The Impact of Cortical Lesions on Thalamo-Cortical Network Dynamics after Acute Ischaemic Stroke: A Combined Experimental and Theoretical Study.

The neocortex and thalamus provide a core substrate for perception, cognition, and action, and are interconnected through different direct and indirect pathways that maintain specific dynamics associated with functional states including wakefulness and sleep. It has been shown that a lack of excitation, or enhanced subcortical inhibition, can disrupt this system and drive thalamic nuclei into an attractor state of low-frequency bursting and further entrainment of thalamo-cortical circuits, also called thalamo-cortical dysrhythmia (TCD). The question remains however whether similar TCD-like phenomena can arise with a cortical origin. For instance, in stroke, a cortical lesion could disrupt thalamo-cortical interactions through an attenuation of the excitatory drive onto the thalamus, creating an imbalance between excitation and inhibition that can lead to a state of TCD. Here we tested this hypothesis by comparing the resting-state EEG recordings of acute ischaemic stroke patients (N = 21) with those of healthy, age-matched control-subjects (N = 17). We observed that these patients displayed the hallmarks of TCD: a characteristic downward shift of dominant α-peaks in the EEG power spectra, together with increased power over the lower frequencies (δ and θ-range). Contrary to general observations in TCD, the patients also displayed a broad reduction in ß-band activity. In order to explain the genesis of this stroke-induced TCD, we developed a biologically constrained model of a general thalamo-cortical module, allowing us to identify the specific cellular and network mechanisms involved. Our model showed that a lesion in the cortical component leads to sustained cell membrane hyperpolarization in the corresponding thalamic relay neurons, that in turn leads to the de-inactivation of voltage-gated T-type Ca2+-channels, switching neurons from tonic spiking to a pathological bursting regime. This thalamic bursting synchronises activity on a population level through divergent intrathalamic circuits, and entrains thalamo-cortical pathways by means of propagating low-frequency oscillations beyond the restricted region of the lesion. Hence, pathological stroke-induced thalamo-cortical dynamics can be the source of diaschisis, and account for the dissociation between lesion location and non-specific symptoms of stroke such as neuropathic pain and hemispatial neglect.

PREMM: preterm early massage by the mother: protocol of a randomised controlled trial of massage therapy in very preterm infants.

BACKGROUND: Preterm infants follow an altered neurodevelopmental trajectory compared to their term born peers as a result of the influence of early birth, and the altered environment. Infant massage in the preterm infant has shown positive effects on weight gain and reduced length of hospital stay. There is however, limited current evidence of improved neurodevelopment or improved attachment, maternal mood or anxiety. The aim of this study is to investigate the effects of infant massage performed by the mother in very preterm (VPT) infants. Effects on the infant will be assessed at the electrophysiological, neuroradiological and clinical levels.  Effects on maternal mood, anxiety and mother-infant attachment will also be measured. METHODS/DESIGN: A randomised controlled trial to investigate the effect of massage therapy in VPT infants. Sixty VPT infants, born at 28 to 32 weeks and 6 days gestational age, who are stable, off supplemental oxygen therapy and have normal cranial ultrasounds will be recruited and randomised to an intervention (infant massage) group or a control (standard care) group. Ten healthy term born infants will be recruited as a reference comparison group. The intervention group will receive standardised massage therapy administered by the mother from recruitment, until term equivalent age (TEA). The control group will receive care as usual (CAU). Infants and their mothers will be assessed at baseline, TEA, 12 months and 24 months corrected age (CA), with a battery of clinical, neuroimaging and electrophysiological measures, as well as structured questionnaires, psychoanalytic observations and neurodevelopmental assessments. DISCUSSION: Optimising preterm infant neurodevelopment is a key aim of neonatal research, which could substantially improve long-term outcomes and reduce the socio-economic impact of VPT birth. This study has the potential to give insights into the mother-baby relationship and any positive effects of infant massage on neurodevelopment. An early intervention such as massage that is relatively easy to administer and could alter the trajectory of preterm infant brain development, holds potential to improve neurodevelopmental outcomes in this vulnerable population. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry: ACTRN12612000335897 . Date registered: 22/3/2012.

Scale-free bursting in human cortex following hypoxia at birth.

The human brain is fragile in the face of oxygen deprivation. Even a brief interruption of metabolic supply at birth challenges an otherwise healthy neonatal cortex, leading to a cascade of homeostatic responses. During recovery from hypoxia, cortical activity exhibits a period of highly irregular electrical fluctuations known as burst suppression. Here we show that these bursts have fractal properties, with power-law scaling of burst sizes across a remarkable 5 orders of magnitude and a scale-free relationship between burst sizes and durations. Although burst waveforms vary greatly, their average shape converges to a simple form that is asymmetric at long time scales. Using a simple computational model, we argue that this asymmetry reflects activity-dependent changes in the excitatory-inhibitory balance of cortical neurons. Bursts become more symmetric following the resumption of normal activity, with a corresponding reorganization of burst scaling relationships. These findings place burst suppression in the broad class of scale-free physical processes termed crackling noise and suggest that the resumption of healthy activity reflects a fundamental reorganization in the relationship between neuronal activity and its underlying metabolic constraints.

Cortical activity differs between position- and force-control knee extension tasks.

Neural control differs between position- and force-control tasks as evident from divergent effects of fatigue and pain. Unlike force-control tasks, position-control tasks focus on a postural goal to maintain a joint angle. Cortical involvement is suggested to be less during postural control, but whether this differs between position- and force-control paradigms remains unclear. Coherence estimates the functional communication between spatially distinct active regions within the cortex (cortico-cortical coherence; CCC) and between the cortex and muscles (corticomuscular coherence; CMC). We investigated whether cortical involvement differed between force-control and more posturally focused, position-control tasks. Seventeen adults performed position- and force-control knee extensor efforts at a submaximal load (10 % maximum voluntary contraction). Surface electromyography was recorded from the right knee extensor and flexor muscles and brain activity using electroencephalography (EEG). CCC and CMC in the beta (13-30 Hz) and gamma (30-45 Hz) frequency bands were calculated between combinations of intra- and inter-hemispheric pairs of electrodes, and between four EEG electrodes that approximated the left motor cortical area, and right knee extensor EMG, respectively. Differences in EEG power and muscle activity were also calculated. CCC was greater across distributed regions in the force-control task. Beta EEG power in the left hemisphere was higher for the position-control task. Although averaged CMC data differed between tasks, there was no task difference for individual CMC data. Muscle activity and force did not differ between tasks. The results demonstrate differential cortical contributions to control force- versus position-control tasks. This might contribute to differences in performance outcomes of these tasks that have been shown previously.

Maturation of corpus callosum anterior midbody is associated with neonatal motor function in eight preterm-born infants.

BACKGROUND: The etiology of motor impairments in preterm infants is multifactorial and incompletely understood. Whether corpus callosum development is related to impaired motor function is unclear. Potential associations between motor-related measures and diffusion tensor imaging (DTI) of the corpus callosum in preterm infants were explored. METHODS: Eight very preterm infants (gestational age of 28-32 weeks) underwent the Hammersmith neonatal neurological examination and DTI assessments at gestational age of 42 weeks. The total Hammersmith score and a motor-specific score (sum of Hammersmith motor subcategories) were calculated. Six corpus callosum regions of interest were defined on the mid-sagittal DTI slice-genu, rostral body, anterior midbody, posterior midbody, isthmus, and splenium. The fractional anisotropy (FA) and mean diffusivity (MD) of these regions were computed, and correlations between these and Hammersmith measures were sought. RESULTS: Anterior midbody FA measures correlated positively with total Hammersmith (rho = 0.929, P = 0.001) and motor-specific scores (rho = 0.857, P = 0.007). Total Hammersmith scores also negatively correlated with anterior midbody MD measures (rho = -0.714, P = 0.047). DISCUSSION: These results suggest the integrity of corpus callosum axons, particularly anterior midbody axons, is important in mediating neurological functions. Greater callosal maturation was associated with greater motor function. Corpus callosum DTI may prove to be a valuable screening or prognostic marker.

Low Prevalence of Use of Allied Health and Community Services for Patients with Cirrhosis in Australia: A Need for Greater Engagement.

Background: Psychosocial, lifestyle and practical needs are not routinely attended to during outpatient hepatology management, and little is known about the type and effectiveness of support services accessed by patients with cirrhosis. We quantified the type and use of community and allied health services in patients with cirrhosis. Methods: The study included 562 Australian adults with a diagnosis of cirrhosis. Health service use was assessed via questionnaire and via linkage to the Australian Medicare Benefits Schedule. Patient needs were assessed using the Supportive Needs Assessment tool for Cirrhosis (SNAC). Results: Although most patients (85.9%) used at least one community/allied health service for support with their liver disease, many reported requiring additional help with psychosocial (67.4%), lifestyle (34.3%) or practical needs (21.9%) that were not met by available services, or patients did not access services. A multidisciplinary care plan or case conference (in the 12 months prior to recruitment) was accessed by 48% of patients, 56.2% reported the use of a general practitioner for support with cirrhosis, and a dietician was the allied health clinician most accessed by patients (45.9%). Despite the high prevalence of psychosocial needs, there was relatively limited use of mental health and social work services (14.1% of patients reported the use of a psychologist), confirmed by a low prevalence of use of mental health services (17.7%) in the linked data. Conclusion: Patients with cirrhosis who have unmet complex physical and psychosocial needs require better strategies to increase their engagement with allied health and community services.

Cognitive impairment in older hospital inpatients: prevalence, care needs and carer perceptions.

Objectives The aim of this study was to describe the prevalence of cognitive impairment in hospital inpatients, the associated need for assistance with activities of daily living (ADL) and carer perceptions of hospital care. Methods A prospective cross-sectional observational study was conducted in a large metropolitan teaching hospital in Brisbane, Australia. Participants were inpatients aged ≥65 years and their carers. Cognitive impairment was measured by clinician auditors using the validated 4 'A's test (4AT), with a score >0 indicating cognitive impairment (1-3, probable dementia; >3, probable delirium). The need for supervision and/or assistance with ADL was recorded from daily nursing documentation. Carers were invited to complete a brief questionnaire. Results In all, 92 of 216 older inpatients (43%) had cognitive impairment, including 52 (24%) with probable delirium. The need for supervision and/or assistance with ADL increased significantly with 4AT score. Fifty-two carers of patients with cognitive impairment reported feeling welcome and that care was safe. They identified opportunities for better information, greater support and more inclusion of carers. Conclusions Cognitive impairment is common in older inpatients and is associated with increased care needs. Workforce planning and health professional training need to acknowledge the needs of patients with cognitive impairment. There are opportunities for greater support and more involvement of carers. What is known about the topic? Cognitive impairment due to delirium and dementia increases with age, and is common in older medical and surgical inpatients. However, cognitive impairment remains under-recognised by healthcare staff. Australian guidelines now recommend routine screening using valid tools, and including carers, when appropriate, when assessing, caring for and communicating with people with cognitive impairment. What does this paper add? This cross-sectional study using the validated 4AT showed 43% of hospital inpatients aged ≥65 years had cognitive impairment. Participants with cognitive impairment had higher care needs and much longer hospitalisations. Carers of people with cognitive impairment reported unmet information needs in hospital and had limited involvement in assessment and care. What are the implications for practitioners? Cognitive impairment is common in older inpatients. Hospitals and healthcare professionals must be prepared and equipped to recognise cognitive impairment, and address the accompanying patient and carer needs.

The Impact of Social Workers in Cirrhosis Care: a Systematic Review.

Purpose of review: To report social workers' involvement in supporting patients with cirrhosis. Recent findings: Six intervention studies (three published in the past 3 years) highlighed the potential role of social worker-led interventions to improve the outcomes of patients with cirrhosis. In studies of patients with alcohol-related liver disease (n = 4), social workers conducted psychosocial assessments, screened for substance use disorder and psychological distress, coordinated referrals to addiction services, and provided relapse prevention therapy. In studies including transplant recipients or candidates (n = 2), social workers focused on psychosocial interventions. In two studies (n = 1 patient with alcohol-related liver disease; n = 1 transplant recipients), social workers provided practical support (e.g., housing, transportation). Most articles provided limited information about the intervention and the role of the social worker, making comparisons of the studies difficult. Summary: More high-quality evidence is needed to formally assess the impact of social workers in improving the outcomes of patients with cirrhosis. Supplementary Information: The online version contains supplementary material available at 10.1007/s11938-022-00381-2.

Infant massage and brain maturation measured using EEG: A randomised controlled trial.

BACKGROUND: Very preterm (VPT) infants develop adverse neurological sequelae from early exposure of the immature brain to the extrauterine environment. AIMS: To determine the effects of infant massage on brain maturation in low-risk VPT infants. STUDY DESIGN: A randomised controlled trial of VPT infants, who received standard care or daily massage therapy, administered by the mother, from 34 weeks' to 40 weeks' corrected age (CA). SUBJECTS: VPT infants (born at 28 weeks to 32 + 6 weeks' gestational age, G.A.) and a healthy at term cohort for comparison. OUTCOME MEASURES: At term equivalent age (39 weeks' to 42 weeks' CA), EEG was recorded to calculate global relative power (GRP), using power spectral analysis. RESULTS: Sixty infants were recruited, and EEGs of 25 massage and 20 standard care infants were analysable. There was no difference between groups in primary outcome (beta GRP). There was a significantly higher central alpha relative power measured in the intervention group infants, compared to standard care (SC) group (mean difference = 1.42, 95 % confidence interval (CI): 0.12 to 2.73; p = 0.03). A massage dose effect was shown by a positive correlation between, massage dose and beta, alpha and theta GRP (r = 0.42, 95%CI = 0.12 to 0.64, r = 0.45; 95%CI = 0.16 to 0.66, r = 0.39; 95%CI = 0.10 to 0.62 respectively) and a negative correlation between massage dose and delta GRP (r = -0.41, 95%CI = -0.64 to -0.12), suggesting that a higher dose of massage is associated with more favourable brain maturation. CONCLUSIONS: Central alpha regional relative power was greater in massaged infants compared to SC group infants, suggesting relatively greater brain maturation in this area. A measurable massage dose effect in favour of greater brain maturation, shows promise for verification in a larger clinical trial.

Experimental Pain Decreases Corticomuscular Coherence in a Force- But Not a Position-Control Task.

Differences in neural drive could explain variation in adaptation to acute pain between postural and voluntary motor actions. We investigated whether cortical contributions, quantified by corticomuscular coherence, are affected differently by acute experimental pain in more posturally focused position-control tasks and voluntary focused force-control tasks. Seventeen participants performed position- and force-control contractions with matched loads (10% maximum voluntary contraction) before and during pain (injection of hypertonic saline into the infrapatellar fat pad of the knee). Surface electromyography (EMG) of right knee extensor and flexor muscles was recorded. Electroencephalography (EEG) was recorded using a 128-channel sensor net. Corticomuscular coherence was calculated between 4 EEG electrodes that approximated the contralateral motor cortical area, and EMG. Coherence, EEG, EMG, and target performance accuracy were compared between task types and pain states. Before pain, coherence EEG and EMG did not differ between tasks. During pain, EMG increased in both tasks, but the force-control task showed greater pain interference (decreased coherence, higher EEG frequencies, and increased force fluctuations). Neural substrates of motor performance of postural functions are changed uniquely by experimental pain, which might be explained by differences in cortical demands. Our results provide new insights into the mechanisms of motor adaptations during acute pain. PERSPECTIVE: Understanding of the mechanisms underlying adaptations to motor function in acute pain is incomplete. Experimental work almost exclusively focuses on voluntary motor actions, but these adaptations may be inappropriate for postural actions. Our results show less pain-related interference in brain activity and its relationship to muscle activation during position-control tasks.

Corrigendum to "A revised glossary of terms most commonly used by clinical electroencephalographers and updated proposal for the report format of the EEG findings. Revision 2017" [Clin. Neurophysiol. Practice 2 (2017) 170-185].

[This corrects the article DOI: 10.1016/j.cnp.2017.07.002.].

Theta oscillations are affected by amnestic mild cognitive impairment and cognitive load.

Amnestic mild cognitive impairment (aMCI) is classified primarily via substantial episodic memory deficits in the absence of a dementia diagnosis. To investigate the potential neurophysiological correlates of such deficits we compared QEEG power between 12 participants with aMCI and 12 healthy matched controls. EEG was acquired during performance of a modified Sternberg word recognition task with low and high memory load conditions. While recognition accuracy of aMCI participants was lower than that of controls, this difference was not significant. Nevertheless the aMCI group demonstrated significantly lower theta power at a number of electrode sites and significant correlations were observed between power at these sites and neuropsychological assessment scores. Furthermore in the aMCI sample only, theta power was significantly lower under high versus low memory load. Given current interpretations of the neural generator(s), as well as the role(s), of theta oscillations in cognitive processes, the present data indicate that aMCI may be associated with disruptions in the operation of neurocognitive networks (e.g., MTL-neocortical), particularly under high cognitive load.

Background EEG features and prediction of cognitive outcomes in very preterm infants: A systematic review.

OBJECTIVES: Very preterm infants are at risk of cognitive impairment, but current capacity to predict at-risk infants is sub-optimal. Electroencephalography (EEG) has been used to assess brain function in development. This review investigates the relationship between EEG and cognitive outcomes in very preterm infants. METHODS: Two reviewers independently conducted a literature search in April 2018 using PubMed, CINAHL, PsycINFO, Cochrane Library, Embase and Web of Science. Studies included very preterm infants (born ≤34 weeks gestational age, GA) who were assessed with EEG at ≤43 weeks postmenstrual age (PMA) and had cognitive outcomes assessed ≥3 months of age. Data on the subjects, EEG, cognitive assessment, and main findings were extracted. Meta-analysis was undertaken to calculate pooled sensitivity and specificity. RESULTS: 31 studies (n = 4712 very preterm infants) met the inclusion criteria. The age of EEG, length of EEG recording, EEG features analysed, age at follow-up, and follow-up assessments were diverse. The included studies were then divided into categories based on their analysed EEG feature(s) for meta-analysis. Only one category had an adequate number of studies for meta-analysis: four papers (n = 255 very preterm infants) reporting dysmature/disorganised EEG patterns were meta-analysed and the pooled sensitivity and specificity for predicting cognitive outcomes were 0.63 (95% CI: 0.53-0.72) and 0.83 (95% CI: 0.74-0.89) respectively. CONCLUSIONS: There is preliminary evidence that background EEG features can predict cognitive outcomes in very preterm infants. Reported findings were however too heterogeneous to determine which EEG features are best at predicting cognitive outcome.

Risk of 12-month mortality among hospital inpatients using the surprise question and SPICT criteria: a prospective study.

OBJECTIVES: People with serious life-limiting disease benefit from advance care planning, but require active identification. This study applied the Gold Standards Framework Proactive Identification Guidance (GSF-PIG) to a general hospital population to describe high-risk patients and explore prognostic performance for 12-month mortality. METHODS: Prospective cohort study conducted in a metropolitan teaching hospital in Australia. Hospital inpatients on a single day aged 18 years and older were eligible, excluding maternity and neonatal, mental health and day treatment patients. Data sources included medical record and structured questions for medical and nursing staff. High-risk was predefined as positive response to the surprise question (SQ) plus two or more SPICT indicators of general deterioration. Descriptive variables included demographics, frailty and functional measures, treating team, advance care planning documentation and hospital utilisation. Primary outcome for prognostic performance was 12-month mortality. RESULTS: We identified 540 eligible inpatients on the study day and 513 had complete data (mean age 60, 54% male, 30% living alone, 19% elective admissions). Of these, 191 (37%) were high-risk; they were older, frailer, more dependent and had been in hospital longer than low-risk participants. Within 12 months, 92 participants (18%) died (72/191(38%) high-risk versus 20/322(6%) low-risk, P<0.001), providing sensitivity 78%, specificity 72%, positive predictive value 38% and negative predictive value 94%. SQ alone provided higher sensitivity, adding advanced disease indicators improved specificity. CONCLUSIONS: The GSF-PIG approach identified a large minority of hospital inpatients who might benefit from advance care planning. Future studies are needed to investigate the feasibility, cost and impact of screening in hospitals.

Quantitative EEG indices of sub-acute ischaemic stroke correlate with clinical outcomes.

OBJECTIVE: We investigated the ability of quantitative electroencephalography (QEEG) measures in sub-acute stroke to assist monitoring or prognostication of stroke evolution. QEEG indices and National Institutes of Health Stroke Scale (NIHSS) scores were compared. METHODS: Ischaemic cortical stroke patients were studied. Resting, 62-channel EEG and NIHSS score were acquired at 49+/-3h post-symptom onset, and NIHSS administered at 30+/-2 days post-stroke. Mean power was calculated for delta (1-4 Hz), theta (4.1-8 Hz), alpha (8.1-12.5 Hz) and beta (12.6-30 Hz) frequency bands, using a 62-channel electrode array and a 19-channel subset. RESULTS: Thirteen patients (6 male, median age 66, range 54-86 years) were studied. Sub-acute delta:alpha power ratio (DAR; r=0.91, P<0.001), relative alpha power (r=-0.82, P<0.01), and NIHSS score (r=0.92, P<0.001) each were significantly correlated with 30-day NIHSS score. The former two significant correlations were upheld in 19-channel EEG data. QEEG measures involving theta or beta power were not significantly correlated with NIHSS scores. CONCLUSIONS: QEEG measures such as DAR demonstrate potential to augment bedside assessment of cerebral pathophysiology and prognostication of stroke evolution. A standard, 19-channel array seems adequate for these purposes. Future studies in larger samples should investigate the potential effects on these measures of sleep state and possible causes of artefacts. SIGNIFICANCE: QEEG measures from a standard number of electrodes, if available rapidly and robust to potential artefacts, may inform future management of stroke patients.

Theta power is reduced in healthy cognitive aging.

The effects of healthy cognitive aging on electroencephalographic (EEG) theta (4.9-6.8 Hz) power were examined during performance of a modified Sternberg, S., 1966. High-speed scanning in human memory. Science 153, 652-654.) word recognition task. In a sample of fourteen young (mean age 21.9 years, range=18-27) and fourteen older (mean age 68.4 years, range=60-80) participants, theta power was found to be significantly lower in older adults during both the retention and recognition intervals. This theta power difference was greatest at the fronto-central midline electrode and occurred in parallel with a small, non-significant decrease in recognition accuracy in the older sample. A significant decrease in older adults' mean theta power was also observed in resting EEG, however, it was of substantially smaller magnitude than the task-related theta difference. It is proposed that a neurophysiological measure(s), such as task-specific frontal midline theta (fmtheta) power, may be a more sensitive marker of cognitive aging than task performance measures. Furthermore, as recent research indicates that fmtheta is generated primarily in the anterior cingulate cortex, the current findings support evidence that the function of brain networks incorporating this structure may be affected in cognitive aging.

Poststroke QEEG informs early prognostication of cognitive impairment.

Cognitive impairment is a common consequence of stroke, but remains difficult to predict. We investigate the ability of early QEEG assessment to inform such prediction, using binary logistic regression. Thirty-five patients (12 female, ages 18-87) suffering middle cerebral artery, ischemic stroke were studied. Resting-state EEG was recorded 48-239 h after symptom onset. Relative power for delta, theta, alpha, and beta bands, delta:alpha ratio, and peak alpha frequency were analyzed. Montreal Cognitive Assessment (MoCA) was administered, where possible, on day of EEG and at median 99 days (range 69-138) poststroke. Eight patients could not complete the baseline MoCA, and four the follow-up MoCA, for varying reasons (most commonly, stroke symptoms). Fifteen patients (48%) had cognitive impairment (MoCA score ≤25) at follow-up. One QEEG index was able to correctly predict presence/absence of cognitive impairment in 24/31 patients (77.4%), whereas predischarge MoCA did so in 23 patients. This index, relative theta frequency (4-7.5 Hz) power, was computed from only three posterior electrodes over the stroke-affected hemisphere. Its predictive accuracy (three electrodes) was higher than that of any "global" QEEG measure (averaged over 19 electrodes). These results may signify association between poststroke alpha slowing and cognitive impairment, which may be mediated by attentional (dys)function, which warrants further investigation. Pending further studies, QEEG measure(s)-from a few electrodes-could inform early prognostication of poststroke cognitive outcomes (and clinical decisions), particularly when cognitive function cannot be adequately assessed (due to symptoms, language, or other issues) or when assessment is equivocal.

Defining abnormal slow EEG activity in acute ischaemic stroke: Delta/alpha ratio as an optimal QEEG index.

OBJECTIVE: Quantitative electroencephalographic (QEEG) indices sensitive to abnormal slow (relative to faster) activity power seem uniquely informative for clinical management of ischaemic stroke (IS), including around acute reperfusion therapies. However these have not been compared between IS and control samples. The primary objective was to identify the QEEG slowing index and threshold value which can most accurately discriminate between IS patients and controls. METHODS: The samples comprised 28 controls (mean age: 70.4; range: 56-84) and 18 patients (mean age: 69.3; range: 51-86). Seven indices were analysed: relative bandpower (delta, theta, alpha, beta), delta/alpha power ratio (DAR), (delta+theta)/(alpha+beta) ratio (DTABR) and QSLOWING. The accuracies of each index for classifying participants (IS or control) were analysed using receiver operating characteristic (ROC) techniques. RESULTS: All indices differed significantly between the samples (p<.001). DAR alone exhibited optimal classifier accuracy, with a threshold of 3.7 demonstrating 100% sensitivity and 100% specificity for discriminating between radiologically-confirmed, acute IS or control. DTABR and relative delta were the next most accurate classifiers. CONCLUSIONS: DAR of 3.7 demonstrated maximal accuracy for classifying all 46 participants as acute IS or control. SIGNIFICANCE: DAR assessment may inform clinical management of IS and perhaps other neurocritical patients.

fMRI evidence of word frequency and strength effects during episodic memory encoding.

Word frequency (WF) and strength effects are two important phenomena associated with episodic memory. The former refers to the superior hit-rate (HR) for low (LF) compared to high frequency (HF) words in recognition memory, while the latter describes the incremental effect(s) upon HRs associated with repeating an item at study. Using the "subsequent memory" method with event-related fMRI, we tested the attention-at-encoding (AE) [M. Glanzer, J.K. Adams, The mirror effect in recognition memory: data and theory, J. Exp. Psychol.: Learn Mem. Cogn. 16 (1990) 5-16] explanation of the WF effect. In addition to investigating encoding strength, we addressed if study involves accessing prior representations of repeated items via the same mechanism as that at test [J.L. McClelland, M. Chappell, Familiarity breeds differentiation: a subjective-likelihood approach to the effects of experience in recognition memory, Psychol. Rev. 105 (1998) 724-760], entailing recollection [K.J. Malmberg, J.E. Holden, R.M. Shiffrin, Modeling the effects of repetitions, similarity, and normative word frequency on judgments of frequency and recognition memory, J. Exp. Psychol.: Learn Mem. Cogn. 30 (2004) 319-331] and whether less processing effort is entailed for encoding each repetition [M. Cary, L.M. Reder, A dual-process account of the list-length and strength-based mirror effects in recognition, J. Mem. Lang. 49 (2003) 231-248]. The increased BOLD responses observed in the left inferior prefrontal cortex (LIPC) for the WF effect provide support for an AE account. Less effort does appear to be required for encoding each repetition of an item, as reduced BOLD responses were observed in the LIPC and left lateral temporal cortex; both regions demonstrated increased responses in the conventional subsequent memory analysis. At test, a left lateral parietal BOLD response was observed for studied versus unstudied items, while only medial parietal activity was observed for repeated items at study, indicating that accessing prior representations at encoding does not necessarily occur via the same mechanism as that at test, and is unlikely to involve a conscious recall-like process such as recollection. This information may prove useful for constraining cognitive theories of episodic memory.

fMRI evidence of word frequency and strength effects in recognition memory.

We used event-related fMRI to investigate the neural correlates of encoding strength and word frequency effects in recognition memory. At test, participants made Old/New decisions to intermixed low (LF) and high frequency (HF) words that had been presented once or twice at study and to new, unstudied words. The Old/New effect for all hits vs. correctly rejected unstudied words was associated with differential activity in multiple cortical regions, including the anterior medial temporal lobe (MTL), hippocampus, left lateral parietal cortex and anterior left inferior prefrontal cortex (LIPC). Items repeated at study had superior hit rates (HR) compared to items presented once and were associated with reduced activity in the right anterior MTL. By contrast, other regions that had shown conventional Old/New effects did not demonstrate modulation according to memory strength. A mirror effect for word frequency was demonstrated, with the LF word HR advantage associated with increased activity in the left lateral temporal cortex. However, none of the regions that had demonstrated Old/New item retrieval effects showed modulation according to word frequency. These findings are interpreted as supporting single-process memory models proposing a unitary strength-like memory signal and models attributing the LF word HR advantage to the greater lexico-semantic context-noise associated with HF words due to their being experienced in many pre-experimental contexts.