Biomedical subjects

R Hans Phaf

Publications and source records attributed to R Hans Phaf.

7 recordsLinked to original sources

PubMed2005

Neurophysiological correlates of increased verbal working memory in high-dissociative participants: a functional MRI study.

BACKGROUND: Dissociation, defined as a disruption in usually integrated mental functions, is found not only in DSM-IV dissociative disorders, but also in post-traumatic stress disorder and eating disorders. Dissociative phenomena are also common in the general population, and may reflect a constitutionally determined cognitive style rather than a pathological trait acquired through experiencing adverse life events. In pathological dissociation, evidence has been presented for episodic memory dysfunction. In contrast, in high-dissociative subjects increased performance has been found for episodic memory and dual task performance. These findings have been linked to changes in working memory capacity. METHOD: In the present study, the authors sought to extend these findings by using functional magnetic resonance imaging during performance of two parametric working memory tasks. We tested 21 healthy low- and high-dissociative participants. RESULTS: High-dissociative participants performed slightly better during both tasks. Imaging data showed that both groups activated similar networks for both tasks, i.e. (bilateral) dorsolateral (DL) and ventrolateral prefrontal cortex (PFC), parietal cortex, and supplementary motor area. Group x task interactions were found in the high-dissociative group in L DLPFC and L parietal cortex; in the low-dissociative group in R fusiform gyrus. The differences in the high-dissociative group were independent from performance differences, implying that high-dissociative subjects generally recruit this network to a greater extent. CONCLUSIONS: These results confirm earlier findings using a verbal WM task in high-dissociative participants, and are compatible with the conceptualization of non-pathological dissociation as an information-processing style, characterized by distinct attentional and mnemonic abilities.

Adult↗

PubMed2004

Dissociative style and individual differences in verbal working memory span.

Dissociative style is mostly studied as a risk factor for dissociative pathology, but it may also reflect a fundamental characteristic of healthy information processing. Due to the close link between attention and working memory and the previous finding of enhanced attentional abilities with a high dissociative style, a positive relationship was also expected between dissociative style and verbal working memory span. In a sample of 119 psychology students, it was found that the verbal span of the high-dissociative group was about half a word larger than of the medium and low-dissociative groups. It is suggested that dissociative style may be one of only very few individual differences that is directly relevant to consciousness research.

Adolescent↗

PubMed2004

Automatic affective evaluation does not automatically predispose for arm flexion and extension.

Affect may have the function of preparing organisms for action, enabling approach and avoidance behavior. M. Chen and J. A. Bargh (1999) suggested that affective processing automatically resulted in action tendencies for arm flexion and extension. The crucial question is, however, whether automaticity of evaluation was actually achieved or whether their results were due to nonautomatic, conscious processing. When faces with emotional expressions were evaluated consciously, similar effects were obtained as in the M. Chen and J. A. Bargh study. When conscious evaluation was reduced, however, no action tendencies were observed, whereas affective processing of the faces was still evident from affective priming effects. The results suggest that tendencies for arm flexion and extension are not automatic consequences of automatic affective information processing.

Adult↗

PubMed2004

Loading working memory enhances affective priming.

Stronger affective priming (Murphy & Zajonc, 1993) with suboptimal (i.e., reduced consciousness) than with optimal (i.e., full consciousness) prime presentation suggests that nonconscious processes form an important part of emotions. Merikle and Joordens (1997) have argued that both impoverished presentation and divided attention can produce suboptimal conditions and result in parallel effects. We manipulated attention by means of a concurrent working memory load while keeping presentation duration constant, as participants evaluated Japanese ideographs that were preceded by happy, neutral, or angry faces (affective priming) and male or female faces (nonaffective priming). In contrast to nonaffective priming, affective priming was larger with divided attention than with focused attention. It is concluded that manipulations of stimulus quality and of attention can both be used to probe the distinction between conscious and nonconscious processes and that the highest chances of obtaining the pattern of stronger priming with suboptimal presentation than with optimal presentation occur in the affective domain.

Affect↗

PubMed2003

A computational study into the evolution of dual-route dynamics for affective processing.

The evolutionary justification by LeDoux (1996) for his dual-route model of fear processing was analyzed computationally by applying genetic algorithms to artificial neural networks. The evolution was simulated of a neural network controlling an agent that gathered food in an artificial world and that was occasionally menaced by a predator. Connections could not change in the agent's "lifetime," so there was no learning in the simulations. Only if the smells of food and predator were hard to distinguish and the fitness reflected time pressures in escaping from the predator did the type of dual processing postulated by LeDoux emerge in the surviving agents. Processing in the "quick and dirty" pathway of the fear system ensured avoidance of both predators and food, but a distinction between food and predator was made only in the long pathway. Elaborate processing inhibited the avoidance reaction and reversed it into an approach reaction to food, but strengthened the avoidance reaction to predators (and more finely tuned the direction of escape). It is suggested that "computational neuroethology" (Beer, 1990) may help constrain reasoning in evolutionary psychology, particularly when applied to specific neurobiological models, and in the future may even generate new hypotheses for cognitive neuroscience.

Adaptation, Biological↗

PubMed2003

Attention as a characteristic of nonclinical dissociation: an event-related potential study.

Individual differences in dissociative style (which is generally considered a risk factor for dissociative pathology) were studied in a nonclinical sample. It was hypothesized that high-dissociative participants would show enhanced attentional abilities toward both relevant and irrelevant stimulus features. In the experiment, threatening and affectively neutral words were classified on their affective valence and the presence of the letter A. To facilitate the full deployment of dissociative abilities, a feature (i.e., negative valence) was included that would automatically attract attention but not interfere with the processing of the central feature. Both the behavioral measures (i.e., reaction time) and the central neural measures (i.e., event-related potentials) showed that the ability to direct attention to the central feature was enhanced in the high dissociators. The high dissociators, moreover, showed evidence of directing attention to both affective valence and the letter A in the letter detection task. It is concluded that dissociative style does not correspond to a damaged or disturbed function but to an enhanced ability to direct and divide attention.

Adult↗

PubMed2003

Directed forgetting between, but not within, dissociative personality states.

To investigate amnesia between identities in dissociative identity disorder (DID), the authors assessed explicit and implicit memory performance on a directed-forgetting task in 12 DID patients who switched from one state to an "amnesic" state between presentation and memory testing. DID patients were instructed either to remember or to forget neutral and emotional words. Besides an overall decrease in explicit memory, patients demonstrated selective forgetting of to-be-forgotten, but not of to-be-remembered words in the amnesic state. Patients did not exhibit any directed forgetting within the same state. Implicit memory was fully preserved across states. Independent of state, patients recalled more emotional than neutral information. These results may extend the conceptualization of memory processes in DID, suggesting an important role for retrieval inhibition.

Adult↗