CNS effects in the correct perspective (original) (raw)
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Current Directions in Psychological Science, 2005
Verbal working memory consists of separable capacities for the retention of phonological and semantic information. Within the phonological domain, there are independent capacities for retaining input-phonological codes and output-phonological codes. The input-phonological capacity does not appear to be critical for language comprehension but is involved in verbatim repetition and long-term learning of new words. The semantic capacity is critical for both comprehension and production and for the learning of new semantic information. Different neural structures appear to underlie these capacities, with a left-parietal region involved in input-phonological retention and a left-frontal region involved in semantic retention.
ARTICLE NO. CC970301 Brain Mechanisms of Cognitive Skills
2014
This article examines the anatomy and circuitry of skills that, like reading, calculating, recognizing, or remembering, are common abilities of humans. While the anatomical areas active are unique to each skill there are features common to all tasks. For example, all skills produce activation of a small number of widely separated neural areas that appear necessary to perform the task. These neural areas relate to internal codes that may not be observed by any external behavior nor be reportable by the performer. There is considerable plasticity to the performance of skills. Task components can be given priority through attention, which serves to increase activation of the relevant brain areas. Attention can also cause reactivation of sensory areas driven by input, but usually only after a delay. The threshold for activation for any area may be temporarily reduced by prior activation (priming or practice). Skill components requiring attention tend to cause interference resulting in t...
Short-term memory demands of reaction-time tasks that differ in complexity
Journal of Experimental Psychology: Human Perception and Performance, 1980
Four experiments were conducted to determine whether the increased reaction time produced by loading memory with a set of irrelevant items depended on the complexity of the stage structure or of the stimulus-response (S-R) mapping rules underlying the task. In each experiment, reaction-time tasks varying in complexity were performed alone and in the retention interval of a short-term memory task requiring ordered recall of eight digits. Experiment 1 compared simple, choice, and go/no-go tasks over 3 days of practice and found no interaction between memory load and task complexity. Experiment 2 replicated the first day of Experiment 1 with more power and again found no interaction. Since the different tasks required different numbers of stages, this ruled out stage structure as a factor loading memory. However, in Experiment 1 and 2, the same subjects performed all three tasks with the same set of letters and may have developed one comprehensive set of mapping rules for all three tasks, essentially eliminating differences in memory demands between tasks. Experiment 3 used different groups of subjects for a simple and a choice task with letters as stimuli to encourage the development of separate, differentially complex mapping rules for each task and found more interference in the choice task than in the simple task. Experiment 4 involved one group that performed the choice task with letters and the simple task with dots presented at different positions in the visual field, and another group that performed the simple task with letters and the choice task with dots. Comparisons within subjects between materials and between subjects within materials showed that with letters as stimuli, the choice task suffered more interference than the simple task. However, the choice task with dots showed no such pattern, perhaps because of high ideomotor compatibility. It is concluded that S-R mapping rules are held in memory to enable performance on reaction-time tasks, and the findings are discussed in terms of strategies, preparation, and attentional control. Reaction-time tasks that require no of short-term memory and suffer interapparent storage of stimulus information ference when capacity is shared with a suffer interference when short-term memory concurrent memory load. The more capacis loaded with a set of irrelevant items. For ity required for the memory load, the less example, the time to decide which of two is available for the reaction-time task, so lines is longer is increased substantially interference should increase with memory when the subject retains a set of eight load. The available data support this consonants (Shulman & Greenberg, 1971). assumption; for a variety of judgments, This article reports an investigation of some the impairment in reaction time is proporaspects of reaction-time tasks that may be tional to the load for loads of five items or responsible for this interference.
Developments in the concept of working memory
Neuropsychology (journal), 1994
The authors summarize developments in the concept of working memory as a multicomponent system, beginning by contrasting this approach with alternative uses of the term working memory. According to a 3-component model, working memory comprises a phonological loop for manipulating and storing speech-based information and a visuospatial sketchpad that performs a similar function for visual and spatial information. Both are supervised by a central executive, which functions as an attentional control system. A simple trace-decay model of the phonological loop provides a coherent account of the effects of word length, phonemic similarity, irrelevant speech, and articulatory suppression in verbal short-term memory tasks. This model of the loop has also proved useful in the analysis of neuropsychological, developmental and, cross-cultural data. The notion of the sketchpad is supported by selective interference with imagery in normal adults and by specific neuropsychological impairment. Analysis of the central executive is illustrated by work on deficits in the ability to coordinate subproccesses in Alzheimer's disease. Some 20 years ago, we proposed that the concept of a unitary short-term memory system should be replaced by that of a multicomponent working memory (Baddeley & Hitch, 1974). The proposal appears to have been a fruitful one. The term working memory has become increasingly common, and we suspect that the majority of those of our colleagues who continue to prefer the older terms of shortterm or primary memory would be sympathetic to the emphasis on the functional role of the system that is implied by the term working memory. At the same time, it is important to note that the term working memory is used in a number of different ways. Leaving aside the very different concept of working memory used in the animal literature (Olton, Walker, & Gage, 1978), there are at least three separate uses of the term in cognitive psychology. First, computational models using a production system architecture use the term to refer to that part of the architecture that holds the relevant productions. It is, however, important to note that working memory in such systems is an assumption that underpins this method of modeling rather than an attempt to represent an important component of human cognition. In Newell's (1990) SOAR architecture, working memory is assumed to be of unlimited capacity and is not in any sense modeled on empirical evidence. That does not of course mean that production system architectures are not, under certain circumstances, used in ways that explicitly attempt to reflect the empicial evidence, and in these cases, some form of limitation on working memory capacity is typically assumed (Just & Carpenter, 1992; Kintsch & van Dijk, 1978). A second interpretation focuses on working memory as a system that combines storage and processing, measuring
Temporal dynamics of brain activation during a working memory task
Nature, 1997
by distinct cortical structures, with the prefrontal cortex housing the executive control processes, and more posterior regions housing the content-specific buffers (for example verbal versus visuospatial) responsible for active maintenance334. However, studies in non-human primates suggest that dorsolateral regions of the prefrontal cortex may also be involved in active mainte-nance5-'. We have used functional magnetic resonance imaging to examine brain activation in human subjects during performance of a working memory task. We used the temporal resolution of this technique to examine the dynamics of regional activation, and to show that prefrontal cortex along with parietal cortex appears to play a role in active maintenance.
Cerebral Cortex, 1998
Working memory (WM), the ability to briefly retain and manipulate information in mind, is central to intelligent behavior. Here we take advantage of the high temporal resolution of electrophysiological measures to obtain a millisecond timescale view of the activity induced in distributed cortical networks by tasks that impose significant WM demands. We examined how these networks are affected by the type and amount of information to be remembered, and by the amount of task practice. Evoked potentials (EPs) were obtained from eight subjects performing spatial and verbal versions of a visual n-back WM task (n = 1, 2, 3) on each of three testing days. In well-trained subjects, WM tasks elicited transient responses reflecting different subcomponents of task processing, including transient (lasting 0.02-0.3 s) task-sensitive and loadsensitive EPs, as well as sustained responses (lasting 1-1.5 s), including the prestimulus Contingent Negative Variation (CNV), and post-stimulus frontal and parietal Slow Waves. The transient responses, with the exception of the P300, differed between the verbal and spatial task versions, and between trials with different response requirements. The P300 and the Slow Waves were not affected by task version but were affected by increased WM load. These results suggest that WM emerges from the formation of a dynamic cortical network linking task-specific processes with non-specific, capacity-limited, higher-order attentional processes. Practice effects on the EPs suggested that practice led to the development of a more effective cognitive strategy for dealing with lower-order aspects of task processing, but did not diminish demands made on higher order processes. Thus a simple WM task is shown to be composed of numerous elementary subsecond neural processes whose characteristics vary with type and amount of information being remembered, and amount of practice.