Selective effect of lithium on cognitive performance in man

Neurocognitive costs and benefits of psychotropic medications in older adults

Psychotropic medications are widely used in older adults and may cause neurocognitive deficits. Older adults are at increased risk of developing adverse effects because of age-related pharmacodynamic and pharmacokinetic changes. This article provides a comprehensive review of the undesirable, and at times beneficial, effects of psychotropic medications. The review covers a wide range of medications that impair executive function, memory, and attention, as well as a much smaller group of medications that lead to improved neurocognitive function. Some of the most commonly used psychotropic medications in older adults, namely, antidepressants, sedatives, and hypnotics, are among the drugs that most consistently lead to cognitive impairments. Medications with anticholinergic properties almost invariably lead to neurocognitive dysfunction, despite symptom improvement. The neurocognitive costs and benefits of psychiatric medications should be considered in the context of disease treatment in older adults.

Differential effects of chronic lithium and valproate on brain activation in healthy volunteers

RATIONALE

Previous functional imaging studies have shown altered brain activity during cognitive task performance in bipolar patients. However, the fact that these patients are often on medication makes it unclear to what extent these changes reflect treatment effects.

OBJECTIVES

This study aims to identify regional brain activity changes occurring following lithium and valproate treatment in healthy volunteers.

METHODS

This was a double-blind, placebo-controlled, study in which volunteers received either 1000 mg sodium valproate (n = 12), 900 mg lithium (n = 9), or placebo (n = 12). Functional images were acquired using functional magnetic resonance imaging (fMRI) while subjects performed three cognitive tasks, a word generation paradigm, a spatial attention task and a working memory task. fMRI was carried out both before and after 14 days of treatment with valproate, lithium or placebo. The changes in the magnitude of the blood-oxygen-level-dependent (BOLD) signal after treatment were compared between the groups using a one-way ANOVA for each task followed by a post-hoc multiple comparisons correction.

RESULTS

A significant group effect was noted in the change in BOLD signal magnitude from baseline to post-treatment, in all three tasks (working memory p< 0.000; spatial attention task p = 0.003; word generation paradigm p = 0.030). In the working memory task, the lithium group had a significant decrease in BOLD signal change, compared with the control group (p< 0.000). A decrease in BOLD signal change was also noted in the valproate group, in the spatial attention task (p = 0.004). Both lithium and valproate groups had a decreased BOLD signal in the verbal task, following treatment, compared with the placebo group (p = 0.061 (lithium approached significance); p = 0.050 (valproate)).

CONCLUSIONS

These findings suggest that lithium and valproate have independent effects on brain activation that vary in a task and region-dependent manner.

Changes in neuronal activation in patients with bipolar disorder during performance of a working memory task

OBJECTIVES

Several lines of evidence suggest that deficits in cognition persist in bipolar patients during periods of euthymia. Working memory impairment has been observed in euthymic bipolar patients and noted to be a significant source of functional deficits in psychiatric disorders. Functional changes associated with these cognitive deficits however, remain poorly understood. We hypothesized that patients with bipolar disorder would demonstrate changes in neuronal activation in specific regions forming part of the working memory network.

METHODS

Fifteen euthymic bipolar patients and fifteen age- and gender-matched healthy controls were recruited. Subjects participated in fMRI scans during which a two-back working memory task alternated with a zero-back control/attention task using a block-design paradigm. Groups were analyzed separately, and intergroup comparisons were made using an exploratory, voxel-by-voxel analysis.

RESULTS

Bipolar patients performed more poorly on the cognitive tasks than did healthy controls (F = 3.77, p = 0.04). After covarying for task performance and reaction time, bipolar patients demonstrated significantly greater activation than healthy subjects in several regions including the fronto-polar prefrontal cortex, temporal cortex, basal ganglia, thalamus, and posterior parietal cortex. No areas showed a significant decrease in activation, compared with healthy controls.

CONCLUSIONS

Our findings suggest that decreased working memory performance in bipolar patients reflects specific neurofunctional deficits. These deficits may represent primary areas of neuropathology or be secondary to neuropathology elsewhere in the working memory network. Continued research utilizing other imaging modalities may further clarify the underlying neuropathology involved in these cognitive deficits.

The effects of lithium on cognition: an updated review

RATIONALE

Adverse cognitive effects associated with lithium are often implicated as contributing to vocational and social impairment, as well as medication noncompliance. As impaired cognitive functioning caused by lithium has clear clinical implications, it is important to determine whether evidence for or against impaired cognitive functioning exists in the literature.

OBJECTIVES

An attempt is made to synthesize findings from previous studies, which assess a variety of cognitive domains, to determine whether conclusions can be drawn regarding lithium-associated cognitive impairment. The "reversibility" of neuropsychological impairment following lithium discontinuation and whether lithium administration has negative cumulative effects on cognition were also reviewed.

METHODS

Key word searches on "Medline" and "Psych Info" were completed for clinical articles that investigated the neuropsychological effects of lithium in clinical and normal populations between 1968 and 2000.

RESULTS

Despite methodological flaws, poor replicability and the subtle cognitive effects of lithium, five consistent findings emerged from the review; impairment on tasks of psychomotor speed, impaired functioning in the majority of studies examining verbal memory, no impairment on tasks of visuo-spatial constructional ability or attention/ concentration, and no negative cumulative effect.

CONCLUSIONS

Many patients administered lithium carbonate complained of mental slowness. Lithium carbonate also appeared to have definite, yet subtle, negative effects on psychomotor speed. Studies reviewed also showed a trend toward impaired verbal memory. Recommendations with respect to future research, methodological and statistical problems, and additional clinical implications are presented.

Dose-response effects of chronic lithium regimens on spatial memory in the black molly fish

Lithium is widely used in the management of bipolar disorder, yet memory impairment is a serious side effect. To assess the effects of lithium on spatial working and reference memories, we have employed a plus maze utilizing spontaneous alternation (SA) and place-learning paradigms in two experiments with the black molly fish. Four treatment groups were gavaged with 20 microl of a 10, 100, or 1000 mM lithium chloride (LiCl) solution or ddH(2)O vehicle every 12 h for 22 to 24 days. On Day 15, subjects began an 8-day SA task or a 10-day place-learning task. Results indicate that there is a significant difference in SA performance among the treatment groups for Days 1, 2, and 3. Results of the place-learning task indicate that the 1 M dose group needed significantly more trials to reach criterion and made significantly fewer correct first choices than the other dose groups. Capillary ion analysis determinations of plasma and brain lithium levels illustrate linear dose-response relationships to doses administered. Regression analyses indicate that there is a relationship between SA performance and plasma/brain lithium levels during the initial part of testing. Collectively, the results indicate that chronic lithium administration impairs spatial working and reference memories.

Lamotrigine in the treatment of bipolar disorder

Lamotrigine has undergone a remarkable series of systematic studies since 1994 that now establish it as an efficacious, well-tolerated treatment in bipolar disorder. Its efficacy principally addresses both acute and maintenance phase benefits on depressive symptomatology. These benefits have been demonstrated in placebo-controlled studies, rapid cycling patients, bipolar I and II patients and monotherapy as well as in combination therapy, although this has been less well studied. The drug is exceptionally well-tolerated in long-term treatment, although initial dosing requires gradual dosage escalation to avoid the risk of inducing serious rashes with features within the spectrum of Stevens-Johnson syndrome. Administration with valproate requires a slower dosage titration, whereas, as with many drugs, administration with carbamazepine requires a more rapid dosage increase. In contrast to marketed antidepressants, lamotrigine appears not to induce manic or hypo-manic episodes, nor to increase cycling frequency. This combination of properties makes it a first-choice treatment for acute bipolar depression and continuation treatment, especially, but not limited to, prophylaxis against recurrent depression and depressive symptoms. Lamotrigine appears not to have acute antimanic properties. A small number of studies suggest a broader spectrum of efficacy, including in some axis I disorders that are comorbidly associated with bipolar disorder.

A double-blind, placebo-controlled study of the effects of lithium on cognition in healthy subjects: mild and selective effects on learning

BACKGROUND

Several studies have shown cognitive impairment in short-term memory, long-term memory and psychomotor speed in bipolar patients taking lithium. The aim of the study was to look at the effect of lithium in normal subjects (N=30) taking lithium for 3 weeks. A comprehensive battery was used to assess attention and memory.

METHODS

Subjects were randomized to double-blind treatment with either lithium (N=15) or placebo (N=15) for a 3-week period. Thirteen participants in the lithium group and 15 in the placebo group completed the study. The lithium and placebo were administered twice daily in doses varying from 1050 to 1950 mg (mean=1569 mg). The initial daily dose was calculated according to the Pepin formula to achieve a blood serum lithium level of about 0.8 mmol/l. Cognitive performance (attention, memory) was assessed in each subjects during three periods, i.e. at baseline, after 3 weeks of lithium or placebo, and 2 weeks after discontinuation of study medication.

RESULTS

In short-term memory tasks, the performance of subjects in the lithium group was worst 3 weeks after lithium treatment compared to 2 weeks after discontinuation. In long-term memory, a significantly higher number of words was recalled by the placebo group but not the lithium group.

CONCLUSIONS

Lithium may have an effect on learning when long-term explicit memory test are administered repeatedly. It means that the practice effect when a subject performs the same task several times is less in the lithium-treated group than in the placebo group. This practice effect is related to the learning of a task.

The effects of methylphenidate and lithium on attention and activity level

Seven psychiatrically hospitalized prepubertal children were treated with methylphenidate, placebo, lithium carbonate alone and in combination with methylphenidate. Children met DSM-III-R criteria for both disruptive behavior disorder and bipolar or major depressive disorder by structured interview and consensus diagnosis. Parents, children, teachers, staff, and raters were blind to medication condition. Children were rated weekly on measures of attention and activity to determine whether medications alone or in combination produced a differential effect on these variables. The nosological and practical implications of the results are discussed.

The effects and after effects of the α2-adrenoceptor antagonist idazoxan on mood, memory and attention in normal volunteers

Idazoxan, an α( 2)-adrenoceptor antagonist, is an effective antidepressant with a mode of action different from that of conventional antidepressants. As it is used as an antidepressant it is important to know whether there are any unwanted CNS side effects. Study of its effects will also provide information on the relationship between noradrenergic function and mood and performance. Twelve normal male volunteers who were given the drug (40 mg orally three times daily for 21 days) were compared with 12 matched controls. A computerized test battery was used to assess mood and various aspects of memory and attention. Many of the tests of memory and attention in the battery have been widely used over the last 20 years, and in addition two new selective attention tasks were included. The subjects were tested 3 days before starting the drug, on days 3 and 17 while on the drug, and after they had stopped taking the drug (4 days after and 24 days after). Control subjects followed a similar testing schedule. The results showed that the drug had no effect on mood, logical reasoning, retrieval from semantic memory or sustained attention. However, the drug did improve one aspect of selective attention (the place repetition effect), although this effect was only observed on the third day on the drug. Overall, the results suggest that idazoxan produces selective performance improvements, and that the measures of selective attention used here may be more sensitive indicators of drug effects than some of the traditional tasks currently in use.

New applications of lithium therapy

Several placebo-controlled double-blind studies have indicated that lithium sometimes augments antidepressants, converting nonresponding patients to responders. Lithium therapy has also benefitted some schizoaffective patients and some alcoholics. Side effects are minimal. Mechanisms involved in lithium's effectiveness have not yet been discovered.