Hemispheric Specialization for Processing Arithmetic in Adults

Event Abstract Back to Event Autistic traits and adaptive coding of face identity Gillian Rhodes1*, Linda Jeffery1, Libby Taylor1 and Louise Ewing1 1 ARC Centre of Excellence in Cognition and its Disorders, School of Psychology, University of Western Australia, Australia Background Our ability to discriminate and recognize thousands of faces despite their similarity as visual patterns relies on adaptive, norm-based, coding mechanisms that are continuously updated by experience. Reduced adaptive coding of face identity has been proposed as a neurocognitive endophenotype for autism, because it is found in autism and in relatives of individuals with autism. Autistic traits can also extend continuously into the general population, raising the possibility that reduced adaptive coding of face identity may be more generally associated with autistic traits. In the present study, we investigated whether adaptive coding of face identity decreases as autistic traits increase in an undergraduate population. Methods Adaptive coding was measured using face identity aftereffects, and autistic traits were measured using the Autism-Spectrum Quotient (AQ) and its subscales. We also measured face and car recognition ability to determine whether autistic traits are selectively related to face recognition difficulties. Results We found that men who scored higher on levels of autistic traits related to social interaction had reduced adaptive coding of face identity. This result is consistent with the idea that atypical adaptive face-coding mechanisms are an endophenotype for autism. Autistic traits were also linked with face-selective recognition difficulties in men. However, there were some unexpected sex differences. In women, autistic traits were linked positively, rather than negatively, with adaptive coding of identity, and were unrelated to face-selective recognition difficulties. Discussion The sex differences observed here indicate that autistic traits can have different neurocognitive correlates in men and women and raise the intriguing possibility that endophenotypes of autism can differ in men and women. However, our results suggest that, at least for men, atypical adaptive coding of faces may be an endophenotype for autism. Acknowledgements This research was supported by the Australian Research Council Centre of Excellence in Cognition and its Disorders (CE110001021), an ARC Professorial Fellowship to Rhodes (DP0877379) and an ARC Discovery Outstanding Researcher Award to Rhodes (DP130102300). We thank Mayu Nishimura and Daphne Maurer for co-creating the Robbers Game used in the Identity Aftereffects task and Ainsley Read for assistance with testing. Ethical approval was granted by the Human Research Ethics Committee of the Univer Keywords: autistic traits, broader autism phenotype, face recognition, face identity aftereffects, adaptive coding, Endophenotypes Conference: ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013. Presentation Type: Oral Topic: Other Citation: Rhodes G, Jeffery L, Taylor L and Ewing L (2013). Autistic traits and adaptive coding of face identity. Conference Abstract: ACNS-2013 Australasian Cognitive Neuroscience Society Conference. doi: 10.3389/conf.fnhum.2013.212.00193 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 15 Oct 2013; Published Online: 25 Nov 2013. * Correspondence: Prof. Gillian Rhodes, ARC Centre of Excellence in Cognition and its Disorders, School of Psychology, University of Western Australia, perth, Australia, gillian.rhodes@uwa.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Gillian Rhodes Linda Jeffery Libby Taylor Louise Ewing Google Gillian Rhodes Linda Jeffery Libby Taylor Louise Ewing Google Scholar Gillian Rhodes Linda Jeffery Libby Taylor Louise Ewing PubMed Gillian Rhodes Linda Jeffery Libby Taylor Louise Ewing Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Event Abstract Back to Event Hemispheric differences in auditory temporal integration as indexed by the T-complex of the auditory event-related potential Karen Clunies-Ross1*, Allison Fox1*, An Nguyen1, Christopher Brydges1 and Veronica Connaughton1 1 University of Western Australia, Psychology, Australia Research in auditory processing implicates the left hemisphere in tasks involving temporal processing. However, recent research indicates that both the left and right auditory cortices are involved. It is suggested that the temporal integration windows over which continuously unfolding perceptual information is combined, are different between the two hemispheres. According to the Asymmetric Sampling in Time hypothesis, the temporal integration window associated with the left hemisphere is ~ 25-50 ms in duration and the temporal integration window associated with the right hemisphere is ~ 200 ms. It was predicted that all paired tones presented with a 25 ms inter-stimulus interval (ISI) or greater, would elicit distinct responses over the left hemisphere. Paired tones presented with a 200 ms ISI would elicit distinct responses over the right hemisphere. Thirty-five undergraduate students (14 male, 21 female; M = 21.26 years, SD = 5.31 years) took part in the study. Auditory event-related potentials were recorded in response to paired-tone stimuli presented at ISIs of 50 and 200 ms. The mean amplitude of the T-complex peaks (Ta and Tb) were quantified. Over the left hemisphere, a distinct T-complex response was elicited by the second tone of the pair at 50 ms inter-stimulus intervals, whereas over the right hemisphere a distinct T-complex was only elicited by the second tone of the pair at 200 ms inter-stimulus intervals. The results suggest that the temporal integration window of the right hemisphere is longer than that of the left hemisphere as indexed by the T-complex. The findings support the Asymmetric Sampling in Time model of asymmetric temporal integration. Keywords: Temporal Integration, auditory processing, event-related potential, hemispheric asymmetry, T-complex, Asymmetric sampling in time Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Sensation and Perception Citation: Clunies-Ross K, Fox A, Nguyen A, Brydges C and Connaughton V (2015). Hemispheric differences in auditory temporal integration as indexed by the T-complex of the auditory event-related potential. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00173 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Miss. Karen Clunies-Ross, University of Western Australia, Psychology, Perth, Australia, karen.clunies.ross@graduate.uwa.edu.au Dr. Allison Fox, University of Western Australia, Psychology, Perth, Australia, allison.fox@uwa.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Karen Clunies-Ross Allison Fox An Nguyen Christopher Brydges Veronica Connaughton Google Karen Clunies-Ross Allison Fox An Nguyen Christopher Brydges Veronica Connaughton Google Scholar Karen Clunies-Ross Allison Fox An Nguyen Christopher Brydges Veronica Connaughton PubMed Karen Clunies-Ross Allison Fox An Nguyen Christopher Brydges Veronica Connaughton Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

A single umbilical artery (SUA) is an independent risk factor for perinatal morbidity and mortality in healthy fetuses. The aims of the study were (1) to determine middle cerebral artery (MCA) blood flow velocimetric values among fetuses without structural or chromosomal anomalies with an SUA and to compare them with nomograms of patients with a 3-vessel cord and (2) to measure the pulsatility index (PI) of the umbilical artery among these patients. The PI values of the MCA and umbilical arteries were determined prospectively among 98 healthy fetuses with an SUA. The PI values were compared with nomograms of patients with a 3-vessel umbilical cord. For the MCA, peak systolic velocity (PSV) was also measured. Patients carrying fetuses with intrauterine growth restriction or congenital anomalies were excluded from the study. Middle cerebral artery PI values below the fifth percentile and PSV values above the 95th percentile adjusted for gestational age were considered abnormal. Gestational age ranged between 22 and 37.9 weeks (median, 30.3 weeks). After adjusting for gestational age, no alterations in the MCA PI and umbilical PI were found in comparison with the normal range for a 3-vessel cord known in the literature. Middle cerebral artery PSV values were also within the normal range for gestational age in all patients. The MCA PI and PSV values among healthy fetuses with an isolated SUA were similar to nomograms for fetuses with a 3-vessel umbilical cord. Therefore, abnormal MCA PI and PSV values among fetuses with an SUA should be treated the same as in patients with a 3-vessel umbilical cord.

The cerebrovascular circulation can be assessed non-invasively in man using transcranial doppler (TCD) velocimetry (1). The change in flow velocity pulse wave is proportional to the change in blood flow in that vessel, assuming cross sectional area of the artery studied to be constant. Such changes have been shown to correlate well with changes in cerebral perfusion in response to hypercapnia (3). TCD estimates of cerebral blood flow is increased when subjects performed both physical and cognitive activities (6) or when they were presented with visual stimuli (2). This suggests that TCD is capable of detecting changes in cerebral blood flow which accompany cerebral activity. In this study we have tested the hypothesis that volitionally controlled breathing is accompanied by an increase in middle cerebral artery (MCA) blood flow velocity (bfv) independent of changes in PCO2.

Hemispheric specialization in mental arithmetic: Insights from functional transcranial Doppler Sonography.

If they are not delivered in a timely fashion, pregnancies complicated by severe intrauterine growth restriction (IUGR) can lead to fetal loss. Conventional fetal well-being tests, including ultrasound measurement of fetal growth rate, biophysical profile, nonstress test, and contraction stress test are used to manage these pregnancies. Some fetuses delivered based on abnormal fetal well-being tests show long-term sequelae. A better understanding of the malfunction of the placenta and its effect on the fetus is desperately required for better management of these cases. We are reporting our experience of 6 such pregnancies followed by fetal middle cerebral artery (MCA) blood flow velocity measurements. There was significant decrease in MCA flow velocities in all of these fetuses compared to normal population (p < 0.05). Reverting to normal values occurred prior to the appearance of abnormal conventional tests, on average 4 days earlier. In other words, normalization of MCA flow velocities was a harbinger of fetal jeopardy. Although our observation includes a small number of patients, there is a potential for use of MCA blood flow velocity measurement to aid us in understanding and managing fetuses with IUGR. This needs to be evaluated in a larger study.

BackgroundThe middle cerebral artery supplies long end-artery branches to perfuse the deep white matter and shorter peripheral branches to perfuse cortical and subcortical tissues. A generalized vasodilatory stimulus such as carbon dioxide not only results in an increase in flow to these various tissue beds but also redistribution among them. We employed a fast step increase in carbon dioxide to detect the dynamics of the cerebral blood flow response.Methodology/Principal FindingsThe study was approved by the Research Ethics Board of the University Health Network at the University of Toronto. We used transcranial ultrasound to measure the time course of middle cerebral artery blood flow velocity in 28 healthy adults. Normoxic, isoxic step increases in arterial carbon dioxide tension of 10 mmHg from both hypocapnic and normocapnic baselines were produced using a new prospective targeting system that enabled a more rapid step change than has been previously achievable. In most of the 28 subjects the responses at both carbon dioxide ranges were characterised by more complex responses than a single exponential rise. Most responses were characterised by a fast initial response which then declined rapidly to a nadir, followed by a slower secondary response, with some showing oscillations before stabilising.Conclusions/SignificanceA rapid step increase in carbon dioxide tension is capable of inducing instability in the cerebral blood flow control system. These dynamic aspects of the cerebral blood flow responses to rapid changes in carbon dioxide must be taken into account when using transcranial blood flow velocity in a single artery segment to measure cerebrovascular reactivity.

There are many unanswered questions about cerebral lateralization. In particular, it remains unclear which aspects of language and nonverbal ability are lateralized, whether there are any disadvantages associated with atypical patterns of cerebral lateralization, and whether cerebral lateralization develops with age. In the past, researchers interested in these questions tended to use handedness as a proxy measure for cerebral lateralization, but this is unsatisfactory because handedness is only a weak and indirect indicator of laterality of cognitive functions1. Other methods, such as fMRI, are expensive for large-scale studies, and not always feasible with children2.Here we will describe the use of functional transcranial Doppler ultrasound (fTCD) as a cost-effective, non-invasive and reliable method for assessing cerebral lateralization. The procedure involves measuring blood flow in the middle cerebral artery via an ultrasound probe placed just in front of the ear. Our work builds on work by Rune Aaslid, who co-introduced TCD in 1982, and Stefan Knecht, Michael Deppe and their colleagues at the University of Münster, who pioneered the use of simultaneous measurements of left- and right middle cerebral artery blood flow, and devised a method of correcting for heart beat activity. This made it possible to see a clear increase in left-sided blood flow during language generation, with lateralization agreeing well with that obtained using other methods3.The middle cerebral artery has a very wide vascular territory (see Figure 1) and the method does not provide useful information about localization within a hemisphere. Our experience suggests it is particularly sensitive to tasks that involve explicit or implicit speech production. The 'gold standard' task is a word generation task (e.g. think of as many words as you can that begin with the letter 'B') 4, but this is not suitable for young children and others with limited literacy skills. Compared with other brain imaging methods, fTCD is relatively unaffected by movement artefacts from speaking, and so we are able to get a reliable result from tasks that involve describing pictures aloud5,6. Accordingly, we have developed a child-friendly task that involves looking at video-clips that tell a story, and then describing what was seen.

Department of Obstetrics and Gynaecology, University of Western Australia, and King Edward Memorial Hospital; and PIVET Laboratory, Cambridge Hospital, Wembley, Perth, Western Australia

Objective To investigate and evaluate the diagnostic value of transcranial doppler ultrasound (TCD) on brain death in patients with severe craniocerebral injury. Methods Forty-two cases of severe craniocerebral injury from Affiliated Hospital of Jining Medical University were divided into brain death group and survival group, according to the clinical prognosis.TCD was conducted to examine brain blood flow numerical and changed characteristics of the spectrum.Average blood flow velocity (Vm), pulse index (PI), diastolic blood flow in reverse (reverberating flow) and small systolic peaks in early systole (wave of spikes) were documented.TCD parameters were compared between the two groups with t test. Results In the brain death group, frequency of reverberating flow was 86.67% and frequency of wave of spikes was 13.33%.In survival group, frequency of reverberating flow was 14.81% and no wave of spikes was recorded.The difference in frequencies of reverberating flow and wave of spikes between the two groups was significant(χ2=28.25, P<0.01). The average speed of bilateral middle cerebral artery blood flow in brain death group((20.02±13.96)cm/s)was significantly reduced compared with survival group((56.81±16.84)cm/s, t=2.30, P<0.05). Pulse index (PI) values in brain death group (4.02±3.49)were significantly increased compared with survival group (1.24±1.03)(t=2.10, P<0.05). Conclusion Reverberating flow or wave of spikes is an important marker for brain death in patients with severe craniocerebral injury.TCD may be applied to clinically confirm the diagnosis of brain death. Key words: Transcranial doppler; Brain death; Diagnosis; Severe brain injury

We thank Dr Shang1 for his interest in our study.2 We assessed cerebral autoregulation based on the relation between fluctuations in arterial pressure and those in middle cerebral artery blood flow before and after pharmacological blockade of 3 proposed mechanisms. The data suggested that α-adrenergic, cholinergic, and myogenic mechanisms collectively accounted for 62% of the relation between pressure and cerebral blood flow. However, implicit in our approach was the assumption that middle cerebral artery blood flow responses encompass the entirety of autoregulation across the cerebrovascular bed within the middle cerebral artery territory. In his letter, Dr Shang suggests that this assumption may be in error. In particular, he points out that regulation of the cerebral vasculature is segmental. First, there are fundamental …

Event Abstract Back to Event Spatial Attention Influences Plasticity Induction in the Motor Cortex Marc Kamke1*, Alexander Ryan2, Martin Sale1, Megan Campbell1, Stephan Riek3, Timothy Carroll3 and Jason Mattingley4 1 The University of Queensland, Queensland Brain Institute, Australia 2 The University of Queensland, The School of Psychology, Australia 3 The University of Queensland, School of Human Movement Studies, Australia 4 The University of Queensland , Queensland Brain Institute and School of Psychology, Australia It is widely accepted that alterations in the strength of communication between neurons, or 'Hebbian' (synaptic) plasticity, plays a major role in the capacity of the adult brain to adapt. Such plasticity is critical for responding to changes in sensory input, learning new skills and behaviours, and recovering from injury to the nervous system. Numerous physiological influences on synaptic plasticity have now been identified, but little is known about how plasticity is affected by cognitive processes. Here, we investigated the influence of visual spatial attention on plasticity induced by external stimulation of the motor cortex. Transcranial magnetic stimulation (TMS) and a paired associative stimulation (PAS) procedure were used to alter functional responses in the thumb area of the primary motor cortex. In different experiments PAS was used to induce either an increase or a decrease in cortical excitability, as indexed by the amplitude of motor-evoked potentials. These PAS-induced effects reflect, respectively, long-term potentiation (LTP)-like and long-term depression (LTD)-like synaptic plasticity. During the induction of plasticity, participants focused their attention on one of two visual stimulus streams located adjacent to each hand. When participants attended to visual stimuli located near the left thumb, which was targeted by the plasticity procedure, LTP-like increases in excitability were enhanced relative to when they attended instead to stimuli located near the right thumb. In contrast, LTD-like decreases in excitability were reduced when attention was directed toward the visual stimuli located near the left, relative to the right, thumb. These findings suggest that voluntary attention can exert an important influence on the functional organisation of the human cortex by both enhancing LTP-like plasticity and suppressing LTD-like effects. Keywords: Attention, Motor Cortex, Transcranial Magnetic Stimulation, plasticity, spatial attention, Paired associative stimulation Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Attention Citation: Kamke M, Ryan A, Sale M, Campbell M, Riek S, Carroll T and Mattingley J (2015). Spatial Attention Influences Plasticity Induction in the Motor Cortex. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00258 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Dr. Marc Kamke, The University of Queensland, Queensland Brain Institute, Brisbane, Australia, m.kamke@uq.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Marc Kamke Alexander Ryan Martin Sale Megan Campbell Stephan Riek Timothy Carroll Jason Mattingley Google Marc Kamke Alexander Ryan Martin Sale Megan Campbell Stephan Riek Timothy Carroll Jason Mattingley Google Scholar Marc Kamke Alexander Ryan Martin Sale Megan Campbell Stephan Riek Timothy Carroll Jason Mattingley PubMed Marc Kamke Alexander Ryan Martin Sale Megan Campbell Stephan Riek Timothy Carroll Jason Mattingley Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Event Abstract Back to Event Distributed and overlapping neural bases for object individuation and identification Claire Naughtin1*, Paul Dux1 and Jason Mattingley1 1 The University of Queensland, School of Psychology, Australia To gain a sense of what, where and when visual information appears in our environment, we rely on two key processes known as object individuation and identification. In object individuation, spatial and temporal cues are used to register an object as a distinct perceptual event relative to other objects. In object identification, featural and related conceptual properties of a stimulus are extracted. It is currently unclear how these two processes are represented in the brain. We explored whether individuation and identification processes are underpinned by distinct neural substrates, and the extent to which brain regions involved in these two operations are consistent across encoding, maintenance and retrieval stages of visual short-term memory. Using functional magnetic resonance imaging we tested for brain regions that were sensitive to the number of physical objects (individuation) or the number of distinct object identities (identification) presented in a display. Across both univariate and multi-voxel pattern analyses, we found a large degree of overlap between these two processes in the brain. In addition, the brain regions recruited for each process varied across each stage of visual short-term memory. Our findings challenge influential models of multiple object encoding in VSTM which argue that individuation and identification are underpinned by a limited set of non-overlapping brain regions. Keywords: fMRI, visual short-term memory, multi-voxel pattern analysis, object identification, object individuation Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Cognition and Executive Processes Citation: Naughtin C, Dux P and Mattingley J (2015). Distributed and overlapping neural bases for object individuation and identification. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00231 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Miss. Claire Naughtin, The University of Queensland, School of Psychology, Brisbane, Australia, claire.naughtin@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Claire Naughtin Paul Dux Jason Mattingley Google Claire Naughtin Paul Dux Jason Mattingley Google Scholar Claire Naughtin Paul Dux Jason Mattingley PubMed Claire Naughtin Paul Dux Jason Mattingley Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Sudden occlusion of the middle cerebral artery (MCA) in normotensive rats increases blood flow through anastomosing branches into the territory of the occluded artery. Three weeks after MCA occlusion, anastomoses to anterior cerebral branches are increased by more than 50% in luminal diameter. One month after MCA occlusion, blood flow and blood flow reserve to the territory of the occluded MCA are returned to normal levels. In stroke-prone spontaneously hypertensive rats (SHRSP), the anastomoses are significantly narrower and blood flow through the anastomoses is less than in normotensive rats. Tissue infarction invariably develops in the territory of the occluded MCA in SHRSP. We propose that the luminal width of the anastomosis is a major determinant of blood flow into the territory of the occluded artery and of the amount of tissue protected from infarction by collateral circulation.

167: Maternal hyperoxia leads to changes in the fetal aortic isthmus doppler waveform