Following a Bachelor of Science in Neuroscience and Psychology (Keele University, UK), I completed a Ph.D investigating the neural basis of affective responses during exercise at different intensities using near infrared spectroscopy (NIRS; University of South Australia). Subsequently, I extended this work to examine the influence of exercise upon inhibitory control, working memory and creativity (Tomsk State University, Russia; University of Nice Sophia Antipolis, France). At Stanford, I am continuing to examine what happens in the brain during exercise that influences the way we think and feel. Studies employ functional NIRS to identify the dose-response effects of the intensity and duration of cycling-based exercise upon brain activity, cognition and mood. These findings will help to develop exercise protocols beneficial for individuals with cognitive dysfunction such as attention deficit/hyperactivity disorder (ADHD).
Honors & Awards
Postdoctoral Award, Maternal and Child Health Research Institute, Stanford University (2018)
Ph.D, University of South Australia, Exercise Neuroscience (2014)
BSc(Hons), University of Keele, UK, Neuroscience & Psychology (2007)
Allan Reiss, Postdoctoral Faculty Sponsor
- The Utility of Functional Near-infrared Spectroscopy for Measuring Cortical Activity during Cycling Exercise MEDICINE AND SCIENCE IN SPORTS AND EXERCISE 2019; 51 (5): 979–87
- Impact of Physical and Cognitive Exertion on Cognitive Control FRONTIERS IN PSYCHOLOGY 2018; 9
The long and winding road: Effects of exercise intensity and type upon sustained attention
PHYSIOLOGY & BEHAVIOR
2018; 195: 82–89
Aerobic exercise enhances the ability to sustain attention (peaking at moderate intensities) by stimulating noradrenergic activity, which affects the fronto-parietal attention network. Prior exercise studies examining attention have focused on the influence of exercise intensity, yet few studies have examined the influence of the type of exercise protocol administered. Here, we propose that sustained attention is greater during (a) moderate compared to low intensity exercise, and (b) moderate intensity exercise administered at a varied-load compared to a constant-load but the same overall intensity. To test this hypothesis, we recorded attentional focus in twelve male cyclists during a sustained attention to response task (SART) in four conditions; at rest, and during exercise at a low constant-, moderate constant- and moderate varied-load intensity. The change in α-amylase (indicative of the noradrenergic response) from saliva samples and activation of the right prefrontal and parietal cortices using near-infrared spectroscopy were recorded. The findings revealed that moderate intensity exercise at a constant-load leads to faster responses and less accuracy in the SART than rest and low intensity exercise. Moderate intensity exercise at a variable-load leads to even faster responses but with no loss of accuracy in the SART. This pattern of results is explained by a larger increase in salivary α-amylase during moderate (constant and varied) intensity cycling and higher activation in the dorso-lateral prefrontal cortex during the varied, but not the constant-load condition. In conclusion, we show that, in addition to exercise intensity, the type of exercise also has important implications upon attentional focus. While moderate intensity exercise generally enhances attentional focus, monotonous exercise at a constant-load may mask such benefits.
View details for PubMedID 30076918
- The importance of understanding the underlying physiology of exercise when designing exercise interventions for brain health JOURNAL OF PHYSIOLOGY-LONDON 2018; 596 (7): 1131–32
Impact of Physical and Cognitive Exertion on Cognitive Control.
Frontiers in psychology
2018; 9: 2369
In a recent study, the differential effects of prolonged physiologically challenging exercise upon two executive processes (cognitive control and working memory) were investigated. However, the impact of exercise on the selective inhibition task employed was debatable and needed further analysis to dissociate the effects induced by exercise intensity from those induced by the time spent on task upon cognitive control outcomes. In this study, we propose a thorough analysis of these data, using a generalized mixed model on a trial-by-trial basis and a new measure of the strength of the automatic response based on reaction time distribution, to disentangle the effect of physical fatigue from cognitive fatigue. Despite the prolonged duration of exercise, no decline in cognitive performance was found in response to physical fatigue. The only change observed during 60-min exercise was an acceleration of the correct trials and an increase of errors for incompatible trials. This pattern, shown during low and physiologically challenging exercise, supports the occurrence of cognitive fatigue induced by the repetition of the cognitive tasks over time.
View details for PubMedID 30538660
View details for PubMedCentralID PMC6277630
Prefrontal oxygenation and the acoustic startle eyeblink response during exercise: A test of the dual-mode model.
2017; 54 (7): 1070-1080
The interplay between the prefrontal cortex and amygdala is proposed to explain the regulation of affective responses (pleasure/displeasure) during exercise as outlined in the dual-mode model. However, due to methodological limitations the dual-mode model has not been fully tested. In this study, prefrontal oxygenation (using near-infrared spectroscopy) and amygdala activity (reflected by eyeblink amplitude using acoustic startle methodology) were recorded during exercise standardized to metabolic processes: 80% of ventilatory threshold (below VT), at the VT, and at the respiratory compensation point (RCP). Self-reported tolerance of the intensity of exercise was assessed prior to, and affective responses recorded during exercise. The results revealed that, as the intensity of exercise became more challenging (from below VT to RCP), prefrontal oxygenation was larger and eyeblink amplitude and affective responses were reduced. Below VT and at VT, larger prefrontal oxygenation was associated with larger eyeblink amplitude. At the RCP, prefrontal oxygenation was greater in the left than right hemisphere, and eyeblink amplitude explained significant variance in affective responses (with prefrontal oxygenation) and self-reported tolerance. These findings highlight the role of the prefrontal cortex and potentially the amygdala in the regulation of affective (particularly negative) responses during exercise at physiologically challenging intensities (above VT). In addition, a psychophysiological basis of self-reported tolerance is indicated. This study provides some support of the dual-mode model and insight into the neural basis of affective responses during exercise.
View details for DOI 10.1111/psyp.12858
View details for PubMedID 28370024
The differential effects of prolonged exercise upon executive function and cerebral oxygenation.
Brain and cognition
2017; 113: 133-141
The acute-exercise effects upon cognitive functions are varied and dependent upon exercise duration and intensity, and the type of cognitive tasks assessed. The hypofrontality hypothesis assumes that prolonged exercise, at physiologically challenging intensities, is detrimental to executive functions due to cerebral perturbations (indicated by reduced prefrontal activity). The present study aimed to test this hypothesis by measuring oxygenation in prefrontal and motor regions using near-infrared spectroscopy during two executive tasks (flanker task and 2-back task) performed while cycling for 60min at a very low intensity and an intensity above the ventilatory threshold. Findings revealed that, compared to very low intensity, physiologically challenging exercise (i) shortened reaction time in the flanker task, (ii) impaired performance in the 2-back task, and (iii) initially increased oxygenation in prefrontal, but not motor regions, which then became stable in both regions over time. Therefore, during prolonged exercise, not only is the intensity of exercise assessed important, but also the nature of the cognitive processes involved in the task. In contrast to the hypofrontality hypothesis, no inverse pattern of oxygenation between prefrontal and motor regions was observed, and prefrontal oxygenation was maintained over time. The present results go against the hypofrontality hypothesis.
View details for DOI 10.1016/j.bandc.2017.02.001
View details for PubMedID 28235695
Extending the limits of force endurance: Stimulation of the motor or the frontal cortex?
Cortex; a journal devoted to the study of the nervous system and behavior
2017; 97: 96–108
Previous findings indicate that facilitation of primary motor cortex (PMC) activity using trans-cranial direct current stimulation (tDCS) could improve resistance to physical fatigue. However, studies have failed to consistently replicate these results. Using non-focal-tDCS during a fatiguing task, recent work showed no enhancement of corticospinal excitability of the PMC despite a longer endurance time and suggested that contamination in other brain regions involved in motor command may have occurred. In accordance with recent evidence supporting the role of the prefrontal cortex (PFC) in exercise maintenance, this double-blind sham-controlled crossover study (N = 22) compared the effect of high definition (HD)-tDCS of the PMC or the PFC on endurance time of a sustained contraction task of the elbow flexor. Brain activity was monitored using near infrared spectroscopy (NIRS) to measure the neurovascular response elicited by HD-tDCS. Electromyography (EMG) and force obtained during maximal voluntary and evoked contractions were assessed before and after the contraction task to explore the effect of brain stimulation on peripheral and central fatigue. While the stimulation affected the brain response in the PFC during the contraction task, no effects of the stimulation were observed on endurance time or fatigue indices. These results are discussed in relation to the neurocognitive models of physical effort.
View details for DOI 10.1016/j.cortex.2017.09.026
View details for PubMedID 29101820
Patterning of Physiological and Affective Responses in Older Adults During Self-Selected Exercise and a Graded Exercise Test
HUMAN KINETICS PUBL INC. 2016: S12
View details for Web of Science ID 000381554400024
A comparison of head motion and prefrontal haemodynamics during upright and recumbent cycling exercise.
Clinical physiology and functional imaging
The aim of this observational study was to compare head motion and prefrontal haemodynamics during exercise using three commercial cycling ergometers. Participants (n = 12) completed an incremental exercise test to exhaustion during upright, recumbent and semi-recumbent cycling. Head motion (using accelerometry), physiological data (oxygen uptake, end-tidal carbon dioxide [PET CO2 ] and heart rate) and changes in prefrontal haemodynamics (oxygenation, deoxygenation and blood volume using near infrared spectroscopy [NIRS]) were recorded. Despite no difference in oxygen uptake and heart rate, head motion was higher and PET CO2 was lower during upright cycling at maximal exercise (P<0·05). Analyses of covariance (covariates: head motion P>0·05; PET CO2 , P<0·01) revealed that prefrontal oxygenation was higher during semi-recumbent than recumbent cycling and deoxygenation and blood volume were higher during upright than recumbent and semi-recumbent cycling (respectively; P<0·05). This work highlights the robustness of the utility of NIRS to head motion and describes the potential postural effects upon the prefrontal haemodynamic response during upright and recumbent cycling exercise.
View details for DOI 10.1111/cpf.12365
View details for PubMedID 27121773
Self-reported tolerance influences prefrontal cortex hemodynamics and affective responses
COGNITIVE AFFECTIVE & BEHAVIORAL NEUROSCIENCE
2016; 16 (1): 63-71
The relationship between cognitive and sensory processes in the brain contributes to the regulation of affective responses (pleasure-displeasure). Exercise can be used to manipulate sensory processes (by increasing physiological demand) in order to examine the role of dispositional traits that may influence an individual's ability to cognitively regulate these responses. With the use of near infrared spectroscopy, in this study we examined the influence of self-reported tolerance upon prefrontal cortex (PFC) hemodynamics and affective responses. The hemodynamic response was measured in individuals with high or low tolerance during an incremental exercise test. Sensory manipulation was standardized against metabolic processes (ventilatory threshold [VT] and respiratory compensation point [RCP]), and affective responses were recorded. The results showed that the high-tolerance group displayed a larger hemodynamic response within the right PFC above VT (which increased above RCP). The low-tolerance group showed a larger hemodynamic response within the left PFC above VT. The high-tolerance group reported a more positive/less negative affective response above VT. These findings provide direct neurophysiological evidence of differential hemodynamic responses within the PFC that are associated with tolerance in the presence of increased physiological demands. This study supports the role of dispositional traits and previous theorizing into the underlying mechanisms (cognitive vs. sensory processes) of affective responses.
View details for DOI 10.3758/s13415-015-0374-3
View details for Web of Science ID 000370842100006
View details for PubMedID 26337703
Patterning of physiological and affective responses in older active adults during a maximal graded exercise test and self-selected exercise
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY
2015; 115 (9): 1855-1866
The American College of Sports Medicine has highlighted the importance of considering the physiological and affective responses to exercise when setting exercise intensity. Here, we examined the relationship between exercise intensity and physiological and affective responses in active older adults.Eighteen participants (60-74 years; 64.4 ± 3.9; 8 women) completed a maximal graded exercise test (GXT) on a treadmill. Since time to exhaustion in the GXT differed between participants, heart rate (HR), oxygen consumption (VO2), affective valence (affect) and rating of perceived exertion (RPE) were expressed relative to the individually determined ventilatory threshold (%atVT).During the GXT, VO2, HR and RPE increased linearly (all P < 0.01). Affect declined initially (but remained positive) (P = 0.03), stabilised around VT (still positive) (P > 0.05) and became negative towards the end of the test (P < 0.01). In a subsequent session, participants completed a 20-min bout of self-selected exercise (at a preferred intensity). Initially, participants chose to exercise below VT (88.2 ± 17.4 %VO2atVT); however, the intensity was adjusted to work at, or above VT (107.7 ± 19.9 %VO2atVT) after 10 min (P < 0.001), whilst affect remained positive.Together, these findings indicate that exercise around VT, whether administered during an exercise test, or self-selected by the participant, is likely to result in positive affective responses in older adults.
View details for DOI 10.1007/s00421-015-3167-z
View details for Web of Science ID 000359741900004
View details for PubMedID 25876526
Can previously sedentary females use the feeling scale to regulate exercise intensity in a gym environment? an observational study.
BMC sports science, medicine and rehabilitation
2015; 7: 30-?
Recent research suggests that the Feeling Scale (FS) can be used as a method of exercise intensity regulation to maintain a positive affective response during exercise. However, research to date has been carried out in laboratories and is not representative of natural exercise environments. The purpose of this study was to evaluate whether sedentary women can self-regulate their exercise intensity using the FS to experience positive affective responses in a gym environment using their own choice of exercise mode; cycling or treadmill.Fourteen females (24.9 years ± 5.2; height 166.7 ± 5.7 cm; mass 66.3 ± 13.4 kg; BMI 24.1 ± 5.5)) completed a submaximal exercise test and each individual's ventilatory threshold ([Formula: see text]) was identified. Following this, three 20 min gym-based exercise trials, either on a bike or treadmill were performed at an intensity that was self-selected and perceived to correspond to the FS value of +3 (good). Oxygen uptake, heart rate (HR) and ratings of perceived exertion (RPE) were measured during exercise at the participants chosen intensity.Results indicated that on average participants worked close to their [Formula: see text] and increased their exercise intensity during the 20-min session. Participants worked physiologically harder during cycling exercise. Consistency of oxygen uptake, HR and RPE across the exercise trials was high.The data indicate that previously sedentary women can use the FS in an ecological setting to regulate their exercise intensity and that regulating intensity to feel 'good' should lead to individuals exercising at an intensity that would result in cardiovascular gains if maintained.
View details for DOI 10.1186/s13102-015-0023-8
View details for PubMedID 26613045
View details for PubMedCentralID PMC4660653
- Frontal asymmetry and affective responses during exercise: An exploratory study using near infrared spectroscopy ELSEVIER SCIENCE BV. 2014: 255
Prefrontal Cortex Haemodynamics and Affective Responses during Exercise: A Multi-Channel Near Infrared Spectroscopy Study
2014; 9 (5)
The dose-response effects of the intensity of exercise upon the potential regulation (through top-down processes) of affective (pleasure-displeasure) responses in the prefrontal cortex during an incremental exercise protocol have not been explored. This study examined the functional capacity of the prefrontal cortex (reflected by haemodynamics using near infrared spectroscopy) and affective responses during exercise at different intensities. Participants completed an incremental cycling exercise test to exhaustion. Changes (Δ) in oxygenation (O2Hb), deoxygenation (HHb), blood volume (tHb) and haemoglobin difference (HbDiff) were measured from bilateral dorsal and ventral prefrontal areas. Affective responses were measured every minute during exercise. Data were extracted at intensities standardised to: below ventilatory threshold, at ventilatory threshold, respiratory compensation point and the end of exercise. During exercise at intensities from ventilatory threshold to respiratory compensation point, ΔO2Hb, ΔHbDiff and ΔtHb were greater in mostly ventral than dorsal regions. From the respiratory compensation point to the end of exercise, ΔO2Hb remained stable and ΔHbDiff declined in dorsal regions. As the intensity increased above the ventilatory threshold, inverse associations between affective responses and oxygenation in (a) all regions of the left hemisphere and (b) lateral (dorsal and ventral) regions followed by the midline (ventral) region in the right hemisphere were observed. Differential activation patterns occur within the prefrontal cortex and are associated with affective responses during cycling exercise.
View details for DOI 10.1371/journal.pone.0095924
View details for Web of Science ID 000335510600055
View details for PubMedID 24788166
View details for PubMedCentralID PMC4006862
Imagery Use and Affective Responses During Exercise: An Examination of Cerebral Hemodynamics Using Near-Infrared Spectroscopy
JOURNAL OF SPORT & EXERCISE PSYCHOLOGY
2013; 35 (5): 503-513
Imagery, as a cognitive strategy, can improve affective responses during moderate-intensity exercise. The effects of imagery at higher intensities of exercise have not been examined. Further, the effect of imagery use and activity in the frontal cortex during exercise is unknown. Using a crossover design (imagery and control), activity of the frontal cortex (reflected by changes in cerebral hemodynamics using near-infrared spectroscopy) and affective responses were measured during exercise at intensities 5% above the ventilatory threshold (VT) and the respiratory compensation point (RCP). Results indicated that imagery use influenced activity of the frontal cortex and was associated with a more positive affective response at intensities above VT, but not RCP to exhaustion (p < .05). These findings provide direct neurophysiological evidence of imagery use and activity in the frontal cortex during exercise at intensities above VT that positively impact affective responses.
View details for Web of Science ID 000326855600006
View details for PubMedID 24197718