The influence of amphetamine on language activation: an fMRI study

An update on medications and noninvasive brain stimulation to augment language rehabilitation in post-stroke aphasia

INTRODUCTION

Aphasia is among the most debilitating outcomes of stroke. Aphasia is a language disorder occurring in 10-30% of stroke survivors. Speech and Language Therapy (SLT) is the gold standard, mainstay treatment for aphasia, but gains from SLT may be incomplete. Pharmaceutical and noninvasive brain stimulation (NIBS) techniques may augment the effectiveness of SLT. Areas covered: Herein reviewed are studies of the safety and efficacy of these adjunctive interventions for aphasia, including randomized placebo-controlled and open-label trials, as well as case series from Pubmed, using search terms 'pharmacological,' 'tDCS' or 'TMS' combined with 'aphasia' and 'stroke.' Expert commentary: Relatively small studies have included participants with a range of aphasia types and severities, using inconsistent interventions and outcome measures. Results to-date have provided promising, but weak to moderate evidence that medications and/or NIBS can augment the effects of SLT for improving language outcomes. We end with recommendations for future approaches to studying these interventions, with multicenter, double-blind, randomized controlled trials.

Psycholinguistics of Aphasia Pharmacotherapy: Asking the Right Questions

BACKGROUND

Among the obstacles to demonstrating efficacy of pharmacological intervention for aphasia is quantifying patients' responses to treatment in a statistically valid and reliable manner. In many of the review papers on this topic (e.g., Berthier et al., 2011; de Boissezon, Peran, de Boysson, & Démonet, 2007; Small & Llano, 2009), detailed discussions of various methodological problems are highlighted, with some suggestions on how these shortcomings should be addressed. Given this deep understanding of caveats associated with the experimental design of aphasia pharmacotherapy studies (e.g., Berthier et al., 2011), investigations continue to produce inconsistent results.

AIM

In this review paper we suggest that inclusion of theory-driven linguistic measures in aphasia pharmacotherapy studies would add an important step toward elucidating precise patterns of improvement in language performance resulting from pharmacotherapeutic intervention.

MAIN CONTRIBUTION

We provide a brief review of the clinical approaches currently used in pharmacotherapy studies of aphasia, which often lack psycholinguistic grounding. We then present ways in which psycholinguistic models can complement this approach, offering a rationale for task selection, and as a result, lead to a better understanding of treatment effects. We then follow with an example of how such an integrative approach can be implemented in studies targeting stress reduction in people with aphasia, via beta-blocking agents, as a means to augment language performance, using the psycholinguistic framework of "linguistic anxiety" outlined in Cahana-Amitay et al, 2011 as our guideline.

CONCLUSION

We conclude that the incorporation of psycholinguistic models into aphasia pharmacotherapy studies can increase the resolution with which we can identify functional changes.

Imaging cognitive deficits in drug abuse

The neuropsychological network is a complex structure. To identify processes location and network capacity the brain imaging techniques together and in combination with other neuropsychological techniques and the expanding of well elaborated designs provide us with a multidimensional understanding, and contributes to the understanding of each illicit drug's character, which is of importance in designing of new treatment programs and clinical practice. Cannabis, MDMA, amphetamine, cocaine, and heroin abusers display both acute effects and chronic effects, deficits in attention, memory, and executive functioning. These deficits may last beyond the period of intoxication and cumulate with years of use. Cannabis users may recruit an alternative neural network as a compensatory mechanism during performance of tasks of attention. There is some evidence indicating the detrimental effects of cannabis on the maturing adolescent brain. Stimulant dependence is characterized by a distributed alteration of functional activation. Attenuated anterior and posterior cingulate activation, reduced inferior frontal and dorsolateral prefrontal cortex activation, and altered posterior parietal activation point towards an inadequate demand-specific processing of information. On an individual level they exhibit process-related brain activation differences that are consistent with a shift from context-specific, effortful processing to more stereotyped, habitual response generation. Finally, opiate use appears to decrease the ability to shift cognitive set and inhibit inappropriate response tendencies.

Biological approaches to aphasia treatment

In this review, we discuss the basic mechanisms of neural regeneration and repair and attempt to correlate findings from animal models of stroke recovery with clinical trials for aphasia. Several randomized controlled clinical trials involving manipulation of different neurotransmitter systems, including noradrenergic, dopaminergic, cholinergic, and glutamatergic systems, have shown signals of efficacy. Biological approaches such as anti-Nogo and cell replacement therapy have shown efficacy in preclinical models but have yet to reach proof of concept in the clinic. Finally, noninvasive cortical stimulation techniques have been used in a few small trials and have shown promising results. It appears that the efficacy of all these platforms can be potentiated through coupling with concomitant behavioral intervention. Given this array of potential mechanisms that exist to augment and/or stimulate neural reorganization after stroke, we are optimistic that approaches to aphasia therapy will transition from compensatory models to models in which brain reorganization is the goal.

Effects of cross-sex hormones on cerebral activation during language and mental rotation: An fMRI study in transsexuals

Androgens and estrogens affect the performance on certain cognitive tests, particularly those measuring verbal fluency and mental rotation. Their effects on cognition have frequently been attributed to changes in cerebral lateralization. This study tested the impact of a reversal of the sex steroid milieu on cerebral activation and lateralization during verbal and spatial tasks in transsexuals. fMRI scans were obtained from 6 female-to-male and 8 male-to-female transsexuals at baseline and after cross-sex steroid treatment. Activation was measured during language and mental rotation tasks. Language activation increased after sex steroid treatment in both groups (F(1,12) =3.7, p=0.08), and total language activity was correlated to post-treatment estradiol levels (rho=0.54, p=0.05). Lateralization was not affected by the reversal of sex steroid milieus (F(1,12)=1.47, p=0.25). Activation during mental rotation did not increase during treatment (F(1,12)=0.54, p=0.34), but post-treatment testosterone levels correlated to total activation during mental rotation (rho=0.64, p=0.01). Findings suggest that sex steroids may influence cerebral activation, but lateralization remains stable.

Cortical lateralization of bilateral symmetric chin movements and clinical relevance in tumor patients—A high field BOLD–FMRI study

Although unilateral lesion studies concerning the opercular part of primary motor cortex report clinically severe motor deficits (e.g. anarthria, masticatory paralysis), functional lateralization of this area has not yet been addressed in neuroimaging studies. Using BOLD-FMRI, this study provides the first quantitative evaluation of a possible cortical lateralization of symmetric chin movements (rhythmic contraction of masticatory muscles) in right-handed healthy subjects and presurgical patients suffering tumorous lesions in the opercular primary motor cortex. Data were analyzed according to "activation volume" and "activation intensity". At group level, results showed a strong left-hemispheric dominance for chin movements in the group of healthy subjects. In contrast, patients indicated dominance of the healthy hemisphere. Here, a clinically relevant dissociation was found between "activation volume" and "activation intensity": Although "activation volume" may be clearly lateralized to the healthy hemisphere, "activation intensity" may indicate residual functionally important tissue close to the pathological tissue. In these cases, consideration of BOLD-FMRI maps with the exclusive focus on "activation volume" may lead to erroneous presurgical conclusions. We conclude that comprehensive analyses of presurgical fMRI data may help to avoid sustained postoperative motor deficits and dysarthria in patients with lesions in the opercular part of primary motor cortex.