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PubMed2005

Neural correlates of prospective and retrospective memory.

This study examines the event-related brain potential (ERP) correlates of retrieval processes in prospective and retrospective memory (i.e., recognition and cued-recall). In contrast to previous research that has compared performance on tasks measuring prospective and retrospective memory, the stimulus materials and encoding and response demands of the prospective and retrospective components of the tasks were reasonably well matched for the two forms of memory. This resulted in the primary difference between the assessments of prospective and retrospective memory being the requirement for self-initiated retrieval in prospective memory. Analyses of mean amplitude measures revealed modulations of the ERPs typically associated with prospective memory (i.e., N300 and prospective positivity) and retrospective memory (i.e., FN400, parietal positivity and frontal slow waves). Partial least squares analyses revealed one latent variable related to the retrieval of a previously studied item that contrasted retrospective hits and prospective hits from ongoing activity trials and prospective lures; and one latent variable uniquely associated with prospective hits. These findings indicate that similar neural processes support retrieval in prospective and retrospective memory and that the realization of intentions is additionally dependent on processes that are uniquely related to prospective memory.

Adolescent↗
PubMed2000

Transcranial magnetic stimulation of primary motor cortex affects mental rotation.

Neuroimaging studies have shown that motor structures are activated not only during overt motor behavior but also during tasks that require no overt motor behavior, such as motor imagery and mental rotation. We tested the hypothesis that activation of the primary motor cortex is needed for mental rotation by using single- pulse transcranial magnetic stimulation (TMS). Single-pulse TMS was delivered to the representation of the hand in left primary motor cortex while participants performed mental rotation of pictures of hands and feet. Relative to a peripheral magnetic stimulation control condition, response times (RTs) were slower when TMS was delivered at 650 ms but not at 400 ms after stimulus onset. The magnetic stimulation effect at 650 ms was larger for hands than for feet. These findings demonstrate that (i) activation of the left primary motor cortex has a causal role in the mental rotation of pictures of hands; (ii) this role is stimulus-specific because disruption of neural activity in the hand area slowed RTs for pictures of hands more than feet; and (iii) left primary motor cortex is involved relatively late in the mental rotation process.

Adult↗
PubMed1996

Mental rotation may underlie apparent object-based neglect.

Previous investigations have suggested that object-based neglect may reflect an impairment in attentional allocation that occurs relative to the intrinsic left and right of objects. We report a patient with apparent "object-based" neglect of 90 degrees rotated stimuli for whom the pattern of neglect was a function of task strategy. When the patient was instructed to visualize the rotated stimuli as if they were upright, i.e. mentally rotate them, he showed apparent "object-based" neglect to the left of the principal axes of the stimuli. In contrast, when instructed to refrain from mental rotation, neglect was apparent only with respect to his left, but not the left of the stimuli. Thus, the apparent "object-based" neglect of this patient may be attributed to a process of mental rotation of objects to upright, and subsequent neglect in viewer-centered or environment-centered coordinates. These data suggest a mechanism whereby object-based and viewer/environment-centered reference frames may be aligned, thereby causing viewer/environment-centered neglect to appear as if object-based.

Aged↗
PubMed1997

Mental rotation and the right hemisphere.

Mental rotation may be considered a prototypical example of a higher-order transformational process that is nonsymbolic and analog as opposed to propositional. It is therefore a paradigm case for testing the view that these properties are fundamentally right-hemispheric. Evidence from brain-imaging, unilateral brain lesions, commissurotomy, and visual-hemifield differences in normals is reviewed. Although there is some support for a right-hemispheric bias, at least for the holistic rotation of relatively simple shapes, it is unlikely that this bias approaches the degree of left-hemispheric dominance for language-related skills. An evolutionary scenario is sketched in which the characteristically symbolic mode of the left hemisphere evolved relatively late and achieved the quality of recursive generativity only in the late stages of hominid evolution. This forced an increasingly right-hemispheric bias onto analog processes like mental rotation. Such processes nevertheless remain important and are integral even to those processes we think of as highly symbolic, such as language and mathematics.

Animals↗
PubMed2001

Transperceptual encoding and retrieval processes in memory: a PET study of visual and haptic objects.

An important objective of functional neuroimaging research is to identify neuroanatomical correlates of memory processes such as encoding and retrieval. In typical studies directed at this goal, however, the to-be-remembered information has been presented in a single perceptual modality. Under these conditions it is not known whether the observed brain activity reflects the studied memory process as such or only the memory process in the given modality. The positron emission tomography (PET) study reported here was designed to identify brain regions involved in encoding and retrieval processes specific to visual and haptic modalities, as well as those common to the two modalities. These latter, common regions, were assumed to be associated with "transperceptual" encoding and retrieval processes. Abstract three-dimensional objects, difficult to describe verbally, served as to-be-remembered materials. A multivariate partial least squares analysis of the PET data revealed that transperceptual encoding processes activated right medial temporal lobe, superior prefrontal cortex bilaterally, and posterior inferior temporal gyrus bilaterally. Transperceptual recognition activations were observed in two right orbitofrontal regions and in anterior cingulate. These results provide initial evidence that some processes involved in memory encoding and retrieval operate beyond perceptual processes and in that sense are transperceptual.

Adult↗
PubMed2000

Divided attention during encoding and retrieval: differential control effects?

Previous studies have shown that divided attention (DA) during retrieval has little effect on recall of episodic memories, although DA during encoding has a large detrimental effect. One possible reason for this asymmetry is that stimulus presentation at encoding is under experimenter control, whereas retrieval operations and responses are under participant control. This experiment tested this possibility by presenting paired-associate word lists for learning and recall, either at a fixed 4-s rate or at a rate controlled by the participant. The results showed that the higher recall levels for DA at retrieval than for DA at encoding held under all combinations of experimenter and participant control. The implications of these results for a fuller understanding of encoding and retrieval processes are discussed.

Adolescent↗
PubMed1982

Orienting task effects on text recall in adulthood.

This investigation examined the effects of orienting task-controlled processing on the text recall of younger (18 to 32 years), middle-aged (39 to 51 years), and older (59 to 76 years) adults. The participants were presented with a 500-word narrative text. Three groups performed orienting tasks (syntactic, stylistic, advice) within an incidental memory paradigm. A fourth group was asked for intentional recall. Analysis indicated a significant age by orienting task interaction. Younger adults recalled more propositions when recall was intentional or when it was preceded by a deep-orienting task than when it was preceded by a shallow-orienting task. Middle-aged and older adults recalled more propositions when recall was intentional than when it was incidental, regardless of the depth of the orienting task. There were no significant differences in intentional recall. In addition, a significant age x orienting task x propositional level interaction indicated that younger adults recalled more of the main ideas of the text following deep processing, whereas the middle-aged and older adults recalled more of these ideas following intentional processing.

Adolescent↗
PubMed1985

Speed of processing in normal aging: effects of speech rate, linguistic structure, and processing time.

Young and elderly adults heard three types of speech materials varying in both length and degree of semantic and syntactic constraints. Time compression was used to vary speech rates systematically to test a speed of processing hypothesis as one explanation of performance deficits associated with normal aging. In addition to segment length effects, the elderly participants showed significantly steeper rates of performance decline with increasing speech rate, with slope constants dependent on the structural constraints of the speech materials. The results are discussed in terms of processing rate hypotheses and context utilization.

Adolescent↗
PubMed2003

Low alpha power (7.5-9.5 Hz) changes during positive and negative affective learning.

There is evidence that the positive and the negative word lists of the Affective Auditory Verbal Learning Test (AAVL) are useful with regard to mood induction. To date, however, changes in brain activation, as indicated by quantitative electroencephalographic recording, have not been examined. Thus, changes in low alpha power (7.5-9.5 Hz) were examined during and after completion of the positive or the negative learning list of the AAVL among 37 undergraduate men and women. Three primary findings from the study include the following: (1) Previously reported recall patterns were replicated; (2) participants who completed the negative list reported a significant decline in mood state at the end of the session; and (3) participants who completed the negative word list evidenced a significant reduction in low alpha power (in comparison with baseline) within the parietal regions. The findings noted above are seemingly counter to contemporary theories of mood regulation (i.e., asymmetrical changes in anterior activity, rather than changes in parietal regions). Although the AAVL may have limited utility as a tool for mood induction, it may serve as a functional tool for examination of the cerebral processes associated with affective verbal memory.

Adolescent↗
PubMed1993

On the origin of functional differences in recollective experience.

Subjects studied target words that were repeated either immediately (lag0) or after six intervening items (lag6). At retention testing, subjects were required to discriminate targets from distractors and, contingent on a 'yes' response, to classify each identified item as one that evoked either a 'remember' (R) response or a 'know' (K) response. An R response indicated recognition based on conscious recollection, and K, recognition without conscious recollection. R responses were significantly greater in lag6 than lag0 whereas the reverse was found for K responses. The data are interpreted as showing that R responses depend on the probability of a target stimulus engaging conscious effortful processing, whereas K responses are increased in the absence of conscious involvement at learning.

Adult↗
PubMed1984

Speed of recall in aging.

This experiment investigated age differences in the speed of verbal recall under experimentally controlled processing conditions. Twelve normal aged and 12 young adults learned a set of items by a procedure that required them to search a list to identify instances of common conceptual categories. This search procedure was used to control for age differences in initial processing. Memory for the target items was tested by free recall and cued recall in which each item was cued by its category label. There were no age differences in either rate of free recall or speed of cued recall under these conditions. This result appears to be inconsistent with the Birren hypothesis, which predicts age differences in the speed of verbal recall. This experiment illustrates the importance of experimentally controlled processing conditions for evaluating of age-related changes in cognitive speed.

Adult↗
PubMedDate not supplied

The flow of thought and the flow of substance in the brain.

Many neuroactive substances undergo cytoplasmic transport along the axons and dendrites of cerebral neurons, and the expression of their activities is determined by the time occupied by their transport. Such substances include cyclic nucleotides which are formed postsynaptically as mediators by several neurotransmitters including catecholamines, and which are capable of acting at numerous postsynaptic sites during their subsequent intracellular translocation. Temporally patterned changes in cell-firing tendency during some seconds or minutes following brief stimuli are attributed to movement of such compound, as is also the subjective sense of a flow of thought. Descriptions are appraised which indicate that components experienced as part of a stream of thought can be initiated by drive-inducing catecholaminergic systems acting through cyclic nucleotides, thus affording endogenous signals that contribute to electrophysiological matching processes in perception and recall. Roles for satiety mechanisms involving opioid peptides are also assessed.

Animals↗