Book Description
This digital document is a journal article from Neuropsychologia, published by Elsevier in . The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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It has been suggested that Parkinson's disease (PD) impairs the ability to learn on the basis of reward or reinforcing feedback i.e., by trial-and-error. In many learning tasks, particular 'dimensions' of stimulus information are relevant whilst others are irrelevant; therefore, efficient performance depends on identifying the dimensions of these 'compound' stimuli and selecting the relevant dimension for further processing. We investigated the ability of patients with PD, as well as patients with Huntington's disease and patients with frontal or temporal lobe lesions, to learn visual discriminations which required either a number of associations to be learned concurrently (the 'eight-pair' task) or the selection of information from compound stimuli (the 'five-dimension' task), both tasks being learned by trial-and-error. None of the basal ganglia disorder patient groups was impaired on the eight-pair task, militating against a crucial role for these brain structures in trial-and-error learning per se. Patients with mild, medicated PD, but not unmedicated PD patients, were impaired at identifying all five feature dimensions in the five-dimension task, implying dopaminergic 'overdosing' of the ability to analyse compound stimuli in terms of their component dimensions. Temporal lobe lesion patients performed similarly, suggesting that the temporal lobe may be the site of the medication overdose effect. Patients with severe, medicated PD were impaired at compound discrimination learning on the five-dimension task in the absence of an underlying impairment in identifying component stimulus dimensions; this pattern resembled that seen in Huntington's disease and frontal lobe lesion patients, implying that fronto-striatal circuitry is involved in the formation of rules based upon selected stimulus dimensions. ... Read more

Book Description
This digital document is a journal article from Cognitive Brain Research, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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The symptoms primarily associated with Parkinson's disease (PD) are of a motor and cognitive nature, but sensory deficits may also be involved. Previous studies have reported disturbed spatial perception in visual and tactile tasks. We have investigated whether PD patients show deficits in auditory spatial perception. For this purpose, we employed a simple task involving left/right judgments about dichotic stimuli presented with various interaural time differences (ITD). The acuity of sound lateralization was significantly reduced in PD: the just noticeable difference (JND) in interaural time seen in PD patients was about twice that seen for age-matched healthy controls. We propose that this deficit may be related to a potential role of the basal ganglia in spatial hearing functions, as has been suggested by neurophysiological and neuroanatomical studies on animals. ... Read more

Book Description
This digital document is a journal article from Brain and Cognition, published by Elsevier in 2005. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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We have hypothesized a distinction between the processes required to control the timing of different classes of periodic movements. In one class, salient events mark successive cycles. For these movements, we hypothesize that the temporal goal is a requisite component of the task representation, what we refer to as event-based timing. In the other class, the successive cycles are produced continuously. For these movements, alternative control strategies can optimize performance, allowing timing to be emergent. In a previous study, patients with cerebellar lesions were found to be selectively impaired on event-based timing tasks; they were unimpaired on a continuously produced task. In the present study, patients with Parkinson's disease were tested on repetitive movement tasks in which timing was either event-based or emergent. Temporal variability on either type of task did not differ between on- and off-medication sessions for the Parkinson's patients nor did patient performance differ from that of controls. These results suggest that the basal ganglia play a minimal role in movement timing and that impairments on event-based timing tasks are specific to cerebellar damage. ... Read more

Book Description
This digital document is a journal article from Neuropsychologia, published by Elsevier in . The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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In this study we examined the effect of dopaminergic modulation on learning and memory. Parkinson's patients were tested 'on' versus 'off' dopaminergic medication, using a two-phase learning and transfer task. We found that dopaminergic medication was associated with impaired learning of an incrementally acquired concurrent discrimination task, while patients withdrawn from dopaminergic medication performed as well as controls. In addition, we found a dissociation of the effect of medication within a single two-phase task: patients tested 'on' medication were not impaired at the ability to generalize based on learned information. The deficit among medicated patients appeared to be related specifically to the concurrent, incremental, feedback-based nature of the task: such a deficit was not found in a version of the task in which demands for concurrent error-processing learning were reduced. Taken together with a growing body of evidence emphasizing a role for midbrain dopamine in error-correcting, feedback-based learning processes, the present results suggest a framework for understanding previously conflicting results regarding the effect of medication on learning and memory in Parkinson's disease. ... Read more

Book Description
This digital document is a journal article from Brain and Cognition, published by Elsevier in 2005. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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The effect of a visual warning signal (1.0-6.5s random foreperiod, FP) on the latency of voluntary (hand-grip) and reflexive (startle-eyeblink) reactions was investigated in Parkinson's disease (PD) patients and in young and aged control subjects. Equivalent FP effects on blink were observed across groups. By contrast, FP effects diverged for voluntary responses across groups with no effect of foreperiod duration for PD patients. The convergence of these results with findings from animal research suggests that interval-timing processes associated with higher level voluntary behaviors are dependent upon intact dopaminergic pathways, while those associated with lower level reflexive behaviors are spared in PD. ... Read more

Book Description
This digital document is a journal article from Neuropsychologia, published by Elsevier in 2005. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Response selection often occurs in a context of competition among conflicting responses. According to recent models, the basal ganglia may play an integral role in resolving this competition by focusing the selection and inhibition of responses. We hypothesized that basal ganglia dysfunction produced by Parkinson's disease (PD) disrupts selection among conflicting responses. Using a version of the Eriksen flanker task, we tested the specific prediction that individuals with PD would experience greater response interference when distractors in the visual field activate a response that conflicts with the target response. In addition, we investigated whether greater response interference induced by these distractors could actually reduce normal response time costs in PD when the task required production of the response opposite the target. Compared to 16 healthy controls (HC), 16 individuals with PD showed an exacerbated slowing when target and distracting stimuli corresponded to conflicting responses. No group differences occurred when targets and distractors corresponded to the same response. Furthermore, the slowing induced by the distractors was reduced in both groups, but more so in PD, when execution of a response opposite the target response (i.e. incompatible response) was required. Moreover, among individuals with PD, the magnitude of the interference produced by the distractors was related to clinical ratings of bradykinesia. These findings are consistent with the hypothesis that basal ganglia dysfunction due to Parkinson's disease disrupts processes that resolve response conflict. ... Read more

Product Description
Topics include:* Drug Induced Dyskinesias: Definition of the Problem, Persistent Dyskinesias in Chronically Hospitalized Mental Patients, Lingual Dyskinesia in Six Patients Receiving Fluphenazine Enanthate, Dyskinesia in Rhesus Monkeys Tested with High Doses of Chlorpromazine, Neurological Examination of Rhesus Monkeys tested with High Doses of Chlorpromazine, and Extrapyramidal Motor Disorders Following Long-Term Treatment with Neuroleptic Drugs.* Other Clinical Movement Disorders: Clinical Manifestations of the Extrapyramidal Diseases, Manganese Effects in Chimpanzees, Abnormal Movements in Patients with Chronic Psychiatric Illnesses.* Anatomy and Physiology: Fiber Connection of the Basal Ganglia, Anatomy of Lingual Movement, Physiological and Psychological Aspects of Basal Ganglia Functions, Intracellular Responses in Caudate and Cortical Lesions, Permanent Ahtetoid and Choreiform Movements after Small Caudate Lesions in the Cat, The Effects of Central Tegmental Lesions of Tardive Dyskinesia.* Pharmacology and Therapy of Basal Ganglia Disorders: Pharmacological Changes of Dopamine Metabolism in the Basal Ganglia, Pharmacological Treatment of Basal Ganglia Disorders, Modification of Parkinsonism - Dyskinesias Accompanying Treatment with Dopa.* Neurosurgery and Laboratory Procedures: Some Surgical Features of Parkinsonism, Oral Dyskinesia Following Stereotactic Thalamotomy for Parkinson's Disease, Humans in Motion - Objective Methods in Measuring Involuntary Movements. ... Read more

Book Description
This digital document is a journal article from Brain and Cognition, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Converging evidence from human lesion, animal lesion, and human functional neuroimaging studies implicates overlapping neural circuitry in ventral prefrontal cortex in decision-making and reversal learning. The ascending 5-HT and dopamine neurotransmitter systems have a modulatory role in both processes. There is accumulating evidence that measures of decision-making and reversal learning may be useful as functional markers of ventral prefrontal cortex integrity in psychiatric and neurological disorders. Whilst existing measures of decision-making may have superior sensitivity, reversal learning may offer superior selectivity, particularly within prefrontal cortex. Effective decision-making on existing measures requires the ability to adapt behaviour on the basis of changes in emotional significance, and this may underlie the shared neural circuitry with reversal learning. ... Read more

Book Description
This digital document is a journal article from Brain and Language, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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A variety of fluent and nonfluent aphasias have been reported after left basal ganglia stroke. It has been speculated that this heterogeneity may reflect variations in cortical hypoperfusion resulting from large vessel stenosis. To test this hypothesis, a consecutive series of 24 patients with left caudate infarct identified with diffusion-weighted imaging underwent language testing and perfusion-weighted imaging <24h from onset of symptoms. Specific regions in perisylvian cortex were rated for the percentage of the region that was hypoperfused. Aphasia type was determined on the basis of speech fluency, comprehension, and repetition performance on the language tests. Association between aphasia type/language impairment and regions of hypoperfusion were identified with Fisher's exact tests. Results demonstrated that in patients with acute left caudate infarct, the presence and type of aphasia reflected regions of hypoperfusion, and generally followed predictions based on chronic lesion studies, regarding anatomical lesions associated with classic aphasia types. ... Read more

Book Description

As the Baby Boomers head toward retirement, the four-volume Encyclopedia of Aging offers a timely resource encompassing all aspects of aging. Covering a variety of disciplinesbiology, medicine, economics, law, psychology, sociology and historythe Encyclopedia also explores related issues such as religion, spirituality, and ethics.

Book Description

Targeted to patients, their families and allied health students, The Gale Encyclopedia of Neurological Disorders provides in-depth coverage of neurological diseases and disorders, including stroke, multiple sclerosis, Parkinson disease, Tourette Syndrome, Alzheimer's disease, cerebral palsy, vertigo, amnesia and epilepsy. Related topics include communication aids, electric personal assistive mobility devices, medications for treating neurological diseases and conditions, understanding the needs of Alzheimer patient caregivers and more. This two-volume set provides an alternative to resources that either fail to explore neurological disease in any depth and or do so at a level not appropriate for students and general readers.

Book Description
This digital document is a journal article from Neurobiology of Learning and Memory, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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Adult male Wistar rats with a substantia nigra pars compacta (SNc) lesion induced by intranigral administration of 1@mmol 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were used as a model of early phase Parkinson's disease (PD). This lesion caused a partial depletion of striatal dopamine (DA). The animals were submitted to a spatial working memory version of the water maze task in which they had to find a hidden (submersed) platform using online-maintained information that the platform remains in the same place during four consecutive trials, but that it is moved to another place every training day. Left, but not right SNc-lesioned rats were impaired in finding the platform in the second trial. This result suggests that the left SNc plays a key role in spatial working memory. Control experiments ruled out the possibility that motor impairment, sensory neglect, and/or impairment in the mental representation of the contralateral spatial environment had affected performance of the SNc-lesioned rats. ... Read more