DSpace Repository :: Browsing by Author "Price, Cathy"

Browsing by Author "Price, Cathy"

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Damage to Broca's area does not contribute to long-term speech production outcome after stroke
(2021) Gajardo-Vidal, Andrea; Lorca, Diego; Team, Ploras; Warner, Holly; Pshdary, Bawan; Crinion, Jennifer; Leff, Alexander; Hope, Thomas; Geva, Sharon; Seghier, Mohamed; Green, David; Bowman, Howard; Price, Cathy
Broca's area in the posterior half of the left inferior frontal gyrus has long been thought to be critical for speech production. The current view is that long-term speech production outcome in patients with Broca's area damage is best explained by the combination of damage to Broca's area and neighbouring regions including the underlying white matter, which was also damaged in Paul Broca's two historic cases. Here, we dissociate the effect of damage to Broca's area from the effect of damage to surrounding areas by studying long-term speech production outcome in 134 stroke survivors with relatively circumscribed left frontal lobe lesions that spared posterior speech production areas in lateral inferior parietal and superior temporal association cortices. Collectively, these patients had varying degrees of damage to one or more of nine atlas-based grey or white matter regions: Brodmann areas 44 and 45 (together known as Broca's area), ventral premotor cortex, primary motor cortex, insula, putamen, the anterior segment of the arcuate fasciculus, uncinate fasciculus and frontal aslant tract. Spoken picture description scores from the Comprehensive Aphasia Test were used as the outcome measure. Multiple regression analyses allowed us to tease apart the contribution of other variables influencing speech production abilities such as total lesion volume and time post-stroke. We found that, in our sample of patients with left frontal damage, long-term speech production impairments (lasting beyond 3 months post-stroke) were solely predicted by the degree of damage to white matter, directly above the insula, in the vicinity of the anterior part of the arcuate fasciculus, with no contribution from the degree of damage to Broca's area (as confirmed with Bayesian statistics). The effect of white matter damage cannot be explained by a disconnection of Broca's area, because speech production scores were worse after damage to the anterior arcuate fasciculus with relative sparing of Broca's area than after damage to Broca's area with relative sparing of the anterior arcuate fasciculus. Our findings provide evidence for three novel conclusions: (i) Broca's area damage does not contribute to long-term speech production outcome after left frontal lobe strokes; (ii) persistent speech production impairments after damage to the anterior arcuate fasciculus cannot be explained by a disconnection of Broca's area; and (iii) the prior association between persistent speech production impairments and Broca's area damage can be explained by co-occurring white matter damage, above the insula, in the vicinity of the anterior part of the arcuate fasciculus.
Dissociating the functions of three left posterior superior temporal regions that contribute to speech perception and production
(2021) Ekert, Justyna; Gajardo-Vidal, Andrea; Lorca, Diego; Hope, Thomas; Dick, Fred; Crinionc, Jennifer; Greend, David; Price, Cathy
Prior studies have shown that the left posterior superior temporal sulcus (pSTS) and left temporo-parietal junction (TPJ) both contribute to phonological short-term memory, speech perception and speech production. Here, by conducting a within-subjects multi-factorial fMRI study, we dissociate the response profiles of these regions and a third region - the anterior ascending terminal branch of the left superior temporal sulcus (atSTS), which lies dorsal to pSTS and ventral to TPJ. First, we show that each region was more activated by (i) 1-back matching on visually presented verbal stimuli (words or pseudowords) compared to 1-back matching on visually presented non-verbal stimuli (pictures of objects or non-objects), and (ii) overt speech production than 1-back matching, across 8 types of stimuli (visually presented words, pseudowords, objects and non-objects and aurally presented words, pseudowords, object sounds and meaningless hums). The response properties of the three regions dissociated within the auditory modality. In left TPJ, activation was higher for auditory stimuli that were non-verbal (sounds of objects or meaningless hums) compared to verbal (words and pseudowords), irrespective of task (speech production or 1-back matching). In left pSTS, activation was higher for non-semantic stimuli (pseudowords and hums) than semantic stimuli (words and object sounds) on the dorsal pSTS surface (dpSTS), irrespective of task. In left atSTS, activation was not sensitive to either semantic or verbal content. The contrasting response properties of left TPJ, dpSTS and atSTS was cross-validated in an independent sample of 59 participants, using region-by-condition interactions. We also show that each region participates in non-overlapping networks of frontal, parietal and cerebellar regions. Our results challenge previous claims about functional specialisation in the left posterior superior temporal lobe and motivate future studies to determine the timing and directionality of information flow in the brain networks involved in speech perception and production.
Enhanced left superior parietal activation during successful speech production in patients with left dorsal striatal damage and error-prone neurotypical participants
(2022) Geva, Sharon; Schneider, Letitia; Khan, Shamima; Lorca, Diego; Gajardo-Vidal, Andrea; PLORAS team; Green, David; Price, Cathy
Functional imaging studies of neurotypical adults report activation in the left putamen during speech production. The current study asked how stroke survivors with left putamen damage are able to produce correct spoken responses during a range of speech production tasks. Using functional magnetic resonance imaging, activation during correct speech production responses was assessed in 5 stroke patients with circumscribed left dorsal striatal lesions, 66 stroke patient controls who did not have focal left dorsal striatal lesions, and 54 neurotypical adults. As a group, patients with left dorsal striatal damage (our patients of interest) showed higher activation than neurotypical controls in the left superior parietal cortex during successful speech production. This effect was not specific to patients with left dorsal striatal lesions as we observed enhanced activation in the same region in some patient controls and also in more error-prone neurotypical participants. Our results strongly suggest that enhanced left superior parietal activation supports speech production in diverse challenging circumstances, including those caused by stroke damage. They add to a growing body of literature indicating how upregulation within undamaged parts of the neural systems already recruited by neurotypical adults contributes to recovery after stroke.
Generalizing post-stroke prognoses from research data to clinical data
(2019) Loughnan, Robert; Lorca, Diego; Gajardo-Vidal, Andrea; Espejo, Valeria; Gillebert, Céline; Mantini, Dante; Price, Cathy; Hope, Thomas
Around a third of stroke survivors suffer from acquired language disorders (aphasia), but current medicine cannot predict whether or when they might recover. Prognostic research in this area increasingly draws on datasets associating structural brain imaging data with outcome scores for ever-larger samples of stroke patients. The aim is to learn brain-behaviour trends from these data, and generalize those trends to predict outcomes for new patients. The practical significance of this work depends on the expected breadth of that generalization. Here, we show that these models can generalize across countries and native languages (from British patients tested in English to Chilean patients tested in Spanish), across neuroimaging technology (from MRI to CT), and from scans collected months or years after stroke for research purposes, to scans collected days or weeks after stroke for clinical purposes. Our results suggest one important confound, in attempting to generalize from research data to clinical data, is the delay between scan acquisition and language assessment. This delay is typically small for research data, where scans and assessments are often acquired contemporaneously. But the most natural, clinical application of these predictions will employ acute prognostic factors to predict much longer-term outcomes. We mitigated this confound by projecting the clinical patients' lesions from the time when their scans were acquired, to the time when their language abilities were assessed; with this projection in place, there was strong evidence that prognoses derived from research data generalized equally well to research and clinical data. These results encourage attention to the confounding role that lesion growth may play in other types of lesion-symptom analysis.
Right cerebral motor areas that support accurate speech production following damage to cerebellar speech areas
(2021) Geva, Sharon; Schneider, Letitia; Roberts, Sophie; Khan, Shamima; Gajardo-Vidal, Andrea; Lorca, Diego; PLORAS team; Hope, Thomas; Green, David; Price, Cathy
Specific regions of the cerebellum are activated when neurologically intact adults speak, and cerebellar damage can impair speech production early after stroke, but how the brain supports accurate speech production years after cerebellar damage remains unknown. We investigated this in patients with cerebellar lesions affecting regions that are normally recruited during speech production. Functional MRI activation in these patients, measured during various single word production tasks, was compared to that of neurologically intact controls, and patient controls with lesions that spared the cerebellar speech production regions. Our analyses revealed that, during a range of speech production tasks, patients with damage to cerebellar speech production regions had greater activation in the right dorsal premotor cortex (r-PMd) and right supplementary motor area (r-SMA) compared to neurologically intact controls. The loci of increased activation in cerebral motor speech areas motivate future studies to delineate the functional contributions of different parts of the speech production network, and test whether non-invasive stimulation to r-PMd and r-SMA facilitates speech recovery after cerebellar stroke.

Browsing by Author "Price, Cathy"

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