J. Carson Smith

State anxiety and affective physiology: effects of sustained exposure to affective pictures.

Effects of sustained exposure to emotional stimuli on affective reactions and their recovery were examined to determine whether increasing exposure to a specific emotional content (e.g., unpleasant) cumulatively affects physiological responses; and whether motivational activation persists following sustained exposure. Participants viewed pleasant, neutral, and unpleasant IAPS pictures, presented in blocks separated by an inter-block interval. With increasing exposure to unpleasant pictures, startle magnitude showed greater potentiation, and corrugator EMG activity increased. Both affective startle and corrugator modulation persisted following exposure to unpleasant pictures. The cumulative effects of sustained exposure to unpleasant pictures were enhanced for those reporting higher state anxiety, consistent with the hypothesis that sustained aversive exposure leads to increased defensive activation. These findings suggest sustained exposure to unpleasant pictures may induce a short-term mood state, and may be a useful paradigm to study individuals who vary in symptoms of anxiety.

Interactive Effects of Physical Activity and APOE-ε4 on BOLD Semantic Memory Activation in Healthy Elders

Evidence suggests that physical activity (PA) is associated with the maintenance of cognitive function across the lifespan. In contrast, the apolipoproteinE-ε4 (APOE-ε4) allele, a genetic risk factor for Alzheimers disease (AD), is associated with impaired cognitive function. The objective of this study was to examine the interactive effects of PA and APOE-ε4 on brain activation during memory processing in older (ages 65-85) cognitively intact adults. A cross-sectional design was used with four groups (n=17 each): (1) Low Risk/Low PA; (2) Low Risk/High PA; (3) High Risk/Low PA; and (4) High Risk/High PA. PA level was based on self-reported frequency and intensity. AD risk was based on presence or absence of an APOE-ε4 allele. Brain activation was measured using event-related functional magnetic resonance imaging (fMRI) while participants performed a famous name discrimination task. Brain activation subserving semantic memory processing occurred in 15 functional regions of interest. High PA and High Risk were associated with significantly greater semantic memory activation (famous>unfamiliar) in 6 and 3 of the 15 regions, respectively. Significant interactions of PA and Risk were evident in 9 of 15 brain regions, with the High PA/High Risk group demonstrating greater semantic memory activation than the remaining three groups. These findings suggest that PA selectively increases memory-related brain activation in cognitively intact but genetically at-risk elders. Longitudinal studies are required to determine whether increased semantic memory processing in physically active at-risk individuals is protective against future cognitive decline.

Electrocortical and electrodermal responses covary as a function of emotional arousal: a single-trial analysis.

Electrophysiological studies of human visual perception typically involve averaging across trials distributed over time during an experimental session. Using an oscillatory presentation, in which affective or neutral pictures were presented for 6 s, flickering on and off at a rate of 10 Hz, the present study examined single trials of steady-state visual evoked potentials. Moving window averaging and subsequent Fourier analysis at the stimulation frequency yielded spectral amplitude measures of electrocortical activity. Cronbachs alpha reached values >.79, across electrodes. Single-trial electrocortical activation was significantly related to the size of the skin conductance response recorded during affective picture viewing. These results suggest that individual trials of steady-state potentials may yield reliable indices of electrocortical activity in visual cortex and that amplitude modulation of these indices varies with emotional engagement.

Detecting changes in human cerebral blood flow after acute exercise using arterial spin labeling: Implications for fMRI

The use of arterial spin labeling to measure cerebral blood flow (CBF) after acute exercise has not been reported. The aims of this study were to examine: (1) the optimal inversion time to detect changes in CBF after acute exercise and (2) if acute exercise alters CBF in the motor cortex at rest or during finger-tapping. Subjects (n=5) performed 30 min of moderate intensity exercise on an electronically braked cycle ergometer (perceived exertion somewhat hard). Before and after exercise, relative CBF was measured using multiple inversion time (TI) pulsed arterial spin labeling (PASL). Two multiple TI runs were obtained at rest and during 4 Hz finger-tapping. Four inversion times (675, 975, 1275, and 1,575 ms) were acquired per run, with 20 interleaved pairs of tag and control images per inversion time (320 s run). The results indicated that global CBF increased approximately 20% following exercise, with significant differences observed at an inversion time of 1,575 ms (p<.05). Finger-tapping induced CBF in the motor cortex significantly increased from before to after exercise at TI=1,575 ms (p<.01). These findings suggest changes in human cerebral blood flow that result from acute moderate intensity exercise can be detected afterwards using PASL at 3T with an inversion time of 1,575 ms. The effect of prior acute exercise to increase motor cortex CBF during the performance of a motor task suggests future use of indices of functional activation should account for exercise-induced changes in cardio-pulmonary physiology and CBF.

Prediction of Cognitive Decline in Healthy Older Adults using fMRI

Few studies have examined the extent to which structural and functional MRI, alone and in combination with genetic biomarkers, can predict future cognitive decline in asymptomatic elders. This prospective study evaluated individual and combined contributions of demographic information, genetic risk, hippocampal volume, and fMRI activation for predicting cognitive decline after an 18-month retest interval. Standardized neuropsychological testing, an fMRI semantic memory task (famous name discrimination), and structural MRI (sMRI) were performed on 78 healthy elders (73% female; mean age = 73 years, range = 65 to 88 years). Positive family history of dementia and presence of one or both apolipoprotein E (APOE) ε4 alleles occurred in 51.3% and 33.3% of the sample, respectively. Hippocampal volumes were traced from sMRI scans. At follow-up, all participants underwent a repeat neuropsychological examination. At 18 months, 27 participants (34.6%) declined by at least 1 SD on one of three neuropsychological measures. Using logistic regression, demographic variables (age, years of education, gender) and family history of dementia did not predict future cognitive decline. Greater fMRI activity, absence of an APOE ε4 allele, and larger hippocampal volume were associated with reduced likelihood of cognitive decline. The most effective combination of predictors involved fMRI brain activity and APOE ε4 status. Brain activity measured from task-activated fMRI, in combination with APOE ε4 status, was successful in identifying cognitively intact individuals at greatest risk for developing cognitive decline over a relatively brief time period. These results have implications for enriching prevention clinical trials designed to slow AD progression.

Rapid picture presentation and affective engagement.

Emotional reactions were assessed to pictorial stimuli presented in a continuous stream at rapid speeds that compromise conceptual memory and the processing of specific picture content. Blocks of unpleasant, neutral, or pleasant pictures were presented at the rate of either three pictures per second or seven pictures per second. Even with rapid presentation rates, startle reflexes, corrugator muscle activity, and skin conductance responses were heightened when viewing unpleasant pictures. These effects were stronger later in the aversive block, suggesting that cumulative exposure increasingly activates the defense system. The findings suggest that, despite conceptual masking inherent in rapid serial visual presentation, affective pictures prompt measurable emotional engagement.

Measures of Physical Ability Are Unrelated to Objectively Measured Physical Activity Behavior in Older Adults Residing in Continuing Care Retirement Communities

OBJECTIVEnTo explore the relationship between measures of physical performance, physical activity, and self-reported physical activity.nnnDESIGNnCross-sectional analysis.nnnSETTINGnContinuing care retirement communities (CCRCs) in the greater Milwaukee area.nnnPARTICIPANTSnOlder adults from independent or assisted living apartments (N=59).nnnINTERVENTIONSnNot applicable.nnnMAIN OUTCOME MEASURESnPhysical performance was measured with comfortable and fast gait speeds and the six-minute walk test. Physical activity was measured by an ankle-mounted accelerometer to observe daily steps; stepping rate was averaged over a 7-day wear time. Self-reported physical activity was measured by the Physical Activity Scale for the Elderly (PASE).nnnRESULTSnParticipants reported walking more steps per day than older adults who are not living in CCRCs. There was no relationship between physical abilities and total steps walked (r=.087-.213, P>.05). No relationship was observed between measures of physical performance or total steps and PASE scores (r=-.034-.177, P = not significant). The relative contributions of physical activity categories to total PASE score were different than published reports for older adults not living in CCRCs.nnnCONCLUSIONSnCommon measures of physical performance often used by clinicians in making decisions on rehabilitation outcomes do not appear to be related to the actual functioning of older adults residing in senior communities. The nature of the environment customized to the needs of the older adult may facilitate increased physical activity participation independent of physical abilities.

Does physical activity influence semantic memory activation in amnestic mild cognitive impairment

The effect of physical activity (PA) on functional brain activation for semantic memory in amnestic mild cognitive impairment (aMCI) was examined using event-related functional magnetic resonance imaging during fame discrimination. Significantly greater semantic memory activation occurred in the left caudate of High- versus Low-PA patients, (P=0.03), suggesting PA may enhance memory-related caudate activation in aMCI.

Attentional Bias to Emotional Stimuli Is Altered During Moderate- but Not High-Intensity Exercise

Little is known regarding how attention to emotional stimuli is affected during simultaneously performed exercise. Attentional biases to emotional face stimuli were assessed in 34 college students (17 women) using the dot-probe task during counterbalanced conditions of moderate- (heart rate at 45% peak oxygen consumption) and high-intensity exercise (heart rate at 80% peak oxygen consumption) compared with seated rest. The dot-probe task consisted of 1 emotional face (pleasant or unpleasant) paired with a neutral face for 1,000 ms; 256 trials (128 trials for each valence) were presented during each condition. Each condition lasted approximately 10 min. Participants were instructed to perform each trial of the dot-probe task as quickly and accurately as possible during the exercise and rest conditions. During moderate-intensity exercise, participants exhibited significantly greater attentional bias scores to pleasant compared with unpleasant faces (p < .01), whereas attentional bias scores to emotional faces did not differ at rest or during high-intensity exercise (p > .05). In addition, the attentional bias to unpleasant faces was significantly reduced during moderate-intensity exercise compared with that during rest (p < .05). These results provide behavioral evidence that during exercise at a moderate intensity, there is a shift in attention allocation toward pleasant emotional stimuli and away from unpleasant emotional stimuli. Future work is needed to determine whether acute exercise may be an effective treatment approach to reduce negative bias or enhance positive bias in individuals diagnosed with mood or anxiety disorders, or whether attentional bias during exercise predicts adherence to exercise.

Visual Threat Detection During Moderate- and High-Intensity Exercise

The aim of the study was to assess performance on a visual threat-detection task during concurrently performed vigorous exercise on a cycle ergometer. Thirty (15 female) participants completed a baseline condition of seated rest and then moderate- and high-intensity exercise. Moderate- and high-intensity exercise conditions were completed on the 2nd day in a counterbalanced order. During each exercise condition, participants responded to 3 × 3 picture matrices (256 trials in each condition) that contained discrepant fear-relevant and discrepant fear-irrelevant pictures (Öhman, Flykt, & Esteves, 2001). Response accuracy was significantly greater, and reaction time was significantly faster, during moderate- and high-intensity exercise compared with the rest condition (ps < .001). The discrepant fear-relevant matrix type was detected significantly more accurately than a discrepant fear-irrelevant matrix (p < .001). The discrepant fear-relevant matrix was detected significantly faster than all other matrix types (p < .001). These results suggest that exercise at a moderate and high intensity may enhance the efficiency of visual detection of both threatening and nonthreatening targets.