Brooke-Mai Whelan

Improved language performance subsequent to low-frequency rTMS in patients with chronic non-fluent aphasia post-stroke

Background:  Low‐frequency repetitive transcranial magnetic stimulation (rTMS) has emerged as a potential tool for neurorehabilitation and remediation of language in chronic non‐fluent aphasia post‐stroke. Inhibitory (1 Hz) rTMS has been applied to homologous language sites to facilitate behavioural language changes. Improvements in picture‐naming performance and speech output over time have been reported.

Higher‐level language deficits resulting from left primary cerebellar lesions

Background: Contemporary neuropsychological studies suggest that cerebellar lesions may impact upon higher‐level cognitive functioning via mechanisms of crossed cerebello‐cerebral diaschisis. Accordingly, right cerebellar lesions have been previously associated with linguistic impairments such as reduced word fluency and agrammatic output. Recently, however, neuroimaging investigations have also identified ipsilateral cerebral hypoperfusion as a consequence of cerebellar lesions, implicating a potential role for the left cerebellum in the mediation of language processes. Aims: The purpose of this research was to investigate the effects of left cerebellar lesions of vascular origin, on general as well as high‐level language skills. Methods & Procedures: Linguistic profiles were compiled for five individuals with left primary cerebellar lesions utilising a comprehensive language test battery. Individual scores relevant to each subtest were compared to a group of non‐neurologically impaired controls. The criterion for anomalous performance was established as ≥ 1.5 SD below the mean of the control group. Outcomes & Results: The findings of this research suggest that higher‐level language deficits may result from left primary cerebellar lesions. All participants demonstrated deficits on measures of word fluency, sentence construction within a set context, producing word definitions, and producing multiple definitions for the same word. Deficits were also noted for several participants on measures of understanding figurative language, forming word associations, identifying and correcting semantic absurdities, and producing synonyms and antonyms. Conclusions: The results presented challenge the notion of a lateralised linguistic cerebellum, supporting a potential role for the left as well as right cerebellar hemispheres in the regulation of language processes, presumably via cerebellar‐basal ganglia/thalamo‐cortical pathways.

Improved receptive and expressive language abilities in nonfluent aphasic stroke patients after application of rTMS: An open protocol case series

BACKGROUND Repetitive transcranial magnetic stimulation (rTMS) has been identified as a potentially valuable tool for the rehabilitation of language impairment after left hemisphere (LH) stroke, in populations of persons with chronic aphasia. Applied to a homologue to Brocas area, rTMS is posited to modulate bilateral language networks, promoting measurable behavioral language change, in accordance with theories of transcallosal disinhibition arising from the damaged LH. OBJECTIVE/HYPOTHESIS The current investigation is an open-label study, presenting detailed case and group presentations on a population of seven nonfluent aphasic participants. Behavioral language performance is presented on expressive and receptive language measures up to 8 months after a 10-day protocol of 1 Hz stimulation. This research aims to provide longitudinal behavioral language outcomes for persons with aphasia, subsequent to rTMS and supplement previous studies to inform the clinical efficacy of rTMS. RESULTS In accordance with previous investigations, significant improvements in picture naming, spontaneous elicited speech and auditory comprehension were found. Time of testing was identified as a significant main effect. Significant improvements in picture naming accuracy and decreases in picture naming latency were also identified. The results demonstrate sustained language improvements up to 8 months subsequent to TMS application. CONCLUSIONS The results of this investigation are consistent with the findings of previous research studies, reporting behavioral language changes after rTMS in nonfluent aphasia. Additional evidence is provided to demonstrate that rTMS may facilitate retrieval mechanisms involved in picture naming.

Defining a role for the subthalamic nucleus within operative theoretical models of subcortical participation in language

Objective:To investigate the effects of bilateral, surgically induced functional inhibition of the subthalamic nucleus (STN) on general language, high level linguistic abilities, and semantic processing skills in a group of patients with Parkinson’s disease. Methods:Comprehensive linguistic profiles were obtained up to one month before and three months after bilateral implantation of electrodes in the STN during active deep brain stimulation (DBS) in five subjects with Parkinson’s disease (mean age, 63.2 years). Equivalent linguistic profiles were generated over a three month period for a non-surgical control cohort of 16 subjects with Parkinson’s disease (NSPD) (mean age, 64.4 years). Education and disease duration were similar in the two groups. Initial assessment and three month follow up performance profiles were compared within subjects by paired t tests. Reliability change indices (RCI), representing clinically significant alterations in performance over time, were calculated for each of the assessment scores achieved by the five STN-DBS cases and the 16 NSPD controls, relative to performance variability within a group of 16 non-neurologically impaired adults (mean age, 61.9 years). Proportions of reliable change were then compared between the STN-DBS and NSPD groups. Results:Paired comparisons within the STN-DBS group showed prolonged postoperative semantic processing reaction times for a range of word types coded for meanings and meaning relatedness. Case by case analyses of reliable change across language assessments and groups revealed differences in proportions of change over time within the STN-DBS and NSPD groups in the domains of high level linguistics and semantic processing. Specifically, when compared with the NSPD group, the STN-DBS group showed a proportionally significant (p<0.05) reliable improvement in postoperative scores achieved on the word test-revised (TWT-R), as well as a reliable decline (p<0.01) in the accuracy of lexical decisions about words with many meanings and a high degree of relatedness between meanings. Conclusions:Bilateral STN-DBS affects certain aspects of linguistic functioning, supporting a potential role for the STN in the mediation of language processes.

Language Disorders Subsequent to Left Cerebellar Lesions: A Case for Bilateral Cerebellar Involvement in Language?

Background: Crossed cerebello-cerebral diaschisis, reflecting a functional depression of supratentorial language areas due to reduced input via cerebello-cortical pathways, may represent the neuropathological mechanism responsible for language deficits associated with cerebellar pathology. Although it has been proposed that language is lateralized to the right cerebellar hemisphere, recent clinical and neuroimaging studies suggest that the cerebellum may bilaterally influence the regulation of language, with the left cerebellar hemisphere also contributing to the mediation of language via ipsilateral cerebello-cortical pathways. Aims: The aim of the study was to determine the effect of left primary cerebellar lesions on general as well as higher-level language function. Methods and Procedures: Linguistic profiles of a group of ten individuals with left primary cerebellar lesions were compared with those of a group of non-neurologically impaired controls matched for age, gender and level of education. Outcomes and Results: The findings confirmed that higher-level language deficits may result from left primary cerebellar lesions possibly as a consequence of ipsilateral cerebral diaschisis. Conclusions: The results challenge the notion of a right lateralized cerebellum and support a role for the left as well as the right cerebellar hemisphere in the regulation of language function.

Delineating communication impairments associated with mild traumatic brain injury: a case report.

BackgroundMild traumatic brain injury (mTBI) without frank neurological disturbance has been linked to persistent physical, cognitive, and affective disturbances in some cases. The cognitive sequelae of this syndrome represent the most frequently studied symptoms, yet the legacy of such injuries on communicative functions remains largely undetermined. MethodsA detailed language profile of a 19-year-old woman, 1 year 10 months following mTBI is compared with a matched normative cohort of 10 participants with nonneurological impairment. ResultsDeficits in attention, lexical access, complex lexical-semantic manipulation, response monitoring, and organization were revealed as a consequence of mTBI. ConclusionsThis profile provides support for hypotheses pertaining to neuronal fallout mechanisms within the frontal lobes as a consequence of mild neurological insult.

Modulation of N400 in chronic non-fluent aphasia using low frequency Repetitive Transcranial Magnetic Stimulation (rTMS)

Low frequency Repetitive Transcranial Magnetic Stimulation (rTMS) has previously been applied to language homologues in non-fluent populations of persons with aphasia yielding significant improvements in behavioral language function up to 43 months post stimulation. The present study aimed to investigate the electrophysiological correlates associated with the application of rTMS through measurement of the semantic based N400 Event-related brain potentials (ERP) component. Low frequency (1 Hz) rTMS was applied to the anterior portion of the homologue to Brocas area (pars triangularis), for 20 min per day for 10 days, using a stereotactic neuronavigational system. Twelve non-fluent persons with aphasia, 2-6 years post stroke were stimulated. Six participants were randomly assigned to receive real stimulation and six participants were randomly assigned to receive a blind sham control condition. ERP measures were recorded at baseline, 1 week and 2 months subsequent to stimulation. The findings demonstrate treatment related changes observed in the stimulation group when compared to the placebo control group at 2 months post stimulation indicating neuromodulation of N400 as a result of rTMS. No treatment related changes were identified in the stimulation group, when compared to the sham group from baseline to 1 week post stimulation. The electrophysiological results represent the capacity of rTMS to modulate neural language networks and measures of lexical-semantic function in participants with non-fluent aphasia and suggest that time may be an important factor in brain reorganization subsequent to rTMS.

Redefining functional models of basal ganglia organization: Role for the posteroventral pallidum in linguistic processing

Traditionally the basal ganglia have been implicated in motor behavior, as they are involved in both the execution of automatic actions and the modification of ongoing actions in novel contexts. Corresponding to cognition, the role of the basal ganglia has not been defined as explicitly. Relative to linguistic processes, contemporary theories of subcortical participation in language have endorsed a role for the globus pallidus internus (GPi) in the control of lexical–semantic operations. However, attempts to empirically validate these postulates have been largely limited to neuropsychological investigations of verbal fluency abilities subsequent to pallidotomy. We evaluated the impact of bilateral posteroventral pallidotomy (BPVP) on language function across a range of general and high‐level linguistic abilities, and validated/extended working theories of pallidal participation in language. Comprehensive linguistic profiles were compiled up to 1 month before and 3 months after BPVP in 6 subjects with Parkinsons disease (PD). Commensurate linguistic profiles were also gathered over a 3‐month period for a nonsurgical control cohort of 16 subjects with PD and a group of 16 non‐neurologically impaired controls (NC). Nonparametric between‐groups comparisons were conducted and reliable change indices calculated, relative to baseline/3‐month follow‐up difference scores. Group‐wise statistical comparisons between the three groups failed to reveal significant postoperative changes in language performance. Case‐by‐case data analysis relative to clinically consequential change indices revealed reliable alterations in performance across several language variables as a consequence of BPVP. These findings lend support to models of subcortical participation in language, which promote a role for the GPi in lexical–semantic manipulation mechanisms. Concomitant improvements and decrements in postoperative performance were interpreted within the context of additive and subtractive postlesional effects. Relative to parkinsonian cohorts, clinically reliable versus statistically significant changes on a case by case basis may provide the most accurate method of characterizing the way in which pathophysiologically divergent basal ganglia linguistic circuits respond to BPVP.

Lingual Kinematics in Dysarthric and Nondysarthric Speakers with Parkinson's Disease

Articulatory dysfunction is recognised as a major contributor to the speech disturbances seen in Parkinsons disease (PD). The present study aimed to compare lingual kinematics during consonant production within a sentence in eight dysarthric (DPD) and seven nondysarthric (NDPD) speakers with PD with those of eleven nonneurologically impaired normal participants. The tongue tip and tongue back movements of the participants during sentence production were recorded using electromagnetic articulography (EMA). Results showed that both the DPD and NDPD had deviant articulatory movement during consonant production that resulted in longer duration of consonant production. When compared with the NDPD group, the DPD group primarily exhibited increased range of lingual movement and compatible duration of production with an accompanying increase in maximum velocity, maximum acceleration, and maximum deceleration. These findings are contrary to proposed theories that suggest articulatory imprecision in dysarthric speakers with PD is the outcome of reduced range of articulatory movement.

Language disorders subsequent to mild traumatic brain injury (MTBI): Evidence from four cases

Background: The majority of cognitive research conducted within the mild traumatic brain injury (MTBI) population has been predominantly neuropsychologically based, lacking in-depth linguistic analysis. The effect of MTBI on language function has received little attention and remains largely unexplored. Aims: This study was undertaken to explore in detail cognitive-linguistic impairments following MTBI, via the application of a comprehensive assessment battery. Methods & Procedures: Four participants with MTBI were administered a comprehensive battery of cognitive-linguistic assessments at 6 months post injury. The control group consisted of 10 age-, sex- and education-level-matched, non-neurologically impaired participants. Non-parametric group comparisons between the MTBI and matched controls participants were carried out, followed by case-by-case analysis. Outcomes & Results: Non-parametric between-group comparisons failed to reveal statistically significant differences between the MTBI and control participants across subtests. In case-by-case analyses, however, below normal performance on a range of subtests was demonstrated by the MTBI participants. Conclusions: Findings suggest high-level cognitive-linguistic deficits may occur as a consequence of MTBI and imply that MTBI mechanisms may have the capacity to alter frontal lobe functioning. It is suggested that more sensitive measures of cognitive and high-level language function are needed in the assessment of MTBI.