Concept: Refractory period
Oscillating neuronal circuits, known as central pattern generators (CPGs), are responsible for generating rhythmic behaviours such as walking, breathing and chewing. The CPG model alone however does not account for the ability of animals to adapt their future behaviour to changes in the sensory environment that signal reward. Here, using multi-electrode array (MEA) recording in an established experimental model of centrally generated rhythmic behaviour we show that the feeding CPG of Lymnaea stagnalis is itself associated with another, and hitherto unidentified, oscillating neuronal population. This extra-CPG oscillator is characterised by high population-wide activity alternating with population-wide quiescence. During the quiescent periods the CPG is refractory to activation by food-associated stimuli. Furthermore, the duration of the refractory period predicts the timing of the next activation of the CPG, which may be minutes into the future. Rewarding food stimuli and dopamine accelerate the frequency of the extra-CPG oscillator and reduce the duration of its quiescent periods. These findings indicate that dopamine adapts future feeding behaviour to the availability of food by significantly reducing the refractory period of the brain’s feeding circuitry.
OBJECTIVE: The male refractory period (MRP) continues to be a topic of discussion and debate within the field of sexual medicine. To date explanations rely on central descending (efferent) influences involving specific neurotransmitter systems. Herein we explore the issue of the male refractory period, identifying problems with current explanations, specifying the parameters of an adequate model, and suggesting possible mechanisms mediating this phenomenon. METHODS: We review the literature regarding existing explanations for the MRP and look to other systems of physiological regulation that might provide a model for the conceptualization of the MRP. RESULTS: Our approach differs from traditional explanations in that it emphasizes the possible roles of various peripheral, rather than central, feedback (afferent) systems that affect peripheral autonomic functioning and response. Yet our approach is consistent with other peripheral regulatory feedback systems controlling autonomic response related to such processes as heart rate, respiration, and gut motility. CONCLUSION: Although direct empirical research supporting our approach is lacking, sufficient evidence exists to support the idea that such processes are not only possible but likely with respect to the male refractory period. We suggest several lines of research that might provide empirical support for this approach.
Computational theories of decision making in the brain usually assume that sensory ‘evidence’ is accumulated supporting a number of hypotheses, and that the first accumulator to reach threshold triggers a decision in favour of its associated hypothesis. However, the evidence is often assumed to occur as a continuous process whose origins are somewhat abstract, with no direct link to the neural signals - action potentials or ‘spikes’ - that must ultimately form the substrate for decision making in the brain. Here we introduce a new variant of the well-known multi-hypothesis sequential probability ratio test (MSPRT) for decision making whose evidence observations consist of the basic unit of neural signalling - the inter-spike interval (ISI) - and which is based on a new form of the likelihood function. We dub this mechanism s-MSPRT and show its precise form for a range of realistic ISI distributions with positive support. In this way we show that, at the level of spikes, the refractory period may actually facilitate shorter decision times, and that the mechanism is robust against poor choice of the hypothesized data distribution. We show that s-MSPRT performance is related to the Kullback-Leibler divergence (KLD) or information gain between ISI distributions, through which we are able to link neural signalling to psychophysical observation at the behavioural level. Thus, we find the mean information needed for a decision is constant, thereby offering an account of Hick’s law (relating decision time to the number of choices). Further, the mean decision time of s-MSPRT shows a power law dependence on the KLD offering an account of Piéron’s law (relating reaction time to stimulus intensity). These results show the foundations for a research programme in which spike train analysis can be made the basis for predictions about behavior in multi-alternative choice tasks.
- Journal of experimental zoology. Part B, Molecular and developmental evolution
- Published 6 months ago
In human females, direct or indirect stimulation of the clitoris plays a central role in reaching orgasm. A majority of women report that penetrative coitus alone is insufficient for triggering orgasm, puzzling researchers who expect orgasm to be an outcome of procreative intercourse. In the present paper, we turn our attention to the evolutionary role that such unreliability of orgasm at coitus might have played in human evolution. We emphasize that we do not thereby attempt an explanation of its origin, but its potential evolutionary effect. The present proposal suggests that the variable female orgasm, the position of the clitoris remote from the vagina, and the mismatch of the male refractory period with the female capacity for multiple orgasms, may have contributed to the evolution of human prosocial qualities.
The preBötzinger Complex (preBötC), a medullary network critical for breathing, relies on excitatory interneurons to generate the inspiratory rhythm. Yet, half of preBötC neurons are inhibitory, and the role of inhibition in rhythmogenesis remains controversial. Using optogenetics and electrophysiology in vitro and in vivo, we demonstrate that the intrinsic excitability of excitatory neurons is reduced following large depolarizing inspiratory bursts. This refractory period limits the preBötC to very slow breathing frequencies. Inhibition integrated within the network is required to prevent overexcitation of preBötC neurons, thereby regulating the refractory period and allowing rapid breathing. In vivo, sensory feedback inhibition also regulates the refractory period, and in slowly breathing mice with sensory feedback removed, activity of inhibitory, but not excitatory, neurons restores breathing to physiological frequencies. We conclude that excitation and inhibition are interdependent for the breathing rhythm, because inhibition permits physiological preBötC bursting by controlling refractory properties of excitatory neurons.
INTRODUCTION: Sexual intercourse, orgasm, and sexual satisfaction are associated with well-being and improved quality of life. The pituitary hormone prolactin (PRL) may have an important role in regulating (and thus indexing) sexual satiety and satisfaction. AIM: Physiological indices to quantify the quality and resulting satisfaction from female orgasm would be valuable. Therefore we aim to validate associations of orgasm-induced PRL surges with women’s orgasm quality and subsequent sexual satisfaction. METHODS: In a prospective study, with a pre-post, single-blinded, cross-over design in a naturalistic field setting, we analyzed the correlation of women’s post-orgasmic serum PRL surges following sexual intercourse with women’s perceived quality of orgasm and resulting sexual satisfaction, as measured by a questionnaire. MAIN OUTCOME MEASURES: PRL levels prior to and following penile-vaginal intercourse with and without orgasm, and scores from the Acute Sexual Experience Scale (ASES) on quality of orgasm and sexual satisfaction. RESULTS: An analysis of variance of the blood samples in nine women indicated large magnitude, significant effects of intercourse orgasm on PRL levels (P = 0.004, eta squared = 0.78), as well as an interaction with the effect of multiple orgasms (P = 0.008, eta squared = 0.80). PRL post/pre ratios and arithmetic difference correlated strongly with orgasm quality (r = 0.85, P = 0.016, and r = 0.69, P = 0.08) and sexual satisfaction (r = 0.75, P = 0.05 and r = 0.77, P = 0.045). CONCLUSION: Women’s intercourse orgasm induced PRL surges are strongly related to the quality of orgasm and subsequent sexual satisfaction. This implies that post-orgasmic PRL surges are an objective index of orgasm and orgasm quality. PRL might be used in future studies on basic research as well as a treatment target in sexual disorders in women.
- Journal of experimental psychology. Learning, memory, and cognition
- Published 5 months ago
A frequent observation in dual-task studies is the backward crosstalk effect (BCE), meaning that aspects of a secondary Task 2 influence Task 1 performance. Up to this point, 2 major types of the BCE were investigated: a BCE based on dimensional overlap between both stimuli and/or responses (the compatibility-based BCE), and a BCE based on whether Task 2 is a go or no-go task (the no-go BCE). Recent evidence suggests that the compatibility-based BCE has its locus inside the response selection stage. The available evidence for the locus of the no-go BCE is still mixed, however. To this end, the 3 experiments reported in the present study used an extended psychological refractory period (PRP) paradigm with 3 subsequent tasks. Applying the locus of slack logic in Experiment 1, the no-go BCE was not absorbed into the cognitive slack and, thus, a locus before response selection could be ruled out. Subsequently applying the effect propagation logic in Experiment 2 and 3, the no-go BCE arising in Task 1 was even inverted in Task 3. Because no propagation of the no-go BCE was observed, a locus before or in response selection could be ruled out. Thus, we conclude that the no-go BCE has its locus during motor execution. Because the no-go BCE and the compatibility-based BCE are located in different stages, we suggest that both types of the BCE do not share a common underlying mechanism. (PsycINFO Database Record
Task preparation in dual-tasking is more complex than preparation for single tasks and involves additional factors such as task prioritization. Utilizing event-related potentials, we sought to disentangle preparatory processes involving preparation on the subtask level and the superordinate dual-task level. Participants worked on a psychological refractory period paradigm in which two temporally overlapping tasks have to be completed in a specified order. Whereas dual-task-related preparation was measured by comparing task-order switches and repetitions, subtask preparation was isolated through error precursors for the individual subtasks. We found that a switch-related posterior positivity was linked to the preparation of the superordinate dual-task set. In contrast, an early frontal modulation and a stimulus-preceding negativity were markers of subtask preparation of Task 1 and Task 2, respectively. Our study provides neural evidence for a hierarchical system of control processes in dual-tasking and confirms assumptions from earlier behavioral and computational studies on strategic task prioritization.
Recent advances in engineering and signal processing have renewed the interest in invasive and surface brain recordings, yet many features of cortical field potentials remain incompletely understood. In the computational study that follows, we show that a model circuit of interneurons, coupled via both [Formula: see text] receptor synapses and electrical synapses, reproduces many essential features of the power spectrum of local field potential (LFP) recordings, such as 1/[Formula: see text] power scaling at low frequency (below 10 Hz), power accumulation in the [Formula: see text]-frequency band (30-100 Hz), and a robust [Formula: see text] rhythm in the absence of stimulation. The low-frequency 1/[Formula: see text] power scaling depends on strong reciprocal inhibition, whereas the [Formula: see text] rhythm is generated by electrical coupling of intrinsically active neurons. As in previous studies, the [Formula: see text] power arises through the amplification of single-neuron spectral properties, owing to the refractory period, by parameters that favor neuronal synchrony, such as delayed inhibition. This study also confirms that both synaptic and voltage-gated membrane currents contribute substantially to the LFP and that high-frequency signals such as action potentials quickly taper off with distance. Given the ubiquity of electrically coupled interneuron circuits in the mammalian brain, they may be major determinants of the recorded potentials.
In human and veterinary medicine, monophasic action potential (MAP) analysis and determination of local refractory periods by contact electrode technique gives valuable information about local cardiac electrophysiological properties. It is used to investigate dysrhythmias and the impact of drugs on the myocardium. Precise measurement of total MAP duration is difficult, therefore the MAP duration is usually determined at a repolarization level of 90% (APD90). Until now, no studies are published about the feasibility of this technique in the standing non-sedated horse. In 6 healthy Warmblood horses, on two different days, an 8F quadripolar contact catheter was passed through a jugular introducer sheath and placed under ultrasound guidance at the level of the intervenous tubercle or right atrial free wall (RA), and in the right ventricular apex (RV) to record the MAP. The MAP amplitude and APD90 were measured at a resting sinus rhythm (heart rate of 30-42 bpm) and at pacing cycle lengths (PCL) of 1000 and 600 ms. The effective refractory period (ERP) was determined at PCL of 1000 and 600 ms.