A E Taylor

Toronto Western Hospital, Toronto, Ontario, Canada

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Publications (14)64.65 Total impact

  • D Knoke, A E Taylor, J A Saint-Cyr
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    ABSTRACT: Patients with Parkinson's disease (PD) are known to be impaired in supraspan verbal learning due to reduced availability of internal encoding capacity. PD patients may suffer from poor semantic, source and sequential processing capacity. Thirty-three patients with idiopathic PD and 42 matched normal control subjects (NC) were administered the California Verbal Learning Test under 3 conditions of graded cueing. While the PD patients benefited significantly and progressively from increasingly explicit cueing, the NC group did not since their performance was optimal even without cueing. Results are discussed in relation to frontal executive control of attentional resources and the establishment of encoding strategies.
    Brain and Cognition 12/1998; 38(2):261-74. · 2.82 Impact Factor
  • A E Taylor, J A Saint-Cyr
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    ABSTRACT: This article discusses the neuropsychological profile of Parkinson's disease from the perspective of cognitive theory, anatomical organization, and unit recording data. Despite the point of origin, methodologically controlled studies are converging to support the position that patients with this disorder suffer selective impairment in the acquisition of novel tasks which rely on internal (subjective) processing for the efficient establishment of new cognitive "habits." The roles of attention and learning as well as of unit activity within the relevant networks are considered. Also included are recent but important concepts from personality theory which potentially enhance understanding of the neuropsychology of Parkinson's disease.
    Brain and Cognition 09/1995; 28(3):281-96. · 2.82 Impact Factor
  • J A Saint-Cyr, A E Taylor, K Nicholson
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    ABSTRACT: When viewed as a whole, these basal ganglia-thalamo-cortical circuits appear to play a modulating role in a wide range of behaviors. At the cortical level, given convergence upon specified regions within the frontal lobes, the behaviors in question would be those dependent upon SMA, premotor, frontal eye fields, dorsolateral, and orbitofrontal outflow targets. Broadly speaking, processes such as the generation, maintenance, switching, and blending of motor, mental, or emotional sets would be involved. Accordingly, in basal ganglia disease, the planning and the execution of the above behavioral domains can be affected. Given the diversity and complexity of activity within the basal ganglia, the consequences of disruption depend largely upon lesion site and the associated interplay of neurochemical factors. For example, in the motor domain, damage to various striatal circuitry levels can result in either hypo- or hyperkinetic disorders of movement. Following this analogy, it might also be said that diverse lesions, depending on site, can result in problems with the development and maintenance of behavioral sets ("hypophrenic") versus problems in relinquishing preferential sets ("hyperphrenic"). These contrasting patterns are best represented in PD and OCD, respectively. In the latter case, however, the "hyperphrenic" pattern would only apply to those behaviors which are part of the obsessional rituals. This suggests that procedural system "overdrive" remains domain-specific as is the case for most operations within the procedural system. To return to the broad principle of habituation, a process first described in the context of the visual system and its connections with the tail of the caudate nucleus, it would be tempting to view PD and OCD as disorders of "under" and "over" habituation to behavioral routines. Unfortunately, the situation has proven to be more complex in view of recent neuropsychological findings (Nicholson et al., in preparation). Using a variety of problem-solving and other cognitive tasks, both PD and OCD patients were found to require more practice and/or the provision of external guidelines to facilitate habit formation. Thus, in both cases, as in other disorders of the basal ganglia, the establishment of useful heuristics by which to direct adaptive behavior suffers. OCD patients therefore appear to have at least two compartmentalized types of basal ganglia dysfunction: the ritualistic compulsions and obsessions as well as the heuristic inefficiency (i.e., poor procedural mobilization). PD patients would also suffer a similar fate as it is known that the degrees of motor versus nonmotor (i.e., procedural) deficit are poorly correlated (42).(ABSTRACT TRUNCATED AT 400 WORDS)
    Advances in neurology 02/1995; 65:1-28.
  • J A Saint-Cyr, A E Taylor, A E Lang
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    ABSTRACT: All medications currently used to treat Parkinson's disease carry some risk of causing confusion, hallucinations, or disruption of such higher-order mental operations as problem-solving and learning. Although the elderly demented patient is at greatest risk, such complications have also been noted during treatment of younger patients. Treatment with anticholinergics may lead to a confusional state and decreased memory function in some patients, especially the elderly and those with preexisting dementia. Monoamine oxidase inhibition is considered quite benign when used alone, but may potentiate certain side effects when used in combination with other compounds. Ergot alkaloid medication, which is usually combined with levodopa, often induces severe psychiatric complications. Typical findings with levodopa treatment indicate little or no positive impact on cognition, apart from nonspecific arousal and alleviation of concomitant depressive affect. Guidelines for the management of neuropsychological and psychiatric side effects are suggested.
    Neurology 01/1994; 43(12 Suppl 6):S47-52. · 8.25 Impact Factor
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    ABSTRACT: Studies utilizing single doses of scopolamine have suggested a role for the cholinergic system in memory. Results are consistent in identifying a selective effect on the early encoding stage of information processing. In terms of long-term administration of anticholinergics, patients with Parkinson's disease often display memory deficits. However, underlying pathology within the forebrain cholinergic system complicates the study of treatment effects in this disorder. We therefore assessed multiple memory routines in 20 cognitively intact patients with dystonia where no such pathology has been identified. Patients were tested before and after 2-4 months of 15-74 mg of trihexyphenidyl daily. Twelve tolerated this regime. Compared to control subjects, matched for age and I.Q., only tests with a single presentation of the material to be remembered were affected at follow-up. The speed of information processing was also significantly reduced. Age was strongly related to memory performance in the patient group alone and interacted with dose and duration of treatment. Results suggest that drug-induced slowing of mentation was responsible for impaired encoding, particularly in older patients. These findings affect treatment strategies, especially now that injections of botulinum toxin have proved to be highly effective for certain forms of focal dystonia.
    Clinical Neuropharmacology 03/1991; 14(1):62-77. · 1.82 Impact Factor
  • A E Taylor, J A Saint-Cyr, A E Lang
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    ABSTRACT: Fifteen untreated patients in the earliest stages of Parkinson's disease were compared to fifteen age- and intellectually matched control subjects on a number of memory tasks assessing short- and long-term recall of both meaningful and unrelated material, semantic relations in the organization of memory, priming, and source forgetting, and the ability to form new stimulus-response associations under conditions of maximal task interference. While patients demonstrated considerable evidence of preserved function, impaired performance on a subgroup of tasks was consistent with selective frontostriatal system involvement. These findings are discussed with reference to the underlying pathological processes in Parkinson's disease.
    Brain and Cognition 08/1990; 13(2):211-32. · 2.82 Impact Factor
  • A E Taylor, J A Saint-Cyr, A E Lang
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    ABSTRACT: Anatomical connections between the frontal lobes and basal ganglia have long suggested joint participation in behavioural operations. Early experiments with nonhuman primates and patients are reviewed, followed by current research investigating the specific cognitive routines at risk in Parkinson disease. An hypothesis regarding the functional contribution of the basal ganglia to the frontostriate system is offered. The basal ganglia are considered to set limits on the context within which mental and motor events occur. It is argued that the nature of such processing is subcognitive.
    Alzheimer Disease and Associated Disorders 02/1990; 4(3):150-60. · 2.73 Impact Factor
  • A E Taylor, J A Saint-Cyr
    Journal of Neuropsychiatry 02/1990; 2(1):92-8. · 2.40 Impact Factor
  • J A Saint-Cyr, A E Taylor, A E Lang
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    ABSTRACT: Patients with early stage Parkinson's disease are shown to be selectively impaired in a cognitive task of procedural learning while remaining intact in recall and recognition tests of declarative memory. In contrast, amnestic patients showed the opposite set of deficits, thus demonstrating a double dissociation. Patients with early Huntington's disease were either comparable to the parkinsonian patients or to amnestics. In the advanced Huntington's group, both procedural learning and declarative memory were impaired. It is argued that cognitive procedural learning depends on the establishment of heuristic strategies through the action of a circuit which involves the neostriatum and the prefrontal cortex.
    Brain 09/1988; 111 ( Pt 4):941-59. · 9.92 Impact Factor
  • A E Taylor, J A Saint-Cyr, A E Lang
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    ABSTRACT: Assumptions regarding increased risk of dementia in Parkinson's disease and of depression mimicking the endogenous form are reviewed and challenged from the perspectives of recent findings in both the neuropsychological and anatomical domains. Evidence suggests that depression, while frequent, behaviourally resembles the reactive variety and that selective impairment of cognitive functions considered to depend upon the integrity of the frontal lobes accompanies this disorder. In this regard, it is speculated that the cognitive alterations seen in non-demented parkinson patients are the consequences of dysfunction of the caudate nucleus which contributes significantly to the normal activities processed through the frontostriate "complex loop".
    The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques 06/1988; 15(2):106-13. · 1.33 Impact Factor
  • A E Taylor, J A Saint-Cyr, A E Lang
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    ABSTRACT: Four groups of patients with Parkinson's disease matched for age, education and IQ were categorized by response to treatment and compared with a normal control group. The patient groups were (1) No Treatment (de novo); (2) Good Response (including minor fluctuations in symptoms); (3) Fluctuations (significant, including 'on-off' phenomena) and/or marked Abnormal Involuntary Movements (dyskinesias); and (4) Poor Response ('secondary treatment failure' characterized by significant deterioration over time in all major symptoms). As a previous investigation had established that neuropsychological tests thought to be sensitive to the functional integrity of the frontal lobes are selectively impaired in Parkinson's disease, the first phase of this study compared the five groups on five such tests and two tests of psychomotor ability. While all patient groups displayed deficits on the psychomotor tests and on several tests associated with frontal lobe function compared with normals, only the Poor Response group was impaired on all tasks. In a second phase, comprehensive testing of additional cognitive processes such as attention, mnemonic, and visuospatial functions, the latter two traditionally thought to depend primarily on posterior cortical regions, revealed no significant cognitive deficits in any patient group. Results are discussed with respect to the involvement of the nigrostriatal and mesocortical dopaminergic systems.
    Brain 03/1987; 110 ( Pt 1):35-51. · 9.92 Impact Factor
  • A E Taylor, J A Saint-Cyr, A E Lang
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    ABSTRACT: This study investigates the hypothesis that, as a consequence of Parkinson's disease, disturbed caudate outflow will lead to deficits in cognitive functions dependent upon the integrity of the prefrontal cortex, the cortical focus of caudatofugal signals. Since Parkinson's disease also involves lesions in extra-striatal midbrain cells which reduce the extrinsic supply of dopamine to this cortical region, such functions are at double risk. Forty nondemented parkinsonian patients were drawn from a pool of 100 consecutive patients and matched with 40 normal control subjects according to age, education, IQ, and sex. All patients were quantitatively rated on neurological indices of disease. Neuropsychological assessment of the patient and normal groups included tests of general intelligence, psychomotor skills, memory, visuospatial and executive functions. No global cognitive decline was observed in the parkinsonian group. Moreover, memory and visuospatial abilities were generally intact. A small cluster of deficits emerged, interpreted as reflecting impairment in the ability to spontaneously generate efficient strategies when relying on self-directed task-specific planning. In addition, several tests thought to be sensitive to frontal lobe function distinguished patients with symptoms strongly lateralized to the right versus left side of the body. Deficits in strategic planning were later investigated in relation to severity of disease and to patient attributes including IQ and age, both of which were relevant to performance on specific tasks. Results were compared with previous investigations in parkinsonian patients and discussed from the perspective of both animal and human studies involving damage to the cerebral cortex and basal ganglia. As the prefrontal cortex is thought to play a crucial role in self-directed behavioural planning, the validity of an outflow model in predicting the consequences of caudate nucleus dysfunction was supported.
    Brain 11/1986; 109 ( Pt 5):845-83. · 9.92 Impact Factor
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    ABSTRACT: The possibility of an 'organically' based depression intrinsic to the pathophysiology of Parkinson's disease (PD) and comparable to endogenous depression (Major Depressive Episode) has been raised. It has also been argued that signs of depression observed in PD are merely the natural reaction of the patients to their progressive and inevitable physical limitations and loss of independent function. Because conventional depression rating scales are limited in scope, a psychometric investigation of depression in PD was pursued. Based on the known impairment of short-term memory (STM) in endogenous depression, which was confirmed in a group of psychiatric patients in the present study, measures of STM were also obtained in groups of depressed and nondepressed PD patients and in 15 normal control subjects. Regardless of depression severity, PD patients performed as well as control subjects and both these groups consistently obtained scores significantly better than those of the endogenously depressed patients. A relative weakness in the PD patients on order-dependent STM tests was further explored and interpreted as an indication of mild frontal lobe dysfunction. It was concluded that PD patients are frequently depressed when confronted with their behavioural limitations and that this reaction may be exacerbated by a form of emotional liability related to pathophysiological processes which may involve prefrontal cortical areas.
    Brain 05/1986; 109 ( Pt 2):279-92. · 9.92 Impact Factor
  • J. A. Saint-Cyr, A. E. Taylor
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    ABSTRACT: [provides] a brief overview of the theoretical basis for the assignment of portions of the basal ganglia (or striatal)-frontal lobe circuitry to a functional subset of the procedural domain / the hypothesis is advanced that these circuits are involved in the mobilization and selection of procedures in either the sensorimotor domain or the more general problem-solving domain / in our [the authors'] view, the declarative system, dedicated to conscious utilization of encoding and retrieval, is designed to be under continuous modification and susceptible to forgetting / in contrast, the procedural system is inaccessible to consciousness and is designed according to principles of sensorimotor developmental adaptation; it thus engenders robust strategies, which may be altered or built upon, but which appear to be more resistant to decay in our [the authors'] view, the declarative system, dedicated to conscious utilization of encoding and retrieval, is designed to be under continuous modification and susceptible to forgetting / in contrast, the procedural system is inaccessible to consciousness and is designed according to principles of sensorimotor developmental adaptation; it thus engenders robust strategies, which may be altered or built upon, but which appear to be more resistant to decay / three converging lines of evidence—neuroanatomical, developmental and behavioral, and cognitive—are presented in support of the present formulation (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Publication Stats

1k Citations
64.65 Total Impact Points

Institutions

  • 1990–1998
    • Toronto Western Hospital
      Toronto, Ontario, Canada
  • 1988–1995
    • University of Toronto
      • • Department of Psychology
      • • Division of Anatomy
      Toronto, Ontario, Canada