Problem solving ability of parkinsonians

A deficit in optimizing task solution but robust and well-retained speed and accuracy gains in complex skill acquisition in Parkinson׳s disease: multi-session training on the Tower of Hanoi Puzzle

INTRODUCTION

There are inconsistent results in the research literature relating to whether a procedural memory dysfunction exists as a core deficit in Parkinson׳s disease (PD). To address this issue, we examined the acquisition and long-term retention of a cognitive skill in patients with moderately severe PD. To this end, we used a computerized version of the Tower of Hanoi Puzzle.

METHODS

Sixteen patients with PD (11 males, age 60.9±10.26 years, education 13.8±3.5 years, disease duration 8.6±4.7 years, UPDRS III "On" score 16±5.3) were compared with 20 healthy individuals matched for age, gender, education and MMSE scores. The patients were assessed while taking their anti-Parkinsonian medication. All participants underwent three consecutive practice sessions, 24-48h apart, and a retention-test session six months later. A computerized version of the Tower of Hanoi Puzzle, with four disks, was used for training. Participants completed the task 18 times in each session. Number of moves (Nom) to solution, and time per move (Tpm), were used as measures of acquisition and retention of the learned skill.

RESULTS

Robust learning, a significant reduction in Nom and a concurrent decrease in Tpm, were found across all three training sessions, in both groups. Moreover, both patients and controls showed significant savings for both measures at six months post-training. However, while their Tpm was no slower than that of controls, patients with PD required more Nom (in 3rd and 4th sessions) and tended to stabilize on less-than-optimal solutions.

CONCLUSIONS

The results do not support the notion of a core deficit in gaining speed (fluency) or generating procedural memory in PD. However, PD patients settled on less-than-optimal solutions of the task, i.e., less efficient task solving process. The results are consistent with animal studies of the effects of dopamine depletion on task exploration. Thus, patients with PD may have a problem in exploring for optimal task solution rather than in skill acquisition and retention per se.

Procedural learning of semantic categorization: a study of 110 non-disabled individuals

PURPOSE

This paper describes a cognitive procedural task in order to study procedural learning of semantic categorization. We evaluated age, educational level and gender effects on semantic procedural skill.

METHODS

The procedural task was developed in our laboratory, applying a manual and serial reaction time paradigm to semantic categorization. We investigated this form of procedural learning in 110 non-disabled subjects.

RESULTS

We observed an improvement of semantic categorization reaction times (RTs) over time from practice, even with new verbal material to categorize. Age, educational level and gender did not influence procedural learning of semantic categorization but women performed faster than men. The results suggest that semantic categorization is susceptible to procedural training.

CONCLUSION

The results suggest that semantic categorization is susceptible to procedural training.

Differential Effect of Right and Left Basal Ganglionic Infarctions on Procedural Learning

OBJECTIVE

To assess the effect of ischemic infarctions affecting the basal ganglia (BG) region on a series of procedural learning tasks.

BACKGROUND

The basal ganglia hypothesis of procedural learning is a matter of debate. As most of the relevant research so far is based on examination of patients suffering from Parkinson disease, this inconsistency might reflect either lesion heterogeneity existing in this pathologic group or the heterogeneity of the procedural learning tasks.

METHOD

Twelve patients with lesions confined to the right (BGr), 10 to the left (BGI) BG region, and 15 matched controls participated in the study. Three procedural learning tasks were used: Tower of Hanoi Puzzle, Mirror Reading, and Porteus Mazes. Declarative memory and general intelligence were also tested.

RESULTS

Verbal declarative memory was impaired in the BG1 group. For each procedural learning task, baseline performance and learning rate were analyzed. Tower of Hanoi Puzzle: Baseline performance of the BG1 group was impaired compared with the other groups. The BGr group was the only group that did not improve over learning trials. MR: Baseline performance of the BGr group was impaired compared with the other groups. The groups' learning rate did not differ significantly. Porteus Mazes: Baseline performance of both patient groups was impaired compared with that of the control group. Learning rate over repetitive trials of the same maze was impaired in the BGr group. However, the transfer of procedural learning to a newly exposed maze was impaired in the BG1 group.

CONCLUSIONS

First, right and left basal ganglia play different roles in different procedural learning tasks. Second, procedural learning is not a unitary capacity subserved by any single neural mechanism.

Motor and non-motor sequence learning in patients with basal ganglia lesions: the case of serial reaction time (SRT)

In order to address the question of whether the basal ganglia are involved exclusively in regulation of motor sequence learning, or if they are involved in non-motor sequence learning as well, two versions of the serial reaction time (SRT) task were administered: First is the standard version of the SRT task in which the sequence is executed motorically, and the second is a non-motor version of the task which requires response only to a particular position of the sequence. Sixteen patients with damage restricted to the region of the basal ganglia and 16 matched control subjects participated in this study. In addition to the motor and non-motor SRT tasks, two declarative memory tests (Visual Paired Associates and Rey Auditory-Verbal Learning Test) were administered to the participants. Results indicate that the two groups did not differ either on learning rate of the two declarative tasks, or on the declarative component of the SRT tasks (i.e., 'generate'). However, the control group was significantly superior to the basal ganglia (BG) group in learning a specific sequence in the motor and non-motor SRT tasks. Results suggest that the basal ganglia are involved in the regulation of non- motor as well as motor sequence learning.

Declarative and procedural learning in Parkinson's disease patients having tremor or bradykinesia as the predominant symptom

The distinction between procedural and declarative memory is widely accepted in the memory literature. Converging evidence makes a strong case that the medial aspects of the temporal lobes and the diencephalon subserve the declarative memory system. However, the neuroanatomy of procedural memory is much less clear. In animal studies, damage to the basal ganglia has been found to affect procedural memory, but studies of patients suffering from degenerative diseases of the basal ganglia (e.g., Parkinson's and Huntington's disease) are less conclusive. Two groups of Parkinson's disease subtypes, with tremor (PDt) and bradykinesia (PDb) as the predominant motor symptom, were compared to controls on declarative and procedural memory tasks. The two patient groups did not differ from each other on the declarative tasks. However, in the procedural learning tasks, the PDb but not the PDt group, was significantly impaired compared to the control group. The results are discussed in terms of the differential involvement of discrete neuroanatomic loops connecting the basal ganglia and the prefrontal cortex.

Learning and forgetting processes in Parkinson's disease: a model-based approach to disentangling storage, retention and retrieval contributions

Learning and forgetting a prose passage was studied in 20 patients with Parkinson's disease and in 20 normal control subjects by means of stochastic models, with the aim of identifying the learning and retaining abilities that are affected by Parkinson's disease. Results suggested that Parkinson's disease patients are impaired in developing automatic processing both during learning and retaining, while functions that require active attention are spared. The automatic/intentional dissociation, which is the hallmark of motor disturbance in Parkinson's disease, extends to memory abilities, and, on the grounds of neuroanatomical, neurochemical and neurophysiological correlates, suggests that the memory deficit in Parkinson's disease may be contingent on a dysfunction of the medial prefrontal-cingulate cortex.

Impaired problem solving in Parkinson's disease: impact of a set-shifting deficit

Parkinson's disease (PD) is associated with specific cognitive deficits in the absence of dementia, including the inability to suppress previously learned responses in a changed context. Our goal was to determine whether this set-shifting deficit is sufficient to account for impaired performance on a problem-solving task, or, instead, whether it is necessary to postulate deficits in one or more other cognitive capacities, such as logical deduction. Deductive reasoning and other conceptual abilities were assessed in 15 nondemented subjects with PD who had never been medicated, 15 nondemented subjects with PD who were currently receiving medication, and 15 healthy elderly control subjects. On a deductive reasoning task, Poisoned Food Problems, the PD groups made more errors than the control group. The PD groups' error pattern was characterized by intrusions of information from previous problems. By contrast, the PD groups made appropriate assessments of redundant and irrelevant information that appeared in these problems, and performed normally on other tests of concept formation and problem solving that did not require set shifting, indicating that the capacities for logical deduction and concept formation were intact. The set-shifting deficit, conceptualized as a difficulty in suppressing a prepotent response, appears to be a primary cognitive impairment in PD and presumably arises from dysfunction of the nigrostriatal-dorsolateral prefrontal cortex complex loop.

Cognitive function in Parkinson's disease: from description to theory

From the large body of empirical evidence on cognitive function in Parkinson's disease, a number of attempts have been made to describe the characteristics of the deficits and the conditions under which they are observed. This review considers descriptions limited to specific domains of cognition such as visuospatial function, memory and 'frontal' function, and more general descriptions relating to 'set-shifting', sequencing, temporal ordering and recency discrimination, the locus of cognitive control and bradyphrenia. Later in the paper an attempt is made to provide some theoretical framework for the various descriptions. Two theories are discussed representing contrasting, but complementary approaches. The first is a 'psychological' theory in which the concept of depleted processing resources is suggested as a possible mechanism to explain the observable deficits. The second is a neurobiological model that attempts to integrate information from diverse sources to provide a model for the neuroanatomical and neurochemical substrate that may underlie some of the behavioural deficits.

Selective visual attention in Alzheimer's and Parkinson's patients: memory- and data-driven control

An automated visual search experiment was carried out on patients with incipient Alzheimer's disease, non-demented Parkinsonians and healthy controls to test for selective attention control within the framework of the Norman and Bobrow (1975) model. The performances of the Parkinsonians and healthy controls were consistent with the predictions of this model but those of the Alzheimer patients were not. These patients appeared to be no longer sensitive to the facilitation supplied by the stimulus context and to spend most of their residual resources on achieving accuracy. The reduction of their attentional resources possibly interferes with the control of the speed-accuracy trade-off.