Audiovisual Lexical Retrieval Deficits Following Left Hemisphere Stroke

Common Neuroanatomical Substrate of Cholinergic Pathways and Language-Related Brain Regions as an Explanatory Framework for Evaluating the Efficacy of Cholinergic Pharmacotherapy in Post-Stroke Aphasia: A Review

Despite the relative scarcity of studies focusing on pharmacotherapy in aphasia, there is evidence in the literature indicating that remediation of language disorders via pharmaceutical agents could be a promising aphasia treatment option. Among the various agents used to treat chronic aphasic deficits, cholinergic drugs have provided meaningful results. In the current review, we focused on published reports investigating the impact of acetylcholine on language and other cognitive disturbances. It has been suggested that acetylcholine plays an important role in neuroplasticity and is related to several aspects of cognition, such as memory and attention. Moreover, cholinergic input is diffused to a wide network of cortical areas, which have been associated with language sub-processes. This could be a possible explanation for the positive reported outcomes of cholinergic drugs in aphasia recovery, and specifically in distinct language processes, such as naming and comprehension, as well as overall communication competence. However, evidence with regard to functional alterations in specific brain areas after pharmacotherapy is rather limited. Finally, despite the positive results derived from the relevant studies, cholinergic pharmacotherapy treatment in post-stroke aphasia has not been widely implemented. The present review aims to provide an overview of the existing literature in the common neuroanatomical substrate of cholinergic pathways and language related brain areas as a framework for interpreting the efficacy of cholinergic pharmacotherapy interventions in post-stroke aphasia, following an integrated approach by converging evidence from neuroanatomy, neurophysiology, and neuropsychology.

Expanded Exploration of the Auditory Naming Test in Patients with Dementia

BACKGROUND

Auditory naming tests are superior to visual confrontation naming tests in revealing word-finding difficulties in many neuropathological conditions.

OBJECTIVE

To delineate characteristics of auditory naming most likely to reveal anomia in patients with dementia, and possibly improve diagnostic utility, we evaluated a large sample of patients referred with memory impairment complaints.

METHODS

Patients with dementia (N = 733) or other cognitive impairments and normal individuals (N = 69) were evaluated for frequency of impairment on variables of the Auditory Naming Test (ANT) of Hamberger & Seidel versus the Boston Naming Test (BNT).

RESULTS

Naming impairment occurred more frequently using the ANT total score (φ= 0.41) or ANT tip-of-the tongue score (TOT; φ= 0.19) but not ANT mean response time compared to the BNT in patients with dementia (p < 0.001). Significantly more patients were impaired on ANT variables than on the BNT in Alzheimer's disease (AD), vascular dementia (VaD), mixed AD/VaD, and multiple domain mild cognitive impairment (mMCI) but not in other dementias or amnestic MCI (aMCI). This differential performance of patients on auditory versus visual naming tasks was most pronounced in older, well-educated, male patients with the least cognitive impairment. Impaired verbal comprehension was not contributory. Inclusion of an ANT index score increased sensitivity in the dementia sample (92%). Poor specificity (41%) may be secondary to the inherent limitation of using the BNT as a control variable.

CONCLUSION

The ANT index score adds diagnostic utility to the assessment of naming difficulties in patients with suspected dementia.

Tasked-Based Functional Brain Connectivity in Multisensory Control of Wrist Movement After Stroke

In this study we documented brain connectivity associated with multisensory integration during wrist control in healthy young adults, aged matched controls and stroke survivors. A novel functional MRI task paradigm involving wrist movement was developed to gain insight into the effects of multimodal sensory feedback on brain functional networks in stroke participants. This paradigm consisted of an intermittent position search task using the wrist during fMRI signal acquisition with visual and auditory feedback of proximity to a target position. We enrolled 12 young adults, 10 participants with chronic post-stroke hemiparesis, and nine age-matched controls. Activation maps were obtained, and functional connectivity networks were calculated using an independent component analysis (ICA) approach. Task-based networks were identified using activation maps, and nodes were obtained from the ICA components. These nodes were subsequently used for connectivity analyses. Stroke participants demonstrated significantly greater contralesional activation than controls during the visual feedback condition and less ipsilesional activity than controls during the auditory feedback condition. The sensorimotor component obtained from the ICA differed between rest and task for control and stroke participants: task-related lateralization to the contralateral cortex was observed in controls, but not in stroke participants. Connectivity analyses between the lesioned sensorimotor cortex and the contralesional cerebellum demonstrated decreased functional connectivity in stroke participants (p < 0.005), which was positively correlated the Box and Blocks arm function test (r² = 0.59). These results suggest that task-based functional connectivity provides detail on changes in brain networks in stroke survivors. The data also highlight the importance of cerebellar connections for recovery of arm function after stroke.