Intraoperative Electrical Stimulation (IES) of the brain is performed to localise and spare language functional areas before extraction of brain tissue in patients with tumors and epilepsy. The procedure is very precise and highly effective. Yet, it is argued that language tests used during IES are too limited. This article presents new language tests that have a potential of minimising post-operative risk to language function. It is a continuation of a previous study (Połczyńska 2008) and it contains extended versions of earlier presented tests, as well as new tests designed in three sets: (1) Grammar-focused tests for the dominant left hemisphere, (2) Non-dominant righthemisphere tests and (3) Tests for the subcortex. To assure maximum safety and efficiency of the tests before they are used during IES for the first time, it is suggested that they are first used with patients with intractable epilepsy who have a multielectrode subdural grid implanted onto their cortex to trace the source of seizures. The subdural grid gives a chance to carry out an electrical stimulation of those areas of the cortex which are covered with a grid. This type of language mapping is carried out in a ward and is not time-limited.
Background. The vowel space area (VSA) has been used as an acoustic metric of dysarthric vowel articulation, but with varying degrees of success. Here we test the hypothesis that the failure of the VSA to differentiate dysarthric from normal vowel articulation has to do in part with statistical "noise" that is introduced by insensitivity of Euclidean distances that define the VSA to vowel centralisation.Methods. Differences in vowel production between 5 dysarthric young men post traumatic brain injury (TBI) and 5 young men who served as healthy controls (HC) were tested with four acoustic metrics: the triangular VSA, constructed with the first (F1) and second (F2) formants of the vowels /i/, /u/, /a/, and the Euclidean distances (EDs) between the vowels /i/ and /u (EDiu), /i/ and /a/ (EDia), and /a/ and /u/ (EDau) that define the VSA. The formant frequencies of these metrics were logarithmically scaled to reduce irrelevant interspeaker variability.Results. The VSA failed to differentiate between the TBI and HC groups, as did the the EDia, and EDau. In contrast, the EDiu effectively differentiated between groups, both statistically (unpaired t-test, p=0.0174) and in terms effect size (1.88, large). The significant difference was in the expected direction, indicating vowel centralisation and articulatory undershoot in the TBI speakers.Conclusion. The VSA is likely to perform poorly as an acoustic metric of dysarthric speech because of "noise" introduced by Euclidian distances (EDs) metrics that are not sensitive to the articulatory abnormality (in this study, the EDia and EDau). Thus, rather than using the VSA, it might be more beneficial to use only those EDs that are likely to be sensitive to vowel centralisation, as might be the case with the EDiu.
Traumatic brain injury (TBI) often results in dysarthria, a motor speech disorder. Two processes often linked with TBI dysarthria are vowel centralisation and incomplete stop articulation. It is not clear to what extent these two processes are interrelated and to what extent they might serve as indices of the severity of dysarthria secondary to TBI. The purpose of this study is to test the hypothesis that patients who centralise vowels will also have difficulties producing stop consonants with complete stricture. Polish dysarthric speakers post TBI (n=6) and ten age-matched healthy controls with normal speech (n=10) performed the Polish Dysarthria Test for TBI Patients (PDTTP) (Połczyńska-Fiszer and Pufal 2006). Three of the TBI subjects had moderate dysarthria and three mild dysarthria. The test investigates phonemes in isolation as well as in diverse phonetic contexts in different elicitation tasks, including spontaneous speech. The data from the PDTTP were transcribed phonetically and analysed acoustically. Vowel centralisation and incomplete stop articulation appear to be strongly correlated (r=0.90). It was found that the degree of TBI dysarthria correlates with the frequency of occurrence of these two processes. Thus, the two processes may serve as important indices of severity of dysarthria in TBI.
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