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.     

Diagnosis and rehabilitation attempt of a patient with acquired deep dyslexia

This study presents a patient (JH) suffering from acquired deep dyslexia. According to a cognitive model of reading, JH exhibited a significant impairment in both the phonological and lexical routes to reading. A rehabilitation program was proposed. We decided to focus on the lexical route using a priming paradigm. The written words were associated with a picture and the patient was invited to construct a mental association between the written word and the image. During five sessions, JH was trained to read 50 words. A pre-test, a post-test, and an 8-month follow-up session consisted of reading 140 written words including the 50 trained words. At the post-test, 90% of the trained words were accurately read. At the follow-up session, JH's reading performance for the trained words was still highly accurate at 84%. This strong effect is discussed and ways of increasing the patient's abilities to read are proposed.     

What you get out of memory depends on the question you ask

Following study, participants received 2 tests. The 1st was a recognition test; the 2nd was designed to tap recollection. The objective was to examine performance on Test 1 conditional on Test 2 performance. In Experiment 1, contrary to process dissociation assumptions, exclusion errors better predicted subsequent recollection than did inclusion errors. In Experiments 2 and 3, with alternate questions posed on Test 2, words having high estimates of recollection with one question had high estimates of familiarity with the other question. Results supported the following: (a) the 2-test procedure has considerable potential for elucidating the relationship between recollection and familiarity; (b) there is substantial evidence for dependency between such processes when estimates are obtained using the process dissociation and remember-know procedures; and (c) order of information access appears to depend on the question posed to the memory system.     

Impaired processing of prosodic and musical patterns after right hemisphere damage

The distinction between the processing of musical information and segmental speech information (i.e., consonants and vowels) has been much explored. In contrast, the relationship between the processing of music and prosodic speech information (e.g., intonation) has been largely ignored. We report an assessment of prosodic perception for an amateur musician, KB, who became amusic following a right-hemisphere stroke. Relative to matched controls, KB's segmental speech perception was preserved. However, KB was unable to discriminate pitch or rhythm patterns in linguistic or musical stimuli. He was also impaired on prosodic perception tasks (e.g., discriminating statements from questions). Results are discussed in terms of common neural mechanisms that may underlie the processing of some aspects of both music and speech prosody.     

Spatial reference and scanning with the left and right hand

Discrepant findings on performance by the two hands in spatial tasks make it difficult to infer spatial coding unambiguously. We tested the hypotheses (a) that the left hand is consistently better in haptic spatial tasks and (b) that adding spatial reference information produces more accurate coding in spatial tasks, independently task and hand effects. Instructions to use external cues from a surrounding frame as well as body-centred cues for reference produced highly significant increases in accuracy in haptic distance and location experiments. The distance experiments showed no hand differences. A small right-hand advantage with longer positioning movements in the recall of locations was significant when combined with left-hand scanning of the frame, but did not relate to reference conditions. Hand use interacted significantly with the location-versus-distance experiments, but showed no interaction with the spatial reference factor, which was highly significant in both experiments. The finding suggests that modes of coding need to be distinguished from cross-lateral effects of sensory input conditions. The study shows that varying reference information offers a potentially useful behavioural tool for distinguishing spatial coding from input and task conditions independently of hand performance. Methodological, practical, and theoretical implications are discussed.     

Directional harmonic theory: a computational Gestalt model to account for illusory contour and vertex formation

Visual illusions and perceptual grouping phenomena offer an invaluable tool for probing the computational mechanism of low-level visual processing. Some illusions, like the Kanizsa figure, reveal illusory contours that form edges collinear with the inducing stimulus. This kind of illusory contour has been modeled by neural network models by way of cells equipped with elongated spatial receptive fields designed to detect and complete the collinear alignment. There are, however, other illusory groupings which are not so easy to account for in neural network terms. The Ehrenstein illusion exhibits an illusory contour that forms a contour orthogonal to the stimulus instead of collinear with it. Other perceptual grouping effects reveal illusory contours that exhibit a sharp corner or vertex, and still others take the form of vertices defined by the intersection of three, four, or more illusory contours that meet at a point. A direct extension of the collinear completion models to account for these phenomena tends towards a combinatorial explosion, because it would suggest cells with specialized receptive fields configured to perform each of those completion types, each of which would have to be replicated at every location and every orientation across the visual field. These phenomena therefore challenge the adequacy of the neural network approach to account for these diverse perceptual phenomena. I have proposed elsewhere an alternative paradigm of neurocomputation in the harmonic resonance theory (Lehar 1999, see website), whereby pattern recognition and completion are performed by spatial standing waves across the neural substrate. The standing waves perform a computational function analogous to that of the spatial receptive fields of the neural network approach, except that, unlike that paradigm, a single resonance mechanism performs a function equivalent to a whole array of spatial receptive fields of different spatial configurations and of different orientations, and thereby avoids the combinatorial explosion inherent in the older paradigm. The present paper presents the directional harmonic model, a more specific development of the harmonic resonance theory, designed to account for specific perceptual grouping phenomena. Computer simulations of the directional harmonic model show that it can account for collinear contours as observed in the Kanizsa figure, orthogonal contours as seen in the Ehrenstein illusion, and a number of illusory vertex percepts composed of two, three, or more illusory contours that meet in a variety of configurations.     

Perceived shifts of flashed stimuli by visible and invisible object motion

Perceived positions of flashed stimuli can be altered by motion signals in the visual field-position capture (Whitney and Cavanagh, 2000 Nature Neuroscience 3 954-959). We examined whether position capture of flashed stimuli depends on the spatial relationship between moving and flashed stimuli, and whether the phenomenal permanence of a moving object behind an occluding surface (tunnel effect; Michotte 1950 Acta Psychologica 7 293-322) can produce position capture. Observers saw two objects (circles) moving vertically in opposite directions, one in each visual hemifield. Two horizontal bars were simultaneously flashed at horizontally collinear positions with the fixation point at various timings. When the movement of the object was fully visible, the flashed bar appeared shifted in the motion direction of the circle. But this position-capture effect occurred only when the bar was presented ahead of or on the moving circle. Even when the motion trajectory was covered by an opaque surface and the bar was flashed after complete occlusion of the circle, the position-capture effect was still observed, though the positional asymmetry was less clear. These results show that movements of both visible and 'hidden' objects can modulate the perception of positions of flashed stimuli and suggest that a high-level representation of 'objects in motion' plays an important role in the position-capture effect.     

Visual and haptic matching of perceived orientations of lines

In this study we investigated the perception and production of line orientations in a vertical plane. Previous studies have shown that systematic errors are made when participants have to match oblique orientations visually and haptically. Differences in the setup for visual and haptic matching did not allow for a quantitative comparison of the errors. To investigate whether matching errors are the same for different modalities, we asked participants to match a visually presented orientation visually, haptically with visual feedback, and haptically without visual feedback. The matching errors were the same in all three matching conditions. Horizontal and vertical orientations were matched correctly, but systematic errors were made for the oblique orientations. The errors depended on the viewing position from which the stimuli were seen, and on the distance of the stimulus from the observer.     

The role of temporal unpredictability for process interference and code overlap in perception-action dual tasks

Two experiments explore interference in dual tasks. The first task required perceptual judgment of the movement direction (left vs right) of a briefly presented stimulus; the second task was a tone-discrimination reaction-time (RT) task. Participants reported their judgment at leisure. In 50% of the trials they were told to ignore the stimulus (no report). The directions of stimulus movement and response in the RT task could either be the same or different, establishing cross-task compatibility (CTC) relations. We varied the degree of temporal unpredictability by using two stimulus-onset asynchronies (SOA, 100 ms vs 1200 ms) for the task stimuli. In Experiment 1, SOA was varied randomly within blocks of trials in one group and between blocks in another group. In Experiment 2, only the short SOA was used in one group and only the long SOA in another group. In both experiments, we observed substantially longer RTs with the short compared with the long SOA, regardless of whether there was temporal certainty (blocked or constant SOA) or uncertainty (random SOA) about stimulus onset. We assume that the process of encoding into short-term memory in one task interferes with concurrent retrieval processes (i.e., response selection) in the other task. This process interference effect was strongly reduced in no-report trials. Furthermore, we found shorter RT in compatible than in incompatible trials. This CTC effect diminished with long SOA but occurred even in no-report trials, implying that it refers to an automatically activated and then decaying code that primes response selection in the RT task.     

Day treatment of patients with personality disorders: experiences from a Norwegian treatment research network

This study sought to investigate the following research questions: Are time-limited day treatment programs for patients with personality disorder (PD) effective outside resourceful university settings, and what are the overall treatment results when the program is implemented on a larger scale? Do all categories and subtypes of PDs respond favorably to such treatment? How intensive should such day treatment programs be? All patients (n = 1,244) were consecutively admitted to eight different treatment programs in the Norwegian Network of Psychotherapeutic Day Hospitals from 1993 to 2000. Altogether, 1,010 patients were diagnosed with PD. Avoidant, borderline, not otherwise specified (NOS), and paranoid PD were the most common conditions. SCID-II and MINI were used as diagnostic instruments. Outcome measures included GAF Global Assessment of Functioning, (GAF; American Psychiatric Association, 1994), SCL-90R, CIP, Quality of Life, work functioning and parasuicidal behavior, measured at admittance, discharge and 1-year follow up. The attrition rate was 24%. The number of dropouts did not improve over time. As a group, completers with PD improved significantly on all outcome variables from admittance to discharge and improvement was maintained or increased at follow up. Treatment results were best for borderline PD, cluster C patients, PD NOS and No PD, and poorer for cluster A patients. Units with a high treatment dosage did not experience better outcomes than those with a low treatment dosage (10 hours per week). Results from the University unit were not better than those from units at local hospitals or mental health centers.