Showing papers in "Neuropsychology (journal) in 1996"

How localized are age-related effects on neuropsychological measures?

Abstract: The primary goal of the current study was to examine the degree of independence of the age-related influences on measures sometimes postulated to be sensitive to functioning in different regions of the brain. It is often assumed that levels of performance on different cognitive measures and the age-related effects on those measures are determined by separate and distinct mechanisms. In the case of measures from neuropsychological tests, the discovery of selective impairments by individuals with damage in particular regions of the brain has led to the inference that various brain structures are specialized for different types of processing. When combined with results indicating age-related deficits on those measures, these findings have led to speculation that certain regions of the brain are more sensitive to age-related decline than others. For example, at different times it has been suggested that the

Dissociations within nondeclarative memory in Huntington's disease.

Abstract: Patients with Huntington's Disease (HD) were tested on 2 tasks, probabilistic classification learning and artificial grammar learning Both tasks are performed normally by amnesic patients and are considered to be independent of declarative memory Patients with HD were severely impaired in probabilistic learning but performed normally in artificial grammar learning The probabilistic classification task may be akin to habit-learning tasks that depend on the neostriatum, whereas artificial grammar learning may depend on changes within neocortex similar to what is thought to occur in perceptual priming The deficit in the probabilistic classification task indicates that impaired nondeclarative learning in patients with HD occurs not only in motor tasks but also in nondeclarative learning tasks that have no motor component Huntington's disease (HD) is an inherited progressive neurological disorder that is characterized by involuntary, choreiform movements, affective disturbance, and progressive cognitive and functional decline The primary neuropathology

Cerebellar involvement in eyeblink classical conditioning in humans.

Abstract: The role of the ipsilateral cerebellum in human eyeblink conditioning was investigated using the 400-ms delay paradigm and testing 14 cerebellar patients (7 with unilateral lesions and 7 with bilateral lesions) and 20 control participants. Patients performed significantly worse with the ipsilesional eye than control participants but showed no difference when tested with (he contralesional eye. Conditioned responses (CRs) totaled 14% for all patients in comparison with 60% for control participants. Data on timed-interval tapping for 6 patients and 14 control participants showed that clock variability was greater with Ihe ipsilesional hand in patients. Only clock variability correlated significantly with percentage of CRs in control participants. Comparisons of paired associate learning and memory for 8 patients and 14 control participants revealed no significant differences. Results confirm that the ipsilateral cerebellum plays a role in eyeblink classical conditioning.

The Right Visual Field Advantage and the Optimal Viewing Position Effect: On the Relation Between Foveal and Parafoveal Word Recognition

Abstract: Recent developments on the optimal viewing position (OVP) effect suggest that it may be caused by the same factors that underlie the right visual field advantage in word recognition. This raises the question of the relationship between foveal and parafoveal word recognition. Three experiments are reported in which participants identified tachistoscopically presented words that were presented randomly in foveal and parafoveal vision. The results show that both the OVP effect and the right visual field advantage for word recognition are part of a larger extended OVP curve that has the shape of a Gaussian distribution with the mode shifted to the left of the center of the stimulus word. The shift of the distribution is a function of word length, but not of presentation duration; it is also slightly moderated by the information value of word beginning and word end. Tachistoscopic visual half field (VHF) studies are frequently used to assess the laterality of cognitive functions. They are based on the fact that stimuli presented in the left half of the visual field (LVF) are initially projected to the right cerebral hemisphere, and stimuli shown in the right half (RVF) are sent to the left cerebral hemisphere. This anatomical feature has been taken as support for the argument that LVF-RVF differences are an index of asymmetric functioning of the two cerebral hemispheres (for reviews see Bradshaw & Nettleton, 1983; Bryden, 1982; Hellige, 1993). Thus, the repeated finding that words are recognized more easily in the RVF than in the LVF is considered a consequence of left-hemisphere dominance for language processing. Further evidence for this position is obtained by finding that individuals with left hand preference show a reduced RVF superiority for word recognition relative to persons with right hand preference (Kim, 1994; but see Brysbaert, 1994c, for a more cautious account). The interpretation of LVF-RVF differences in word processing as an indication of laterality has not remained unchallenged, however. At least three alternative explanations of the RVF superiority have been proposed. The first considers the

Selective interference with the maintenance of location information in working memory.

Abstract: In 3 experiments, the nature of the events that interfere with spatial working memory was examined in order to clarify the roles of imagery, attention, and other processes in the short-term maintenance of location information. Looking and pointing at secondary task stimuli selectively interfered with memory for the locations of primary task stimuli. Secondary tasks that involved either mentally rotating primary task stimuli or making color or shape discriminations about primary or secondary task stimuli interfered with spatial working memory only if the required response was visually guided, but not if the response was verbal. Taken together, these findings support P.S. Goldman-Rakic's (1987) hypothesis regarding multiple representational domains and are consistent with known properties and connections of neurons believed to subserve the perception and maintenance of spatial information. A working memory task may be defined as one that requires holding onto information for a short time while it or other information is processed. Baddeley has proposed that there is a working memory system, specialized for concurrent storage and manipulation of information that is engaged by such tasks (for a recent overview, see Baddeley & Hitch, 1994). On the basis of studies of both intact and brain-damaged subjects (for a review, see Gathercole, 1994), Baddeley and his colleagues have divided the working memory system into three components: a phonological store for verbal information, a visuospatial sketchpad for visuospatial information, and a central executive that directs activities involved in manipulating and maintaining information in the two specialized stores. Perhaps the most studied example is the role of covert articulatory rehearsal in refreshing information in the phonological store. Performing a secondary task that requires articulation of verbal material decreases verbal memory span, a finding consistent with the hypothesized role of subvocalization in maintaining verbal information (e.g., Baddeley, Lewis, & Vallar, 1984). Much of the supporting evidence for the visuospatial component of Baddeley's model also comes from studies that use dual task procedures. These studies were designed to determine whether visuospatial and verbal working memory involve separate resources, and they have demonstrated that secondary verbal tasks interfere with memory for verbal information to a much greater extent than they interfere

Working Memory Impairments in Multiple Sclerosis: Evidence From a Dual-Task Paradigm

Abstract: The aim of this study was to investigate working memory in multiple sclerosis (MS) patients. To test the hypothesis that the central executive system (CES) of working memory is impaired, 36 MS patients were administered a dual-task paradigm in which a judgment of line orientation measure was performed concurrently with finger tapping, humming a melody, or reciting the alphabet. MS patients exhibited a significantly greater decrement in performance than controls during the more demanding dual-task conditions (concurrent humming or alphabet recitation) as compared with the single-task condition. Dual-task performance in MS patients correlated with performance on the Paced Auditory Serial Addition Test but not with other cognitive or clinical measures. The authors conclude that MS patients have a working memory deficit reflecting an impaired central executive system. Moreover, impairments in speed of information processing in MS patients are associated with this CES deficit. Memory dysfunction is the most common cognitive impairment observed in patients with multiple sclerosis (MS). A long-term memory deficit in these patients is well documented (Grafman, Rao, & Litvan, 1990), but most early studies of MS patients have concluded that short-term memory (STM) is intact. Support for this claim was derived from the observation of a normal digit span, as well as an intact recency effect on supraspan list learning, measures commonly used to assess STM (Caine, Bamford, Schiffer, Shoulson, & Levy, 1986; Rao, Hammeke, McQuillen, Khatri, & Lloyd, 1984). Although most studies continue to focus on the long-term memory impairments in MS patients (Rao, Leo, & Aubin-Faubert, 1989), evidence is accumulating that STM deficits may also exist (Grigsby, Ayarbe, Kravcism, & Busenbark, 1994; Rao et al., 1993). However, the nature of these deficits remain unclear. The purpose of this study was to further investigate STM processing in MS patients. Several experimental tasks have been useful for identifying impairment in various aspects of STM in MS patients. One experimental measure, the Brown-Peterson task (Peterson & Peterson, 1959), measures consolidation of information in STM and the effect of interference on temporarily stored information. With this task, two groups of investigators (Beatty, Goodkin, Monson, Beatty, & Hertsgaard, 1988; Grant,

Lexical, Sublexical, and Implicit Memory Processes in Healthy Young and Healthy Older Adults and in Individuals With Dementia of the Alzheimer Type

Abstract: Five groups of participants—healthy young, healthy young-old, healthy old-old, very mildly demented, and mildly demented individuals of the Alzheimer type (DAT)—participated in a 2-phase experiment that entailed a rhyme judgment task followed by a lexical decision task, in which half of the stimuli were earlier presented in the rhyme judgment task. The results of the rhyme task indicated that healthy young and older adults did not produce an influence of word frequency on rhyme decisions. However, the 2 groups of DAT individuals produced large word-frequency effects primarily for the nonrhyming pairs. The results of the lexical decision task indicated that (a) repetition facilitated lexical decisions to words, whereas there was evidence of inhibition for nonwords; and (b) there was an increasing influence of word frequency across the 5 groups of participants. The results are interpreted with respect to attentional control of appropriate (lexical and sublexical) processing pathways and the nature of processes that are disrupted and those that remain uninfluenced in healthy aging and DAT.

Central executive aspects of attention in subacute severe and very severe closed head injury patients: Planning, inhibition, flexibility, and divided attention

Abstract: Central executive aspects of attention were investigated in a group of 20 closed head injury (CHI) patients with an average posttraumatic amnesia duration of 23.9 days, tested in the first half year after injury. Four aspects were distinguished: planning, inhibition, flexibility, and divided attention. Tasks allowed assessment of these with experimental or statistical control for the individual speed of information processing. This precaution appears necessary because slow information processing is a pervasive effect of CHI and may cause spurious effects on complex cognitive tasks under time pressure. Strong effects of CHI were shown on speed of information processing. Controlling this factor, central executive aspects of attention were normal, on average. A tentative analysis of the results in relation to severity indicated that less severely injured patients are better in this respect than controls, and more severely injured patients are worse. In comparison with the healthy control group, the performance of those with milder injuries appears to be characterized by greater cautiousness and increased mental effort.

Explicit and Implicit Memory in the Elderly: Evidence for Double Dissociation Involving Medial Temporal- and Frontal-Lobe Functions

Abstract: Rotman Research Institute of Baycrest Centre for Geriatric Care Groups of normal old people living in institutions or in the community and young adults were administered tests of implicit (IM) and explicit (EM) memory with word-stem (WSC) and word-fragment (WFC) completion paradigms. Neuropsychological tests sensitive to frontal and medial temporal lobe function were also administered. Age differences were observed on both tests of EM and on all neuropsychological tests. Priming effects on WSC were smaller in the institutionalized group than the other 2 groups. Comparisons of EM and IM test results with neuropsychological test scores revealed several effects, including significant correlations (a) between EM scores on both tests and performance on standard memory tests in both aged groups and (b) between IM scores of both aged groups on WSC and frontal-lobe test performance. The results provide evidence of a double dissociation with respect to involvement of brain regions in EM and IM. They also indicate that repetition priming in WSC and WFC involve different mechanisms and that frontal-lobe dysfunction is a factor in reduced priming on the WSC test. Memory loss is a frequent complaint of the elderly, but extensive research over several decades has shown that not all aspects of memory function decline at the same rate. Age differences favoring young adults are most consistently re- ported on explicit (or direct) tests of memory that use recall or recognition techniques to assess conscious recollection of contextually based information. This type of memory loss is often attributed to progressive deterioration of the hippocam- pus, a medial temporal lobe brain region that is critical to memory function and known to be particularly sensitive to the aging process (Albert & Stafford, 1986; Milner, 1966; Tomlin- son, 1972). Implicit (or indirect) tests of memory do not refer to specific events. In these tests, memory is assessed by the effects of experience on some measure of performance that does not involve conscious awareness of any part of the prior experi- ence. Tests of general knowledge, skill learning, and repetition priming in which exposure to a word biases subsequent Gordon Winocur, Rotman Research Institute of Baycrest Centre for Geriatric Care, Toronto, Ontario, Canada, Department of Psychol- ogy, Trent University, Peterborough, Ontario, Canada, and Depart- ments of Psychology and Psychiatry, University of Toronto, Toronto, Ontario, Canada; Morris Moscovitch, Department of Psychology, Erindale College, University of Toronto and Rotman Research Insti- tute of Baycrest Centre for Geriatric Care; Donald T. Stuss, Rotman Research Institute of Baycrest Centre for Geriatric Care and Depart- ments of Psychology and Medicine (Neurology), University of Toronto, Toronto, Ontario, Canada. This research was supported by grants from the Medical Research Council of Canada and the Ontario Mental Health Foundation. We thank Lars Nyberg and Marko Jelicic for comments on an earlier version of this article. Portions of this research were presented at the Annual Meeting of the Memory Disorders Research Society, Boston, October 1994. Correspondence concerning this article should be addressed to Gordon Winocur, Rotman Research Institute of Baycrest Centre for Geriatric Care, 3560 Bathurst Street, North York, Ontario, Canada, M6A 2El. Electronic mail may be sent to winocur@psych.utoronto.ca. identification in a word completion test are common examples of implicit tests of memory. In general, cognitive processes that underlie normal performance on such tests are preserved in old age (see Howard, 1991; Light & LaVoie, 1993, for reviews), but there are notable exceptions (Chiarello & Hoyer, 1988; Davis et al., 1990; Howard, Shaw, & Heisey, 1986; Hultsch, Masson, & Small, 1991; Rose, Yesavage, Hill, & Bower, 1986). A primary purpose of the present study was to investigate one type of implicit memory (word-stem completion) on which age differences have been reported and to examine these differences from a neuropsychological perspective. Word completion as a measure of priming is usually studied in one of two ways. In word-fragment completion, the individual is presented initially with the complete word and then at test is given a sample of the word's letters (e.g.,

Impairment of memory for spatial context in schizophrenia.

Abstract: A group of 33 patients with schizophrenia were compared with control participants using a spatial memory task in which words were presented on locations of a grid. In the first part of the experiment, recognition of target information (words) was tested. In the second, 2 tasks of spatial location (contextual information) were given involving different sets of words placed in different locations: A location memory task (determining which word was in a particular spatial location) explored an associative form of spatial memory, and a relocation task (determining where a particular word was located) explored an associative and a nonassociative form of spatial memory. Patients were more impaired with regard to the location memory task than to the target recognition and relocation tasks. The impairment was negatively correlated with Stroop task performance. The results suggest that schizophrenia is associated with a spatial context memory deficit, which could be due to defective associations between target and spatial information. This deficit seemed to be related to frontal dysfunction.

Impaired Retrieval From Remote Memory in Patients With Frontal Lobe Damage

Abstract: University of California, Davis, and Veterans AffairsMedical Center, MartinezPatients with unilateral dorsolateral frontal lobe lesions and matched controls were given 2 tests ofremote memory for public information, the Public Events Test and the Famous Faces Test. Onboth tests, the patients with frontal lobe lesions exhibited impaired recall for remote information.Recognition memory was relatively preserved. Provision of semantic and phonemic cues in theFamous Faces Test did not completely compensate for their recall deficit. These findings suggestthat the remote memory impairment exhibited by frontal patients may be related to deficits instrategic search of memory. These deficits in retrieval from remote memory extend the array ofmemory deficits associated with damage to the frontal lobes.Frontal lobe lesions have been associated with a variety ofmemory impairments, including deficits in short-term memory,free recall, metamemory, and memory for temporal informa-tion (for review, see Fuster, 1989; Shimamura, 1994; Stuss,Eskes, & Foster, 1994). Yet patients with frontal lobe lesionscan exhibit normal performance on standard clinical assess-ments of new learning ability (e.g., Wechsler Memory Scale—Revised; WMS-R; Wechsler, 1987), suggesting that theirmemory deficits are not due to severe anterograde amnesia(Janowsky, Shimamura, Kritchevsky, & Squire, 1989). Rather,the pattern of memory deficits suggests an impairment instrategic processes associated with organization and monitor-ing at encoding and retrieval. Indeed, the relationship betweenfrontal lobe function and strategic processing have beendeveloped in a variety of theories about the frontal lobes (seeBaddeley, 1986; Moscovitch, 1994; Norman & Shallice, 1986;Shimamura, 1994).Organizational problems related to deficits in strategicprocesses are highlighted by the performance of frontal lobepatients on tests of free recall (Janowsky et al., 1989; Jetter,Poser, Freeman, & Markowitsch, 1986; Incisa della Rocchetta,1986; Incisa della Rocchetta, & Milner, 1993; Stuss, Alex-ander, et al., 1994). For example, patients with frontal lobelesions are less likely to engage in useful memory strategies,

Motor skills have diverse neural bases: Spared and impaired skill acquisition in Huntington's disease.

Abstract: The striatum contributes to the learning of some, but not all, motor skills. The researchers suggest that the striatum plays a role when participants learn a repeating sequence of movements, but it does not contribute when they learn a new mapping between perceptual cues and the appropriate motor response. The researchers tested patients with striatal damage due to Huntington's disease (HD) on 2 versions of a tracking task. In 1 task, the target moved randomly, allowing participants to learn the relationship between the joystick and cursor. Patients showed normal learning. In the other task, the target moved in a repeating pattern, and participants could improve performance by learning the repeating sequence of movements necessary to track the pattern. Patients were impaired on this task. Learning sequences is impaired in HD, whereas learning new mappings between perceptual cues and responses is not. It has been suggested that the striatum is crucial to the acquisition of motor skill (Hikosaka, 1993; Mishkin, Malamut, & Bachevalier, 1984). This suggestion is supported by lesion studies and functional imaging studies. Patients with striatal abnormalities due to Huntington's disease (HD) or Parkinson's disease (PD) are impaired in acquiring new motor skills (e.g., Harrington, Haaland, Yeo, & Marder, 1990; Heindel,

Greater Relative Impairment of Object Recognition Than of Visuospatial Abilities in Alzheimer's Disease

Abstract: Histological investigation in Alzheimer's disease (AD) has indicated that the concentration of neurofibrillary tangles in inferotemporal cortex (IT) is greater than that found in posterior parietal cortex (PPC) Researchers hypothesized that the relative degree of impairment of visual function subserved by each of these cortical areas should reflect the disproportionate distribution of neuropathological changes Eleven AD patients and 16 elderly controls received 8 tests of visual function, 4 of which have been shown previously to be selectively affected by IT lesions and 4 that are selective for PPC lesions AD patients were significantly impaired on all 8 tests, but multivariate analysis indicated a relatively greater impairment on tests of IT function The greater impairment of visual function mediated by IT relative to function mediated by PPC is consistent with differential degradation of the respective cortical areas