41 research outputs found
Memory and DTF
No full textAnalysis of functional connectivity between hippocampus and neocortex in control and Alzheimer's disease mice APP/PS1 in the context of spatial memory consolidation using Directed Transfer Function.</p
Epaxial and Limb Muscle Activity During Swimming and Terrestrial Stepping in the Adult Newt,<i>Pleurodeles waltl</i>
No full textDelvolvé, Isabelle, Tiaza Bem, and Jean-Marie Cabelguen. Epaxial and limb muscle activity during swimming and terrestrial stepping in the adult newt, Pleurodeles waltl. J. Neurophysiol. 78: 638–650, 1997. We have investigated the patterns of activation of epaxial musculature during both swimming and overground stepping in an adult newt ( Pleurodeles waltl) with the use of electromyographic (EMG) recordings from different sites of the myomeric muscle dorsalis trunci along the body axis. The locomotor patterns of some limb muscles have also been investigated. During swimming, the epaxial myomeres are rhythmically active, with a strict alternation between opposite myomeres located at the same longitudinal site. The pattern of intersegmental coordination consists of three successively initiated waves of EMG activity passing posteriorly along the anterior trunk, the midtrunk, and the posterior trunk, respectively. Swimming is also characterized by a tonic activation of forelimb (dorsalis scapulae and extensor ulnae) and hindlimb (puboischiotibialis and puboischiofemoralis internus) muscles and a rhythmic activation of muscles (latissimus dorsi and caudofemoralis) acting both on limb and body axis. The latter matched the activation pattern of epaxial myomeres at the similar vertebral level. During overground stepping, the midtrunk myomeres express single synchronous bursts whereas the myomeres of the anterior trunk and those of the posterior trunk display a double bursting pattern in the form of two waves of EMG activity propagating in opposite directions. During overground stepping, the limb muscles and muscles acting on both limb and body axis were found to be rhythmically active and usually displayed a double bursting pattern. The main conclusion of this investigation is that the patterns of intersegmental coordination during both swimming and overground stepping in the adult newt are related to the presence of limbs and that they can be considered as hybrid lampreylike patterns. Thus it is hypothesized that, in newt, a chain of coupled segmental oscillatory networks, similar to that which constitutes the central pattern generator (CPG) for swimming in the lamprey, can account for both trunk motor patterns if it is influenced by limb CPGs in a way depending on the locomotor mode. During swimming, the segmental networks located close to the girdles receive extra tonic excitation coming from the limb CPGs, whereas during stepping, the axial CPGs are entrained to some extent by the limb oscillators.</jats:p
Supplementary materials to "Do altruists like equity?“
No full textSupplementary materials to "Bem, T., Pokarowski, P., & Meyrand, P. (2019). Do altruists like equity? Social Psychological Bulletin, 14(1), Article e28284. https://doi.org/10.32872/spb.v14i1.282841. Dataset (occurences and timing) [PDF]; 2. Instructions for participants [PDF]notReviewedpublishedVersio
Neuro-economics in chicks: Foraging choices based on amount, delay and cost
No full textStudies on the foraging choices are reviewed, with an emphasis on the neural representations of elementary factors of food (i.e., amount, delay and consumption time) in the avian brain. Domestic chicks serve as an ideal animal model in this respect, as they quickly associate cue colors with subsequently supplied food rewards, and their choices are quantitatively linked with the rewards. When a pair of such color cues was simultaneously presented, the trained chicks reliably made choices according to the profitability of food associated with each color. Two forebrain regions are involved in distinct aspects of choices; i.e., nucleus accumbens–medial striatum (Ac-MSt) and arcopallium intermedium (AI), an association area in the lateral forebrain. Localized lesions of Ac-MSt enhanced delay aversion, and the ablated chicks made impulsive choices of immediate reward more frequently than sham controls. On the other hand, lesions of AI enhanced consumption-time aversion, and the ablated chicks shifted their choices toward easily consumable reward with their impulsiveness unchanged; delay and consumption time are thus doubly dissociated. Furthermore, chicks showed distinct patterns of risk-sensitive choices depending on the factor that varied at trials. Risk aversion occurred when food amount varied, whereas consistent risk sensitivity was not found when the delay varied; amount and delay were not interchangeable. Choices are thus deviated from those predicted as optima. Instead, factors such as amount, delay and consumption time could be separately represented and processed to yield economically sub-optimal choices
Characterisation of Multiple Patterns of Activity in Networks of Relaxation Oscillators with Inhibitory and Electrical Coupling
No full textShort Duty Cycle Destabilizes a Half-Center Oscillator, But Gap Junctions Can Restabilize the Anti-Phase Pattern
No full textDo Altruists Like Equity?
No full textAltruism and inequity aversion are often conceptually interrelated, which implies that altruistic and selfish humans may respond differently to disadvantageous inequity conditions. However, a correlation between altruism and inequity responses has thus far not been directly tested experimentally. We have addressed this question using an experimental paradigm inspired by animal experiments in which adult humans work for real food rewards. We have studied whether subjects' responses to different reward distributions were altered by being exposed to equitable or non-equitable situations. In the control conditions, subjects expressed either a strong altruistic attitude, choosing to work for their partner's welfare in the majority of trials, or mostly rejected this course of action. These purely altruistic and selfish behaviors were also expressed after being exposed to disadvantageous inequity, but priming with equitable conditions significantly reduced their occurrence. This implies an important role of inequity pressure, which is presumably present in modern society, in shaping human-helping attitudes
Variety of alternative stable phase-locking in networks of electrically coupled relaxation oscillators.
No full textWe studied the dynamics of a large-scale model network comprised of oscillating electrically coupled neurons. Cells are modeled as relaxation oscillators with short duty cycle, so they can be considered either as models of pacemaker cells, spiking cells with fast regenerative and slow recovery variables or firing rate models of excitatory cells with synaptic depression or cellular adaptation. It was already shown that electrically coupled relaxation oscillators exhibit not only synchrony but also anti-phase behavior if electrical coupling is weak. We show that a much wider spectrum of spatiotemporal patterns of activity can emerge in a network of electrically coupled cells as a result of switching from synchrony, produced by short external signals of different spatial profiles. The variety of patterns increases with decreasing rate of neuronal firing (or duty cycle) and with decreasing strength of electrical coupling. We study also the effect of network topology--from all-to-all--to pure ring connectivity, where only the closest neighbors are coupled. We show that the ring topology promotes anti-phase behavior as compared to all-to-all coupling. It also gives rise to a hierarchical organization of activity: during each of the main phases of a given pattern cells fire in a particular sequence determined by the local connectivity. We have analyzed the behavior of the network using geometric phase plane methods and we give heuristic explanations of our findings. Our results show that complex spatiotemporal activity patterns can emerge due to the action of stochastic or sensory stimuli in neural networks without chemical synapses, where each cell is equally coupled to others via gap junctions. This suggests that in developing nervous systems where only electrical coupling is present such a mechanism can lead to the establishment of proto-networks generating premature multiphase oscillations whereas the subsequent emergence of chemical synapses would later stabilize generated patterns
Occurrences of asymmetrical 2-phase patterns as a function of electrical conductance and group size ratio.
No full text<p>Domains of stability of asymmetrical 2-phase behaviors in fully coupled (A) and N<sup>cc</sup>2 networks (B) for different levels of noise are shown. Whereas in fully coupled network almost all asymmetrical network divisions are equally stable (A) the ring connectivity strongly promotes symmetrical patterns (B). Parameters: N = 24.</p
Position of a critical deflection of a trajectory as a function of number of phases in the pattern.
No full text<p>A. Phase plane evolution of cells expressing the 3-phase activity pattern. Shown are the cells trajectory (solid grey curve) and cells nullcline (solid black curve). During the active phase of one group of cells (black disc) two other groups (light grey and dark grey circles) evolve at a different distance to the knee (DTK) of the nullcline. A deflection closer to the knee is critical for stability of the pattern. From here cells (dark grey circle) will jump up below the knee and cease the solution if a slight increasing of g<sup>el</sup> (Δg<sup>el</sup> = 0.001) shifts the nullcline up. Note that for cells evolving at the upper deflection much larger increment of g<sub>el</sub> would be necessary to produce a jump. B. A distance Δg<sup>el</sup> from the given point in (g<sup>el</sup>, N<sup>cc</sup>) space to a value of g<sup>el</sup> where a transition to synchrony occurs, is plotted against DTK for 2, 3 and 4-phase solutions. For each of N<sup>cc</sup> = 2, 10, 23 in the 2 and 3-phase solution (see crosses, open circles, full circles, respectively, B1-2) and for N<sup>cc</sup> = 2, 6, 10 in the 4-phase solution (see crosses, diamonds and open circles, respectively, B3) 3 values of g<sup>el</sup> were chosen: very small (g<sup>el</sup> = 0.01), close to the value for which a transition to IP occurs and an intermediate value of g<sup>el</sup>. Note that a range of g<sup>el</sup>, in which a given solution exists, diminishes with increasing number of phases and so does the range of DTK (cf. B1–B3). Only robustness of the 2-phase solution (AP) is dependent on the connectivity pattern (cf. B1 with B2-3). Parameters: N = 24. Phase plane coordinates: <i>V</i> (abscissa), <i>W</i> (ordinate).</p
