Explicit and procedural memory in Parkinson's disease

Retrograde procedural memory is impaired in people with Parkinson's disease with freezing of gait

Background

Freezing of gait (FOG), is associated with impairment of different cognitive functions. Previous studies hypothesized that FOG may be due to a loss of automaticity.

Research question

To explore whether FOG is associated with impairment in cognitive functions, focusing on retrograde procedural memory, the memory responsible for the automatic, implicit stored procedures that have been acquired in earlier life stages.

Methods

In this cross-sectional, case-control study, 288 people with typical Parkinson's disease (PD) from the Luxembourg Parkinson's Study were assigned to Freezers (FOG+) and non-Freezers (FOG-) based on the MDS-UPDRS 2.13 (self-reported FOG episodes) and 3.11 (FOG evaluated by clinicians during gait assessment). Both groups were matched on age, sex and disease duration. Global cognition (MoCA), retrograde procedural memory and visuo-constructive abilities (CUPRO), psychomotor speed and mental flexibility (TMT) were assessed. Furthermore, we repeated our analyses by additionally controlling for depression (BDI-I).

Results

Besides lower global cognition (MoCA; p = 0.007) and mental flexibility (TMT-B and Delta-TMT; p < 0.001), FOG+ showed a lower performance in retrograde procedural memory (CUPRO-IS1; p < 0.001) compared to FOG-. After controlling additionally for depression, our main outcome variable CUPRO-IS1 remained significantly lower in FOG+ (p = 0.010).

Conclusion

Our findings demonstrated that besides lower global cognition and mental flexibility scores, FOG+ showed lower performance in retrograde procedural memory compared to matched FOG-control patients, even when accounting for factors such as age, sex, disease duration or depression.

Significance

In the context of limited treatment options, especially for non-invasive therapeutic approaches, these insights on procedural memory and FOG may lead to new hypotheses on FOG etiology and consequently the development of new treatment options.

Probabilistic classification and gambling in patients with schizophrenia receiving medication: comparison of risperidone, olanzapine, clozapine and typical antipsychotics

RATIONALE

We have previously shown that patients with schizophrenia treated with typical antipsychotics were impaired on the weather prediction probabilistic classification learning (PCL) task that relies on striatal function, and that similar patients treated with atypical antipsychotics were impaired on the Iowa gambling task (IGT) that depends on medial prefrontocortical function.

OBJECTIVES

We tested the hypothesis that test performance of patients treated with risperidone will be more similar to those treated with typical rather than atypical antipsychotics.

RESULTS

Groups of schizophrenia patients treated with risperidone, olanzapine, clozapine or typical antipsychotics did not differ on the Positive and Negative Syndrome Scale or the Mini Mental State Exam (MMSE) but scored lower than controls on the MMSE. For the PCL task, patients treated with clozapine improved over trials while those treated with typical antipsychotics, olanzapine, or risperidone did not. For the IGT, patients treated with typical antipsychotics or risperidone improved over trials while those treated with clozapine or olanzapine did not.

CONCLUSIONS

Results generally supported the hypothesis that patients treated with risperidone perform more like those treated with typical antipsychotics than those treated with other atypical antipsychotics.

Concurrent validity of the tower tasks as measures of executive function in adults: a meta-analysis

Executive function refers to a variety of behaviors and abilities related to planning and strategy use, as well as to the maintenance of attention and behavior in the pursuit of some goal. Many instruments have been designed for the purpose of assessing executive function, and the tower tasks represent a specific group of measures commonly used in the assessment of this construct. This review and meta-analysis examines the theoretical and psychometric basis for the use of the various tower tasks in neuropsychological assessment of adults. Neuroimaging and electrophysiological evidence are consistent with theoretical hypotheses of frontal involvement (e.g., planning and strategy use) in tower task performance. Further, adults with various disorders of presumed neurological basis demonstrate impaired performance on tower tasks. Implications for the use of tower tasks in practice and research are discussed.

Treatment of dementia in parkinsonian syndromes with cholinesterase inhibitors

In Parkinsonian syndromes behavioural symptoms and dementia can be even more debilitating than motor symptoms and are an important predictor for nursing home placement and mortality. Neuropathologically, dementia seems to be primarily related to cortical changes rather than to subcortical alterations. Concerning neurotransmitter systems, the cholinergic system has been proposed to play a key role in cognitive disturbances. Based on studies with patients with Alzheimer disease, the application of cholinesterase inhibitors is vividly discussed also for dementia associated with parkinsonian syndromes. This review focuses on the specific symptoms of dementia in different parkinsonian syndromes and critically questions the effect of cholinergic treatment on cognitive functions in patients with extrapyramidal syndromes and dementia. There is evidence that medication with some cholinesterase inhibitors can enhance cognition as well as activities of daily living in dementia with Parkinson's disease and seems to reduce behavioural disturbances in both dementia with Parkinson's disease and dementia with Lewy bodies. The effect of treatment with cholinesterase inhibitors in progressive supranuclear palsy and corticobasal degeneration warrants carefully designed studies including a sufficient number of patients and symptom-adopted dementia scales.

Modifications in avoidance reactions of mice, on a second exposure to the hot plate, resist to various amnesia-inducing treatments

The avoidance responses of mice exposed to the hot plate (55 degrees C) were found to be modified when tested a second time. In fact, when forepaws licking was no longer observed, the rearing was clearly anticipated (7 s instead of 15 s) as well as jumping (24 s instead of 55 s). These modifications of avoidance strategies as well as their latencies were still observed even 24 days after the first exposure. Avoidance responses were prevented by morphine or haloperidol injected prior to the first exposure, but not with scopolamine or diazepam. These modifications were not affected in mice injected with morphine or submitted to either a supramaximal electroshock or to ether anesthesia delivered immediately after the first hot plate exposure. Among the various known types of memory, these modifications could be linked to procedural memory.

Reduced plasma levels of tyrosine, precursor of brain catecholamines, and of essential amino acids in patients with severe traumatic brain injury after rehabilitation11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors(s) or upon any organization with which the author(s) is/are associated

OBJECTIVE

To investigate whether levels of plasma tyrosine and tryptophan, precursors of brain catecholamine and serotonin neurotransmitters, respectively, and other essential amino acids (EAA) may return to normal in patients with severe traumatic brain injury (TBI) after 2 months in a hospital rehabilitation center.

DESIGN

Peripheral plasma concentrations of tyrosine, tryptophan, and other EAAs in subjects with severe TBI, both at admission (44+/-11d postinjury) and at discharge from the center (110+/-15d after acute event) were compared with concentrations in control subjects.

SETTING

Tertiary care rehabilitation setting in Italy.

PARTICIPANTS

Ten men (26.6+/-12.6y) with TBI and 6 healthy subjects (controls) matched for age, sex, voluntary loss of body weight, and sedentary lifestyle.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Concentrations of brain neurotransmitter precursor amino acids and of EAA.

RESULTS

On admission, patients had lower plasma tyrosine, leucine, valine, methionine, and phenylalanine concentrations than did control subjects. The plasma concentrations of tryptophan were similar in the 2 groups. These amino acid abnormalities were still present at discharge.

CONCLUSION

The levels of plasma tyrosine and many EAA in patients with TBI did not recover by discharge (110+/-15d) from rehabilitation. Plasma tryptophan concentrations were similar in patients and controls.

Sequence learning in Parkinson's disease: the effect of spatial stimulus-response compatibility

Patients with Parkinson's disease (PD) have repeatedly demonstrated reduced sequence-specific learning effects in serial reaction time tasks (SRTs). Previous research with PD patients has mainly employed the 'classical' SRT task, involving a spatially compatible assignment of stimuli and responses. From cognitive research, it is known that spatial compatibility triggers rapid, automatic responses in the direction of the stimulus. Automatic responding has shown to be disinhibited in PD patients and may therefore interfere with stimulus anticipation during the learning process. The aim of the present study was to test this hypothesis by investigating if reduced sequence-specific learning depends on spatial stimulus-response compatibility. PD patients and age-matched controls were examined either with an SRT variant involving central stimulus presentation, thereby preventing automatic linking of stimulus and response locations, or with a spatially compatible SRT task. Patients showed reduced sequence-specific learning effects only when the stimulus-response assignment was spatially compatible. This pattern of results confirms the hypothesis that sequence learning deficits in PD may result from a predominance of automatic response activation over learning-based stimulus anticipations during the learning phase.

Psychomotor and cognitive effects of piribedil, a dopamine agonist, in young healthy volunteers

Piribedil is a dopamine agonist acting on D2 and D3 central nervous system dopamine receptors. This drug has been administered to 12 young healthy male volunteers (age 22 +/- 2 years) according to a single center randomized, double-blind, two ways cross-over, placebo controlled trial, including a washout period of one week. Placebo and piribedil were administered by a single intravenous infusion over 2 h (3 mg). Psychomotor performance and cognitive functions were assessed through a standardized and computerized psychometric tests battery and a continuous electroencephalogram (EEG) mapping. Piribedil improved simple reaction time (P=0.02), immediate (P=0.045 and 0.004), and delayed free recall (P=0.05), dual coding test (P=0.02) and increased theta and fast beta waves on the EEG (P < 0.05 and 0.001, respectively). No deleterious effect was observed on the tests exploring attention and concentration via the other procedures. It is concluded that a single intravenous perfusion of piribedil 3 mg improves alertness and the information processing speed within the central nervous system, in healthy volunteers.

Dopamine-antagonistic, anticholinergic, and GABAergic effects on declarative and procedural memory functions

Declarative and procedural memory functions are related to dissociable neuroanatomic substrates. In the present study differential effects of pharmacologically induced changes in dopaminergic, GABAergic, and cholinergic activity in the brain on declarative (object and face recognition, immediate and delayed word recall) and procedural memory processes (compensatory tracking) were investigated. In a double-blind design, either 3 mg of haloperidol, 11 mg of midazolam, 1 mg of scopolamine, or placebo were administered to 80 healthy volunteers randomly assigned to one of the four drug conditions. Although all three drugs produced a detrimental effect on immediate and delayed word recall, recall performance was substantially more impaired by the benzodiazepine midazolam than by either haloperidol or scopolamine. While recognition of faces was affected by neither of the drugs, performance on object recognition was significantly decreased by midazolam as compared to placebo. Procedural learning was markedly impaired by all drugs but, again, the observed effect was most pronounced with midazolam. Additional analyses of measures of subjective activation, cortical arousal, and psychomotor performance argued against the assumption that the observed memory-impairing effects were secondary to drug-induced sedation. The overall pattern of results revealed that memory processes are much more susceptible to changes in GABAergic than in dopaminergic or cholinergic neurotransmitter activity. Furthermore, the present findings point to the conclusion that the modulating effects of dopaminergic, GABAergic, and cholinergic neurotransmitter systems on declarative and procedural memory functions are less specific than suggested by neuropsychological studies in patients.

Expletives: neurolinguistic and neurobehavioral perspectives on swearing

Severe aphasia, adult left hemispherectomy, Gilles de la Tourette syndrome (GTS), and other neurological disorders have in common an increased use of swearwords. There are shared linguistic features in common across these language behaviors, as well as important differences. We explore the nature of swearing in normal human communication, and then compare the clinical presentations of selectively preserved, impaired and augmented swearing. These neurolinguistic observations, considered along with related neuroanatomical and neurochemical information, provide the basis for considering the neurobiological foundation of various types of swearing behaviors.