Consciousness and the brainstem

In the first part of this article we summarize a theoretical framework and a set of hypotheses aimed at accounting for consciousness in neurobiological terms. The basic form of consciousness, core consciousness is placed in the context of life regulation; it is seen as yet another level of biological processing aimed at ensuring the homeostatic balance of a living organism; and the representation of the current organism state within somato-sensing structures is seen as critical to its development. Core consciousness is conceived as the imaged relationship of the interaction between an object and the changed organism state it causes. In the second part of the article we discuss the functional neuroanatomy of nuclei in the brainstem reticular formation because they constitute the basic set of somato-sensing structures necessary for core consciousness and its core self to emerge. The close relationship between the mechanisms underlying cortical activation and the bioregulatory mechanisms outlined here is entirely compatible with the classical idea that the reticular formation modulates the electrophysiological activity of the cerebral cortex. However, in the perspective presented here, that modulation is placed in the setting of the organism's homeostatic regulation.     

What is a visual object? Evidence from target merging in multiple object tracking

The notion that visual attention can operate over visual objects in addition to spatial locations has recently received much empirical support, but there has been relatively little empirical consideration of what can count as an 'object' in the first place. We have investigated this question in the context of the multiple object tracking paradigm, in which subjects must track a number of independently and unpredictably moving identical items in a field of identical distractors. What types of feature clusters can be tracked in this manner? In other words, what counts as an 'object' in this task? We investigated this question with a technique we call target merging: we alter tracking displays so that distinct target and distractor locations appear perceptually to be parts of the same object by merging pairs of items (one target with one distractor) in various ways - for example, by connecting item locations with a simple line segment, by drawing the convex hull of the two items, and so forth. The data show that target merging makes the tracking task far more difficult to varying degrees depending on exactly how the items are merged. The effect is perceptually salient, involving in some conditions a total destruction of subjects' capacity to track multiple items. These studies provide strong evidence for the object-based nature of tracking, confirming that in some contexts attention must be allocated to objects rather than arbitrary collections of features. In addition, the results begin to reveal the types of spatially organized scene components that can be independently attended as a function of properties such as connectedness, part structure, and other types of perceptual grouping.     

How much observational data is enough? An empirical test using marital interaction coding

Using three different samples of couples (clinic, nondistressed community, and engaged), we found that 15 minutes was sufficient to witness enough behavior to make reliable (i.e., internally consistent) estimations of most Rapid Marital Interaction Coding System (Heyman & Vivian, 1993) code frequencies. Ten minutes is sufficient for many codes of interest. The ease in which "how much time is necessary" calculations can be made should entice behavioral investigators from a variety of content areas to publish such figures. By empirically investigating a factor that in most fields becomes reified through convention, investigators can conduct observational research that is both maximally efficient and maximally scientifically defensible.     

Long-term, non-specific spinal pain: reliable and valid subgroups of patients

The aim of this study was to identify reliable and valid subgroups of spinal pain patients, using data from the Swedish version of the Multidimensional Pain Inventory (MPI-S). A second aim was to test the generalisability of the three patient profiles described in earlier studies on the MPI ("adaptive coper", "dysfunctional" and "interpersonally distressed" patients). The study base consisted of two samples of individuals suffering from long-term, non-specific spinal pain and the results were validated across these samples. Cluster analysis was used to detect distinct groups of patients and the validity of these subgroups was evaluated on variables not used to generate the cluster solution. One subgroup was characterised by lower pain severity, lower interference with everyday activities, lower affective distress and higher life control than the other two subgroups. This patient profile was similar to the MPI adaptive coper patients. A second subgroup resembled the dysfunctional patient profile, thus displaying a worse adjustment to chronic pain than the AC patients. The third patient group reported significantly lower levels of social support from "significant others" than the other subgroups. This patient profile was similar to that of the interpersonally distressed patient group. Taken together, the results support the reliability, validity and generalisability of three subgroups of chronic pain patients derived from the MPI-S.     

Bulimics' responses to food cravings: is binge-eating a product of hunger or emotional state?

This study examined the roles of hunger, food craving and mood in the binge-eating episodes of bulimic patients, and identified the critical factors involved in the processes surrounding binge-eating episodes that follow cravings. This was a prospective study of the binge-eating behaviour of 15 women with bulimia nervosa. The participants used food intake diaries and Craving Records to self-monitor their nutritional behaviour, hunger levels and affective state. Cravings leading to a binge were associated with higher tension, lower mood and lower hunger than those cravings not leading to a binge. Levels of tension and hunger were the critical discriminating variables. The findings of the study support empirical evidence and models of emotional blocking in binge-eating behaviour and challenge the current cognitive starve-binge models of bulimia. The role of food cravings in the emotional blocking model is discussed in terms of a classically conditioned motivational state. Implications for treatment are addressed.     

Does visual word identification involve a sub-phonemic level?

The phonological codes activated in visual word recognition can be thought of minimally as strings of discrete and unstructured phoneme-like units. We asked whether these codes might additionally express a letter string's phonological form at a featural or gestural level. Specifically, we asked whether the priming of a word (e.g. sea, film, basic) by a rhyming non-word would depend on the non-word's phonemic-feature similarity to the word. The question was asked within a mask--prime--target--mask sequence with both brief (57 ms in Experiments 1 and 2) and long (486 ms in Experiment 1) prime durations. Non-word primes that differed from their targets by a single phonemic feature (initial voicing as in ZEA, VILM, PASIC) led to faster target lexical decisions than non-word primes that differed by more than a single phonemic feature (e.g. VEA, JILM, SASIC). Visual word recognition seems to involve a sub-phonemic level of processing.     

Children's avoidance of lexical overlap: a pragmatic account

Children tend to choose an unfamiliar object rather than a familiar one when asked to find the referent of a novel name. This response has been taken as evidence for the operation of certain lexical constraints in children's inferences of word meanings. The present studies test an alternative--pragmatic--explanation of this phenomenon among 3-year-olds. In Study 1 children responded to a request for the referent of a novel label in the same way that they responded to a request for the referent of a novel fact. Study 2 intimated that children assume that labels are common knowledge among members of the same language community. Study 3 demonstrated that shared knowledge between a speaker and listener plays a decisive role in how children interpret a speaker's request. The findings suggest that 3-year-olds' avoidance of lexical overlap is not unique to naming and may derive from children's sensitivity to speakers' communicative intentions.