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 (HFHPV; 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 medialprefrontal, 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. KeywordsCentral cardiac autonomic regulation; Heart period; High-frequency heart period variability; Positron emission tomography The cortical and subcortical brain systems that regulate cardiac autonomic activity during behavior have been detailed by extensive research in nonhuman animals (reviewed by Bennarroch, 1997;Buchanan & Powell, 1993;Loewy & Spyer, 1990 NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptHurley, Ruit, & Frysztak, 1993). An open question is whether similar brain systems regulate behaviorally integrated cardiac autonomic activity in humans. Answering this question is important because the brain's regulation of cardiac autonomic activity is purported to influence a range of behavioral processes: attending to novel stimuli (Porges, 1995), processing environmental information (Lacey & Lacey, 1974), making decisions (Damasio, 1994), experiencing fear and anxiety (Berntson, Sarter, & Cacioppo, 1998), perceiving pain (Dworkin et al., 1994;Rosen et al., 1996), and reacting to stressors (Lovallo & Gerin, 2003) are examples of such processes.Drawing on the support of nonhuman animal research, the cortical brain systems that are hypothesized to regulate cardiac autonomic activity during behavior include the medialprefrontal (Brodmann Areas 10 and 11), insular, and anterior cingulate (Brodmann Areas 24, 25, and 32) regions of the cortex. A prevailing view is that these cortical systems act as a network with subcortical systems to initiate and represent cardiac autonomic adjustments that support behavioral responses to environmental, psychological, and social stimuli (Bennarroch, 1997;Cechetto, 1994;Groenewegen & Uylings, 2000;Loewy & Spyer, 1990;Thayer & Lane, 2000). Subcortical regions that are thought to regulate behaviorally integrated cardiac ...

This study used functional magnetic resonance imaging to examine the effects of acute tryptophan (TRP) depletion (ATD), a wellrecognized method for inducing transient cerebral serotonin depletion, on brain activity during probabilistic reversal learning. Twelve healthy male volunteers received a TRP-depleting drink or a balanced amino-acid drink (placebo) in a double-blind crossover design. At 5 h after drink ingestion, subjects were scanned while performing a probabilistic reversal learning task and while viewing a flashing checkerboard. The probabilistic reversal learning task enabled the separate examination of the effects of ATD on behavioral reversal following negative feedback and negative feedback per se that was not followed by behavioral adaptation. Consistent with previous findings, behavioral reversal was accompanied by significant signal change in the right ventrolateral prefrontal cortex (PFC) and the dorsomedial prefrontal cortex. ATD enhanced reversal-related signal change in the dorsomedial PFC, but did not modulate the ventrolateral PFC response. The ATD-induced signal change in the dorsomedial PFC during behavioral reversal learning extended to trials where subjects received negative feedback but did not change their behavior. These data suggest that ATD affects reversal learning and the processing of aversive signals by modulation of the dorsomedial PFC.

Memory performance in hypertensive individuals is related to a blunted regional cerebral blood flow (rCBF) response, particularly in parietal cortex. Potentially compensatory rCBF responses appear to occur in midbrain and correlate with prefrontal rCBF.

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The effect of social rejection on cardiac and brain responses was examined in a study in which participants had to decide on the basis of pictures of virtual peers whether these peers would like them or not. Physiological and behavioral responses to expected and unexpected acceptance and rejection were compared. It was found that participants expected that about 50% of the virtual judges gave them a positive judgment. Cardiac deceleration was strongest for unexpected social rejection. In contrast, the brain response was strongest to expected acceptance and was characterized by a positive deflection peaking around 325 ms following stimulus onset and the observed difference was maximal at fronto-central positions. The cardiac and electro-cortical responses were not related. It is hypothesized that these differential response patterns might be related to earlier described differential involvement of the dorsal and ventral portion of the anterior cingulate cortex.