The Default Mode Network and Recurrent Depression: A Neurobiological Model of Cognitive Risk Factors

A neurobiological account of cognitive vulnerability for recurrent depression is presented based on recent developments of resting state neural networks. We propose that alterations in the interplay between task positive (TP) and task negative (TN) elements of the Default Mode Network (DMN) act as a neurobiological risk factor for recurrent depression mediated by cognitive mechanisms. In the framework, depression is characterized by an imbalance between TN-TP components leading to an overpowering of TP by TN activity. The TN-TP imbalance is associated with a dysfunctional internally-focused cognitive style as well as a failure to attenuate TN activity in the transition from rest to task. Thus we propose the TN-TP imbalance as overarching neural mechanism involved in crucial cognitive risk factors for recurrent depression, namely rumination, impaired attentional control, and cognitive reactivity. During remission the TN-TP imbalance persists predisposing to vulnerability of recurrent depression. Empirical data to support this model is reviewed. Finally, we specify how this framework can guide future research efforts.     

Temporal discounting of monetary rewards in children and adolescents with ADHD and autism spectrum disorders

It has been difficult to differentiate attention‐deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) in terms of some aspects of their cognitive profile. While both show deficits in executive functions, it has been suggested that they may differ in their response to monetary reward. For instance, children with ADHD prefer small immediate over large delayed rewards more than typically developing controls. One explanation for this is that they discount the value of rewards to a higher degree as they are moved into the future. The current study investigated whether children with ADHD can be differentiated from those with ASD in terms of reward discounting. Thirty‐nine children (8–16 y) with ADHD, 34 children with ASD and 46 typically developing controls performed a hypothetical monetary temporal discounting task. Participants were instructed to make repeated choices between small variable rewards (0, 5, 10, 20, 30€) delivered immediately and large rewards delivered after a variable delay. Children with ADHD but not ASD discounted future rewards at a higher rate than typically developing controls. These data confirm steeper discounting of future rewards in ADHD and add to a small but growing literature showing that the psychological profile of ADHD can be distinguished from that of ASD in terms of disrupted motivational processes.     

Medical ethics in an era of bioethics: Resetting the medical profession’s compass

What it means to be a medical professional has been defined by medical ethicists throughout history and remains a contemporary concern addressed by this paper. A medical professional is generally considered to be one who makes a public promise to fulfill the ethical obligations expressed in the Hippocratic Code. This presentation summarizes the history of medical professionalism and refocuses attention on the interpersonal relationship of doctor and patient. This keynote address was delivered at the Founders of Bioethics International Congress (June, 2010).     

The interruptive effect of pain on attention

Pain is known to disrupt attentional performance in both healthy adults and patients with chronic pain. Exactly which aspects of attentional function are affected are, however, still to be determined. The primary aim of this investigation was to systematically examine the effects of experimentally induced pain on a range of attentional performance tasks. Following a review of tests of attentional disruption, seven best candidate tasks were selected and examined across seven experiments. The tasks were: continuous performance, flanker, endogenous precueing, n-back, inhibition, attentional switching, and divided attention. Healthy adult participants performed each of these tasks under three different conditions: a painful heat sensation, a warm heat sensation, and a nonheat control. Pain differentially affected attentional performance across these tasks; pain-related attentional impairment was found on the n-back, attentional switching, and divided attention tasks, but not on the other tasks. This finding suggests that the aspects of attention most affected by pain are those essential for the completion of complex tasks that require the processing of multiple cues and control over attentional deployment. These results are discussed in the context of an emerging view of pain as a demand for executive control and the development of measures that could be used to examine attentional disruption in the context of pain.     

Utopia and heightened consciousness

Utopia should not be seen as the end‐point of a continuum of material progress, but as a society whose members enjoy a consciousness raised to its highest attainable level of intensity and value. The urge towards heightened consciousness is seen as a primary, pleasure‐driven human impulse, comparable in scope and intensity to the sex drive and perhaps still more fundamental, in that it emanates from the primordial human organ, the brain. The article explores ways in which an ‘inhibition barrier’ at present limiting the intensity of individual and general consciousness and arising from survival‐orientated modes of perception and feeling, might be raised or removed by a specific modification both of basic mental structures governing perception and conceptualization, and of economic structures, enabling a more efficient but non‐competitive mode of generating and distributing wealth. Insights derived from the psychology of art are thus applied more widely to the process of social living, to generate a concept of an attainable Utopia which would redirect human motivation away from ecologically destructive preoccupations.     

Book Reviews

Abstract

The aim of this paper is to identify what I take to be the main conceptual problem in Lewis’ semantics for counterfactuals when the Limit Assumption (LA) is not satisfied, what I call the Discrimination Problem (DP), and to present and discuss a modification of Lewis’ semantics that aims at solving DP. First, I outline Lewis’ semantics, highlighting the aspects that will be relevant for our discussion. Second, I present DP and discuss it with a heuristic example. Third, I present the new proposal and comment some formal consequences and the objections they give rise to. Fourth, I present an allegedly equivalent version of the proposal and discuss the difference between counterfactuals and strict conditionals. Finally, I defend that the two proposals are different and argue for the first one as the best way of capturing two intuitions that seem in conflict when the LA is not satisfied. I conclude with a dilemma: either the proposal here defended works or LA is inescapable. Thus, if the proposal doesn’t work, the paper must then be considered as an indirect defense of the Limit Assumption.     

Information encoding in short firing rate epochs by single neurons in the primate temporal visual cortex

Abstract

The information available about face identity from the firing rate and from temporal encoding in the spike train of single neurons recorded in the temporal lobe visual cortical areas of rhesus macaques was analysed using principal component and information theory analyses of smoothed spike trains. The neurons analysed had responses selective for faces. The stimulus set consisted of 20 different faces. The first principal component provided by a considerable extent the most information (57%) available in principal components 1–5, with the second adding 18%, the third 16%, and the fourth and fifth adding 9%. For each image, the weighting on the first principal component was highly correlated with the mean firing rate of the neuron to that image. The information available from the firing rate of the neuron was very close to that available in the first principal component. Information theory analysis showed that in short epochs (e.g. 50 msec) the information available from the firing rate can be as high, on average, as 65% of that available from the firing rate calculated over 400 msec, and 38% of that available from principal components 1–3 in the 400-msec period. It was also found that 30% of the information calculated from the first three principal components is available in the firing rates calculated over epochs as short as 20 msec. More information was available near the start of the neuronal response, and the information available from short epochs became less later in the neuronal response. Taken together, these analyses provide evidence that a short period of firing taken close to the start of the neuronal response provides a reasonable proportion of the total information that would be available if a long period of neuronal firing (e.g. 400 msec) were utilized to extract it, even if temporal encoding were used. The implications of these and related findings are that at least for rapid object recognition, each cortical stage provides information to the next in a short period of 20–50 msec, does not rely on temporal encoding, and completes sufficient computation to provide an output to the next stage in this same 20- to 50-msec period.     

Multiple repetition priming of faces: Massed and spaced presentations

Previously viewing a face typically leads to a decrease in the amount of time taken to later identify it (“repetition priming”). Five repetition priming experiments are reported, which investigate whether multiple presentations of a face increase the amount of repetition priming. The results demonstrate similar amounts of priming from massed multiple presentations of the same face or a series of different images (freeze frames selected from a moving clip and presented in sequence), compared with a single unchanging presentation (Experiments 1 and 2). This is true even when different images are presented at prime and test (Experiment 3). However when multiple presentations were presented in a spaced fashion, with one or more intervening items between each repeat, there was significantly more priming in the multiple than single presentation condition (Experiment 4). This was true even when the face was named only once in both the multiple and single spaced conditions (Experiment 5). The results are discussed in relation to face motion.     

Digit ratio (2D:4D), academic performance in computer science and computer-related anxiety

Being able to use information communication technology (ICT) effectively has become an essential element of participation within an increasingly digital culture. However, there are differences in participation within this digital culture. Prenatal testosterone exposure is thought to influence the development of numeric capabilities and relate to levels of anxiety, both of which contribute towards engagement with ICT. This study examined whether an index of prenatal exposure to testosterone, digit ratio (2D:4D), is related to successful involvement within a computer-technology context - performance in a Java programming course. Three studies (N = 73,75,65) identified a consistent negative correlation between 2D:4D digit ratio and attainment (r ≈ −0.2). A fourth study (N = 119) found that 2D:4D digit ratio positively correlated with two indices of computer-related anxieties, as well as anxiety sensitivity (r = 0.32/0.51). These results suggest that males and females who have been exposed to higher levels of testosterone within the womb perform better upon academic assessments of Java-related programming ability within computer science education, and have lower levels of computer-related anxieties outside computer science education. Thus, the 2D:4D index of prenatal testosterone exposure correlated with the two factors that directly impact upon ICT engagement, which is increasingly essential to effectively participate within educational and occupational environments.