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Assessment of the stroke patient
Published in Christos Tziotzios, Jesse Dawson, Matthew Walters, Kennedy R Lees, Stroke in Practice, 2017
Christos Tziotzios, Jesse Dawson, Matthew Walters, Kennedy R Lees
Test repetition by asking the patient to repeat the above phrases or longer sentences; more traditional internists will command ‘Repeat the phrase “no ifs, ands, or buts’’’. Inability to perform this task may be due to articulation problems (as above) or conductive dysphasia. This results from a lesion in the arcuate fasciculus or other fibres linking Wernicke’s and Broca’s areas; patients fail to repeat sentences but fluency and comprehension are adequate. Repitition helps assess speech in laconic patients giving one-word answers in the history and may reveal any of the four types of dysphasia.
Mapping The Cerebral Cortex
Published in Andrew P. Wickens, A History of the Brain, 2014
Wernicke’s new model also made some interesting predictions, especially as it implied the existence of a direct pathway passing from Wernicke’s region to Broca’s area. Although Wernicke was not aware of any such system of fibres,9 he was able to predict the consequences of their damage. Using little more than his imagination, Wernicke reasoned if a patient had damage to this connection, they would still be able to comprehend language since the ‘sound area’ of the temporal lobe was intact. In addition, the same person would have fluent speech as the frontal motor area still functioned normally. The deficit, therefore, must involve the passing of linguistic information, and Wernicke deduced this would manifest itself by the person being unable to fluently or accurately repeat words spoken to them. We now know Wernicke was remarkably prescient. Patients with this type of brain damage (i.e. to the arcuate fasciculus) do indeed have problems repeating verbal material, especially abstract words, despite being fully aware of their mistakes. Today, this type of neurological condition is called conduction aphasia.
Examination of the Nervous System
Published in John W. Scadding, Nicholas A. Losseff, Clinical Neurology, 2011
Tim Fowler, John Scadding, Nick Losseff
The speech areas are connected by the arcuate fasciculus (Figure 3.7). A lesion in this pathway may separate the two sites, allowing fluent paraphasic speech with preserved comprehension, so-called conduction aphasia. In such patients, repetition is highly abnormal. In some aphasic patients the deficit appears to be one of naming, word finding, anomic aphasia. This may occur with lesions in the left temporo-parietal region, including the angular gyrus, when it may be associated with alexia and agraphia. A rare symptom complex also arising from lesions in the region of the angular gyrus is Gerstmann’s syndrome. This combines agraphia, acalculia, right–left disorientation and finger agnosia. In general, cortical lesions in the dominant hemisphere disrupt spontaneous speech and repetition. Subcortical lesions (transcortical aphasia) leave repetition intact, although understanding may be impaired (Table 3.4).
Reorganized functional connectivity of language centers as a possible compensatory mechanism for basal ganglia aphasia
Published in Brain Injury, 2020
Li Xu, Lin Huang, Wei Cui, Qian Yu
Language functions are closely associated with conventional language centers in the cortex, primarily in the Broca’s area, Wernicke’s area and the arcuate fasciculus which connects them. The language function is highly lateralized. In majority of the population, the language centers reside in the left hemisphere of the brain (1–4). As we understand the brain functions better, a more complex cortical region surrounding the two language centers known as the perisylvian language network has been proposed to be responsible for language functions (5,6). For a long period of time, this language network in the cortical region is believed to be the main anatomical substrate of language. In contrast to this view, there is mounting evidence suggesting that language is not limited to the cortical level, but also involves subcortical structures (7–10). The basal ganglia, which comprises a set of subcortical nuclei including the striatum, the globus pallidus, the substantia nigra, and the subthalamic nucleus, are thought to be primarily linked to motor functions (11). Nevertheless, a number of studies have revealed the non-motor functions of basal ganglia in higher cognitive tasks, particularly in language and speech tasks (11–14). For example, lesions in the basal ganglia as a result of stroke frequently lead to atypical and transient aphasia (15). Neurodegenerative diseases that damage basal ganglia would also impair language functions to a certain extent (16–18).
Deficient Response to Altered Auditory Feedback in Dyslexia
Published in Developmental Neuropsychology, 2018
M.R. van den Bunt, M.A. Groen, S. W. van der Kleij, M.W. Noordenbos, E. Segers, K.R. Pugh, L. Verhoeven
These temporo-parietal and (inferior) frontal areas are interconnected by the arcuate fasciculus (AF), a white matter bundle adjacent (Schmahmann & Pandya, 2006) or part of (Kamali et al., 2014) the Superior Longitudinal Fasciculus (SLF), which makes the AF/SLF a logical choice as a tract to focus on in the context of the research questions of the current study. The AF/SLF is classically thought to be involved in the sensorimotor control of speech. For instance, conduction aphasia, characterized by difficulties in speech repetition while speech perception and production as such are intact, is often related to deficiencies in the fractional anisotropy in the AF/SLF (Catani & Mesulam, 2008; but see Bernal & Ardila, 2009). This is usually taken as evidence of impaired communication between the auditory cortex and speech motor areas. Importantly, an electrocorticography study showed that communication along the AF/SLF is indeed bidirectional (Matsumoto et al., 2004). Communication from motor and inferior frontal areas to (auditory) sensory areas in this way concurs with the proposed neurocomputational models of speech feed-forward and feedback mechanisms (Guenther et al., 2006), in which an afferent copy of the motor commands to the articulators is sent to sensory areas to compare intended speech with the produced speech.
The impact of phonological versus semantic repetition training on generalisation in chronic stroke aphasia reflects differences in dorsal pathway connectivity
Published in Neuropsychological Rehabilitation, 2018
Rachel Holland, Sasha L. Johns, Anna M. Woollams
In order to isolate and quantify the damage to connectivity along the dorsal and ventral pathways for each patient, smoothed and normalised ACMs were used as a mask against the standard SPM template. The resulting image was then subtracted from the template to generate a difference image for each patient. These difference images were then overlaid on the white matter template to highlight the differing extent of damage to underlying white matter connectivity. Both patients had disruption to the integrity of the arcuate fasciculus, the key tract of the dorsal pathway. This is consistent with the known role of the arcuate fasciculus in repetition (Saur et al., 2008) and the nonword repetition deficits seen in both DM and JS. DM had moderate damage along the arcuate fascicle, focused in the posterior segment (highlighted in green in panel F of Figure 4) of the dorsal pathway, while JS had more severe damage along the arcuate fascicle, particularly at the intersection of the anterior and longitudinal segment (highlighted in violet in panel F of Figure 4).