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PubMed2006

Evidence for a double dissociation between spatial-simultaneous and spatial-sequential working memory in visuospatial (nonverbal) learning disabled children.

The paper describes the performance of three children with specific visuospatial working memory (VSWM) impairments (Study 1) and three children with visuospatial (nonverbal) learning disabilities (Study 2) assessed with a battery of working memory (WM) tests and with a number of school achievement tasks. Overall, performance on WM tests provides evidence of a double dissociation between spatial-simultaneous processes, underpinning the memorization item positioning in a spatial configuration, and spatial-sequential processes, which allow memorization of the presentation order. In both groups of children of the two studies, a selective impairment either on spatial-sequential or on spatial-simultaneous working memory tasks was observed. These data support the existence of -simultaneous and -sequential modality-dependent processes in visuospatial working memory and confirm the importance of distinguishing between different subtypes of visuospatial (nonverbal) learning-disabled children.

Child↗
PubMed2003

Repetition blindness for words yet repetition advantage for nonwords.

Accuracy of report of words in a rapidly presented sequence is reduced if 1 word is a repetition of a previous word. This is repetition blindness. If, however, the items are pronounceable nonwords, or pseudohomophones, repetition improves recall. A repetition advantage for nonwords also occurs when subjects merely count the items or when the item between the critical nonwords is a familiar word. Familiarizing subjects with the nonwords improved the level of recall but did not affect the repetition advantage. These results are considered in relation to token individuation and other accounts of repetition blindness. The findings suggest that for identical linguistic stimuli the types bound to episodic memory tokens that are vulnerable to repetition blindness are lexical units.

Adolescent↗
PubMed2006

Interactions between encoding and retrieval in the domain of sequence-learning.

In this article, the authors propose to characterize sequence learning in terms of automatic versus non-automatic processing and to apply this contrast independently to knowledge acquisition and retrieval. In several experiments of sequence learning, automaticity of both the acquisition and retrieval of the acquired knowledge was independently assessed. It was found that the sequence learning order can be demonstrated under all combinations of knowledge acquisition and retrieval. In particular, at least in the simple sequences the authors used, this applies in cases in which both the acquisition and the retrieval of knowledge are strictly automatic--that is, when neither is required for the task nor beneficial to deliberate behavior. The proposed framework has implications for the notion of sequence learning and the investigation of learning in general.

Association Learning↗
PubMed2005

Lag-1 sparing in the attentional blink: benefits and costs of integrating two events into a single episode.

When people monitor a visual stream of rapidly presented stimuli for two targets (T1 and T2), they often miss T2 if it falls into a time window of about half a second after T1 onset--the attentional blink. However, if T2 immediately follows T1, performance is often reported being as good as that at long lags--the so-called Lag-1 sparing effect. Two experiments investigated the mechanisms underlying this effect. Experiment 1 showed that, at Lag 1, requiring subjects to correctly report both identity and temporal order of targets produces relatively good performance on T2 but relatively bad performance on T1. Experiment 2 confirmed that subjects often confuse target order at short lags, especially if the two targets are equally easy to discriminate. Results suggest that, if two targets appear in close succession, they compete for attentional resources. If the two competitors are of unequal strength the stronger one is more likely to win and be reported at the expense of the other. If the two are equally strong, however, they will often be integrated into the same attentional episode and thus get both access to attentional resources. But this comes with a cost, as it eliminates information about the targets' temporal order.

Adult↗
PubMed1995

Implicit learning and concept learning.

In Experiments 1 and 2, subjects were exposed to letter strings that followed a pattern--the second letter was always the same. This exposure was disguised as a test of immediate memory. Following this training, subjects could discriminate new letter strings following the pattern from letter strings not following the pattern more often than would be expected by chance, which is the traditional evidence for concept learning. Discrimination was also better than would be predicted from subjects' explicit report of the pattern, demonstrating the co-occurrence of concept learning and implicit learning. In Experiment 3, rules were learned explicitly. Discrimination was worse than would be predicted from subjects' explicit report, validating the implicit learning paradigm. In Experiment 4, deviations from a prototypical pattern were presented during training. In the test of discrimination, prototypes were as familiar as old deviations and more familiar than new deviations, even when considering only implicit knowledge. Experiment 5 found implicit knowledge of a familiar concept. These results are consistent with the hypothesis that the distinguishing features of a concept can be learned implicitly, and that one type of implicit learning is concept learning.

Adult↗
PubMed1982

Encoding strategies used by young and elderly adults in a keeping track task.

College students and older adults (mean ages 20.4 and 71.5 years) performed in a "keeping track" task that required them to recall, in response to probe questions, the most recently presented of each of a fixed set of categories. Questions alternated with presentations of new sets of items. Response accuracy, reaction times, and verbal reports provided information on the participants' strategies. The findings were consistent with the view (e.g., Hasher & Zacks, 1979) that older adults' poorer memory results from reduced use of effortful strategies. The older persons used fewer active encoding strategies than the college students and were less accurate and slower to respond. A subgroup of the elderly adults reported some active encoding activities; they performed more like the college students than the remaining elderly participants. A follow-up study in which college students were allowed reduced opportunity for active encoding produced performance intermediate between the other two groups.

Adolescent↗
PubMed1979

Assessment of cognitive asymmetries in brain-damaged and normal subjects: validation of a test battery.

A test battery designed to assess cognitive functions normally related to the left and right cerebral hemispheres was validated on 30 patients with unilateral (16 right, 14 left) lesions. The tests were preselected to reflect typical functioning of the hemispheres according to general agreement in the literature. A Cognitive Laterality Quotient (CLQ) was calculated from the difference in performance between the "right" and "left" test batteries and, therefore, reflected the relative functioning attributed to the right and left hemispheres. Using the CLQ measurement and a control group of 30 non-neurological patients matched for age and education, 28 out of 30 brain-damaged patients (93%) were categorised correctly according to side of lesion; the other two were considered to have either abnormal lateralisation (one was left handed) or asymmetrical premorbid cognitive profiles. Using only one (paired) test whose two subparts were designed to vary only slightly in task requirements to measure either right or left functioning, 29 out of 30 patients were correctly categorised. It is suggested that the concept of relative assessment of basic cognitive functions is more fruitful than general assessment of intellectual functions for use in diagnosis and rehabilitation of neurological patients or normal subjects with developmental or acquired behavioural cognitive abnormalities.

Adult↗
PubMed1994

Effect of multimodal stimulus presentation on recall.

This study was conducted to investigate how the mode of stimulus presentation affects recall in the classroom environment. 289 undergraduates were randomly assigned to one of 7 experimental groups. All subjects were presented the same stimuli in one of 7 possible modes: (1) Printed Word, (2) Spoken Word, (3) Picture, (4) Printed Word + Spoken Word, (5) Picture + Spoken Word, (6) Picture + Printed Word, and (7) Printed Word, Picture + Spoken Word. 30 words, 6 from each of 5 categories, were presented to each group. A new stimulus was presented every 5 sec. Subjects were to recall (in writing) as many stimuli as possible in 5 min. regardless of order. One-way between groups analyses of variance were conducted on recall and cluster index scores. A significant main effect of mode of presentation showed that recall was best for the Picture or multimodal group (Printed Word, Picture + Spoken Word). Groups receiving only the spoken or printed word showed significantly poorer recall than the multimodal groups. No statistically significant differences between groups were found on the cluster index score. It appears that the simultaneous presentation of redundant stimuli in multiple modalities does support the multiple-resource hypothesis by displaying enhanced recall when information is available from multiple attentional resources.

Adolescent↗
PubMed2006

Sequential modulations of correspondence effects across spatial dimensions and tasks.

In two experiments, we explored sequential modulations of correspondence effects in a prime-target paradigm. In Experiment 1, the participants responded to the direction of target arrows that were preceded by prime arrows with a corresponding or noncorresponding direction. This produced a prime-target correspondence effect that was reduced when the preceding trial contained a noncorresponding prime-target event. This sequential modulation of the correspondence effect was observed even when neither stimuli nor responses were repeated from one trial to the next, ruling out explanations of sequential modulations in terms of stimulus or response repetitions. Experiment 2 combined the prime-target correspondence effect with a Simon-type correspondence effect. Both effects were reduced following noncorrespondence of the same type and, to a lesser extent, following noncorrespondence of the other type. Altogether, these results suggest that part of the sequential modulation of correspondence effects reflects an adaptation to a preceding response conflict independently of the peripheral stimulus events that produced this conflict.

Adolescent↗
PubMed2006

Recency effects in HIV-associated dementia are characterized by deficient encoding.

The aim of the present study was to investigate the nature and cognitive mechanisms of serial position learning effects in HIV-associated dementia (HAD). Participants were 16 persons with HAD, 50 non-demented persons with HIV-infection, and 50 demographically comparable HIV-seronegative participants. HAD participants, relative to both comparison groups, exhibited reduced middle region (p<0.01) and elevated recency region (p<0.05) recall on the Hopkins Verbal Learning Test-Revised, but no primacy region effect (p>0.10). On recognition testing, the HAD group was impaired in discriminating targets from distractors (p<0.01) in all three serial position regions; however, they were not impaired on measures of retrieval (p>0.10) within these same regions. In sum, HAD participants relied disproportionately on recency regions of the list, indicating a passive recall style of echoing only the words within their auditory attention span. Interestingly, HAD participants did not evidence significant improvement on measures of recognition, a finding that suggests that the serial position effects are most consistent with a primary encoding deficit.

AIDS Dementia Complex↗
PubMed1991

Memory for temporal order in schizophrenia.

Memory for temporal order information was examined in patients with chronic schizophrenia using the recency discrimination task. In this task, subjects were shown a pair of previously studied words and were asked to choose which one of the two words they had seen more recently. In addition, subjects performed the Wisconsin Card Sorting Test (WCST). The results showed that schizophrenic patients differed from normal control subjects in their performance on the recency discrimination task. In addition, for schizophrenic patients, performance on the recency discrimination task was inversely related to the number of perseverative errors on the WCST. These results provide further evidence of prefrontal-type cognitive deficits in schizophrenia.

Adult↗
PubMed1994

Aetiological variation in the amnesic syndrome: comparisons using the list discrimination task.

In this study, the performance of amnesic patients with presumed temporal lobe damage was compared with that of patients with presumed diencephalic damage using the temporal list discrimination task. The two patient groups performed similarly on a measure of recognition, but the diencephalic group was impaired relative to the temporal lobe group on a measure of temporal discrimination. Discrimination performance in the temporal lobe group was significantly correlated with recognition memory. The data are interpreted as showing a qualitative difference in the form of amnesia arising from damage centred on the medial temporal lobes compared with that centred on the midline diencephalon.

Adult↗
PubMed1994

The effects of lesions to the fornix and dorsomedial thalamus on concurrent discrimination learning by rats.

Rats with lesions in either the fornix or the thalamic nucleus medialis dorsalis were unimpaired on the acquisition of two object discrimination tasks. The same animals were then tested on a concurrent learning task in which various object discriminations were presented at different rates during the same session. This arrangement was primarily designed to minimise any response bias effects. Animals were able to acquire the various concurrent tasks, even when only one trial per day was given for a particular discrimination. It was found that fornix lesions had little or no effect and only produced a mild impairment when the rate of stimulus presentation resembled that used in typical concurrent tasks. Lesions of medialis dorsalis produced a more general, but again mild, deficit. In a final task, the animals were trained to discriminate between two stimuli composed of common elements arranged in different spatial combinations. Fornix lesions impaired acquisition of this spatial configural discrimination, while lesions of medialis dorsalis had a variable effect. The results indicate that fornix lesions can spare concurrent discrimination learning, and that any deficits may be related to interference effects associated with common elements in the stimuli. Lesions in medialis dorsalis appear to affect the initial learning of reward-based performance rules.

Animals↗
PubMed2005

Orientation-invariant object recognition: evidence from repetition blindness.

The question of whether object recognition is orientation-invariant or orientation-dependent was investigated using a repetition blindness (RB) paradigm. In RB, the second occurrence of a repeated stimulus is less likely to be reported, compared to the occurrence of a different stimulus, if it occurs within a short time of the first presentation. This failure is usually interpreted as a difficulty in assigning two separate episodic tokens to the same visual type. Thus, RB can provide useful information about which representations are treated as the same by the visual system. Two experiments tested whether RB occurs for repeated objects that were either in identical orientations, or differed by 30, 60, 90, or 180 degrees . Significant RB was found for all orientation differences, consistent with the existence of orientation-invariant object representations. However, under some circumstances, RB was reduced or even eliminated when the repeated object was rotated by 180 degrees , suggesting easier individuation of the repeated objects in this case. A third experiment confirmed that the upside-down orientation is processed more easily than other rotated orientations. The results indicate that, although object identity can be determined independently of orientation, orientation plays an important role in establishing distinct episodic representations of a repeated object, thus enabling one to report them as separate events.

Adult↗