A common neural scale for the subjective pleasantness of different primary rewards.

When an economic decision is taken, it is between goals with different values, and the values must be on the same scale. Here, we used functional MRI to search for a brain region that represents the subjective pleasantness of two different rewards on the same neural scale. We found activity in the ventral prefrontal cortex that correlated with the subjective pleasantness of two fundamentally different rewards, taste in the mouth and warmth on the hand. The evidence came from two different investigations, a between-group comparison of two independent fMRI studies, and from a within-subject study. In the latter, we showed that neural activity in the same voxels in the ventral prefrontal cortex correlated with the subjective pleasantness of the different rewards. Moreover, the slope and intercept for the regression lines describing the relationship between activations and subjective pleasantness were highly similar for the different rewards. We also provide evidence that the activations did not simply represent multisensory integration or the salience of the rewards. The findings demonstrate the existence of a specific region in the human brain where neural activity scales with the subjective pleasantness of qualitatively different primary rewards. This suggests a principle of brain processing of importance in reward valuation and decision-making

Representational capacity of a set of independent neurons

The capacity with which a system of independent neuron-like units represents a given set of stimuli is studied by calculating the mutual information between the stimuli and the neural responses. Both discrete noiseless and continuous noisy neurons are analyzed. In both cases, the information grows monotonically with the number of neurons considered. Under the assumption that neurons are independent, the mutual information rises linearly from zero, and approaches exponentially its maximum value. We find the dependence of the initial slope on the number of stimuli and on the sparseness of the representation.Comment: 19 pages, 6 figures, Phys. Rev. E, vol 63, 11910 - 11924 (2000

Reduced long-range dependence combining Poisson bursts with on--off sources

A workload model using the infinite source Poisson model for bursts is combined with the on--off model for within burst activity. Burst durations and on--off durations are assumed to have heavy-tailed distributions with infinite variance and finite mean. Since the number of bursts is random, one can consider limiting results based on "random centering" of a random sum for the total workload from all sources. Convergence results are shown to depend on the tail indices of both the on--off durations and the lifetimes distributions. Moreover, the results can be separated into cases depending on those tail indices. In one case where all distributions are heavy tailed it is shown that the limiting result is Brownian motion. In another case, convergence to fractional Brownian motion is shown, where the Hurst parameter depends on the heavy-tail indices of the distribution of the on, off and burst durations.Comment: Published in at http://dx.doi.org/10.1214/09-BJPS105 the Brazilian Journal of Probability and Statistics (http://www.imstat.org/bjps/) by the Brazilian Statistical Association/Institute of Mathematical Statistics (http://www.redeabe.org.br/

Experiential Learning as an Adjunct to the Basic Course: Student Responses to a Pedagogical Model

An experiential learning model requiring regular weekly attendance at a communication lab, videotaped classroom presentations, and journal submissions as adjunctive course requirements is described as assessed. A content analysis of lab evaluation forms and journal entries clearly shows that the model works. Students report they enjoy the experience, improve their interpersonal skills, become more sensitive communicators, experience personal growth, and feel they are more successful in classroom presentations as a results of the lab experience

Extending the impulse response in order to reduce errors due to impulse noise and signal fading

A finite impulse response (FIR) digital smearing filter was designed to produce maximum intersymbol interference and maximum extension of the impulse response of the signal in a noiseless binary channel. A matched FIR desmearing filter at the receiver then reduced the intersymbol interference to zero. Signal fades were simulated by means of 100 percent signal blockage in the channel. Smearing and desmearing filters of length 256, 512, and 1024 were used for these simulations. Results indicate that impulse response extension by means of bit smearing appears to be a useful technique for correcting errors due to impulse noise or signal fading in a binary channel

Neural systems underlying decisions about affective odors.

Decision making about affective value may occur after the reward value of a stimulus is represented and may involve different brain areas to those involved in decision-making about the physical properties of stimuli, such as intensity. In an fMRI study, we delivered two odors separated by a delay, with instructions on different trials to decide which odor was more pleasant or more intense or to rate the pleasantness and intensity of the second odor without making a decision. The fMRI signals in the medial pFC area 10 and in regions to which it projects, including the ACC and insula, were higher when decisions were being made compared with ratings, implicating these regions in decision-making. Decision-making about affective value was related to larger signals in the dorsal part of medial area 10 and the agranular insula, whereas decisions about intensity were related to larger activations in the dorsolateral pFC, ventral premotor cortex, and anterior insula. For comparison, the mid-OFC had activations related not to decision making but to subjective pleasantness ratings, providing a continuous representation of affective value. In contrast, areas such as medial area 10 and the ACC are implicated in reaching a decision in which a binary outcome is produced

A theoretical model of neuronal population coding of stimuli with both continuous and discrete dimensions

In a recent study the initial rise of the mutual information between the firing rates of N neurons and a set of p discrete stimuli has been analytically evaluated, under the assumption that neurons fire independently of one another to each stimulus and that each conditional distribution of firing rates is gaussian. Yet real stimuli or behavioural correlates are high-dimensional, with both discrete and continuously varying features.Moreover, the gaussian approximation implies negative firing rates, which is biologically implausible. Here, we generalize the analysis to the case where the stimulus or behavioural correlate has both a discrete and a continuous dimension. In the case of large noise we evaluate the mutual information up to the quadratic approximation as a function of population size. Then we consider a more realistic distribution of firing rates, truncated at zero, and we prove that the resulting correction, with respect to the gaussian firing rates, can be expressed simply as a renormalization of the noise parameter. Finally, we demonstrate the effect of averaging the distribution across the discrete dimension, evaluating the mutual information only with respect to the continuously varying correlate.Comment: 20 pages, 10 figure

Communication Lab Peer Facilitators: What\u27s in It for Them?

Peer tutors have been used extensively within the communication discipline to enhance students\u27 learning experiences (Hill, 1981; Webb & Lane, 1986). Research suggests that peer tutoring can have positive rewards for tutors and tutees (Goodland & Hurst, 1989; Topping, 1996). However, there is little to no research that explores the benefits received by peer tutors who run small group communication lab sessions for basic communication course students. The qualitative data from focus group indicate that peer facilitators experienced: 1) self-development in terms of their self-esteem, confidence, and respect from themselves and others; 2) improved public speaking skills and better interpersonal relationship with family and friends, other peer facilitators, and individuals in positions of authority; and 3) external rewards in that they felt better prepared for post baccalaureate programs and to compete in the workplace. The results of this study may be used as a basis for more in-depth research on the benefits derived from the peer facilitation experience in the basic communication course