription and analysis of the patients oral reading revealed a profound disassociation in grapheme‐to‐phoneme conversion resulting in the production of neologisms in single‐word reading, which was further contaminated by perseveration. Outcomes and Results: An analysis of the neologisms in reading aloud revealed that not just one process had contributed to their production; rather there were multiple mechanisms that were noted to be operational in the genesis of neologisms. Conclusions: Neologisms can occur independently of impaired auditory comprehension; they can also extend beyond spontaneous verbal output and there are many linguistic processes that contribute to the genesis of neologism, with recurrent perseveration serving a crucial productive role in constructing the surrogate words that “mask” the deep retrieval blocks of words.

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 (see references in Discussion section), auditory sensations have not been analyzed in relation to perceptual categories of pitch.