Illuminating the Black Box: Investigating Prefrontal Cortical Hemodynamics during Exercise with Near-Infrared Spectroscopy

Abstract

Near-infrared spectroscopy (NIRS) presents an appealing option for investigating hemodynamic changes in the cerebral cortex during exercise. This review examines the physical basis of NIRS and the types of available instruments. Emphasis is placed on the physiological interpretation of NIRS signals. Theories from affective neuroscience and exercise psychobiology, including Davidson's prefrontal asymmetry hypothesis, Dietrich's transient hypofrontality hypothesis, and Ekkekakis's dual-mode model, are reviewed, highlighting the potential for designing NIRS-based tests in the context of exercise. Findings from 28 studies involving acute bouts of exercise are summarized. These studies suggest that the oxygenation of the prefrontal cortex increases during mild-to-moderate exercise and decreases during strenuous exercise, possibly proximally to the respiratory compensation threshold. Future studies designed to test hypotheses informed by psychological theories should help elucidate the significance of these changes for such important concepts as cognition, affect, exertion, and central fatigue.Keywords: near-infrared spectroscopy, prefrontal asymmetry, exercise intensity, affective responsesOne of the benefits of neuroscience for psychology, according to Peter Lang (1994), is that it can help "limit inference and . . . keep our cognitive theories away from empty boxology" (p. 219). In other words, neuroscientific knowledge can steer psychological theorizing in the right direction (and away from the wrong direction) by suggesting what is possible (and what is impossible) at the level of the nervous system. For example, is "mind over muscle" true? Some may believe so. In fact, some have argued so. But is this really possible? Does the central nervous system have the necessary anatomical features and neurophysiological functions that would permit, for example, consciousness to become completely impervious to afferent muscular cues or volition to exert unlimited control over muscular contractions? Having an understanding of what the brain "does" during exercise could help reformulate, refine, or place important boundary conditions on these and numerous other theoretical propositions.The author is with the Department of Kinesiology, Iowa State University, Ames, IA. 506Ekkekakis Unfortunately, the progress made by exercise neuroscience has been slow (Dishman, 2005). In particular, knowledge of what happens in the brain during a bout of exercise remains sketchy. A relatively small number of animal studies have provided insights into areas implicated in cardiovascular and locomotor control. However, most psychologists would probably be more interested in the function of the frontal lobes, where animal-to-human inferences are limited or impossible, given the dramatic interspecies differences in that particular region. In psychological research, the puzzle of the function of the various subdivisions of the frontal cortex is systematically and painstakingly being solved using the imaging tools of modern human neuroscience. For e...

Heart failure impairs cerebral oxygenation during exercise in patients with COPD

“…Exercise cerebral oxygenation (Cox) (as noninvasively determined by nearinfrared spectroscopy) depends upon the dynamic balance between the instantaneous rate of oxygen delivery and oxygen utilisation [3]. KOIKE et al [4], for instance, reported that congestive heart failure (CHF) HFrEF was associated with appreciable decreases in COx during exertion.…”

“…Indeed, mean arterial pressure, a major determinant of cerebral blood flow [8], was reduced throughout the exercise tests and related to COx in COPD+HFrEF. Slight impairments in mean arterial pressure might reduce cerebral blood flow, particularly in the presence of impaired autoregulation and excessive sympathetic drive [3,8]. There is also some evidence that decreased cardiac output may impair exercise COx, independent of mean arterial pressure [8].…”

“…Our data suggest that pharmacological treatment of HFrEF should take into consideration that the pre-frontal cortex is particularly sensitive to pressure perfusion impairments in patients with COPD. Impaired exercise DCOx is an independent prognostic factor in patients with cardiovascular disease and a predictor of cerebral ischaemic events [3]. It is noteworthy that stroke is more frequent in COPD patients when HFrEF coexists [9].…”

The Benefits of High Intensity Exercise on the Brain of a Drug Abuser

“…The NIRS allows quantification of oxyhemoglobin (O 2 Hb), deoxyhemoglobin (HbH) and total hemoglobin (HbT) according to absorbance at specific wavelengths (Ekkekakis, 2009). We used O 2 Hb since it is the best indicator of cerebral blood flow changes, according to Hoshi and colleagues (Hoshi, Kobayashi, & Tamura, 2001).…”

What Does Cerebral Oxygenation Tell Us About Central Motor Output?

“…The amplitudes of changes in oxy and deoxyhaemoglobin within the motor cortex areas have been shown to be dependent on the force production: the stronger the push, the higher the oxyhaemoglobin (Shibuya and Tachi, 2006;Smith et al, 2003). However, at low levels of force, there might be no detection by the NIRS systems (at least 10% of maximal voluntary contraction needed); while at high levels (about 50% of maximal voluntary contraction and above) there might be no plateau but only a peak in oxyhaemoglobin (Ekkekakis, 2009). This type of activation pattern is valid only for steady systemic variables (ie.…”