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.     

Measures of visuospatial short-term memory: the Knox Cube Imitation Test and the Corsi Blocks Test compared

The present investigation analyzes the characteristics of two tasks that have been considered as a measure of visuospatial abilities: The Knox Cube Imitation Test and the Corsi Blocks Test. The former was originally devised by Knox (1913) to diagnose mental retardation in potential immigrants to the United States, while the latter has been specifically designed to be used in neuropsychological practice by Corsi (1972). Although both tasks have been widely used in the past, there is little empirical research investigating the characteristics of these tasks from a theoretical point of view. In order to do so, we carried out two parallel experiments in which both tasks were presented in a baseline condition as well as in association with three different concurrent tasks (i.e., articulatory suppression, spatial tapping, and random generation) supposed to tap the various components of working memory. Results showed that neither of the tasks can be considered as a pure measure of visuospatial processing and that, at the same time, it is necessary to reconsider the architecture of working memory in order to suggest a more integrated functioning of the system.     

Spatial biases in peripersonal space in sighted and blind individuals revealed by a haptic line bisection paradigm

Our representation of peripersonal space does not always accurately reflect the physical world. An example of this is pseudoneglect, a phenomenon in which neurologically normal individuals bisect to the left of the veridical midpoint, reflecting an overrepresentation of the left portion of space compared with the right one. Consistent biases have also been observed in the vertical and radial planes. It is an open question whether these biases depend on normal visual experience for their occurrence. Here we systematically investigated this issue by testing blindfolded sighted and early blind individuals in a haptic line bisection task. Critically, we found a robust leftward bias in all participants. In the vertical and radial planes, sighted participants showed a consistent downward and proximal bias. Conversely, the directional bias in blind participants was dependent on the final movement direction; thus, there was no general bias in either direction. These findings are discussed in terms of different reference frames adopted by sighted and blind participants when encoding space.     

The Influence of Reduced Visual Acuity on Age-Related Decline in Spatial Working Memory: An Investigation

ABSTRACT

To investigate the relationship between visual acuity and cognitive function with aging, we compared low-vision and normally-sighted young and elderly individuals on a spatial working memory (WM) task. The task required subjects to memorise target locations on different matrices after perceiving them visually or haptically. The haptic modality was included as a control to look at the effect of aging on memory without the confounding effect of visual deficit. Overall, age and visual status did not interact to affect WM accuracy, suggesting that age does not exaggerate the effects of visual deprivation. Young participants performed better than the elderly only when the task required more operational processes (i.e., integration of information). Sighted participants outperformed the visually impaired regardless of testing modality suggesting that the effect of the visual deficit is not confined to only the most peripheral levels of information processing. These findings suggest that vision, being the primary sensory modality, tends to shape the general supramodal mechanisms of memory.     

Interfering with activity in the dorsomedial prefrontal cortex via TMS affects social impressions updating

In our everyday social interactions we often need to deal with others’ unpredictable behaviors. Integrating unexpected information in a consistent representation of another agent is a cognitively demanding process. Several neuroimaging studies point to the medial prefrontal cortex (mPFC) as a critical structure in mediating social evaluations. Our aim here was to shed light on the possible causal role of the mPFC in the dynamic process of forming and updating social impressions about others. We addressed this issue by suppressing activity in the mPFC by means of 1 Hz offline transcranial magnetic stimulation (TMS) prior to a task requiring participants to evaluate other agents’ trustworthiness after reading about their social behavior. In two different experiments, we found that inhibiting activity in the mPFC increased perceived trustworthiness when inconsistent information about one agent’s behavior was provided. In turn, when only negative or positive behaviors of a person were described, TMS over the mPFC did not affect judgments. Our results indicate that the mPFC is causally involved in mediating social impressions updating—at least in cases in which judgment is uncertain due to conflicting information to be processed.     

Remembering the Grocery Shopping List: a Study on Metacognitive Biases

Three experiments examined the influence on memory monitoring and memory control of typicality and frequency of purchase of grocery items. On the basis of normative data, food items were divided into three categories: T+F+ (items typically bought in an Italian food store, and of frequent purchase for university students), T+F− (items typical but not frequently purchased) and T−F− (items low in both characteristics). Experiment 1 revealed that despite an equal recall of the three categories of items, ease of learning judgments were significantly lower for T−F− items. In Experiments 2 and 3, T−F− items were also treated differently than the two other types, when subjects had to decide which items to select for an additional check, and when they had to apportion their study time. Overall, data show that biases independent of the memory state of an item can influence memory monitoring. In addition, the same biases appear to influence the cognitive behaviour, suggesting that monitoring can have an impact on subsequent cognitive behaviour independent of the memorization processes. © 1997 by John Wiley & Sons, Ltd.     

Supramodality effects in visual and haptic spatial processes

In this article, the authors investigated unimodal and cross-modal processes in spatial working memory. A number of locations had to be memorized within visual or haptic matrices according to different experimental conditions known to be critical in accounting for the effects of perception on imagery. Results reveal that some characteristics of the generated mental image remained strictly inherent to the modality in which information was acquired; in general, accuracy was higher when configurations were visually rather than haptically explored (Experiments 1 and 3). Interestingly, the same pattern emerged when the effects of simultaneous versus sequential processing of the stimuli inherent to vision and haptics were isolated from perceptual modality (Experiment 2). Supramodal elements were also identified (Experiment 3) that were specifically associated to the nature of the cognitive processes, regardless of the original characteristics of the sensory information. These data indicate that both unimodal modality-specific and higher order supramodal mechanisms are simultaneously used in spatial processes.     

The effects of age and professional expertise on working memory performance

Differences in professional choice and experience may explain age differences in working memory performance of elderly people. The aim of this study was to examine whether expertise and prolonged practice in verbal and visuo‐spatial abilities reduce age differences in laboratory working memory tasks. The effects of age and expertise on working memory performance were examined in three age groups in two different experiments. Firstly, the role of visuo‐spatial expertise was analysed by examining age differences in architects. Secondly, people with extensive experience in verbal abilities (literary people) were tested in order to evaluate the effect of professional verbal experience. Architects and literary people outperformed a group of unselected age peers on tasks related to professional expertise only, but not on general working memory tests. There was no interaction between age and experience, suggesting that professional experience does not increase differences between experts and non experts and cannot modulate age‐related effects. Copyright © 2008 John Wiley & Sons, Ltd.     

Gender differences in memory for object and word locations

It has been hypothesized that gender differences in visuo-spatial working memory (VSWM) are larger in tasks requiring active elaboration of the material. In the present study we explored this issue by using an object relocation task, with both verbal and visual stimuli. The involvement of active processes was manipulated through the type of transformation required on the stimulus and through the introduction of different kinds of interference. In the three experiments reported, participants were shown either words or cartoon object icons in different locations and had to relocate them in either the same format or in the opposite one (object icons could be transformed into words and vice versa). Males outperformed females in the most demanding conditions, in which object icons and words were presented together in the encoding phase, and both had to be transformed in the recall phase; or when more demanding interferences were used. Our data suggest that the retention strategy was similar for the two groups and that the gender effect is related to a selective female difficulty associated with the increase in active VSWM processing. These findings further support the hypothesized distinction between the passive and active components of VSWM and illustrate the role that this distinction might play in accounting for individual differences.     

Passive and active processes in visuo-spatial memory: double dissociation in developmental learning disabilities

The distinction between passive and active visuo-spatial memory has been useful to interpret various pattern of deficits reported in individual differences studies. However, this interpretation raises the issue of task difficulty, since active tasks could be failed simply because more complex and the corresponding deficit could reflect a reduced capacity of the system. We describe two children with Nonverbal Learning Disability whose performance provides evidence of a dissociation between passive and active memory processes. One of the children showed a selective impairment in passive tasks and performed flawlessly in active tasks, whereas the second child displayed the opposite pattern. These data suggest that a qualitative difference between passive and active processes does exist and that differences in performance do not reflect a lower/higher level of task difficulty. Further, these data underlie the importance of formulating theoretical models of visuo-spatial memory including both material-related (i.e., visual vs spatial) and process-related (i.e., passive vs active) distinctions.