Modality-specific effects in inhibitory mechanisms: the interaction of peripheral and central components in working memory

Working memory is a complex system assumed to encompass both storage and processing components. At the same time, several authors have suggested the existence of separate peripheral modality-specific subsystems, in particular a verbal and a visuo-spatial mechanism. In the present research, we explored the hypothesis that modality-specific mechanisms may also operate in the central processing component. Inhibitory control has traditionally been considered as a typical function of the central executive, devoted to selecting, processing, and eliminating irrelevant information. We designed verbal and visuo-spatial tasks involving similar procedures and comparable levels of inhibitory control. Results indicate that accuracy profiles are similar in the two conditions; however, the patterns of data measuring inhibitory control, i.e., percentage of intrusion errors, are opposite in the case of verbal (intrusions decreased in more complex trials) and visuo-spatial (intrusions increased in more complex trials) material. These data are consistent with theoretical models of working memory suggesting that modality-specific effects emerge even in central processes and that both material-dependent and process-dependent features must be considered in working memory tasks.     

Antigravity hills are visual illusions

Antigravity hills, also known as spook hills or magnetic hills, are natural places where cars put into neutral are seen to move uphill on a slightly sloping road, apparently defying the law of gravity. We show that these effects, popularly attributed to gravitational anomalies, are in fact visual illusions. We re-created all the known types of antigravity spots in our laboratory using tabletop models; the number of visible stretches of road, their slant, and the height of the visible horizon were systematically varied in four experiments. We conclude that antigravity-hill effects follow from a misperception of the eye level relative to gravity, caused by the presence of either contextual inclines or a false horizon line.     

Psychiatric chrono‐epidemiology: its relevance for the study of aggression

Chrono‐epidemiology is the study of the distribution of health events according to time. The time intervals taken into account have cyclic patterns and include circadian, weekly, seasonal, and circannual rhythms. In the behavioural field, chrono‐epidemiology can be and has been applied to studies concerning the causes of death (suicide and homicide), clinical events such as admissions to and contacts with mental healthcare services, and the seasonal distribution of crime involving the use of violence. Frequently reported findings include clear circadian and seasonal rhythms present in the phenomenon of suicide (rhythms more evident in the case of violent suicide); seasonal rhythms in the expression of aggression by patients hospitalised for mental illness; and a circannual recurrence of crimes with a violent component. The intrinsic circadian and seasonal rhythms of some neuronal systems, particularly those of serotonin, involved in the control of mood and impulses, are thought to favour the behavioural rhythms observed, although the contribution of socio‐environmental factors, such as the fluctuation of supportive networks according to time, is also acknowledged. By demonstrating non‐casual recurrence of certain behaviour and by exploring the socio‐biological basis of the rhythms beneath these recurrences, chrono‐epidemiology may offer important etiologic and preventive clues to the understanding of the biological and environmental correlates of aggressive behaviour. Aggr. Behav. 28:477–490, 2002. © 2002 Wiley‐Liss, Inc.     

Zebra finches and Dutch adults exhibit the same cue weighting bias in vowel perception

Vocal tract resonances, called formants, are the most important parameters in human speech production and perception. They encode linguistic meaning and have been shown to be perceived by a wide range of species. Songbirds are also sensitive to different formant patterns in human speech. They can categorize words differing only in their vowels based on the formant patterns independent of speaker identity in a way comparable to humans. These results indicate that speech perception mechanisms are more similar between songbirds and humans than realized before. One of the major questions regarding formant perception concerns the weighting of different formants in the speech signal (“acoustic cue weighting”) and whether this process is unique to humans. Using an operant Go/NoGo design, we trained zebra finches to discriminate syllables, whose vowels differed in their first three formants. When subsequently tested with novel vowels, similar in either their first formant or their second and third formants to the familiar vowels, similarity in the higher formants was weighted much more strongly than similarity in the lower formant. Thus, zebra finches indeed exhibit a cue weighting bias. Interestingly, we also found that Dutch speakers when tested with the same paradigm exhibit the same cue weighting bias. This, together with earlier findings, supports the hypothesis that human speech evolution might have exploited general properties of the vertebrate auditory system.     

Some reflections on the unique time of Nachträglichkeit in theory and clinical practice

Of the various forms that the matter of time assumes in analysis, Nachträglichkeit represents Freud’s first intuition on the subject. The focus of this article is directed toward the specific temporal dimension that the concept of Nachträglichkeit expresses, and how that dimension, which overturns linear time, is expressed in clinical work. The concept of Nachträglichkeit is approached from a theoretical point of view, tracing back the role and development that this notion has had in psychoanalytic Freudian and post‐Freudian thinking. The goal of this article is to demonstrate how Nachträglichkeit represents the unique temporal movement of the analytic session and the characteristic positioning of the mind of the analyst at work. Three clinical examples are presented. The analytic scene is formulated as occurring in two times, and through the working through that takes place, patients can recover the enigmatic ‘remainder’, which is consequently traumatic and which has compulsively accompanied them through the various times of their existence. Nachträglichkeit, as a non‐linear temporality, introduces a unique dimension into the clinical work that influences listening to and interpretation of the material. The recognition of that (trauma, infantile sexuality, non‐linear temporality) has consequences for the analyst’s way of working in session and on the interpretation of clinical material, as I will try to show through my theoretical exposition and clinical examples.     

Gaze direction and facial expressions exert combined but different effects on attentional resources

Gaze direction and facial expressions are critical components of face processing and have been shown to influence attention deployment. We investigated whether gaze direction (direct vs. averted) combined with a neutral or angry expression modulates the deployment of attentional resources over time. In a Rapid Serial Visual Presentation (RSVP) paradigm participants had to decide the gender of a neutral or an angry target face with direct or averted gaze (T1) and then to judge the orientation of a target picture of a landscape (T2), following the face at different time intervals. Results showed no attentional blink effect (i.e., no deterioration in T2 accuracy) when T1 was an angry face with direct gaze, whereas it was present for angry faces with averted gaze or neutral faces with either averted or direct gaze. These findings are consistent with appraisal theories and are discussed against the background of automatic processing of threat stimuli.     

Low diversity and low frequency of participation in leisure activities compromise working memory efficiency in young adults

People perform leisure activities (LA) every day; pursuits that entail applying cognitive, physical and social abilities. As in old age, doing LA during early and middle adulthood is related to a reduced risk of dementias, probably by generating a cognitive reserve. As it is possible that a relation between doing LA and working memory (WM) efficiency exists in young adults, we assessed whether the diversity and frequency of LA are related to WM efficiency in this population. Ninety-three healthy young subjects solved the n-back task at two levels of difficulty (2, 3), and answered an LA questionnaire on the activities in which they had participated in the month prior to the experiment. Subjects were classified separately on their scores for (1) diversity (high/low) and (2) frequency (high/low) in order to test the relation between each variable and WM efficiency. Though no differences were found, a subsequent analysis of the average of diversity and frequency ratios of LA performance taken together-the diversity/frequency index-showed that low diversity plus low frequency was significantly associated with reduced WM efficiency at this age; results that suggest that frequent participation in diverse LA during youth is related to WM efficiency.     

Unique sudden onsets capture attention even when observers are in feature-search mode

Two sources of attentional capture have been proposed: stimulus-driven (exogenous) and goal-oriented (endogenous). A resolution between these modes of capture has not been straightforward. Even such a clearly exogenous event as the sudden onset of a stimulus can be said to capture attention endogenously if observers operate in singleton-detection mode rather than feature-search mode. In four experiments we show that a unique sudden onset captures attention even when observers are in feature-search mode. The displays were rapid serial visual presentation (RSVP) streams of differently coloured letters with the target letter defined by a specific colour. Distractors were four #s, one of the target colour, surrounding one of the non-target letters. Capture was substantially reduced when the onset of the distractor array was not unique because it was preceded by other sets of four grey # arrays in the RSVP stream. This provides unambiguous evidence that attention can be captured both exogenously and endogenously within a single task.