Showing papers on "Working memory published in 1993"

The neural correlates of the verbal component of working memory.

Abstract: By repeating words 'in our head', verbal material (such as telephone numbers) can be kept in working memory almost indefinitely. This 'articulatory loop' includes a subvocal rehearsal system and a phonological store. Little is known about neural correlates of this model of verbal short-term memory. We therefore measured regional cerebral blood flow, an index of neuronal activity, in volunteers performing a task engaging both components of the articulatory loop (short-term memory for letters) and a task which engages only the subvocal rehearsal system (rhyming judgement for letters). Stimuli were presented visually and the subjects did not speak. We report here that comparisons of distribution of cerebral blood flow in these conditions localized the phonological store to the left supramarginal gyrus whereas the subvocal rehearsal system was associated with Broca's area. This is, to our knowledge, the first demonstration of the normal anatomy of the components of the 'articulatory loop'.

Working Memory and Language

Abstract: Introduction to Working Memory. The Development of Working Memory. Vocabulary Acquisition. Speech Production. Introduction to Reading Development. Phonological Processing and Reading Development. Visual Word Recognition. Language Comprehension. Theoretical and Practical Issues.

Responses of monkey dopamine neurons to reward and conditioned stimuli during successive steps of learning a delayed response task

Abstract: The present investigation had two aims: (1) to study responses of dopamine neurons to stimuli with attentional and motivational significance during several steps of learning a behavioral task, and (2) to study the activity of dopamine neurons during the performance of cognitive tasks known to be impaired after lesions of these neurons Monkeys that had previously learned a simple reaction time task were trained to perform a spatial delayed response task via two intermediate tasks During the learning of each new task, a total of 25% of 76 dopamine neurons showed phasic responses to the delivery of primary liquid reward, whereas only 9% of 163 neurons responded to this event once task performance was established This produced an average population response during but not after learning of each task Reward responses during learning were significantly more numerous and pronounced in area A10, as compared to areas A8 and A9 Dopamine neurons also showed phasic responses to the two conditioned stimuli These were the instruction cue, which was the first stimulus in each trial and indicated the target of the upcoming arm movement (58% of 76 neurons during and 44% of 163 neurons after learning), and the trigger stimulus, which was a conditioned incentive stimulus predicting reward and eliciting a saccadic eye movement and an arm reaching movement (38% of neurons during and 40% after learning) None of the dopamine neurons showed sustained activity in the delay between the instruction and trigger stimuli that would resemble the activity of neurons in dopamine terminal areas, such as the striatum and frontal cortex Thus, dopamine neurons respond phasically to alerting external stimuli with behavioral significance whose detection is crucial for learning and performing delayed response tasks The lack of sustained activity suggests that dopamine neurons do not encode representational processes, such as working memory, expectation of external stimuli or reward, or preparation of movement Rather, dopamine neurons are involved with transient changes of impulse activity in basic attentional and motivational processes underlying learning and cognitive behavior

Spatial working memory in humans as revealed by PET

Abstract: The concept of working memory is central to theories of human cognition because working memory is essential to such human skills as language comprehension and deductive reasoning. Working memory is thought to be composed of two parts, a set of buffers that temporarily store information in either a phonological or visuospatial form, and a central executive responsible for various computations such as mental arithmetic. Although most data on working memory come from behavioural studies of normal and brain-injured humans, there is evidence about its physiological basis from invasive studies of monkeys. Here we report positron emission tomography (PET) studies of regional cerebral blood flow in normal humans that reveal activation in right-hemisphere prefrontal, occipital, parietal and premotor cortices accompanying spatial working memory processes. These results begin to uncover the circuitry of a working memory system in humans.

Functional activation of the human frontal cortex during the performance of verbal working memory tasks.

Abstract: Regional cerebral blood flow was measured with positron emission tomography during the performance of verbal working memory tasks. The same type of verbal response (i.e., reciting numbers) was required in the control and the two experimental tasks. In the control task, the subjects were required to count aloud. In the two experimental tasks, the subjects were required to maintain within working memory the numbers they generated (self-ordered task) or the numbers generated by the experimenter (externally ordered task). Examination of the difference in activation between these conditions revealed strong bilateral activation within the mid-dorsolateral frontal cortex during both experimental tasks. There was, however, no evidence of additional activation within the mid-dorsolateral frontal cortex when monitoring self-generated responses as compared with the monitoring of externally generated responses. These results provide evidence regarding the role of the mid-dorsolateral frontal cortex in mnemonic processing that are in agreement with recent findings from work with non-human primates.

The Frontal Lobes and Voluntary Action

Abstract: 1. Voluntary action 2. Motor cortex (area 4) 3. Lateral premotor cortext (area 6) 4. Medial premotor cortex (area 6) 5. Premotor area 8 6. Dorsal prefrontal cortex (areas 4, 6 and 9) 7. Ventral prefrontal cortex (areas 11, 12, 13 and 14) 8. Basal ganglia 9. The organisation of the frontal lobe 10. Thought and voluntary action 11. Speech

Activity of neurons in anterior inferior temporal cortex during a short- term memory task

Abstract: Inferior temporal (IT) cortex of primates is known to play an important role in visual memory. Previous studies of IT neurons during performance of working memory tasks have found modulation of responses when a current stimulus matched an item in memory; however, this effect was lost if other stimuli intervened in the retention interval. To examine how IT cortex retains memories while new stimuli are activating the cells, we recorded from IT neurons while monkeys performed a delayed matching-to-sample task, with multiple intervening items between the sample and matching test stimulus. About half of the cells responded differently to a test stimulus if it matched the sample, and this difference was maintained following intervening stimuli. For most of the affected cells, the responses to matching stimuli were suppressed; however, for a few cells the opposite effect was seen. Temporal contiguity alone could not explain the results, as there was no modulation of responses when a stimulus on one trial was repeated on the next trial. Thus, an active reset mechanism appears to restrict the memory comparison to just the stimuli presented within a trial. The suppressive effects appear to be generated within or before IT cortex since the suppression of response to matching stimuli began almost immediately with the onset of the visual response. The memory of the sample stimulus affected not only the responses to matching stimuli but also those to nonmatching stimuli. There was suggestive evidence that the more similar a nonmatching stimulus to the sample, the more the response was suppressed. About a quarter of the cells showed stimulus-selective activity in the delay interval following the sample. However, this activity appeared to be eliminated by intervening stimuli. Thus, it is unlikely that delay-interval activity in IT contributed to the performance of this particular version of delayed matching to sample. To determine how much information about the match-nonmatch status of the stimulus was conveyed by individual neurons, we analyzed the responses with discriminant analysis. The responses of an individual IT neuron could be used to classify a stimulus as matching or nonmatching on about 60% of the trials. To achieve the same performance as the animal would require averaging the responses of a minimum of 25 IT neurons. There was no evidence that mnemonic information was carried by temporal variations in the spike trains. By contrast, there was a modest amount of temporal variation in sensory responses to different visual stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)

Prefrontal neuronal activity in rhesus monkeys performing a delayed anti-saccade task.

Abstract: Patients with damage to the dorsolateral prefrontal cortex are impaired on cognitive tasks such as the Wisconsin Card Sort Test, the Stroop Test and an anti-saccade paradigm, in which sensory-guided habitual responses must be suppressed in favour of conceptually or memory-guided responses. We report here recordings from prefrontal neurons in rhesus monkeys trained to perform a delayed anti-saccade task based on tests that have been used with humans. Activity in the same prefrontal neurons was recorded across conditions when saccades were made toward a remembered target, and also when this prepotent response was suppressed and a saccade in the opposite direction required. Our findings show that most prefrontal neurons code the location of the visual stimulus in working memory, and that this memory can be engaged to suppress as well as prescribe a response. These results establish, in a subset of prefrontal neurons, the iconic nature of the memory code, and suggest a role for visual memory in response suppression.

Dissociation of human mid-dorsolateral from posterior dorsolateral frontal cortex in memory processing.

Abstract: Work with non-human primates had previously demonstrated that the mid-dorsolateral frontal cortex, which comprises cytoarchitectonic areas 46 and 9, plays a critical role in the performance of non-spatial self-ordered working memory tasks, whereas the immediately adjacent posterior dorsolateral frontal cortex (area 8) is critical for the learning and performance of visual conditional associative tasks. The present study used positron emission tomography with magnetic resonance imaging to demonstrate the existence, within the human brain, of these two functionally distinct subdivisions of the lateral frontal cortex. These findings provide direct evidence that, just as the monkey brain, the human lateral frontal cortex is functionally heterogeneous and that comparable anatomical areas underlie similar functions in the two species.

Dorsolateral prefrontal lesions and oculomotor delayed-response performance: evidence for mnemonic "scotomas"

Abstract: The spatial memory functions of the monkey's prefrontal cortex were examined with oculomotor delayed-response (ODR) paradigms that required the animal to remember the spatial location of peripheral visual cues, while maintaining fixation on a central visual target during the presentation of each cue and during a subsequent 1.5–8 sec delay period. Four rhesus monkeys received unilateral or serial prefrontal lesions in and around the principal sulcus after they reached criterion performance on the ODR tasks. Unilateral lesions disrupted the performance of memory-guided eye movements to spatial cues in the visual field contralateral to the hemisphere in which the lesion was placed. Memory-guided eye movements to ipsilateral cues were mildly affected by unilateral lesions, and these lesions had little or no effect on performance in visually guided control tasks. With addition of a second lesion in the opposite hemisphere, the deficit was extended to include the opposite hemifield. The impairment was characterized by eye movements of inappropriate direction, and, excepting the one lesion that extended into the frontal eye field region of the arcuate sulcus, saccadic reaction times and velocities were the same before and after the lesions. The effect of the lesions was delay dependent: performance was rarely altered at the shortest (1.5 sec) delay but became progressively worse as the delay period was lengthened. The present results strengthen the evidence that the delayed-response deficits of monkeys with prefrontal lesions are caused by failure to maintain a transient memory “trace” in working memory, and indicate for the first time that working memory mechanisms are lateralized: memories for visuo- spatial coordinates in each hemifield are processed primarily in the contralateral prefrontal cortex. These findings provide evidence for the concept of mnemonic hemianopias and mnemonic scotomas, that is, memory deficits for particular hemifields or visual field locations, unaccompanied by simple sensory or motor deficits.

Procedural learning in Parkinson's disease and cerebellar degeneration

Abstract: We compared procedural learning, translation of procedural knowledge into declarative knowledge, and use of declarative knowledge in age-matched normal volunteers (n = 30), patients with Parkinson's disease (n = 20), and patients with cerebellar degeneration (n = 15) by using a serial reaction time task. Patients with Parkinson's disease achieved procedural knowledge and used declarative knowledge of the task to improve performance, but they required a larger number of repetitions of the task to translate procedural knowledge into declarative knowledge. Patients with cerebellar degeneration did not show performance improvement due to procedural learning, failed to achieve declarative knowledge, and showed limited use of declarative knowledge of the task to improve their performance. Both basal ganglia and cerebellum are involved in procedural learning, but their roles are different. The normal influence of the basal ganglia on the prefrontal cortex may be required for timely access of information to and from the working memory buffer, while the cerebellum may index and order events in the time domain and be therefore essential for any cognitive functions involving sequences.

Irrelevant tones produce an irrelevant speech effect : Implications for phonological coding in working memory

Abstract: A series of studies addresses the possibility that tones disrupt serial recall of visually presented material in the same way as speech. A stream of changing tones is as disruptive of visual serial recall as 4 syllables (Experiments 1 and 2). Similar effects were also shown with a repeated syllable that changed only in pitch (Experiment 3). Just as for speech, the effect of tones is not at encoding but during storage of the serial lists (Experiments 4 and 5). The results suggest that speech and tones are equipotent in their capacity to disrupt short-term memory. A «blackboard» model of working memory to account for the effects is outlined

A unified account of cognitive impairments following frontal lobe damage: the role of working memory in complex, organized behavior.

Abstract: A computer model is presented that performs 4 tasks sometimes impaired by frontal damage: motor sequencing, the Stroop task, the Wisconsin Card Sorting Test, and a context memory task. In each task, patterns of performance typical of frontal-damaged patients are shown to result from the same type of damage to the model, specifically, weakening of associations among elements in working memory. The simulation shows how a single underlying type of damage could result in impairments on a variety of seemingly distinct tasks. Furthermore, the hypothesized damage affects the processing components that carry out the task rather than a distinct central executive.

Neuronal activity related to visual recognition memory: long-term memory and the encoding of recency and familiarity information in the primate anterior and medial inferior temporal and rhinal cortex.

Abstract: Recordings of the activity of 2705 single neurones were made in entorhinal and perirhinal cortex, area TG of the temporal lobe, and the inferior temporal cortex both during monkeys' performance of a serial recognition memory task using complex pictures and when monkeys were shown objects. Responses of 120 (9.7%) of the visually responsive neurones recorded were significantly smaller to the second than to the first presentations of unfamiliar stimuli. The incidence of such responses was highest in perirhinal cortex plus areas TE1 and TE2 of the temporal lobe, intermediate in lateral entorhinal cortex and areas TE3 and TG, and lowest in other parts of entorhinal and inferior temporal cortex. Response decrements were maintained across 20 or more intervening presentations of other stimuli for the majority of the neurones tested. Responses of 43 (14.4%) of the visually responsive neurones tested were significantly greater to unfamiliar than to highly familiar stimuli. Such differential responses were found only in lateral entorhinal and perirhinal cortex plus areas TG, TE1, TE2 and TE3. For 6 neurones the response difference was significant even when the familiar stimuli had not been seen for more than 24 h: such neurones demonstrate access to information stored in long-term memory for more than 24 h. Seven familiarity neurones signalled information concerning the relative familiarity of stimuli but not information concerning how recently they were last seen; 58 recency neurones signalled information concerning the recency of presentation of stimuli, but not their relative familiarity. Thus certain neurones demonstrate the separable encoding of recency and familiarity information. Neurones signalling information of use for recognition memory are found in cortex close to the rhinal sulcus where lesions result in major deficits in the performance of recognition memory tasks. The conjunction of these findings provides strong evidence for the importance of these neurones and this cortex for processes (recency and familiarity discrimination) necessary for recognition and working memory. The possible relation of the neuronal responses to priming memory is also discussed.

Facts and fiction about memory aging: a quantitative integration of research findings

Abstract: A meta-analytic literature review on adult age differences in speed of search in short-term memory (12 studies), memory span (40 studies), list recall (68 studies), paired-associate recall (21 studies), and prose recall (39 studies) is presented. Results show that age differences are quite large (depending on the task, elderly people can be situated between the 3rd and the 38th percentile of the adult age memory performance distribution) and quasi-omnipresent, even under conditions of cued recall or semantic task orientation. Evidence for age sensitivity is found for the process of categorization of lists, but not for semantic processing, association strategies, imagery, nor for extracting main points from prose material. The elderly population benefits more than the young from the possibility of reviewing lists or texts. Differences between young adults and old-old adults are larger than between young adults and the young-old for speed of search in short-term memory and prose recall only. In two out of the five tasks, lower education is reliably associated with larger age differences.

Memory for spatial locations, motor responses, and objects : triple dissociation among the hippocampus, caudate nucleus, and extrastriate visual cortex

Abstract: Based on behavioral procedures aimed at measuring working or data-based memory for spatial location, response, and visual object information, it is shown that there is a triple dissociation among the hippocampus, caudate nucleus, and extrastriate visual cortex in mediating spatial location, response, and visual object information, respectively. The hippocampus appears to subserve only spatial location, the caudate nucleus only response, and the extrastriate visual cortex only visual object information. The results support the neurobiological foundation of the attribute memory model.

Phonological working memory: a critical building block for reading development and vocabulary acquisition?

Abstract: In this article we review findings from a recent longitudinal study of the contribution of phonological working memory to vocabulary acquisition and reading development. A total of 80 children were tested initially at school entry at the age of four years, and were tested in three further waves at ages 5, 6, and 8 years. The results indicate that phonological memory skills constrain vocabulary growth during the first year or so in school but that subsequently, vocabulary knowledge is a pacemaker in the development relationship with memory. Phonological memory skill in prereading children was found to be significantly linked with scores on a reading test at age 8 which encourages the use of a phonological recoding strategy. The theoretical and practical implications of the findings, and important areas for future research, are discussed.

Phonological working memory in very young children

Abstract: By Gathercole, Susan E.; Adams, Anne-Marie Developmental Psychology. Vol 29(4), Jul 1993, 770-778. Abstract This study was designed to establish whether phonological working memory skills could be assessed in children below 4 yrs of age. A group of 2- and 3-yr-old children were tested on 3 phonological memory measures (digit span, nonword repetition, and word repetition) and were also given tasks that tapped other cognitive skills. Scores on the 3 phonological memory tasks were closely related. In addition, repetition performance was linked with both vocabulary knowledge and articulation rate. Results indicate that phonological memory skills can be reliably assessed in very young children by using conventional serial span and repetition procedures. (PsycINFO Database Record (c) 2008 APA, all rights reserved)

Working memory and strategies in syllogistic-reasoning tasks

Abstract: It has often been asserted that working-memory limitations are a major factor contributing to problem difficulty; for example, Johnson-Laird’s (1983) mental-models theory appeals to working memory limitations to explain the difficulty of syllogistic reasoning. However, few studies have directly explored working memory in problem solving in general or syllogistic reasoning in particular. This paper reports two studies. In the first, working-memory load was varied by presenting syllogistic tasks either verbally or visually (so that the premises were continuous1y avai1ab1e for inspection). A significant effect of memory load was obtained. In the second study, premises were presented visually for a subject-determined time. Dual-task methods were used to assess the role of working-memory components, as identified in Baddeley’s (1986) model. Syllogistic performance was disrupted by concurrent random-number generation but not by concurrent articulatory suppression or by concurrent tapping in a preset pattern. Furthermore, the concurrent syllogism task interfered with random generation and to a lesser extent with articulatory suppression, but not with tapping. We conclude that while the central-executive component of working memory played a major role in the syllogistic-task performance reported here, the articulatory loop had a lesser role, and the visuospatial scratch pad was not involved.

A connectionist approach to the prefrontal cortex.

Abstract: Recent data from studies of the prefrontal cortex (PFC) in humans and laboratory animals are reviewed with particular reference to the anatomical substrates of prefrontal neuropsychological function in health and disease. The PFC has been shown to have a unique pattern of supramodal connectivity with intracortical and subcortical circuits that place the PFC in an anatomical position to subserve "executive" cognitive functions and modulate limbic information to relate to basal ganglia circuits in a highly specific manner and to uniquely control the neurochemical elements of attention and reward. PFC connectivity is also consistent with current hypotheses about prefrontal neuropsychology, which emphasize conscious, goal-directed behavior guided by past experience. PFC connectivity explains the frequency with which prefrontal dysfunction is seen in disease states, which, on the basis of neuroimaging and neuropathology data, can be categorized as either intrinsic or dysconnection disorders.

Individual difference and contextual variables influence spatial memory in younger and older adults

Abstract: This study examined the influence of individual difference and contextual variables on the magnitude of age differences in memory for spatial location. Younger adults and 2 samples of older adults that differed in educational attainment, verbal intelligence, and working memory ability were compared. Ss studied and later recreated an arrangement of small objects that were placed on a plain map or a visually distinctive model. The objects were either unrelated or categorically related items. The results indicated that distinctive context enhanced spatial memory, and the magnitude of the benefit was generally comparable across age groups and stimulus sets. Hierarchical regression analyses confirmed that working memory resources accounted for a sizable proportion of age-related variance in memory for spatial location. The implications of these results for current views on age-related differences in memory for spatial location are discussed.

Linguistic and Cognitive Correlates of Academic Skills in First and Second Languages

Abstract: Using the theoretical frameworks proposed by Cummins (1981a) and Bialystok and Ryan (1985), this research was designed to shed light on the relationship between cognitive correlates and linguistic skills in first (L1) and second (L2) language, and the extent to which performance on academic tasks in L2 can be predicted by these factors. The study was conducted with 73 Grade 5–7 children attending a bilingual English-Hebrew day school. The test battery included a measure of intelligence, measures of linguistic knowledge in L1, measures of reading comprehension in L1 and L2 and static and working memory measures in L1 and L2. Evidence was found for the theoretical notion that with increased speed of basic processing in L2, higher level cognitive processes involved in linguistic and oral communication in academic settings are facilitated. Additionally, results suggest that children who can more systematically employ analytic functions in their L1 are more likely to do so in their L2 as well, and that performance on linguistically demanding tasks such as reading in L2 can be more accurately predicted with the aid of information on memory storage and executive control functions, in combination with underlying intelligence and L2 oral proficiency. Results highlight the important role that memory plays in performing linguistic tasks in L2 and help to explain underlying ability factors related to Cummins' interdependence hypothesis.

Frontal granular cortex input to the cingulate (M3), supplementary (M2) and primary (M1) motor cortices in the rhesus monkey

Abstract: Although frontal lobe interconnections of the primary (area 4 or M1) and supplementary (area 6m or M2) motor cortices are well understood, how frontal granular (or prefrontal) cortex influences these and other motor cortices is not. Using fluorescent dyes in rhesus monkeys, we investigated the distribution of frontal lobe inputs to M1, M2, and the cingulate motor cortex (area 24c or M3, and area 23c). M1 received input from M2, lateral area 6, areas 4C and PrCO, and granular area 12. M2 received input from these same areas as well as M1; granular areas 45, 8, 9, and 46; and the lateral part of the orbitofrontal cortex. Input from the ventral part of lateral area 6, area PrCO, and frontal granular cortex targeted only the ventral portion of M1, and primarily the rostral portion of M2. In contrast, M3 and area 23c received input from M1, M2; lateral area 6 and area 4C; granular areas 8, 12, 9, 46, 10, and 32; as well as orbitofrontal cortex. Only M3 received input from the ventral part of lateral area 6 and areas PrCO, 45, 12vl, and the posterior part of the orbitofrontal cortex. This diversity of frontal lobe inputs, and the heavy component of prefrontal input to the cingulate motor cortex, suggests a hierarchy among the motor cortices studied. M1 receives the least diverse frontal lobe input, and its origin is largely from other agranular motor areas. M2 receives more diverse input, arising primarily from agranular motor and prefrontal association cortices. M3 and area 23c receive both diverse and widespread frontal lobe input, which includes agranular motor, prefrontal association, and frontal limbic cortices. These connectivity patterns suggest that frontal association and frontal limbic areas have direct and preferential access to that part of the corticospinal projection which arises from the cingulate motor cortex.

Working memory and the self-ordered pointing task: Further evidence of early prefrontal decline in normal aging

Abstract: Two major lines of investigation are currently clarifying the nature of the impairment of working memory associated with normal aging. Cognitive psychology has formulated the problem in terms such as the balance of impairment of encoding, retrieval, storage and/or attention, whereas neuropsychology has formulated the problem in terms such as the balance of frontal (executive) versus temporal (mnemonic) degeneration. The findings of this study support the contention that the primary impairment of working memory in early normal aging is an active attentional executive processing deficit. Specifically, on the Self-Ordered Pointing Task, there is significantly ineffective exploitation of top-down clustering strategy as a function of aging. On this task, self-organization of encoding and retrieval must occur simultaneously with ongoing responding. The finding cannot be explained as an impairment of encoding, retrieval, storage, or build-up and/or release of proactive interference, since indexes of these did not discriminate young-adult from middle-aged samples.

Posterior Cingulate Cortex and Spatial Memory: A Microlimnology Analysis

Abstract: The neurobiology of cingulate cortex is like a dog. Each of the four areas of study— anatomy, physiology, chemistry, and behavior—forms one of the dog’s legs. No one notices it when we are simply sitting still, but if we get together and try to get up and run, it is clearly a three-legged dog. An understanding of the contributions of area 29 neurons to the control of behavior is only now beginning to emerge, and it is becoming clear to us that this circuitry makes a unique contribution to memory processes; one that includes, but is not limited to, the spatial domain. Our experiments over the past 10 years have shown that circuitry in area 29 exerts a powerful influence in the spatial guidance of behavior. Its contribution bears family resemblances both to posterior parietal cortex and to the hippocampal formation.