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Biomedical subjects

Michael J Hogan

Publications and source records attributed to Michael J Hogan.

10 recordsLinked to original sources
PubMed2006

Electrophysiological and information processing variability predicts memory decrements associated with normal age-related cognitive decline and Alzheimer's disease (AD).

Recent theoretical models of cognitive aging have implicated increased intra-individual variability as a critical marker of decline. The current study examined electrophysiological and information processing variability and memory performance in normal younger and older controls, and older adults with Alzheimer's disease (AD). It was hypothesized that higher levels of variability would be indicative of age-related and disease-related memory deficits. Results indicated both implicit and explicit memory deficits associated with AD. Consistent with previous research, behavioral speed and variability emerged as sensitive to age- and disease-related change. Amplitude variability of P3 event-related potentials was a unique component of electrophysiological activity and accounted for significant variance in reaction time (RT) mean and RT standard deviation, which in turn accounted for significant variance in memory function. Results are discussed in light of theoretical and applied issues in the field of cognitive aging.

Adult↗
PubMed2006

Adverse outcomes of renovascular hypertension during pregnancy.

BACKGROUND: A 26-year-old primigravida, with no history of hypertension, presented at 20 weeks of gestation with severe pre-eclampsia. A pelvic ultrasound revealed intrauterine fetal death, probably caused by placental abruption. The pregnancy was terminated by induction with oxytocin, followed by a vaginal breech delivery. The patient remained hypertensive for 8 weeks after delivery. INVESTIGATIONS: Physical examination, laboratory investigation, renal angiogram and renal-vein renin sampling. DIAGNOSIS: An atrophic right kidney secondary to an occluded right renal artery, probably caused by dissected fibromuscular dysplasia; a contralateral high-grade stenosis secondary to fibromuscular dysplasia. MANAGEMENT: Right nephrectomy and angioplasty of the left renal artery.

Abortion, Induced↗
PubMed2006

Age at death of people with an intellectual disability in Ireland.

This study examined the age at death of people with an intellectual disability in Ireland. Using data from the National Intellectual Disability Database, the average age at death of 1120 people who died between 1996 and 2001 was 45.68 years, with no difference in lifespan between men and women. A more severe level of intellectual disability predicted shorter lifespan. In general, those requiring lower levels of day-to-day support and supervision had a longer lifespan. Those living in the family home had the shortest lifespan while those in hospital residential environments had the longest lifespan. Those not attending any day service had a longer lifespan than those attending a range of day services. There were also differences in age at death across different health board regions. These findings are discussed in light of their implications for service planning.

Adolescent↗
PubMed2004

Behavioural and physiological impairments of sustained attention after traumatic brain injury.

Sustaining attention under conditions of low external demand taxes our ability to stay on task and to avoid more appealing trains of thought or environmental distractions. By contrast, a stimulating, novel environment engages attention far more freely without the subjective feeling of having to override monotony. Our ability to maintain a goal-directed focus without support from the environment requires the endogenous control of behaviour. This control can be modulated by fronto-parietal circuits and this ability is compromised following traumatic brain injury (TBI) leading to increased lapses of attention. In this paper, we further explore a laboratory paradigm that we argue is particularly sensitive to sustained attention as opposed to other aspects of attentional control involving the selection and management of goals in working memory. The paradigm (fixed sequence Sustained Attention to Response Task--SARTfixed) involves withholding a key press to an infrequent no-go target embedded within a predictable sequence of numbers. We demonstrate that TBI patients in this study make disproportionately more errors than controls on this task. An analysis of response times (RTs) and EEG alpha power across the task demonstrates group differences preceding the critical no-go trial. Controls demonstrate a lengthening of RTs accompanied by desynchronization of power within the alpha band (approximately 10 Hz) preceding the no-go trial. Conversely, the TBI group showed a shortening of RTs during this period with no evidence of alpha desynchronization. These findings suggest that TBI patients may have dysfunctional alpha generators as a consequence of their injury that impairs endogenous control during the task.

Adult↗
PubMed2003

Memory-related EEG power and coherence reductions in mild Alzheimer's disease.

OBJECTIVES: To examine memory-related EEG power and coherence over temporal and central recording sites in patients with early Alzheimer's disease (AD) and normal controls. METHOD: EEG was recorded from central (Fz, Cz and Pz) and temporal (T3 and T4) electrodes while ten very mild AD patients and ten controls performed a Sternberg-type memory scanning task with three levels of working memory load. Spectral power in delta (0-3 Hz), theta (3-5 Hz), lower alpha1 (5-7 Hz), lower alpha2 (7-9 Hz), upper alpha (9-11 Hz) and beta (15-30 Hz) was averaged for temporal and central electrodes. Coherence was averaged between central electrodes, between central and right temporal electrodes and between central and left temporal electrodes. RESULTS: While behavioral performance of very mild AD patients did not differ significantly from that of normal controls, findings suggest that normal controls but not AD patients respond to memory demands by increasing upper alpha power over temporal cortex. When compared with normal controls, AD patients had reduced upper alpha coherence between central and right temporal cortex. DISCUSSION: Results are consistent with previous research on the role of upper alpha in semantic memory and suggest that very mild AD may inhibit selective synchronization of upper alpha in temporal lobes. Reduced coherence between central and temporal cortex is discussed in light of a neurological model of AD that hypothesizes reduced electrocortical efficiency and a breakdown of neural network communication to temporal lobes possibly resulting from temporal lobe atrophy.

Aged↗
PubMed2002

A comparison of responses to a health and lifestyle questionnaire completed before and then after blood pressure screening.

Changes over a 2-week period in self-reported health and lifestyle information were examined and related to medical feedback provided prior to the second self-report. The study group consisted of 128 females and 73 males ranging in age from 35 to 85 with a mean age of 55.5 years. On two occasions subjects completed self-assessment questionnaires including 52 items covering symptomatology and various lifestyle behaviours. Before the second self-assessment, subjects were classified as cases if their blood pressure was borderline or hypertensive according to World Health Organization guidelines or as controls otherwise. Subjects were informed of this classification. Across questions, the percentage disagreement between reports ranged from 0.0% to 44.1% with a median of 17.5% and with case-control differences significant at the 10% level for four questions. The mean difference between responses was significantly different from 0 at the 10% level for 15 questions with case-control differences significant at the 10% level for 6 questions. For 2 questions, the significance level of the association of response with case-control status changed from a value greater than 20% based on responses before feedback to a value less than 5% based on responses after feedback. Some evidence of recall bias was found.

Adult↗
PubMedDate not supplied

Divided attention in older but not younger adults is impaired by anxiety.

It has been hypothesized that the disruptive effects of negative emotional states, such as anxiety and depression, may contribute to poorer performance in older age. Some studies have reported that higher levels of anxiety are associated with poorer cognitive performance in older adults but not younger adults. The author examined if age and anxiety interact with performance by comparing the performance of normal healthy younger and older adults on cognitive and motor tests under conditions of selective and divided attention. Ninety-two older adults (mean age=70.1 years, SD=7.1 years) and 78 younger adults (mean age=18.8 years, SD=1.9 years), matched on education, vocabulary, and self-reported health, performed a word-comparison and pursuit-rotor task under conditions of selective and divided attention. Anxiety was assessed using the Speilberger State-Trait anxiety scale. The hypothesis was supported: higher anxiety was associated with poorer divided attention performance in older, but not younger, adults. Anxiety was not associated with poorer motor performance in older adults. Implications of the results for cognitive-resource theories of aging cognition are discussed.

Adult↗
PubMedDate not supplied

The effects of attention switching on encoding and retrieval of words in younger and older adults.

Two experiments examined the interaction between aging, attention switching, encoding process, and recognition memory using different versions of a cued attention switching paradigm. In Experiment 1, 30 younger and 35 older adults encoded words based on font color, meaning, or by explicit learning with a color response during performance of a choice-reaction time (RT) task. Attention switches were cued by means of stimulus location, and occurred on average every seven trials. In Experiment 2, attention switching was precued from a central fixation point and the number of critical switch trials was increased, occurring on average every four trials. Memory was assessed in both experiments by means of a forced-choice recognition task. Results indicated that, relative to color encoding, older adults benefited more than younger adults from semantic encoding, but less from explicit learning instructions. Attention switching disrupted encoding task performance of older adults more than that of younger adults, but recognition memory was generally unaffected. Results are discussed in light of theoretical models of aging memory that posit a role for executive control processing.

Adolescent↗