Characterization of the planarian surface electroencephalogram.

BACKGROUND: Despite large morphological differences between the nervous systems of lower animals and humans, striking functional similarities have been reported. However, little is known about how these functional similarities translate to cognitive similarities. As a first step towards studying the cognitive abilities of simple nervous systems, we here characterize the ongoing electrophysiological activity of the planarian Schmidtea mediterranea. One previous report using invasive microelectrodes describes that the ongoing neural activity is characterized by a 1/fx power spectrum with the exponent 'x' of the power spectrum close to 1. To extend these findings, we aimed to establish a recording protocol to measure ongoing neural activity safely and securely from alive and healthy planarians under different lighting conditions using non-invasive surface electrodes. RESULTS: As a replication and extension of the previous results, we show that the ongoing neural activity is characterized by a 1/fx power spectrum, that the exponent 'x' in living planarians is close to 1, and that changes in lighting induce changes in neural activity likely due to the planarian photophobia. CONCLUSIONS: We confirm the existence of continuous EEG activity in planarians and show that it is possible to noninvasively record this activity with surface wire electrodes. This opens up broad possibilities for continuous recordings across longer intervals, and repeated recordings from the same animals to study cognitive processes.

Artificial neural network performance based on correlation analysis qualitatively comparable with human performance in behavioral signal detection experiments.

Standard Gaussian signal detection theory (SDT) is a widely used approach to assess the detection performance of living organisms or technical systems without looking at the inner workings of these systems like neural or electronic mechanisms. Nevertheless, a consideration of the inner mechanisms of a system and how they produce observed behaviors should help to better understand the functioning. It might even offer the possibility to demonstrate isolated pattern separation processes directly in the model. To do so, modeling the interaction between the entorhinal cortex (EC) and the hippocampal subnetwork dentate gyrus (DG) via the perforant path reveals the decorrelation network's mode of operation. We show that the ability to do pattern separation is crucial for high-performance pattern recognition, but also for lure discrimination, and depends on the proportionality between input and output network. NEW & NOTEWORTHY We elucidate the interplay of the entorhinal cortex and the hippocampal dentate gyrus during pattern separation tasks by providing a new simulation model. Functional memory formation and processing of similar memory content is illuminated from within the system. For the first time orthogonalized spiking patterns are evaluated with signal detection theory methods, and the results are applied to clinically established and novel tests.

Discounting Behavior in Problem Gambling.

Problem gamblers discount delayed rewards more rapidly than do non-gambling controls. Understanding this impulsivity is important for developing treatment options. In this article, we seek to make two contributions: First, we ask which of the currently debated economic models of intertemporal choice (exponential versus hyperbolic versus quasi-hyperbolic) provides the best description of gamblers' discounting behavior. Second, we ask how problem gamblers differ from habitual gamblers and non-gambling controls within the most favored parametrization. Our analysis reveals that the quasi-hyperbolic discounting model is strongly favored over the other two parametrizations. Within the quasi-hyperbolic discounting model, problem gamblers have both a significantly stronger present bias and a smaller long-run discount factor, which suggests that gamblers' impulsivity has two distinct sources.

Oscillatory brain activity associated with skin conductance responses in the context of risk.

Understanding the neural correlates of risk-sensitive skin conductance responses can provide insights into their connection to emotional and cognitive processes. To provide insights into this connection, we studied the cortical correlates of risk-sensitive skin conductance peaks using electroencephalography. Fluctuations in skin conductance responses were elicited while participants played a threat-of-shock card game. Precise temporal information about skin conductance peaks was obtained by applying continuous decomposition analysis on raw electrodermal signals. Shortly preceding skin conductance peaks, we observed a decrease in oscillatory power in the frequency range between 3 and 17 Hz in occipitotemporal cortical areas. Atlas-based analysis indicated the left lingual gyrus as the source of the power decrease. The oscillatory power averaged across 3-17 Hz showed a significant negative relationship with the skin conductance peak amplitude. Our findings indicate a possible interaction between attention and threat perception.NEW & NOTEWORTHY We studied neural oscillations associated with risk-sensitive skin conductance responses. Going beyond previous studies, we applied methods with high-temporal resolution to account for the temporal properties of the sympathetic activity. Preceding skin conductance peaks, we observed decreased occipital cortex oscillatory power and a relationship between the oscillatory power decrease and the skin conductance peak amplitude. Our study suggests an interaction between attention and emotion such as threat perception reflected in skin conductance responses.

On the Role of the Excitation/Inhibition Balance of Homeostatic Artificial Neural Networks.

Homeostatic models of artificial neural networks have been developed to explain the self-organization of a stable dynamical connectivity between the neurons of the net. These models are typically two-population models, with excitatory and inhibitory cells. In these models, connectivity is a means to regulate cell activity, and in consequence, intracellular calcium levels towards a desired target level. The excitation/inhibition (E/I) balance is usually set to 80:20, a value characteristic for cortical cell distributions. We study the behavior of these homeostatic models outside of the physiological range of the E/I balance, and we find a pronounced bifurcation at about the physiological value of this balance. Lower inhibition values lead to sparsely connected networks. At a certain threshold value, the neurons develop a reasonably connected network that can fulfill the homeostasis criteria in a stable way. Beyond the threshold, the behavior of the artificial neural network changes drastically, with failing homeostasis and in consequence with an exploding number of connections. While the exact value of the balance at the bifurcation point is subject to the parameters of the model, the existence of this bifurcation might explain the stability of a certain E/I balance across a wide range of biological neural networks. Assuming that this class of models describes the self-organization of biological network connectivity reasonably realistically, the omnipresent physiological balance might represent a case of self-organized criticality in order to obtain a good connectivity while allowing for a stable intracellular calcium homeostasis.

An evaluation of psychophysical models of auditory change perception.

In many psychophysical experiments, the participant's task is to detect small changes along a given stimulus dimension or to identify the direction (e.g., upward vs. downward) of such changes. The results of these experiments are traditionally analyzed with a constant-variance Gaussian (CVG) model or a high-threshold (HT) model. Here, the authors demonstrate that for changes along three basic sound dimensions (frequency, intensity, and amplitude-modulation rate), such models cannot account for the observed relationship between detection thresholds and direction-identification thresholds. It is shown that two alternative models can account for this relationship. One of them is based on the idea of sensory quanta; the other assumes that small changes are detected on the basis of Poisson processes with low means. The predictions of these two models are then compared against receiver operating characteristics (ROCs) for the detection of changes in sound intensity. It is concluded that human listeners' perception of small and unidimensional acoustic changes is better described by a discrete-state Poisson model than by the more commonly used CVG model or by the less favored HT and quantum models.

Echoic memory in pigeons.

It is unknown whether birds are able to retain the memory of purely sensory auditory information such as white noise over an extended period of time. In a Pavlovian heart rate conditioning paradigm, four pigeons were trained to associate a mild electric shock with periodic random waveforms, and no shock with aperiodic noise. Periodic waveform detection requires echoic memory, i.e., the online retention of a waveform pattern over a limited time. Starting with 40ms, the waveform period was increased after successful learning until no significant stimulus discrimination could be found. Significant discrimination was achieved at periods of up to 2560ms. This is the first demonstration that echoic memory performance in birds is clearly superior to cats and gerbils, and comparable to naive human performance.

The decay of pitch memory during rehearsal.

The present study investigates the decay of pitch memory over time. In a delayed pitch comparison paradigm, participants had to memorize the pitch of a Shepard tone, with silent, overt, or without any rehearsal. During overt rehearsal, recordings of the rehearsing were effectuated. Performance was best for silent rehearsal and worst for overt rehearsal. The differences, although partially significant, were not marked. The voice pitch during overt rehearsal was compatible with a random walk model, providing a possible explanation of why rehearsal does not improve the retention of the pitch trace.

More Is not Always Better: The Differentiated Influence of Empathy on Different Magnitudes of Creativity.

Recently, researchers have argued about the importance of social aspects in creativity. Based on these arguments, one could hypothesize that if creativity is indeed about social aspects, then a social ability, such as empathy, will be relevant for creativity as an "interface" allowing the person to connect with others. A thorough review of the literature suggests that the association between empathic abilities and creativity may not be as straightforward as this hypothesis and also two recent empirical studies have suggested. This could be attributed to the fact that creativity may involve quite different levels such as creative achievement or everyday creativity. We suggest that social interaction, and with it empathy, plays a larger role in creative achievement than in everyday creative activities. Furthermore, we argue that too much empathy hinders everyday creativity. To explore the impact of empathy on different magnitudes of creativity, we applied two different self-report measures of creativity: creative achievement was measured by the Creative Achievement Questionnaire, while everyday creative activity was measured by the Creative Behavior Inventory. We used the Interpersonal Reactivity Index to measure empathy. Empathy had a positive correlation to achievement, but an inverted-U relationship to everyday creativity. We conclude that more connectedness is not always better for creativity. Therefore, the relevance of social aspects for creativity should not be generalized, but may depend on the magnitude of creativity considered.

It's all about gains: Risk preferences in problem gambling.

Problem gambling is a serious socioeconomic problem involving high individual and social costs. In this article, we study risk preferences of problem gamblers including their risk attitudes in the gain and loss domains, their weighting of probabilities, and their degree of loss aversion. Our findings indicate that problem gamblers are systematically more risk taking and less sensitive toward changes in probabilities in the gain domain only. Neither their risk attitudes in the loss domain nor their degree of loss aversion are significantly different from the controls. Additional evidence for a similar degree of sensitivity toward negative outcomes is gained from skin conductance data-a psychophysiological marker for emotional arousal-in a threat-of-shock task. (PsycINFO Database Record

Sensitivity towards fear of electric shock in passive threat situations.

Human judgment and decision-making (JDM) requires an assessment of different choice options. While traditional theories of choice argue that cognitive processes are the main driver to reach a decision, growing evidence highlights the importance of emotion in decision-making. Following these findings, it appears relevant to understand how individuals asses the attractiveness or riskiness of a situation in terms of emotional processes. The following study aims at a better understanding of the psychophysiological mechanisms underlying threat sensitivity by measuring skin conductance responses (SCRs) in passive threat situations. While previous studies demonstrate the role of magnitude on emotional body reactions preceding an outcome, this study focuses on probability. In order to analyze emotional body reactions preceding negative events with varying probability of occurrence, we have our participants play a two-stage card game. The first stage of the card game reveals the probability of receiving an unpleasant electric shock. The second stage applies the electric shock with the previously announced probability. For the analysis, we focus on the time interval between the first and second stage. We observe a linear relation between SCRs in anticipation of receiving an electric shock and shock probability. This finding indicates that SCRs are able to code the likelihood of negative events. We outline how this coding function of SCRs during the anticipation of negative events might add to an understanding of human JDM.

Auditory sensory memory for random waveforms in the Mongolian gerbil.

Mongolian gerbils (N = 21) were trained to discriminate between continuous and repeated auditory white noise. While for periods up to 40 ms of the repeated noise spectral effects make this a perceptual task, longer periods require auditory sensory memory to solve the task. Short periods (20 ms) could easily be discriminated by naive gerbils (discrimination performance, i.e. hit rate minus false alarm rate >80% after 8 days of training). Discrimination was more difficult for longer periods (100 ms: discrimination performance approximately 50% after 18 days of training). By long-term training (156 days) using an optimized training paradigm two further gerbils learned to discriminate up to a period length of 360 ms but could not proceed at 400 ms. While this falls short of human performance, it demonstrates for the first time sensory memory for random waveforms in animals.

Cats can detect repeated noise stimuli.

We assessed the ability of cats to detect repeated noise (RN), a stimulus generated by seamlessly presenting short segments of white noise in a continuous loop, in a modified go-nogo task. A recent study of the gerbil suggested that animals might have an extremely limited ability to detect RN compared to human subjects. We find that cats can discriminate RN from continuous noise with reasonable accuracy until the period length of the RN sequence reaches 450-500 ms. This is slightly longer than the maximum detectable RN period length found in gerbils, but falls far short of human performance.

The memory of noise.

The memory of auditory random waveforms (i.e., noise) is a special case of auditory memory for sensory information. Five experiments are reported that evaluate the dynamics of this storage system as well as interactions with new input. Periodic waveforms can be discriminated from uncorrelated noise by naive listeners up to a cycle length of 20 s, with the major decline in performance between 5 and 10 s. Even single repetitions of a piece of the waveform can be detected up to a stimulus onset asynchrony (SOA) of 6 s. The capacity of this storage system is limited to a few items of, in total, a few hundred milliseconds length. Within this capacity, however, items do not interfere strongly. These results are compatible with the view that auditory sensory memory is a modality-specific module of short-term memory.

Physiological correlates and emotional specificity of human piloerection.

Piloerection is known as an indicator of strong emotional experiences. However, little is known about the physiological and emotional specificity of this psychophysiological response. In the presented study, piloerection was elicited by audio stimuli taken from music and film episodes. The physiological response accompanying the incidence of piloerection was recorded with respect to electrodermal, cardiovascular and respiratory measures and compared to a matched control condition. The employment of an optical recording system allowed for a direct and objective assessment of visible piloerection. The occurrence of piloerection was primarily accompanied by an increase of phasic electrodermal activity and increased respiration depth as compared to a matched control condition. This physiological response pattern is discussed in the context of dominant theories of human piloerection. Consideration of all available evidence suggests that emotional piloerection represents a valuable indicator of the state of being moved or touched.

Increased activation of the human cerebellum during pitch discrimination: a positron emission tomography (PET) study.

Recent years have seen a growing debate concerning the function of the cerebellum. Here we used a pitch discrimination task and PET to test for cerebellar involvement in the active control of sensory data acquisition. Specifically, we predicted greater cerebellar activity during active pitch discrimination compared to passive listening, with the greatest activity when pitch discrimination was most difficult. Ten healthy subjects were trained to discriminate deviant tones presented with a slightly higher pitch than a standard tone, using a Go/No Go paradigm. To ensure that discrimination performance was matched across subjects, individual psychometric curves were assessed beforehand using a two-step psychoacoustic procedure. Subjects were scanned while resting in the absence of any sounds, while passively listening to standard tones, and while detecting deviant tones slightly higher in pitch among these standard tones at four different performance levels. Consistent with our predictions, 1) passive listening alone elicited cerebellar activity (lobule IX), 2) cerebellar activity increased during pitch discrimination as compared to passive listening (crus I and II, lobules VI, VIIB, and VIIIB), and 3) this increase was correlated with the difficulty of the discrimination task (lobules V, VI, and IX). These results complement recent findings showing pitch discrimination deficits in cerebellar patients (Parsons et al., 2009) and further support a role for the cerebellum in sensory data acquisition. The data are discussed in the light of anatomical and physiological evidence functionally connecting auditory system and cerebellum.

A continuous measure of phasic electrodermal activity.

Electrodermal activity is characterized by the superposition of what appear to be single distinct skin conductance responses (SCRs). Classic trough-to-peak analysis of these responses is impeded by their apparent superposition. A deconvolution approach is proposed, which separates SC data into continuous signals of tonic and phasic activity. The resulting phasic activity shows a zero baseline, and overlapping SCRs are represented by predominantly distinct, compact impulses showing an average duration of less than 2 s. A time integration of the continuous measure of phasic activity is proposed as a straightforward indicator of event-related sympathetic activity. The quality and benefit of the proposed measure is demonstrated in an experiment with short interstimulus intervals as well as by means of a simulation study. The advances compared to previous decomposition methods are discussed.

Decomposition of skin conductance data by means of nonnegative deconvolution.

Skin conductance (SC) data are usually characterized by a sequence of overlapping phasic skin conductance responses (SCRs) overlying a tonic component. The variability of SCR shapes hereby complicates the proper decomposition of SC data. A method is proposed for full decomposition of SC data into tonic and phasic components. A two-compartment diffusion model was found to adequately describe a standard SCR shape based on the process of sweat diffusion. Nonnegative deconvolution is used to decompose SC data into discrete compact responses and at the same time assess deviations from the standard SCR shape, which could be ascribed to the additional process of pore opening. Based on the result of single non-overlapped SCRs, response parameters can be estimated precisely as shown in a paradigm with varying inter-stimulus intervals.

Objective and continuous measurement of piloerection.

Increasing attention is drawn to the investigation of piloerection (or goose bumps) in response to strong emotional experiences. This research is complicated by the need to rely on self-report measures. This article proposes an efficient method for the objective and continuous measurement of piloerection. It is based on an optical recording device combined with a discrete Fourier transform analysis quantifying the frequency power related to visible piloerection. The validity of the method was demonstrated in a proof-of-principle experiment involving a person with the exceptional ability to control the erection of his hair. The method reliably mapped all occurrences of visible piloerection and provided insight into the temporal dynamics of the underlying physiological process. It thus proved suitable for future experimental investigation of human piloerection.