Biomedical subjects

J Richard Jennings

Publications and source records attributed to J Richard Jennings.

At least 19 recordsLinked to original sources

PubMed2006

Higher blood pressure predicts lower regional grey matter volume: Consequences on short-term information processing.

Hypertension is a risk factor for diffuse brain atrophy. Yet, there is little evidence that higher blood pressure predicts focal brain atrophy, as indicated by a lower volume of regional brain tissue. This voxel-based morphometry study tested (a) whether higher blood pressure predicts lower regional grey or white matter volume and (b) whether a blood-pressure-related reduction in regional brain tissue volume predicts poorer neuropsychological test performance. Participants were 76 men (M age = 61.33, SD = 4.95 years) and 58 women (M age = 59.86, SD = 5.10 years) without a cardiovascular, cerebrovascular, or neuropsychiatric disease. Results showed that among men, higher resting systolic blood pressure predicted lower grey matter volume in the supplementary motor area and adjacent superior frontal gyrus, the anterior cingulate cortex, and middle temporal gyrus. Among men, lower grey matter volume in the supplementary motor area also predicted a slower time to complete the Trail Making Part B Test of executive control and a poorer recall of items from the Four-word Short-term Memory Test of working memory. These relationships were independent of age, total brain tissue volume, educational history, severity of carotid atherosclerosis, and the extent of periventricular and subcortical white matter lesions. Among women, no statistically significant relationships were found between blood pressure, regional brain tissue volume, and cognitive function. These findings suggest a functional relationship among men between higher blood pressure, lower regional grey matter volume, and poorer cognitive function that is independent of other risk factors and confounding medical conditions.

Aged↗

PubMed2005

White-coat hypertension and autonomic nervous system dysregulation.

BACKGROUND: White-coat hypertension, defined as high blood pressure (BP) on clinical assessment but normal BP elsewhere or on ambulatory measurement, is a common but poorly understood phenomenon. The current study asks whether individuals with white-coat hypertension have abnormal autonomic-cardiac regulation, similar to that observed in sustained or persistent hypertension. METHODS: Participants were men (ages 40 to 70 years; 63% white, 37% African American) not receiving any cardiovascular medications who were classified as persistent hypertensive (n = 40), white-coat hypertensive (n = 40), or normotensive (n = 40) on the basis of clinic and daytime ambulatory BP, using a threshold criterion for hypertension of 140/90 mmHg. Persistent and white-coat hypertensive subjects were matched on ethnicity and clinic BP, and white-coat hypertensive subjects and normotensive subjects were matched on race and daytime ambulatory BP. Frequency domain analysis of resting beat-to-beat heart rate variability (HRV) was used to estimate parasympathetic and sympathetic control of the heart. RESULTS: Relative to normotensive subjects, both persistent and white-coat hypertensive subjects had lower high-frequency (HF) (P < .03) and low-frequency (LF) power (P < .051) and thus less parasympathetic activity. In addition, white-coat and persistent hypertensive subjects had significantly greater LF/HF ratios, indicating greater sympathetic-to-parasympathetic activity, as compared with normotensive subjects (P < .03). CONCLUSIONS: These findings suggest similarities between persistent and white-coat hypertensive subjects reflecting attenuated parasympathetic control of the heart. In addition, the association between white-coat hypertension and autonomic dysregulation, particularly diminished parasympathetic tone, may serve as a mechanism for increased risk for cardiovascular events in affected individuals.

Adult↗

PubMed2005

Preparation for speeded action as a psychophysiological concept.

Mental preparation aids performance and induces multiple physiological changes that should inform concepts of preparation. To date, however, these changes have been interpreted as being due to a global preparatory process (e.g., attention or alertness). The authors review psychophysiological and performance investigations of preparation. Concepts of the central regulation of action offer an integrative framework for understanding the psychophysiology of preparation. If people process multiple streams of information concurrently, then preparatory processing requires a form of supervisory attention- central regulation to maintain unity of action. This concept is consistent with existing psychophysiological results and links them to current views of information processing. Conversely, psychophysiological measures may provide indices to test concepts within theories of the central regulation of action.

Arousal↗

PubMed2005

Anterior cingulate activity correlates with blood pressure during stress.

The anterior cingulate cortex presumptively regulates blood pressure reactions to behavioral stressors. There is little evidence in humans, however, that stressor-evoked changes in blood pressure correlate with concurrent changes in anterior cingulate activity. Using fMRI, we tested whether changes in mean arterial blood pressure correlate with ongoing changes in blood oxygen level dependent (BOLD) activation in 9 women and 11 men who completed a stressful Stroop color-word interference task. Higher mean arterial pressure during the Stroop task correlated with greater BOLD activation in two regions of the cingulate cortex (perigenual and mid-anterior) and in other networked brain regions, including the insula, thalamus, and periaqueductal gray. These results support the hypothesis that the anterior cingulate cortex regulates blood pressure reactions to behavioral stressors in humans.

Blood Pressure↗

PubMed2004

Comparing extent of activation: a robust permutation approach.

The number of contiguous voxels activated in a brain image can differ between groups or conditions even though the amplitude of activation does not markedly differ. Existing techniques test for differences in amplitude given that extent (number of contiguous voxels) exceeds some threshold. We present a technique that tests for differences in extent of activation given that amplitude of activation exceeds some threshold. The technique was motivated by apparent differences in extent of regional cerebral blood flow (rCBF) between hypertensive and normotensive participants performing cognitive tasks. These data are used to illustrate our test for extent of activation. We threshold the estimated parameter map for each subject, count the number of voxels exceeding the threshold over a defined region enclosing activated cortical area, and test the hypothesis of difference in the number of activated voxels between the two groups. Due to the large number of zeros resulting from the thresholding and the occurrence of extreme observations, we use a Robust permutation test [Lambert, D., 1985. Robust two-sample permutation tests. Ann. Stat., 13, 606-625], which is based on the sum of censored log-likelihood ratios. This statistic has desirable properties relative to the usual permutation test in contaminated distributions, i.e., idealized histogram with outliers, and provides an appropriate and robust test of extent of activation between conditions or groups.

Adult↗

PubMed2004

Exaggerated blood pressure responses during mental stress are prospectively related to enhanced carotid atherosclerosis in middle-aged Finnish men.

BACKGROUND: Hemodynamic reactions to mental stress may contribute to atherosclerosis. We previously observed cross-sectional relationships between blood pressure reactions to a standardized stress battery and carotid intima-media thickness (IMT) in the Kuopio Ischemic Heart Disease (KIHD) study. These are the first prospective results on this relationship. METHODS AND RESULTS: Men from 4 age cohorts (42 to 60 years old at study onset) were challenged with a standardized mental stress battery, and heart rate and blood pressure reactions were assessed. Ultrasound measures of common carotid IMT were collected at this time and 7 years later as noninvasive markers of atherosclerosis. Data were collected from a sample of 756 men at both times. Systolic blood pressure reactions to mental stress at study onset were positively related to mean carotid IMT 7 years later (beta=0.035, P=0.001, by blood pressure quartile, IMT=0.91, 0.93, 0.96, 1.00 mm) and to the progression of IMT (beta=0.020, P=0.006, by blood pressure quartile, DeltaIMT=0.08, 0.09, 0.11, 0.11 mm). Similar significant relations were shown for maximal IMT and plaque height. Diastolic blood pressure responses were less strongly related to carotid IMT than were systolic responses. Heart-rate responses were unrelated. Adjustment for standard risk factors did not substantially reduce the relation between systolic blood pressure reactivity and the progression of mean carotid IMT (standardized beta=0.059, P=0.026), maximal carotid IMT (standardized beta=0.084, P=0.006), or plaque height (standardized beta=0.093, P=0.008). CONCLUSIONS: The degree of systolic blood pressure reactivity to mental challenge is prospectively related to carotid IMT in middle-aged and older men, independent of known risk factors.

Adult↗

PubMed2004

Phasic heart rate responses to performance feedback in a time production task: effects of information versus valence.

This study examined the cardiac concomitants of feedback processing in a time production task derived from [Mittner et al., J. Cogn. Neurosci. 9 (1997) 788]. Participants performed the time production task (i.e. 1-s intervals) under two conditions. In the experimental condition, feedback informed them that the produced interval was within or outside the acceptable range (too long or too short). In the other, yoked-control, condition feedback was unrelated to the actual estimate. The performance findings indicated that in the experimental condition, participants tended to adjust the new interval in the direction indicated by the feedback. In the control condition, however, the adjustments were largely unrelated to the information provided by the feedback. Heart rate slowed to feedback stimuli indicating that the estimate was outside the acceptable range. Surprisingly, cardiac slowing did not discriminate between experimental and control conditions. This finding seems to suggest that heart rate is sensitive to the valence rather than the information provided by the feedback. This finding is discussed vis-à-vis current neuroimaging and psychophysiological studies of performance monitoring.

Adolescent↗

PubMed2004

Cognitive influences in postural control of patients with unilateral vestibular loss.

The aim of this study was to investigate the interference between postural control and cognitive processing in patients with surgically confirmed unilateral vestibular lesions. These patients were well-compensated for vestibular lesions with no symptoms of dizziness or definable postural deficit. We hypothesized that attentional processes would play a greater role in postural control of these patients compared to healthy age-matched controls suggesting that successful compensation for a vestibular impairment involves ongoing increased attentional resources, and is not an automatic process. To explore this hypothesis, we used a dual-task paradigm that combined postural challenges with concurrently performed cognitive tasks. The postural conditions were seated, standing on a fixed floor, standing on a sway-referenced floor, and standing on a translating floor. Cognitive tasks were simple, inhibitory, and forced choice reaction time (RT) tasks. Patients had slower RTs compared to the controls under all conditions, including the seated condition. This effect was particularly large for the choice and inhibitory tasks. Both groups had increased RTs as the postural task became more challenging. Postural sway increased similarly in the patients and controls when performing the RT tasks for all postural conditions. These results suggest that patients with vestibular lesions that are well-compensated require increased attention compared to healthy controls; however, this increased demand on attention extends beyond postural control. The site of action may be at the sensory integration level resolving multiple sensory signals for spatial orientation.

Adult↗

PubMed2004

Developmental change in feedback processing as reflected by phasic heart rate changes.

Heart rate was recorded from 3 age groups (8-10, 12, and 20-26 years) while they performed a probabilistic learning task. Stimuli had to be sorted by pressing a left versus right key, followed by positive or negative feedback. Adult heart rate slowed following negative feedback when stimuli were consistently mapped onto the left or right key (response-dependent condition) but not when responses to stimuli were always followed by negative feedback (uninformative condition). Young children's heart rate showed slowing following both response-dependent and uninformative negative feedback. These findings suggest that the ability to assess the relevance of performance feedback improves with age, resulting in improved adjustment to dynamical changes in the task environment.

Adolescent↗

PubMed2004

Regional cerebral blood flow correlates with heart period and high-frequency heart period variability during working-memory tasks: Implications for the cortical and subcortical regulation of cardiac autonomic activity.

The aim of the present study was to characterize the functional relationships between behaviorally evoked regional brain activation and cardiac autonomic activity in humans. Concurrent estimates of regional cerebral blood flow (rCBF; obtained by positron emission tomography), heart period, and high-frequency heart period variability (HF-HPV; an indicator of cardiac parasympathetic activity) were examined in 93 adults (aged 50-70 years) who performed a series of increasingly difficult working-memory tasks. Increased task difficulty resulted in decreased heart period (indicating cardioacceleration) and decreased HF-HPV (indicating decreased cardiac parasympathetic activity). Task-induced decreases in heart period and HF-HPV were associated with concurrent increases and decreases in rCBF to cortical and subcortical brain regions that are speculated to regulate cardiac autonomic activity during behavioral processes: the medial-prefrontal, insular, and anterior cingulate cortices, the amygdala-hippocampal complex, and the cerebellum. These findings replicate and extend a small number of functional neuroimaging studies that suggest an important role for both cortical and subcortical brain systems in human cardiac autonomic regulation.

Aged↗

PubMed2004

The cardiac cycle time effect revisited: temporal dynamics of the central-vagal modulation of heart rate in human reaction time tasks.

Lacey and Lacey (1974) suggested that during reaction time tasks higher brain centers dynamically adjust efferent vagal nerve pulses to the sino-atrial node of the heart, inducing phase-dependent heart rate changes. Since then, animal and human neuro-physiological results have provided evidence for this hypothesis. Higher subcortical and cortical brain centers may have reciprocal interactive pathways relating to autonomic control comparable to those at the level of peripheral autonomic changes and brain stem reflexes. In humans such central effects may be observed in the short latency vagal control of heart rate that has been studied mostly in reaction time (RT) tasks. RT task parameters modulate vagal pulses to the cardiac sino-atrial node (SAN), which in turn exerts a phase-dependent change in the ongoing cardiac interbeat interval. Simulations of human RT task effects in an animal model of heart rate change support this hypothesis. The current study examined evidence for vagal control of three human phasic heart rate responses in RT tasks. The evidence indicates that the initiation of an RT response triggers a reflexive shift from vagal activation to vagal inhibition. This shift is cardiac cycle phase dependent. Graded anticipatory cardiac deceleration during the warning interval of an RT task varies with task relevance and time uncertainty. This response may be part of a control process engaged in time keeping. Hence, temporal variables mediate the central-autonomic-vagal modulation of heart rate.

Animals↗

PubMed2004

Effect of preparation on dual-task performance in postural control.

The authors applied an overlapping-task design to study the interaction between postural control and cognitive task processes in young (n = 10) and older (n = 10) adults. A rapid destabilizing floor translation was followed at specific time intervals by a simple auditory reaction time (RT) task. The translations were preceded by either an informational cue or no cue. Interference between postural task demands and the RT task was found only in the first 50 ms. Cueing also had an effect on both the onset of the postural recovery response and RT performance. The results suggest (a) only a brief interference between postural and cognitive processing demands in relatively easy tasks, (b) competition for a common central mechanism, possibly a response-selection mechanism, and (c) no differential impact of aging on that interaction.

Adult↗

PubMed2003

Visual-vestibular stimulation interferes with information processing in young and older humans.

Attention has been implicated in postural control and other tasks requiring sensory integration. The purpose of this study was to investigate the role of attention in sensory-motor processing of vestibular and combined visual-vestibular information during seated rotations using a dual-task interference approach. We hypothesized that auditory information processing would be influenced by concurrent visual-ocular, vestibulo-ocular, or combined visual-vestibulo-ocular processing. We further hypothesized that the effect would be greater in older subjects. Twenty older subjects (10 women, 10 men, 69.3+/-3.2 years) and 20 young subjects (10 women, 10 men, 23.5+/-2.9 years) were asked to perform information-processing tasks while they underwent several types of vestibular, visual-vestibular, and ocular motor paradigms. The information-processing tasks were: (1) an auditory simple reaction-time task (SRT), (2) an auditory go-no-go (disjunctive) reaction-time task (DRT), and (3) an auditory forced-choice task (CRT). The visual-vestibular-ocular motor conditions included: (1) no movement/darkness (NO), (2) no movement/fixation (FIX), (3) no movement/pursuit (P), (4) earth-vertical axis rotation (EVAR) in darkness, (5) EVAR with fixation (E-FIX), (6) off-vertical axis rotation (OVAR) in darkness, and (7) OVAR with fixation (O-FIX). Results showed that older subjects had longer reaction times for all combinations of stimulus condition and reaction-time task compared with young subjects. Compared with the NO baseline, reaction times during EVAR were longer for young and older subjects and during OVAR were longer for the young subjects. For FIX and P, the reaction times during P exceeded those during FIX and during NO for both groups. For E-FIX and O-FIX, reaction times did not differ from those during EVAR and OVAR. The interference with information processing by concurrent vestibular stimulation in the dark may be based upon cortical inhibition of auditory processes by vestibular stimulation. Eye movements induced by EVAR showed an increased phase lead during reaction-time tasks, suggesting altered vestibulo-ocular reflex (VOR) dynamics, possibly based on cerebellar-mediated changes in velocity storage. Since fixation of a head-fixed visual target did not add to the effect of rotation in the dark, a further implication of our results is that VOR-fixation while performing a concurrent information-processing task may be accomplished primarily by VOR suppression rather than by VOR cancellation.

Acoustic Stimulation↗

PubMed2003

Cardiac concomitants of feedback processing.

This study examined the heart rate changes associated with positive and negative performance feedback in a probabilistic learning task derived from Holroyd and Coles (Psychological Review, 109 (2002) 679). In this task, subjects were presented with six stimuli and asked to respond by pressing a left versus right key. Responses were followed by positive or negative feedback. Subjects had to infer the S-R mapping rule on the basis of feedback provided to them. Two stimuli were consistently mapped onto the left versus right key (100% mapping). Two other stimuli were randomly mapped onto the keys (50% mapping) and responses to the two remaining stimuli received always positive or negative feedback (always condition). Negative feedback was associated with heart rate slowing in the 100% condition. Heart rate slowed following both positive and negative feedback in the 50% condition, but only when the previous encounter with the stimulus was followed by alternate feedback. Heart rate did not differentiate between positive and negative feedback in the always condition. The results were interpreted in support of the hypothesis assuming that heart rate slowing is elicited when performance-based expectations are violated.

Adult↗

PubMed2003

Sensitivity to interference and response contingencies in attention-deficit/hyperactivity disorder.

BACKGROUND: Current theories on ADHD suggest executive and motivational deficits, but it remains unclear whether these are separate deficits or a unitary deficit. METHOD: ADHD children and matched controls performed on a hybrid disjunctive-choice reaction time task in which target stimuli could be surrounded by flankers signaling either the appropriate response, the competing response, or response inhibition. The task was performed under three conditions; reward only, reward and occasional punishment, and equal probability of reward and punishment. Heart rate and skin conductance measures were taken during task performance. RESULTS: Contrary to control children, ADHD children slowed their responses when flankers cueing the appropriate response surrounded the stimulus. Flankers cueing incorrect responses further slowed ADHD children relative to control children. ADHD children also responded less accurately under the threat of punishment. Phasic heart rate did not differ between groups, but immediate reward feedback induced greater heart rate responses in control than in ADHD children. Contrary to expectations, groups did not differ in skin conductance responses. CONCLUSIONS: ADHD children appear deficient in approach tendencies in the presence of imminent reward, rather than unresponsive to punishment or negative feedback. Executive inhibition and motivational inhibition seemed to exert separate effects on behavior of children with ADHD.

Attention Deficit Disorder with Hyperactivity↗

PubMed2003

Mental rotation delays the heart beat: probing the central processing bottleneck.

We tested the hypothesis that mental rotation would delay response-related processing as indicated by transient slowing of the heart beat. Thirty college-age subjects (half female) were presented with normal and mirror image letters rotated at 0, 60, 120, and 180 degrees. Three letters were assigned to a right-hand response; a separate three to a left-hand response. Responses were only required for letters in one orientation, mirror or normal. Continuous measures of interbeat interval (IBI) of the heart, respiration, and muscle tension were collected. Performance results were largely consistent with prior findings. Greater angular displacement of the stimuli was associated with greater lengthening of IBI immediately after the stimulus. IBI was influenced equally by angle of rotation in respond and inhibit trials. The lengthening of IBI was interpreted as due to a delay in response selection and execution due to mental rotation.

Adult↗

PubMed2002

Cardiac timing and the central regulation of action.

The central control of information processing necessarily entails a selection between actions that are implicit in different processing streams. We argue that this selection for action also adjusts the autonomic support for action. When actions are transiently undefined during the transition between actions, the time between heartbeats increases (heart rate transiently slows). This is particularly clear when actions are imminent but their identity is undefined, e.g. due to a delay while prepotent actions are inhibited in order to map a required action. We review results from a number of experiments supporting this perspective. These results suggest that central inhibition of representations of action influences heartbeat timing as well as more peripheral inhibition of overt responses. Given that inhibitory processes characteristic of central response selection induce transient heartbeat slowing, then this change is an interesting converging measure of the state of central response selection in combination with performance measures.

Attention↗

PubMed2002

Vagal function in health and disease: studies in Pittsburgh.

The integration of behavioral processes with changes in vagally-controlled heart rate has been the focus of our investigations. A series of studies is reviewed showing that central and peripheral response inhibition is a primary source of transient, vagally-induced cardiac slowing during information processing. Individual differences in such responses are then shown to relate to the amplitude of cardiovascular responses to stressors. Overall, the specificity and sensitivity of vagal responses to higher level cortical function is supported by our research.

Cerebral Cortex↗