Effect of cardiovascular biofeedback on nursing staff stress: a randomized controlled clinical trial.

OBJECTIVE: to assess the effect of cardiovascular biofeedback on nursing staff stress when compared to an activity without self-monitoring. METHOD: a randomized controlled clinical trial, carried out with nursing professionals from a university hospital. The intervention group (n=58) performed cardiovascular biofeedback, and the control (n=57) performed an online puzzle without self-monitoring, totaling nine meetings over three weeks. The outcome was assessed using the Stress Symptoms and Work-Related Stress scales, and the biological marker heart rate variability. The generalized estimating equations method was used. RESULTS: the intervention had no effect on self-reported instruments (p>0.050). However, there was an effect of time (p<0.050) on all heart rate variability indicators, demonstrating changes over the sessions. CONCLUSION: cardiovascular biofeedback showed promising results in the biological marker, suggesting that it can be used in nursing staff as a complementary therapy by promoting better autonomic nervous system regulation.

Daily biofeedback to modulate heart rate oscillations affects structural volume in hippocampal subregions targeted by the locus coeruleus in older adults but not younger adults.

Using data from a clinical trial, we tested the hypothesis that daily sessions modulating heart rate oscillations affect older adults' volume of a region-of-interest (ROI) comprised of adjacent hippocampal subregions with relatively strong locus coeruleus (LC) noradrenergic input. Younger and older adults were randomly assigned to one of two daily biofeedback practices for 5 weeks: (1) engage in slow-paced breathing to increase the amplitude of oscillations in heart rate at their breathing frequency (Osc+); (2) engage in self-selected strategies to decrease heart rate oscillations (Osc-). The interventions did not significantly affect younger adults' hippocampal volume. Among older adults, the two conditions affected volume in the LC-targeted hippocampal ROI differentially as reflected in a significant condition × time-point interaction on ROI volume. These condition differences were driven by opposing changes in the two conditions (increased volume in Osc+ and decreased volume in Osc-) and were mediated by the degree of heart rate oscillation during training sessions.

The Effect of Heart Rate Variability Biofeedback on Basketball Performance Tests.

The purpose of this study is to investigate the effects of 10-week heart rate variability biofeedback training on basketball skills, free throws, and heart rate variability parameters. Twenty-four basketball players (experimental, n = 12 and control, n = 12) aged 18-24 years volunteered to participate in this study. The experimental group participated in a 10-week heart rate variability biofeedback and basketball training program, while the control group only participated in the 10-week basketball training session. Basketball free-throw performance, basketball skills, and heart rate variability tests were conducted on the experimental and control groups before and after the 10-week intervention. Consequently, we discovered that basketball free-throw performance, breathing frequency, and heart rate variability parameters, which reflect vagal modulation of parasympathetic activity, improved in participants who underwent the 10-week heart rate variability biofeedback and basketball training, and not in those who took basketball training only. Our findings propose that heart rate variability biofeedback, alongside basketball workouts, can contribute to better basketball free-throw performance potentially through improved autonomic nervous system functioning.

Effect of a slow-paced breathing with heart rate variability biofeedback intervention on pro-inflammatory cytokines in individuals with panic disorder - A randomized controlled trial.

A generalized proinflammatory state has been observed in individuals with panic disorder (PD). There is evidence that slow-paced breathing (SPB) with heart rate variability-biofeedback (HRV-BF) strengthens the nervus vagus with its anti-inflammatory pathway. Therefore, with this randomized controlled trial we aimed to investigate the effect of a four-week SPB with HRV-BF intervention on pro-inflammatory cytokines in people with PD. Fifty-five individuals with PD (mean age: 37.22 ± 15.13 years) were randomly allocated either to SPB-HRV-BF (intervention group) or to HRV-Sham-BF (active control group). SPB-HRV-BF was performed over four weeks while cytokine concentration and HRV during a short-term resting condition were measured before and after intervention. SPB-HRV-BF decreased concentration of Tumor Necrosis Factor alpha (TNF-alpha) (F(1, 53) = 4.396, p ≤ .05, η2 = 0.077) in individuals with PD. In addition, SPB-HRV-BF demonstrated an increase in the HRV-time and frequency domain parameters SDNN, Total Power and LF during short-term resting condition. There was no intervention effect in HRV-Sham-BF group. In conclusion, SBP-HRV-BF as a non-pharmacological treatment may reduce pro-inflammatory cytokine TNF-alpha via the cholinergic anti-inflammatory pathway in individuals with PD. Based on the generalized proinflammatory state in PD, decreasing TNF-alpha is highly beneficial to reduce risk of cardiovascular diseases and metabolic syndrome.

Gut-Brain Coupling and Multilevel Physiological Response to Biofeedback Relaxation After a Stressful Task Under Virtual Reality Immersion: A Pilot Study.

Human physiological reactions to the environment are coordinated by the interactions between brain and viscera. In particular, the brain, heart, and gastrointestinal tract coordinate with each other to provide physiological equilibrium by involving the central, autonomic, and enteric nervous systems. Recent studies have demonstrated an electrophysiological coupling between the gastrointestinal tract and the brain (gut-brain axis) under resting-state conditions. As the gut-brain axis plays a key role in individual stress regulation, we aimed to examine modulation of gut-brain coupling through the use of an overwhelming and a relaxing module as a first step toward modeling of the underlying mechanisms. This study was performed in 12 participants who, under a virtual reality environment, performed a 9-min cognitive stressful task followed by a 9-min period of relaxation. Brain activity was captured by electroencephalography, autonomic activities by photoplethysmography, and electrodermal and gastric activities by electrogastrography. Results showed that compared with the stressful task, relaxation induced a significant decrease in both tonic and phasic sympathetic activity, with an increase in brain alpha power and a decrease in delta power. The intensity of gut-brain coupling, as assessed by the modulation index of the phase-amplitude coupling between the normogastric slow waves and the brain alpha waves, decreased under the relaxation relative to the stress condition. These results highlight the modulatory effect of biofeedback relaxation on gut-brain coupling and suggest noninvasive multilevel electrophysiology as a promising way to investigate the mechanisms underlying gut-brain coupling in physiological and pathological situations.

Short-term efficacy of home-based heart rate variability biofeedback on sleep disturbance in patients with incurable cancer: a randomised open-label study.

OBJECTIVES: Early palliative care reportedly contributes to the quality of life by improving coping skills in patients with cancer. The aims of the study are to (1) Build a self-coping system that makes it possible to perform a session of home-based heart rate variability biofeedback (HRV-BF) with resonant breathing in patients with sleep disturbance and to acquire its techniques early on, and (2) Examine its short-term efficacy and feasibility. METHODS: A randomised, open-label, comparative study was conducted in the presence or absence of home-based HRV-BF with resonant breathing using a portable HRV-BF device prior to bedtime. The participants were 50 patients with incurable cancer with sleep disturbance who underwent a hospital practice of HRV-BF with resonant breathing. The primary end point was the rate of change in sleep efficiency for 10-14 days. The Japanese version of the Pittsburgh Sleep Quality Index (subjective indicator) and actigraphy sleep parameters (objective indicators) were used for sleep assessments. RESULTS: The completion rate and implementation rate in the home-based HRV-BF group (n=25) were 96.0% and 91.4%, respectively. This group showed a significant improvement in sleep efficiency, sleep duration and the low-frequency component of HRV. Sleep latency worsened in this group, but a significant difference was not observed. CONCLUSIONS: A home practice of HRV-BF with resonant breathing made it possible to acquire its techniques early on and improve sleep and autonomic function; therefore, our study showed high short-term efficacy and feasibility required for a self-coping system.

Efficacy of Electromyographic Biofeedback in Muscle Recovery after Meniscectomy in Soccer Players.

Electromyographic biofeedback (EMG-BF) is a therapeutic technique that has been used successfully in the rehabilitation of injuries. Although it has been applied to athletes, its use in this field is not very widespread. The objective of this study is to analyze its effectiveness in the recovery of electromyographic activity of the quadriceps after meniscectomy, evaluated through isometric contraction of the vastus lateralis. The sample comprised ten professional footballers in the Spanish League (2nd Division A) who had previously suffered a meniscus injury in their knee and had undergone a meniscectomy. The intervention consisted of EMG-BF treatment lasting between 6 and 10 sessions. The electromyographic signal was recorded using a Thought Technology ProComp Infiniti 8-channel biofeedback unit with a sampling rate of 2048 samples/second. For each session, a within-subject ABA design of 6 or 10 trials per session was used, with three pre- and three post-measures, which determined the gain for each session. The results indicated (1) improvements in all cases, (2) EMG-BF was effective, (3) the working model was statistically significant with an explained variance of between 67% and 75%, and (4) the generalizability analysis showed that the results are reliable and generalizable. The results indicate that EMG-BF is effective in neuromuscular rehabilitation after this type of intervention.

Feasibility of a Novel Video Game-Based Electromyography Biofeedback System in Patients With Knee Osteoarthritis.

CONTEXT: A novel virtual game system Knee Biofeedback Rehabilitation Interface for game-based home therapy (KneeBright) was developed for strength training using integrated electromyography biofeedback of the quadriceps muscle to control the game. The study aimed to compare the KneeBright and electromyography biofeedback interface among patients with knee osteoarthritis. DESIGN: Controlled before and after design. METHODS: Nineteen patients with knee osteoarthritis took part in this laboratory-based study. Exercise sessions took place on 2 separate days. During session 1, participants used a conventional electromyography biofeedback system while performing 3 sets of lower body exercises with emphasis on maximal muscle activation, endurance, and precision. During session 2, participants used the KneeBright game to match the exercise sets in the first session. For both sessions, knee extension torque during the isometric muscle activation exercises and time to voluntary additional exercise were recorded. Patient engagement was assessed using the technology acceptance model and System Usability Score questionnaires. RESULTS: The peak knee extension torque produced during the control exercise session and the KneeBright exercise session were positively correlated. Knee extension torque generated during KneeBright game exercise sessions was increased by an average of 25% compared to the control sessions (2.14 vs 1.77 N·m/kg, P = .02). The mean technology acceptance model score for the KneeBright system was 3.4/5 and the mean System Usability Score was 79, both indicating positive patient engagement. CONCLUSIONS: Patients using the KneeBright game produced greater knee torque than patients using the conventional system, had positive levels of engagement, and exercised longer with the KneeBright game.

Evaluation of Heart Rate Variability and Application of Heart Rate Variability Biofeedback: Toward Further Research on Slow-Paced Abdominal Breathing in Zen Meditation.

This review summarizes my own involvement in heart rate variability (HRV) and HRV biofeedback studies, as a tribute to the late Dr. Evgeny Vaschillo. I first review psychophysiological studies on behavioral stress and relaxation performed in my laboratory using an assessment of cardiac parasympathetic activity. Although magnitude of high-frequency (HF) component of HRV corresponding respiratory sinus arrhythmia (RSA) is widely used as an index of cardiac parasympathetic function, a respiratory confound during stress or relaxation may have interfered with the proper assessment of the HF HRV. An enhanced method under frequency-controlled respiration at 0.25 Hz provided a reliable assessment of cardiac parasympathetic activity. I then review findings from HRV biofeedback research in my laboratory. Based on the hypothesis that RSA measured as an HF component of HRV represents cardiorespiratory resting function, it was demonstrated that HRV biofeedback before sleep enhanced the magnitude of HF HRV during sleep, a cardiorespiratory resting function. Moreover, by focusing on the spectral peak of the low-frequency (LF) component of HRV, paced breathing at the LF-peak frequency was shown to increase baroreflex sensitivity. Finally, I describe the potential of slow-paced abdominal breathing (i.e., Tanden breathing) performed in Zen meditation. The concept of Tanden breathing as described in a regimen from early modern Japan is introduced, and recent research findings on slow-paced abdominal breathing are summarized. Future research directions of slow-paced abdominal breathing are also discussed.

Visualization, Self-Efficacy, and Locus of Control in a Virtual Reality Biofeedback Video Game for Anxiety Regulation.

The current study aimed to identify specific feedback mechanics and psychological processes that may contribute to positive outcomes in biofeedback applications for anxiety regulation. Specifically, using a dismantling study design, the unique impact of visualizations that directly mirror users' breathing was examined in relation to anxiety regulation as well as locus of control and self-efficacy. Following an anxiety induction, participants (N = 67) were randomly assigned to play one of two variations of a biofeedback video game. In both versions, players' in-game movement was contingent on their breathing; however, the experimental condition additionally included visualizations that directly mirrored players' breathing. Changes in self-reported state anxiety and physiological arousal were measured as well as the level of internal control and self-efficacy participants experienced while playing the game. Results showed that all participants were able to effectively reduce their anxiety and arousal, but no condition differences were found. Implementing mirroring visualizations did not contribute to individuals' ability to self-regulate nor their self-efficacy or locus of control above and beyond receiving feedback based on their in-game movement. Overall, individuals who experienced higher self-efficacy and a stronger internal locus of control were better able to regulate their anxiety, but no clear links were found with changes in self-reported physiological arousal. In light of these results, we recommend the continued exploration of the role of specific design choices and intervention components as well as underlying mechanisms of change in biofeedback interventions, especially pertaining to how individuals perceive themselves and their ability to change.

Pelvic floor physical therapy in patients with chronic anal fissure: a randomized controlled trial.

BACKGROUND: A chronic anal fissure is a common, painful condition with great impact on daily life. The exact pathogenesis has not been fully elucidated and treatment varies. A large percentage of patients experience pelvic floor dysfunction (dyssynergia and increased pelvic floor muscle tone). The aim of our study was to investigate the effect of pelvic floor physical therapy in patients with chronic anal fissure. METHODS: Between December 2018 and July 2021, at the Proctos Clinic in the Netherlands, patients with chronic anal fissure and pelvic floor dysfunction were randomly assigned to an intervention group, receiving 8 weeks of pelvic floor physical therapy including electromyographic biofeedback or assigned to a control group receiving postponed pelvic floor physical therapy. The primary outcome was muscle tone at rest during electromyographic registration of the pelvic floor before and after pelvic floor physical therapy. Secondary outcomes contained healing of the fissure, pain ratings, improvement of pelvic floor function, and complaint reduction measured with a proctology-specific patient-reported outcome measurement. Endpoints were measured at 8- and 20-week follow-up. RESULTS: One hundred forty patients were included in the study, 68 men (48.6%) and 72 women (51.4%) with a mean age of 44.5 ± 11.1 (range 19-79) years. Mean resting electromyographic values of the pelvic floor in the intervention group significantly improved from pre- to post-treatment (p < 0.001) and relative to controls (mean estimated difference between groups - 1.88 µV; 95% CI, - 2.49 to - 1.27 (p < 0.001) at first follow-up and remained significant from baseline at 20-week follow-up (p < 0.001). The intervention group performed better compared to the control group on all secondary outcomes, i.e., healing of the fissure (55.7% of the patients vs 21.4% in control, pain ratings (p < 0.001), diminished dyssynergia (p < 0.001), complaint reduction (p < 0.001), and decrease of pelvic floor muscle tone (p < 0.05) at first follow-up. CONCLUSIONS: The findings of this study provide strong evidence that pelvic floor physical therapy is effective in patients with chronic anal fissure and pelvic floor dysfunction and supports its recommendation as adjuvant treatment besides regular conservative treatment.

Learned self-regulation in top-level managers through neurobiofeedback training improves decision making under stress.

Top-level management teams are particularly exposed to stress factors as they frequently have to make important decision under stress. While an existing body of research evidence suggests that stress negatively affects decision-making processes, very little is known about possible strategies to reduce these negative effects. The aim of the current work is to investigate the effect of training self-regulation ability through neurobiofeedback on managers' intertemporal and risky decision making. Twenty-three managers were assigned to the experimental or the control condition. All participants performed, two decisional tasks, before and after a training phase. The tasks were administered through mouse tracker software, in order to measure participants' delay discounting and risk taking propensity on both explicit and implicit choice parameters. During the training phase, the experimental condition received a training protocol based on stress assessment tests via neurobiofeedback signals (i.e., temperature and skin conductance), with the goal of improving self-regulation ability while the control condition was administered a control training. The main result of this study is to have conclusively demonstrated that NBF training increases an individual's ability to self-regulate stress-related psychophysiological phenomena. Consequently, the improved ability to manage one's own reaction to stress enables a reduction in instinctive behavior during a probabilistic choice task.

Neurophysiologic Reactions during Heart Rate Variability Biofeedback Session in Adolescents with Different Risk of Internet Addiction.

The aim of this study was to determine electroencephalogram (EEG) in a session of heart rate variability biofeedback (HRV BF) in adolescents with different Internet addiction (IA) risks. In total, 100 healthy adolescents aged 16-17 years with minimal risk of IA (Group I, 35%), pronounced risk of IA (Group II, 51%), and stable pattern of IA (Group III, 14%) using the Chen Internet Addiction Scale were examined. HRV and EEG parameters were determined at baseline (5 min), and then during the short-term HRV BF session (5 min), in order to increase the total power (TP, ms2) of the HRV spectrum. Against the background of an increase in the TP and a decrease in sympathetic activity, an increase in alpha EEG was revealed, especially in Groups I and II. The greatest increase in the power of beta1-activity of EEG in the frontal, central, and temporal brain regionswas found in Groups I and II. In adolescents with a pronounced risk of IA, HRV BF is accompanied by a severe activation of the brain systems, while in persons with a stable type of IA, the least brain reactivity is shown, especially in the beta1 EEG band.

My Life in HRV Biofeedback Research.

This paper reviews the published work of me along with my students and close colleagues on the topic of heart rate variability biofeedback (HRVB). It includes early research by Vaschillo documenting resonance characteristics of the baroreflex system that causes large oscillations in heart rate when breathing at resonance frequency, research on heart rate variability as a marker of parasympathetic stress response in asthma, and HRVB as a treatment for asthma and depression. Many questions about HRVB remain unresolved, and important questions for future research are listed.

The Effects of Heart Rate Variability (HRV) Biofeedback on HRV Reactivity and Recovery During and After Anger Recall Task for Patients with Coronary Artery Disease.

Patients with coronary artery disease (CAD) often experience anger events before cardiovascular events. Anger is a psychological risk factor and causes underlying psychophysiological mechanisms to lose balance of the autonomic nervous system (ANS). The heart rate variability (HRV) was the common index for ANS regulation. It has been confirmed that heart rate variability biofeedback (HRV-BF) restored ANS balance in patients with CAD during the resting state. However, the effects of HRV-BF during and after the anger event remain unknown. This study aimed to examine the effects of HRV-BF on ANS reactivity and recovery during the anger recall task in patients with CAD. This study was a randomized control trial with a wait-list control group design, with forty patients in the HRV-BF group (for six sessions) and 44 patients in the control group. All patients received five stages of an anger recall task, including baseline, neutral recall task, neutral recovery, anger recall task, and anger recovery. HRV reactivity in the HRV-BF group at the post-test was lower than that in the control group. HRV recovery at the post-test in the HRV-BF group was higher than that in the control group. The HRV-BF reduced ANS reactivity during anger events and increased ANS recovery after anger events for CAD patients. The possible mechanisms of HRV-BF may increase total HRV, ANS regulation, and baroreflex activation at anger events for patients with CAD, and may be a suitable program for cardiac rehabilitation.

A Method for More Accurate Determination of Resonance Frequency of the Cardiovascular System, and Evaluation of a Program to Perform It.

This study validated a more exact automated method of determining cardiovascular resonance frequency (RF) against the "stepped" protocol described by Lehrer et al. (Appl Psychophysiol Biofeedback 25(3):177-191, https://doi.org/10.1023/a:1009554825745 , 2000; in Foundations of heart rate variability biofeedback: A book of readings, The Association for Applied Psychophysiology and Biofeedback, pp 9-19, 2016). Thirteen participants completed a 15-min RF determination session by each method. The "stepped" protocol assesses HRV in five 3-min stationary windows from 4.5 to 6.5 breaths per minute (bpm), decreasing in 0.5 bpm steps. Multiple criteria, subjectively weighted by the clinician, determines RF. For this study, the proposed method used a sliding window with a fixed rate of change (67.04 ms per breath) at each of 78 breath cycles ranging from 4.25 to 6.75 bpm. Its algorithm analyzes IBI to locate the midpoint of the 1-min region of stable maximum peak-trough variability. RF is quantified from breath duration at that point. The software generates a visual display of superimposed HR and breathing data. Thus, the new method fully automates RF determination. Eleven of the 13 matched pairs fell within the 0.5 bpm resolution of the stepped method. Comparisons of LF power generated by the autoregressive (AR) spectral method showed a strong correlation in LF power production by the stepped and sliding methods (R = 0.751, p = 0.000). The "sliding" pacing protocol was favored by 69% of participants (p < 0.02). The new, fully-automated, method may facilitate both in-person and remote HRV biofeedback training. Software is available open-source.

Effect of a Biofeedback Intervention on Heart Rate Variability in Individuals With Panic Disorder: A Randomized Controlled Trial.

OBJECTIVE: Some individuals with panic disorder (PD) display reduced heart rate variability (HRV), which may result in an increased risk of cardiovascular mortality. Heart rate variability-biofeedback (HRV-BF) training has been shown to improve the modulation of the autonomic activity. Therefore, this randomized controlled trial was conducted to investigate the effect of a 4-week HRV-BF intervention in individuals with PD. HRV-BF training improved the modulation of the autonomic activity. Therefore, with this randomized controlled trial, we aimed to investigate the effect of a 4-week HRV-BF intervention in people with PD. METHODS: Thirty-six women and 16 men with PD (mean age = 35.85 [15.60] years) were randomly allocated either to HRV-BF with 0.1-Hz breathing as intervention group or to HRV-Sham-BF as active control group. HRV-BF was performed for 4 weeks, whereas HRV was measured both during a short-term resting condition and during a paced breathing condition before and after intervention. RESULTS: HRV-BF with 0.1-Hz breathing increased HRV and reduced panic symptoms in individuals with PD. HRV-BF with 0.1-Hz breathing demonstrated an increase in the time and frequency domain parameters of HRV during the short-term resting condition (ΔPost-Pre root mean square successive differences: 5.87 [14.03] milliseconds; ΔPost-Pre standard deviation of all NN intervals: 11.63 [17.06] milliseconds; ΔPost-Pre total power: 464.88 [1825.47] milliseconds2; ΔPost-Pre power in low-frequency range 0.04-0.15 Hz: 312.73 [592.71] milliseconds2), a decrease in the heart rate during the paced breathing condition (ΔPost-Pre: -5.87 [9.14] beats/min), and a decrease in the Panic and Agoraphobia Scale (ΔPost-Pre: -3.64 [6.30]). There was no intervention effect in the HRV-Sham-BF group. CONCLUSIONS: HRV-BF as a noninvasive and nonpharmacological treatment seems to be an important intervention option to improve reduced HRV and decrease panic symptoms in individuals with PD. Future studies are needed to establish whether these effects translate to reductions in the risk of cardiovascular disease in PD.

Asymmetric Frequency-Specific Feedforward and Feedback Information Flow between Hippocampus and Prefrontal Cortex during Verbal Memory Encoding and Recall.

Hippocampus and prefrontal cortex (PFC) circuits are thought to play a prominent role in human episodic memory, but the precise nature, and electrophysiological basis, of directed information flow between these regions and their role in verbal memory formation has remained elusive. Here we investigate nonlinear causal interactions between hippocampus and lateral PFC using intracranial EEG recordings (26 participants, 16 females) during verbal memory encoding and recall tasks. Direction-specific information theoretic analysis revealed higher causal information flow from the hippocampus to PFC than in the reverse direction. Crucially, this pattern was observed during both memory encoding and recall, and the strength of causal interactions was significantly greater during memory task performance than resting baseline. Further analyses revealed frequency specificity of interactions with greater causal information flow from hippocampus to the PFC in the delta-theta frequency band (0.5-8 Hz); in contrast, PFC to hippocampus causal information flow were stronger in the beta band (12-30 Hz). Across all hippocampus-PFC electrode pairs, propagation delay between the source and target signals was estimated to be 17.7 ms, which is physiologically meaningful and corresponds to directional signal interactions on a timescale consistent with monosynaptic influence. Our findings identify distinct asymmetric feedforward and feedback signaling mechanisms between the hippocampus and PFC and their dissociable roles in memory recall, demonstrate that these regions preferentially use different frequency channels, and provide novel insights into the electrophysiological basis of directed information flow during episodic memory formation in the human brain.SIGNIFICANCE STATEMENT Hippocampal-PFC circuits play a critical role in episodic memory in rodents, nonhuman primates, and humans. Investigations using noninvasive fMRI techniques have provided insights into coactivation of the hippocampus and PFC during memory formation; however, the electrophysiological basis of dynamic causal hippocampal-PFC interactions in the human brain is poorly understood. Here, we use data from a large cohort of intracranial EEG recordings to investigate the neurophysiological underpinnings of asymmetric feedforward and feedback hippocampal-PFC interactions and their nonlinear causal dynamics during both episodic memory encoding and recall. Our findings provide novel insights into the electrophysiological basis of directed bottom-up and top-down information flow during episodic memory formation in the human brain.

A direct interareal feedback-to-feedforward circuit in primate visual cortex.

The mammalian sensory neocortex consists of hierarchically organized areas reciprocally connected via feedforward (FF) and feedback (FB) circuits. Several theories of hierarchical computation ascribe the bulk of the computational work of the cortex to looped FF-FB circuits between pairs of cortical areas. However, whether such corticocortical loops exist remains unclear. In higher mammals, individual FF-projection neurons send afferents almost exclusively to a single higher-level area. However, it is unclear whether FB-projection neurons show similar area-specificity, and whether they influence FF-projection neurons directly or indirectly. Using viral-mediated monosynaptic circuit tracing in macaque primary visual cortex (V1), we show that V1 neurons sending FF projections to area V2 receive monosynaptic FB inputs from V2, but not other V1-projecting areas. We also find monosynaptic FB-to-FB neuron contacts as a second motif of FB connectivity. Our results support the existence of FF-FB loops in primate cortex, and suggest that FB can rapidly and selectively influence the activity of incoming FF signals.