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Biomedical subjects

N Cowan

Publications and source records attributed to N Cowan.

At least 19 recordsLinked to original sources
PubMed1997

Impaired precision, but normal retention, of auditory sensory ("echoic") memory information in schizophrenia.

Working memory is the type of memory that allows one to hold information in mind while working on a task or problem. The present study investigated attention-independent auditory sensory ("echoic") memory in 18 schizophrenic participants and 17 controls. Schizophrenic participants showed impaired delayed tone matching performance in comparison with controls. However, when groups were matched for performance at 1 s by varying the difficulty of the task across groups, schizophrenic participants showed normal retention of information as reflected in normal tone matching performance. These findings demonstrate that schizophrenic may be in the sensitivity of the system rather than the duration for which memory traces were retained.

Adult↗
PubMed1997

Constraints on Awareness, Attention, Processing, and Memory: Some Recent Investigations with Ignored Speech

We discuss potential benefits of research in which attention is directed toward or away from a spoken channel and measures of the allocation of attention are used. This type of research is relevant to at least two basic, still-unresolved issues in cognitive psychology: (a) the extent to which unattended information is processed and (b) the extent to which unattended information that is processed can later be remembered. Four recent studies of this type that address these questions in various ways (Cowan, Lichty, & Grove, 1990; Wood & Cowan, 1995a,b; Wood, Stadler & Cowan, in press) are reviewed as illustrations. We conclude from these studies that (a) unattended information appears to be partially processed automatically, though attention enhances the processing considerably, and (b) the unattended information that is processed may not be retrievable in direct or many indirect memory tasks, though it remains possible that there is an automatically stored memory trace (e.g., one that could produce semantic priming).

Journal Article↗
PubMed1996

Neuronal abnormalities in microtubule-associated protein 1B mutant mice.

Microtubules play an important role in establishing cellular architecture. Neuronal microtubules are considered to have a role in dendrite and axon formation. Different portions of the developing and adult brain microtubules are associated with different microtubule-associated proteins (MAPs). The roles of each of the different MAPs are not well understood. One of these proteins, MAP1B, is expressed in different portions of the brain and has been postulated to have a role in neuronal plasticity and brain development. To ascertain the role of MAP1B, we generated mice which carry an insertion in the gene by gene-targeting methods. Mice which are homozygous for the modification die during embryogenesis. The heterozygotes exhibit a spectrum of phenotypes including slower growth rates, lack of visual acuity in one or both eyes, and motor system abnormalities. Histochemical analysis of the severely affected mice revealed that their Purkinje cell dendritic processes are abnormal, do not react with MAP1B antibodies, and show reduced staining with MAP1A antibodies. Similar histological and immunochemical changes were observed in the olfactory bulb, hippocampus, and retina, providing a basis for the observed phenotypes.

Animals↗
PubMed1996

The development of memory for ignored speech.

Previous studies of the development of children's memory have focused on attended stimuli. Here we examine short-term memory for spoken words that were ignored at the time of their presentation. In Experiment 1, a visual matching task was interrupted occasionally by a set of picture alternatives. The participant was to select the picture matching the most recently heard word, which had been presented 1, 5, or 10 s ago. An age difference in memory was found, but performance levels were quite high. Experiment 2 employed an alternative visual task to tie up phonological processing, bringing performance levels down to a more sensitive range. An age difference in the persistence of memory was obtained under these circumstances. We conclude that relatively attention-free properties of short-term memory may change with development in childhood.

Age Factors↗
PubMed1996

Estimating unconscious processes: implications of a general class of models.

Jacoby and his colleagues (e.g., L. L. Jacoby, J. P. Toth, & A. P. Yonelinas, 1993) have shown how the mnemonic contributions of conscious recollection and unconscious familiarity can be separated using a process-dissociation procedure based on a comparison of tasks in which consciously recollected material is to be included in vs. excluded from the responses. However, the estimate of unconscious familiarity depends on the assumptions of the model. This article describes a more general class of models in which the ratio of overlap between conscious and unconscious processes remains fixed and shows that this class of models (which includes the redundancy and exclusivity models as extreme cases) yields improbable results.

Humans↗
PubMed1996

Can We Resolve Contradictions between Process Dissociation Models?

Wainwright and Reingold (1996) presented equations for various versions of the process dissociation procedure that has been used to separate conscious and unconscious memory processes. In the present reply it is suggested that these equations, though helpful, may not capture some of the key theoretical possibilities that could help to resolve apparent contradictions and paradoxes in the empirical literature. Specifically, there could be an independence of processes that might be estimated to a sufficient degree of accuracy for some theoretical purposes despite a violation of the assumption of stochastic independence.

Journal Article↗
PubMed1995

The cocktail party phenomenon revisited: attention and memory in the classic selective listening procedure of Cherry (1953).

Though E. C. Cherry (1953) examined the recall of information from an irrelevant spoken channel in selective listening, the relationship between attention and subsequent recall still has not been examined adequately. It was examined here in 4 experiments, 3 of which were designed to identify conditions under which some participants, but not others, would notice a change from forward to backward speech. Only participants who shifted attention toward the irrelevant channel during the backward speech later recalled hearing it. In those whose attention shifted, shadowing errors peaked dramatically about 15 s after the change. There was no evidence of direct or indirect memory for phrases presented in the irrelevant channel. The results contradict models of attention stating that listeners process task-irrelevant information extensively without diverting resources used in shadowing.

Attention↗
PubMed1995

The cocktail party phenomenon revisited: how frequent are attention shifts to one's name in an irrelevant auditory channel?

N. Moray's (1959) well-known study of the "cocktail party phenomenon" suggested that participants sometimes notice their name embedded in an ignored auditory channel. However, the empirical finding was preliminary in nature and never has been directly replicated. This was done with improved methodological controls, and the relationship between on-line attention shifts to one's name and subsequent recollection of the name in a sample of 34 undergraduates was examined. Similar to N. Moray, only 34.6% of the participants recalled hearing their name in the channel to be ignored. Only those participants showed on-line evidence of attention shifts, and those shifts occurred only for the two items following the name. The results suggest that participants who detected their name monitored the irrelevant channel for a short time afterward.

Affect↗
PubMed1995

Can auditory memory for tone pitch be rehearsed?

This study investigated whether nonverbal auditory memory representations can be affected by rehearsal strategies. The comparison of the pitches of 2 tones separated by a silent, variable delay interval was examined in 2 experiments, both when participants were instructed to rehearse the pitch of the first tone covertly during the intertone interval and when such rehearsal was prevented by 1 of 2 attention-demanding distractor tasks. In both experiments, delayed tone comparison performance was superior when participants were permitted to rehearse, and the type of distractor task (verbal vs. auditory) had no effect on performance under distraction instructions. The results suggest that auditory imagery can be used strategically to slow the rate of decay of auditory information for tone pitch.

Female↗
PubMed1995

Sequential memory in children with and without language impairment.

Serial recall was studied in children with language impairment and two groups of normally achieving controls: a group matched for age and a younger group matched for reading and memory capacity. Participants were presented lists of digits that were one item longer than their memory span, in conditions requiring either written or oral recall. Digit lists were presented either with or without a final nonword item, or "suffix," that was capable of interfering with memory for items at the end of the list. The main finding was that the list-final suffix effect was substantially larger than normal in children with language impairment, even though other aspects of their recall were normal. This deficiency in children with language impairment was evident only under a scoring system that credited recall of items in their correct serial positions, not under scoring systems that credited memory for the presence of items or their sequence. Results are interpreted according to the hypothesis that children with language impairment are more dependent upon relatively unanalyzed acoustic and phonetic representations of speech than are other children.

Child↗
PubMed1995

Auditory sensory ("echoic") memory dysfunction in schizophrenia.

OBJECTIVE: Studies of working memory dysfunction in schizophrenia have focused largely on prefrontal components. This study investigated the integrity of auditory sensory ("echoic") memory, a component that shows little dependence on prefrontal functioning. METHOD: Echoic memory was investigated in 20 schizophrenic subjects and 20 age- and IQ-matched normal comparison subjects with the use of nondelayed and delayed tone matching. RESULTS: Schizophrenic subjects were markedly impaired in their ability to match two tones after an extremely brief delay between them (300 msec) but were unimpaired when there was no delay between tones. CONCLUSIONS: Working memory dysfunction in schizophrenia affects brain regions outside the prefrontal cortex as well as within.

Acoustic Stimulation↗
PubMed1995

Timed reactions to an object in apparent motion: evidence on Cartesian and non-Cartesian perceptual hypotheses.

In three experiments on apparent motion, subjects were to press a computer key as quickly as possible either when the apparently moving stimulus passed the midpoint of its trajectory or when it reached the endpoint. If motion is perceived as a trajectory through a series of spatial locations, and if this type of percept is the basis of deliberate responding (assumptions that can be considered Cartesian in origin), then reaction times should be faster to the midpoint than to the endpoint. In contrast to these assumptions, there was no difference between reaction times to these two points. Alternative accounts of the results are discussed.

Attention↗
PubMed1994

Knowing trends.

Explore the source record for details and available documents.

Career Choice↗
PubMed1993

Process formation in Sf9 cells induced by the expression of a microtubule-associated protein 2C-like construct.

To understand the roles of various microtubule-associated proteins (MAPs) in the development of axons and dendrites, we have expressed individual neuronal MAPs in normally rounded Sf9 host cells. We previously reported that expression of tau protein in these cells results in the elaboration of long processes containing dense bundles of microtubules (MTs). These bundles generally terminate in the hillock region of the cell body, and almost all of the MTs within the bundles are oriented with their plus ends distal to the cell body. Here we report the expression of a construct that approximates the MAP2C sequence and also induces the elaboration of processes with dense bundles of predominantly plus-end-distal MTs. Whereas tau generally results in a single process, there is a significantly greater tendency for the MAP2C-like construct to induce multiple processes. In contrast to the tau processes, the MT bundle in these processes extends far into the cell body. This latter observation suggests that MAP2C and tau have different effects on MT assembly and/or transport events in the cell. Although both of these MAPs can organize MTs that are competent to participate in process formation, the detailed organization of MTs induced by each of the two constructs is distinctive, and these differences may be relevant to axonal and dendritic differentiation.

Animals↗
PubMed1993

Memory prerequisites of mismatch negativity in the auditory event-related potential (ERP).

The mismatch negativity (MMN) is a component of the auditory event-related brain potential that occurs in response to infrequent changes in the physical properties of homogeneous series of sounds, even when subjects are instructed to ignore the auditory channel of stimulation. It has been proposed (e.g., Näätänen, 1990) that the MMN is generated by an automatic process in which a difference between the deviant sound and the previous, standard sound is detected by the brain. However, it is unclear how the form of memory involved is related to the rest of the memory system. The present study indicates that, for an MMN to be elicited in response to a change in tone frequency, the representation of the standard tone must be both (a) well-established as a standard in memory, and (b) in a currently active state. The relation between physiological and psychological aspects of memory representation is discussed.

Acoustic Stimulation↗