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Biomedical subjects

W Milberg

Publications and source records attributed to W Milberg.

At least 19 recordsLinked to original sources
PubMed2002

Triangular backgrounds shift the bias of line bisection performance in hemispatial neglect.

OBJECTIVE: Patients with left neglect on line bisection show normal implicit sensitivity to manipulations of both the stimulus and the visual background. Three experiments were designed to define this sensitivity more exactly. METHODS: Normal controls and patients with left neglect performed a series of horizontal line bisection tasks. Independent variables were the configurations of the backgrounds for the line-rectangle, square, circle, left and right pointing isosceles triangles-and whether the background was the shape of the piece of paper or an outline drawn on a standard piece of paper. In a separate experiment different components of the triangle were outlined on a piece of paper. Deviation from true midpoint was calculated. RESULTS: Simply placing the target lines in a symmetric background such as a square or circle did not reliably reduce neglect. A triangle asymmetric in the horizontal plane caused a shift in bisection away from the triangle's vertex. With right pointing triangles the perceived midpoint shifted to the left of true centre (crossed over). The effects of the triangles were comparable in the patients and the controls when controlled for baseline bisection bias. The critical components of the triangles were the angular legs. This effect of background was not influenced by lesion site or by hemianopia. CONCLUSIONS: Patients with left visual neglect remain sensitive to covert manipulations of the visual background that implicitly shift the perceived midpoint of a horizontal line. This effect is strong enough to eliminate neglect on a bisection task. The mechanism of this effect is expressed through preattentive visual capacities.

Aged↗
PubMed2001

Stroke risk predicts verbal fluency decline in healthy older men: evidence from the normative aging study.

Risk factors for stroke cause ischemic changes in the cerebral white matter that may affect frontal lobe functions more than other brain functions. Therefore, stroke risk could specifically affect performance on behavioral indexes traditionally associated with frontal lobe function such as verbal fluency. The authors examined this hypothesis in 235 healthy older men (mean age = 66.41 years) who received concurrent medical and neuropsychological examinations twice at a 3-year interval. Relations between stroke risk and decline in verbal fluency, memory, and visuospatial performance were analyzed through regression, controlling for age and education. Age was associated with decline in all cognitive functions; stroke risk was associated with decline only on verbal fluency. The relation between stroke risk and fluency decline was 80% as large as that between age and fluency decline. These results suggest that stroke risk rivals the effects of aging on verbal fluency performance.

Aged↗
PubMed2000

The mapping from sound structure to the lexicon in aphasia: evidence from rhyme and repetition priming.

Two studies were conducted to explore the hypothesis that Broca's and Wernicke's aphasics have deficits arising from the processes involved in activating the lexicon from phonological form. The first study explored whether phonologically similar lexical entries differing only in their initial consonants show "rhyme priming." Results revealed that Broca's aphasics failed to show facilitation when the target was identical to the prime (i.e. identity priming) and they showed significant inhibition when targets were preceded by rhyming words. Wernicke's aphasics showed a pattern of results similar to that of normal subjects, i.e., identity priming and rhyme priming as well as significantly slower reaction-times in the rhyming condition compared to the identity condition. The second study investigated form-based repetition priming in aphasic patients at a number of intervals including when no other stimuli intervened between repeated stimuli (0 lag) or when 4, 8, or 12 stimuli intervened. Results showed that, unlike old normal subjects who showed repetition priming for both words and nonwords, both Broca's and Wernicke's aphasics showed repetition priming for word targets only. Moreover, in contrast to old normal subjects who showed a greater magnitude of priming at 0 lag for word targets, neither Broca's aphasics or Wernicke's aphasics showed priming at 0 lag. Implications of these findings are considered with respect to the hypotheses that Broca's and Wernicke's aphasics have deficits in the nature of the activation patterns within the lexicon itself and in auditory (working) memory.

Aged↗
PubMed2000

Preattentive and attentive visual search in individuals with hemispatial neglect.

Preattentive and attentive visual processing was examined in patients with hemispatial neglect, hemispatial neglect with hemianopia, and control participants. In the preattentive search task, targets possessed a unique feature that was not shared by distractors. In the attentive search task, targets lacked a feature that was present in the distractors. Preattentive search was normal in 3 neglect patients with cortical lesions but not in 2 neglect patients with hemianopia. A 4th neglect patient without hemianopia with a subcortical infarct abnormally used serial search mechanisms in the preattentive task. Neglect patients were characteristically impaired in the contralesional field in the attentive search task. This study demonstrates preserved explicit detection of visual features in cases of hemispatial neglect.

Adult↗
PubMed1999

Alterations in the dynamics of semantic activation in Alzheimer's disease: evidence for the Gain/Decay hypothesis of a disorder of semantic memory.

While it has been commonly assumed that a deficit in semantic memory underlies many of the clinical and cognitive features of early Alzheimer's disease (AD), there has been little agreement on what constitutes a proper theoretical description of this impaired system. Currently, most theories of this disorder fall into two categories: those that posit degraded semantic representations, and those that posit impaired retrieval operations with relatively intact semantic representations. It is argued that each position has both empirical and logical disadvantages that have prevented the development of a consensus on how to describe the pathology of semantic memory in AD. In this paper we present the details and supportive evidence for an alternative account of the semantic memory deficit of AD: the Gain/Decay hypothesis. The core claim of the Gain/Decay hypothesis is that a reduction in the time constant of spreading activation in AD produces dynamic changes in the availability of semantic representations that depend on the time frame in which this information must be accessed. The implications of this hypothesis for a range of experimental and clinical phenomena are discussed, as are possible biological correlates of the hypothesized alterations in the modulation of activation.

Aged↗
PubMed1996

Issues in the assessment of cognitive function in dementia.

The increasing prevalence of elderly patients presenting with disorders of cognitive functioning suggestive of dementia, coupled with limits in resources available to address these problems, is going to necessitate the development of new technologies to be used for assessment. These measures should be efficient, designed to reflect both the current knowledge of brain function and the developmental characteristics of older patients. Though few current measures of cognitive function meet these goals, neuropsychological "microbatteries" such as the DRS and NCSE may serve as models for a new generation of cognitively specific assessment instruments.

Aged↗
PubMed1996

Preserved semantic priming effect in alexia.

BH, a left-handed patient with alexia and nonfluent aphasia, was presented with a lexical-decision task in which words and pronounceable pseudowords were preceded by semantically related or unrelated picture primes (Experiment 1). In Experiment 2, BH was given an explicit reading task using the word lists from Experiment 1. Performance on Experiment 2 disclosed severe reading deficits in both oral reading and semantic matching of the words to pictures. However, in Experiment 1, BH demonstrated a significant semantic priming effect, responding more accurately and more quickly to words preceded by related primes than by unrelated primes. The present results suggest that even in a patient with severe alexia, implicit access to semantic information can be preserved in the absence of explicit identification. The possibility of categorical gradient in implicit activation (living vs. nonliving) in BH was also discussed, which, however, needs to be clarified in the further investigation.

Brain↗
PubMed1991

A further analysis of perceptual identification priming in alcoholic Korsakoff patients.

Alcoholic Korsakoff patients have been shown to have normal repetition priming for words, but impaired priming for pseudowords, on perceptual identification tasks. Because real words, but not pseudowords, have semantic representations, successful priming of real words has been attributed to semantic activation. Alternatively, however, priming might reflect the perceptual, i.e. orthographic and phonological familiarity associated with real words in comparison with pseudowords. In order to examine which of these factors accounts for normal priming by amnesics, Experiment 1 was designed to contrast perceptual identification priming for words, pseudowords and pseudohomonyms (e.g. "phaire"). On this task, Korsakoff patients showed normal priming for real words and for pseudohomonyms, but significantly impaired priming for pseudowords. It was felt that since pseudohomonyms are orthographically unfamiliar but could access semantics through their phonological route, activation of a semantic representation rather than perceptual familiarity might be the critical factor underlying successful priming. Experiment 2 was then designed to further explore the robustness of this semantically mediated priming by presenting different word types within the same study list. Under these conditions, Korsakoffs' pseudohomonym priming was consistently below normal. This suggests that priming in Korsakoff patients depends upon the conceptual salience of the stimuli and not solely on semantic activation.

Alcohol Amnestic Disorder↗
PubMed1990

Intact priming of patterns despite impaired memory.

The priming of patterns was examined in normal control subjects (NCS) and in the amnesic patient H.M., whose anterograde amnesia followed bilateral medial temporal-lobe excision 33 years earlier. Despite H.M.'s impaired recognition of the patterns, he demonstrated a pattern priming effect equivalent in magnitude to that of the NCS. The results demonstrated that intact priming with novel, nonverbal material can occur despite severe amnesia. Pattern priming may reflect adaptive visual processes involved in learning novel perceptual organizations of known visual codes, such as letters, words, shapes, and objects.

Amnesia↗
PubMed1989

Reaction time methodology and the aphasic patient: a reply to Hagoort (1988).

P. Hagoort (1988, Brain and Language, 36, 335-348) suggests that the results of an experiment conducted with aphasic patients reported by W. Milberg, S. E. Blumstein, and B. Dworetzky (1987, Brain and Language, 31, 138-150) are "difficult to interpret in terms of a selective access model for normal processing because of a confound caused by the use of repeated lexical decision targets." We argue that the use of repeated lexical decision targets and other methodological compromises are necessary for using the lexical decision reaction time paradigm with aphasic patients. Furthermore, the minor differences between our data and those presented by Hagoort do not undermine our claims concerning semantic processing in different subgroups of aphasics, nor our comparisons of these patients to normal subjects.

Aphasia↗
PubMed1989

Semantic processing in patients with Alzheimer's disease.

Ten patients with dementia of the Alzheimer type and 10 normal controls performed a lexical decision, semantic facilitation task. The performance of the patients differed from that seen in normals. A post hoc subdivision of the data suggested that the diviation from normality was not uniform throughout the patient population. Six of the 10 Alzheimer patients showed an advantage of related primes over unrelated primes, while 4 of the 10 were actually faster in the unrelated condition than in the related condition. Nevertheless, both group of Alzheimer patients showed lexical decision latency differences between unrelated and related prime words, suggesting that patients with Alzheimer's disease are sensitive to the semantic relationships between words.

Aged↗
PubMed1989

Cognitive differences between patients with progressive supranuclear palsy and Alzheimer's disease.

Sixteen patients with dementia of the Alzheimer type (AD) and nine patients with Progressive Supranuclear Palsy (PSP) were administered a battery of neuropsychological tasks that assessed a cross-section of cognitive abilities. The subjects were equated in terms of overall level of impairment. There was no difference between the groups on the WAIS subtests that were administered (Vocabulary, Digit Span Forward, Similarities, Block Design). There was a striking difference between the AD and PSP patients on tests of verbal and nonverbal memory, as assessed by the Wechsler Memory Scale. The memory performance of the PSP patients did not, in fact, differ from a group of normal controls. In addition, there was a double-dissociation between the AD and PSP patients on tasks that evaluated naming and verbal fluency.

Aged↗
PubMed1988

Phonological processing and lexical access in aphasia.

This study explored the relationship between on-line processing of phonological information and lexical access in aphasic patients. A lexical decision paradigm was used in which subjects were presented auditorily with pairs of words or word-like stimuli and were asked to make a lexical decision about the second stimulus in the pair. The initial phonemes of the first word primes, which were semantically related to the real word targets, were systematically changed by one or more than one phonetic feature, e.g., cat-dog, gat-dog, wat-dog. Each of these priming conditions was compared to an unrelated word baseline condition, e.g., nurse-dog. Previous work with normals showed that even a nonword stimulus receives a lexical interpretation if it shares a sufficient number of phonetic features with an actual word in the listener's lexicon. Results indicated a monotonically decreasing degree of facilitation as a function of phonological distortion. In contrast, fluent aphasics showed priming in all phonological distortion conditions relative to the unrelated word baseline. Nonfluent aphasics showed priming only in the undistorted, related word condition relative to the unrelated word baseline. Nevertheless, in a secondary task requiring patients to make a lexical decision on the nonword primes presented singly, all aphasics showed phonological feature sensitivity. These results suggest deficits for aphasic patients in the various processes contributing to lexical access, rather than impairments at the level of lexical organization or phonological organization.

Adult↗
PubMed1988

Learning of a complex arithmetic skill in amnesia: evidence for a dissociation between compilation and production.

Two patients with severe amnesia following rupture of anterior communicating artery aneurysms were able to learn a complex algorithm for mentally squaring two-digit numbers. Although both patients learned the algorithm at a similar rate, one patient's improvement was accounted for by savings in the steps of the algorithm. The other patient, however, showed little improvement in the steps while performance of the whole algorithm improved dramatically. Neither patient showed savings in the Hebb Digit Span procedure. The results suggested a dissociation between amnesics in their capacity to learn the constituent "productions" or steps of a skill and their capacity to organize those productions into a single coherent act.

Adult↗
PubMed1988

Teaching an amnesic a complex cognitive skill.

G.P., a Korsakoff's amnesic, was able to learn an algorithm for squaring two-digit numbers mentally over a 7-day period at a rate comparable to that of age-matched controls. He failed to show normal positive transfer to specific problems or to specific numbers used in components of the task. He also exhibited slight improvement in simple naming speed, forward digit span, simple multiplication speed, but no apparent improvement for the recall of repeated supraspan digit strings. He was unable to state the algorithm he had learned to square two-digit numbers, though he could implement it successfully. The results suggest that the compilation of a skill may involve two dissociable components: composition and proceduralization, with the former, but not the latter, occurring at normal rates for Korsakoff's amnesics.

Aged↗
PubMed1988

Changes in naming ability with age.

We administered to 80 optimally healthy subjects, 30-80 years old, the Boston Naming Test, a test of confrontation naming. Results indicated that naming ability remains fairly stable across the adult life span until individuals are in their 70s, at which point there is a significant decline in performance (p less than or equal to .0001). Semantic errors (i.e., circumlocutions, semantically related associates, and nominalizations) and perceptual errors increase with age. Lexical errors (i.e., phonologically related real words and phonologically related nonwords) do not increase with age. Results of multiple regressions that included other neuropsychological variables indicate that estimated IQ, but not new learning ability, predicts a subject's naming score.

Adult↗