Short-term memory impairment in chronic schizophrenics.

Assessed the short-term memory capacities of 4 chronic, schizophrenic and 4 nonschizophrenic psychiatric patients who served as controls. The information to be remembered was presented both visually and verbally and was later probed for after a variable interval by either visual or verbal cues. Schizophrenics and controls did not differ with respect to which type of cue retrieved more of the information, suggesting that the modality in which the information was stored was the same for both groups. However, schizophrenics were markedly inferior to controls regarding both the initial acquisition of information and the maintenance of it in storage. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short-term memory for the timing of auditory and visual signals.

Short-term memory for the timing of irregular sequences of signals has been said to be more accurate when the signals are auditory than when they are visual. No support for this contention was obtained when the signals were beeps vs flashes (Exps 1 and 3) nor when they were sets of spoken vs typewritten digits (Exps 4 and 5). On the other hand, support was obtained both for beeps vs flashes (Exps 2 and 5) and for repetitions of a single spoken digit vs repetitions of a single typewritten digit (Exp 6) when the Ss silently mouthed a nominally irrelevant item during sequence presentation. Also, the timing of sequences of auditory signals, whether verbal (Exp 7) or nonverbal (Exps 8 and 9), was more accurately remembered when the signals within each sequence were identical. The findings are considered from a functional perspective. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short-term memory for simultaneously presented visual and auditory signals in the pigeon.

Conducted 3 divided-attention experiments with 8 adult Silver King pigeons, in which matching to the visual or auditory component of a tone–light compound was compared with matching to visual or auditory elements as sample stimuli, to investigate Ss' short-term memory for simultaneously presented visual and auditory signals. In 0-sec delayed and simultaneous matching procedures, Ss were able to match visual signals equally well when presented alone or with a tone. Tones were matched at a substantially lower level of accuracy when presented with light signals than when presented as elements. The interfering effect of a signal light on tone matching was not related to the signaling value of the light, and the prior presentation of light proactively interfered with auditory delayed matching. Findings indicate a divided-attention process in which auditory processing is strongly inhibited in the presence of visual signals. (32 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Integration of visual patterns in schizophrenics.

In an earlier study (see record 1979-26172-001), the present authors found poor prognosis schizophrenics deficient in integrating sentences into a single idea. The present study explored their ability to integrate in a less complex task that used visual patterns. 60 male psychiatric inpatients (schizophrenic or nonpsychotic) and 15 controls (mean age, approximately 32 yrs) completed the Shipley-Institute of Living Scale. They were then presented a series of letterlike forms that were transformations of each other. After initial presentation, Ss were given an incidental recognition test. All Ss remembered the stimuli in an integrated fashion. This demonstrates that schizophrenics are capable of the complex organization of disparate stimuli even when that organization is not specifically required. It is suggested that abstraction of the basic meaning of simple visual stimuli is intact in schizophrenics, but that processing of complex event information in either verbal or visual stimuli is deficient in poor prognosis schizophrenics. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short-term retention in acute and chronic paranoid schizophrenics.

Administered 4 short-term memory tasks to 10 acute and 10 chronic paranoid schizophrenics (age ranges 17-45 and 21-58, respectively) and 10 18-54 yr old nonprofessional hospital staff members. Each task involved the recall of a different type of material varying in meaningfulness from letter trigrams to real word triads. Recall of the material always followed 15 sec of distracting activity designed to prevent rehearsal. Acute paranoid Ss tended to overinclude intralist and extralist responses especially when the more meaningful material was used, while the chronic Ss tended to omit many more responses (p     

Short-term memory in autism spectrum disorder.

Three experiments examined verbal short-term memory in comparison and autism spectrum disorder (ASD) participants. Experiment 1 involved forward and backward digit recall. Experiment 2 used a standard immediate serial recall task where, contrary to the digit-span task, items (words) were not repeated from list to list. Hence, this task called more heavily on item memory. Experiment 3 tested short-term order memory with an order recognition test: Each word list was repeated with or without the position of 2 adjacent items swapped. The ASD group showed poorer performance in all 3 experiments. Experiments 1 and 2 showed that group differences were due to memory for the order of the items, not to memory for the items themselves. Confirming these findings, the results of Experiment 3 showed that the ASD group had more difficulty detecting a change in the temporal sequence of the items. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual and memory search by process schizophrenics.

Compared the response times (RTs) of 20 process schizophrenics (10 paranoid and 10 nonparanoid) and 20 nonhospitalized controls (mean ages 39.2, 30.0, and 34.1 yrs, respectively) on a hybrid visual and memory search task in which Ss searched displays of up to 15 letters, reporting whether or not displays contained a target, which in different conditions was drawn from a memorized set of 1, 3, or 6 letters. RTs of all groups increased linearly with the product of the number in the memorized target set and the number of displayed letters. Although the intercepts and RTs of the schizophrenics (there were no paranoid–nonparanoid differences) exceeded those of controls, no group differences were found in slopes or in rates of increase in RT as a function of the number of memorized or displayed items. Results are interpreted in terms of a model proposed by W. Schneider and R. M. Shiffrin (1977), which indicates that process schizophrenics are retarded in processes associated with response production but not in a variety of processing stages involved in the comparison of displayed and memorized information. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Binding in short-term visual memory.

The integration of complex information in working memory, and its effect on capacity, shape the limits of conscious cognition. The literature conflicts on whether short-term visual memory represents information as integrated objects. A change-detection paradigm using objects defined by color with location or shape was used to investigate binding in short-term visual memory. Results showed that features from the same dimension compete for capacity, whereas features from different dimensions can be stored in parallel. Binding between these features can occur, but focused attention is required to create and maintain the binding over time, and this integrated format is vulnerable to interference. In the proposed model, working memory capacity is limited both by the independent capacity of simple feature stores and by demands on attention networks that integrate this distributed information into complex but unified thought objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short-term memory scanning in schizophrenic young adults.

Used the Sternberg item-recognition procedure to investigate the process of short-term memory scanning and recognition of common English words in 16 schizophrenics, 16 nonschizophrenic psychiatric patients, and 16 normals (college students). The S was required to respond as quickly and accurately as possible to whether a probe word matched the word or words shown a few seconds earlier. Results show that the 3 groups' response latencies increased at approximately equal rates as the memory set size increased, but the overall response latencies of both patient groups were profoundly slower than normals. All 3 groups revealed a significant serial position effect and a logarithmic reaction time function for the positive probe. No single model of the scanning strategy appears to fit straight-forwardly to the present data. It is concluded that the schizophrenics' short-term memory scanning was intact, and their slowness in response is, therefore, to be understood in terms of some dysfunction in their stimulus encoding, response selection, and/or response execution. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assessing visual memory disorders.

The Biber Figure Learning Test (BFLT) was administered to 19 patients with right- and 20 with left-hemisphere cerebrovascular accidents, 11 severe amnesics and 42 controls. Results indicate that the BFLT reliably assesses impairments in long-term visual memory independent of primary visuoperceptual, visuoconstructional, and language deficits. Healthy controls showed no effects of education and minimal age effects on the BFLT. Normal learning curves were found for cortical lesions patients, but their overall scores were below those of normals. Amnesics with subcortical-limbic pathology showed grossly impaired acquisition, retention, and recognition memory, but normal short-term visual memory and primary visuoperceptual/visuoconstructional abilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pigeon visual memory capacity.

Four experiments examined visual memory capacity in 13 White Carneaux pigeons. In Exp I, Ss learned to discriminate between 80 pairs of random shapes. Memory for 40 of those pairs was only slightly poorer following 490 days without exposure. In Exp II, 80 pairs of photographic slides were learned; 629 days without exposure did not significantly disrupt memory. In Exp III, 160 pairs of slides were learned; 731 days without exposure did not significantly disrupt memory. In the final experiment, Ss learned to respond appropriately to 40 pairs of slides in the normal orientation and to respond in the opposite way when the slides were left–right reversed. After an interval of 751 days, there was a transient disruption in discrimination. These experiments demonstrate that pigeons have a heretofore unsuspected capacity with regard to both breadth and stability of memory for abstract stimuli and pictures. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A picture integration task for measuring iconic memory in schizophrenics.

Two previous studies by the 1st author et al (1977) and G. Sperling (1960) using different techniques (partial report and backward masking) have found at least some subgroups of schizophrenics deficient in iconic memory. Both hypothesized that the icon in some schizophrenics might be either weakly formed, limited in capacity, or abnormal in duration, but neither study was able to test the qualities of the icon independent of possible transfer difficulties. The present study with 50 male 18–55 yr old psychiatric patients (35 schizophrenics and 15 nonpsychotics) developed a picture integration task that was analogous to C. W. Eriksen and J. F. Collins's (1973) random dot integration. With this task, the capacity and decay of the icon independent of transfer to short-term store was assessed. The icon itself was found intact in all schizophrenics. Other explanations are suggested for schizophrenics' inadequate partial report and backward masking performance. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Performance of process schizophrenics on tasks involving visual search.

Compared the response times of 32 process schizophrenics and 16 nonhospitalized matched controls on 3 visual search tasks. Exp I involved the location of a target letter within an array of different background letters. Other experiments required a same–different response. Exp II involved the identification of a single different letter set within the uniform context of a square display formed by up to 40 replicates of another letter. Exp III presented 2 3–6 letter clusters in a single horizontal line. The 2 clusters were identical or had 1 different letter. Word and nonword clusters were used. Paranoid and nonparanoid groups did not differ on any measure. Schizophrenic response times were about 1 sec longer, but measures of rate of increase in response time with number of letters displayed did not generally differ significantly between groups. Schizophrenics tended to make more errors. Experimental manipulations affected the response times and error rates of schizophrenics and controls alike, and to much the same degree. Results suggest that process schizophrenics are not abnormally slow when extracting information from visual displays, and they appear to perform operations and strategies similar to those of normals when doing so. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scanning time of schizophrenics and normals for visual designs.

Measured the time to locate a target design in an array of 4 designs by 12 process and 12 reactive schizophrenics and 12 hospitalized and 12 nonhospitalized normal controls. Designs and arrays differed in the size of the rotation and reflection equivalence sets from which they were selected. Differences in mean reaction time (RT) attributable to these characteristics were found as expected. Schizophrenics performed slower than the nonhospitalized normals. The mean RT of hospitalized normals, mostly spinal cord injury patients, fell between that of the process and reactive schizophrenics. No Group * Stimulus Condition interaction effects were found. Results are interpreted as not supporting leading theories of schizophrenic deficit. (21 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention gating in short-term visual memory.

Investigated attention shift to a stream of numerals, in rapid serial visual presentation, using 3 graduate students with normal or corrected-to-normal vision. Ss detected a target embedded in a stream of letters presented at the left of fixation and, as quickly as possible, shifted their attention to a stream of numerals at the right of fixation. They attempted to report, in order, the 4 earliest occurring numerals after the target. Numerals appeared at rates of 4.6, 6.9, 9.2, and 13.4 sec. Analyses demonstrated that, for all Ss, targets, and numeral rates, the relative position of numerals in the response sequence showed clustering, disorder, and folding. Reported numerals tended to cluster around a stimulus position 400 msec after the target. Numerals were reported in an apparently haphazard order. The actual order of report resulted from a mixture of correctly ordered numerals with numerals ordered in the direction opposite to their order of presentation. Results are quantitatively described by a strength theory of order and are efficiently predicted by a computational attention gating model (AGM). The AGM may be derived from a more general attention model that assumes that (a) after detection of the target, an attention gate opens briefly to allow numerals to enter a visual short-term memory and (b) subsequent order of report depends on both item strength (how wide the gate was open during the numeral's entry) and on order information (item strength times cumulative strength of prior numerals). (78 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Parrel processing in visual short-term memory.

Visual short-term memory for the contrast and spatial frequency of sinusoidal gratings was measured in a delayed discrimination task in which the 2 stimuli to be compared were separated in time by 1-10 s interstimulus intervals (ISIs). Delayed discrimination thresholds for spatial frequency and contrast were compared, both when the 2 types of thresholds were measured in separate blocks of trials and when the 2 types of measures were randomly intermixed in an uncertainty paradigm, which required participants to process information about both dimensions on each trial. In both cases, accuracy of memory for spatial frequency was independent of ISI, but memory for contrast decreased as ISI increased. Performance was lower in the uncertainty case, but only by an amount predicted by statistical decision theory for independent sources. The results are consistent with a model assuming a set of parallel special-purpose visual discrimination and short-term memory mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exploring developmental differences in visual short-term memory and working memory.

Although visuospatial short-term memory tasks have been found to engage more executive resources than do their phonological counterparts, it remains unclear whether this is due to intrinsic differences between the tasks or differences in participants’ experience with them. The authors found 11-year-olds’ performances on both visual short-term and working memory tasks to be more greatly impaired by an executive suppression task (random number generation) than were those of 8-year-olds. Similar findings with adults (e.g., Kane & Engle, 2000) suggest that the imposition of a suppression task may have overloaded the older children’s executive resources, which would otherwise be used for deploying strategies for performing the primary tasks. Conversely, the younger children, who probably never had the capacity or know-how to engage these facilitative strategies in the first place, performed more poorly in the single task condition but were less affected in the dual task condition. These findings suggest that differences in the children’s ability to deploy task-relevant strategy are likely to account for at least part of the executive resource requirements of visual memory tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short-term memory for reaching to visual targets: psychophysical evidence for body-centered reference frames

Pointing to a remembered visual target involves the transformation of visual information into an appropriate motor output, with a passage through short-term memory storage. In an attempt to identify the reference frames used to represent the target position during the memory period, we measured errors in pointing to remembered three-dimensional (3D) targets. Subjects pointed after a fixed delay to remembered targets distributed within a 22 mm radius volume. Conditions varied in terms of lighting (dim light or total darkness), delay duration (0.5, 5.0, and 8.0 sec), effector hand (left or right), and workspace location. Pointing errors were quantified by 3D constant and variable errors and by a novel measure of local distortion in the mapping from target to endpoint positions. The orientation of variable errors differed significantly between light and dark conditions. Increasing the memory delay in darkness evoked a reorientation of variable errors, whereas in the light, the viewer-centered variability changed only in magnitude. Local distortion measurements revealed an anisotropic contraction of endpoint positions toward an "average" response along an axis that points between the eyes and the effector arm. This local contraction was present in both lighting conditions. The magnitude of the contraction remained constant for the two memory delays in the light but increased significantly for the longer delays in darkness. These data argue for the separate storage of distance and direction information within short-term memory, in a reference frame tied to the eyes and the effector arm.     

Organization of visual short-term memory.

The authors examined the organization of visual short-term memory (VSTM). Using a change-detection task, they reported that VSTM stores relational information between individual items. This relational processing is mediated by the organization of items into spatial configurations. The spatial configuration of visual objects is important for VSTM of spatial locations, colors, and shapes. When color VSTM is compared with location VSTM, spatial configuration plays an integral role because configuration is important for color VSTM, whereas color is not important for location VSTM. The authors also examined the role of attention and found that the formation of configuration is modulated by both top-down and bottom-up attentional factors. In summary, the authors proposed that VSTM stores the relational information of individual visual items on the basis of global spatial configuration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)